To make wind power more competitive, it is necessary to reduce turbine downtime and reduce costs associated with wind turbine Operation and Maintenance (O&M). Incorporating machine learning in developing condition-based predictive maintenance methodologies for wind turbines can enhance their efficiency and reliability. This paper presents a monitoring method that utilizes Base Density for the Support Vector Machine (BDSVM) and the evolutionary Fourier spectra of vibrations. This method allows smart monitoring of the function evolution of the turbine. A complex optimal function (FO) for 5-degree order has been developed that will be the boundary function of the BDSVM to timely determine the magnitude, frequency, and place of the failure occurring in wind turbine drive.

The paper provides and comments on the results of studies of the effect of sandstone-based abrasives and quartz sand alone on the wear of martensitic surfaces of wear-resistant steels. The wear process was examined on a ring-on-ring test rig seeking to determine the mass decrement parameter which characterised wear. The tests were conducted for three sandstone varieties: Carboniferous, Permian, and Cretaceous, and they made it possible to determine that the most intense process of deterioration of wear-resistant steels took place in the presence of quartz sand grain, while less intense wear was observed in the case of sandstone-based abrasives. The mass decrement values established in the presence of the sandstones in question did not differ significantly between individual sandstone varieties. Based on a surface damage analysis, the basic damage mechanism was found to be micro-scratching, however, with regard to the sandstones examined, it was also determined that individual grains could be pressed into surface irregularities, as well as that films of soft hematite cement developed in the Permian sandstone and that inclusions of carbonaceous matter were formed in the Carboniferous sandstone. With reference to the wear process observations, a wear model was described for the surface of the steels examined in the presence of sandstone-based abrasives.

Pin-on-plate and pin-on-disk wear tests are typically used for assessing the wear behavior of a given material coupling. Such a behavior is frequently described by a wear coefficient k, which is estimated, according to the Archard’s law, as the ratio between the measured wear volume V and the product of the applied normal force F and the sliding distance s, i.e. k=V/(F s). This study demonstrates that such a relationship is correct for pin-on-plate but not for pin-on-disk, particularly for flat-ended pins. Both analytical and finite element models of the two tests were developed, considering three different distances pin-disk axis. As results, wear volumes, pressure and wear depth maps were examined and compared for the same sliding distance. Though this study is focused only on the initial transient part of the wear tests, some interesting aspects arose: i) rotational effect in pin-on-disk tests affects k estimation, especially when the pin is near to the disk axis; ii) a simple analytical function is defined to correct the wear volume estimation for pin-on-disk tests; iii) due to the different sliding distances of contact points in pin-on-disk tests, pressure redistribution occurs with higher values on the inner side (closer to disk axis); the opposite trend is observed in wear depth maps. From a computational point of view, the pin-on-disk problem, only apparently simple, required very small time increments to correctly describe the circular trajectories of points, with high computational costs. Numerical strategies are currently under investigation to extend the study to the steady state phase of both tests.

This work aims to explore the impact of side loads, drill-pipe tool-joint (DP-TJ) speed (RPM), and mud type on the austenitic stainless steel SM2535-110 casing wear characteristics. Actual field drill pipe tool joints, casings, and drilling muds are used in this study. The results of the study show that under both types of lubrication, the wear volume increased with radial load and DP-TJ speed. SM2535-110 casing specimens tested under oil-based mud (OBM) lubrication had higher casing wear volumes than those obtained under water-based mud (WBM) lubrication. This unexpected behavior is mainly due to the increase in the surface hardness of the casing specimens tested under WBM. The results also show that the specific wear factor (K) values of specimens tested under WBM are in general 2 to 4 times higher than those obtained under OBM. While K values under WBM increase with both the side load and RPM, those under OBM show a sharp decrease with RPM. This behavior under OBM is due to this lubricant’s higher viscosity and the change of lubrication regime from thin film to thick film lubrication at higher RPM. Scanning electron microscopy (SEM) and the digital microscopic imaging (DMI) of SM235-110 casing specimens show that an aggressive combination of adhesive, abrasive, and plastic deformation was observed under WBM, while the dominant wear mechanism under OBM is abrasive wear.

Manufacturing of grinding wheels is continuously adapting to new industrial requirements. New abrasives and new wheel configurations, together with wheel wear control allow for grinding process optimization. However, the wear behavior of the new abrasive materials is not usually studied from a scientific point of view due to the difficulty to control and monitor all the variables affecting the tribochemical wear mechanisms. In this work an original design of pin on disk tribometer is developed in a CNC grinding machine. An Alumina grinding wheel with special characteristics is employed and two types of abrasive are compared: White Fused Alumina (WFA) and Sol-Gel Alumina (SG). The implemented tribometer reaches sliding speeds of between 20 and 30 m/s and real contact pressures up to 190 MPa. The results show that the wear behavior of the abrasive grains is strongly influenced by their crystallographic structure and the tribometer appears to be a very good tool for characterizing the wear mechanisms of grinding wheels, depending on the abrasive grains.

Outer particles collision with certain dynamic object is not a pure impact wear behavior; it is typically accompanied by sliding wear phenomena. This study aimed investigating the impact-sliding wear performance of three different TC17 titanium alloys. One was untreated, and the other two were subjected to laser shock peening (LSP) by 5 and 7 J pulse energy, respectively. Wear test was performed on a novel impact-sliding wear testing rig, which can realize multiple impact-sliding motions by changing motion parameters in x and z directions. Present results showed that wear resistance of both treated samples improved compared with the untreated alloy. Given the increase in wear cycles, increment in wear rate of the untreated sample was constantly higher than those of treated samples. All results can be attributed to the increase in surface hardness of the material and residual compressive stress, which was also introduced after LSP.

Multiple engineering projects have confirmed that hydraulic machinery operating in sediment-laden rivers suffers from sediment abrasion. Guide vanes are among the most severely worn flow-passing components and have long been a key research focus in hydraulic machinery. This study conducted wear tests using asymmetric incoming flow with a 10° impact angle and an NACA0012 aluminum alloy airfoil as the research object. The development of wear was analyzed, revealing that it primarily occurs at the airfoil’s leading edge and progresses through three stages: initiation, development, and stabilization. The Finnie model was used to analyze the initial wear mechanism, with calculated results closely matching the latest wear outcomes. In the initial stage, wear rate density was influenced by particle impact velocity, angle, volume fraction, and y-direction shear stress. A low-velocity zone near the impact point, combined with rebounding particles causing secondary impacts, increases particle volume fraction and wear rate density. These secondary impacts are the primary causes of wear on both the upstream and downstream surfaces. Furthermore, flow separation downstream of the leading edge makes this region highly susceptible to wear. This study provides valuable insights for addressing wear in hydraulic machinery for practical engineering applications.

Bandsaw blades are typical band-shaped cutting tools characterized by low stiffness and micro-level cutting depth, resulting in distinct wear mechanisms compared to rigid cutting tools. In this study, the wear curve and wear mechanisms of bandsaw tooth during the bandsawing of Cr12MoV cold-working steel was investigated. The tool life was divided into two stages: a rapid wear stage (Stage I) and a homogeneous wear stage (Stage II). In Stage I, the wear was dominated by chipping although multiple wear mechanisms were found due to the relatively poor manufacturing accuracy compared to rigid cutting tools, which results in remarkable differences among the cutting depths of individual teeth. In Stage II, abrasive and adhesive wear were the primary wear mechanisms instead of chipping, which was related to the microstructure of Cr12MoV. Furthermore, methods for increasing the bandsaw performance were proposed based on the tooth wear mechanisms.

Bandsaw blades are typical band-shaped cutting tools characterized by a low stiffness and micro-level cutting depth, resulting in distinct wear mechanisms compared to rigid cutting tools. In this study, the evolution of bandsaw tooth wear mechanisms during the bandsawing of Cr12MoV cold-working steel was investigated. The tool life was divided into two stages according to the tooth wear mechanism: a rapid wear stage (Stage I) and a homogeneous wear stage (Stage II). In Stage I, the wear mechanism was dominated by chipping, although multiple wear mechanisms were found because of the relatively poor manufacturing tolerance compared to rigid cutting tools, resulting in remarkable differences between the cutting depths of the individual teeth. In Stage II, abrasive and adhesive wear were the primary wear mechanisms instead of chipping, due to the decreased width and setting magnitude tolerance after Stage I. Furthermore, methods for increasing the bandsaw performance were proposed based on the tooth wear mechanisms.

Technological equipment in quarries that extract and deliver aggregates for different uses operates in a predetermined flow depending on the type of rocks exploited and the dimensional characteristics imposed on the final products. In this context, the interruptions in operation required to replace high-wear parts (such as the teeth of excavators and bucket loaders) must be limited as much as possible through technological solutions to increase their service life. The evolution of the wear of the teeth of the quarry equipment that come into direct contact with the rocks was concretely established in the production process, in parallel with the wear values obtained by simulating the wear phenomenon in laboratory conditions, in order to validate the data collected during the operation of the machines. Preventive-repetitive maintenance, within the activities of reconditioning the worn surfaces of the teeth, through the charging process by manual electric welding with covered electrodes, was applied directly to the machine, which led to the shortening of the interruptions in operation necessary to replace these spare parts.

To increase the power density of the electromechanical drive train of wind turbines, journal bearings can be used as planetary gear bearings instead of rolling bearings. This technological change presents new challenges. For example, wind turbine drive systems are subject to dynamic and low-speed operating conditions which can lead to an accelerated abrasive wear of the journal bearings. In addition, oil supply failure or peak loads due to wind gusts and grid and power converter faults could potentially result in catastrophic failure due to adhesive wear in a very short time. Such operating characteristics are, therefore, critical regarding the journal bearing wear lifetime and must be considered in the design. The successful implementation of journal bearings in wind turbines depends on a reliable estimation of adhesive and abrasive wear. In this paper, five different models for the wear calculation of journal bearings are evaluated regarding their suitability of wear calculation of planetary gear bearings in wind turbines. For this purpose, the following evaluation criteria were defined: parameter uncertainty, parametrization effort, in particular number of parameters, parameterization method and load case dependency of parameters and calculation effort. In order to be able to evaluate the wear models, the wear models are numerically implemented and the wear of a test journal bearing is exemplarily calculated under load conditions, which are comparable to load conditions in a wind turbine. Relevant influences from the wind turbine system such as lubricant, material and manufacturing dependent surface influences like roughness and hardness are considered. The wear models are evaluated with respect to their fulfillment of the defined criteria. The resulting evaluation allows the selection of a wear model that can be used to calculate the wear of planetary gear journal bearings in wind turbines, considering the available input variables.

The exfoliation of graphene has opened a new frontier in material science with a focus on 2D materials. The unique thermal, physical and chemical properties of these materials have made them one of the choicest candidates in novel mechanical and nano-electronic devices. Notably, 2D materials such as graphene, MoS2, WS2, h-BN, and Black Phosphorus have shown outstanding lowest frictional coefficients and wear rates, making them attractive materials for high-performance nano-lubricants and lubricating applications. The objective of this work is to provide a comprehensive overview of the most recent developments in the tribological potentials of 2D materials. At first, the essential physical, wear, and frictional characteristics of the 2D materials including their production techniques are discussed. Subsequently, the experimental explorations and theoretical simulations of the most common 2D materials are reviewed in regards to their tribological applications such as their use as solid lubricants and surface lubricant nano-additives. The effects of micro/nano textures on friction behavior are also reviewed. Finally, the current challenges in tribological applications of 2D materials and their prospects are discussed.

In this study, Fe-Mo-B based hardfacing electrodes containing different amounts of Mo were coated on an AISI 1020 steel substrate using the electric arc welding method. The findings show that molybdenum is highly effective on the microstructure and minor changes in the coating composition affect the phases and morphological properties. In the hardness tests, an increase of 73% was achieved in the Fe14Mo2B4 based hardfacing coating compared to the base material and a 30% increase compared to the Fe16B4 based coating. The highest macro hardness value was measured as 56.4 HRC and the highest phase hardness was measured as 3228 HV in the FeMo2B2 phase. The lowest wear rate was measured in the Fe14Mo2B2 based coating. The wear rate of the Fe14Mo2B4 based coating was 8.1 times lower than that of the substrate material and 4.7 times lower than that of the Fe16B4 based coating. According to corrosion test results, the highest corrosion resistance was obtained in Fe16B4 based coating. The current density value of the Fe16B4 based coating was measured to be 13.6 times lower than that of the substrate material.

Light alloys machining is a widely implemented process that have usually used in presence of cutting fluids to reduce the wear impact and increase tool life. However, current environmental protection policies require their elimination in order to improve process sustainability. This fact forces to work under aggressive cutting conditions, producing adhesion wear that affects the integrity of the part surface. This study describes cutting tool wear mechanisms in machining of UNS A92024 samples under dry cutting conditions. EDS analysis showed the different composition of the adhered layers, while roughness was also positively affected by the change of the cutting geometry produced in the tool.

The paper presents theoretical notions with practical applications for establishing of one dental bur lifetime (durability and reliability based on the active part wear considering a series of statistical indicators. For the justification application of theoretical notions in practice, a conical-cylindrical dental bur was studied experimentally, to obtain a series of data in the work process, necessary for statistical calculation. The parameter taken into consideration in this paper is mass lost through the dental bur active part wear, tested. This is useful for the dental bur lifetime establishment and its extension or even optimization in operation. The loss of mass of the dental bur active part is analyzed in the work process by the results and experimental data obtained and validated by a numerical calculation statistical-mathematical. The numerical calculation approximates very well the mass lost through the wear at different rotation speeds and operation times, with those experimentally determined ones, based on which it was established lifetime. The results showed that the dental bur works with high yield in the first 20 hours of work, , after which it should be replaced with a new one.

The fracture strength was compared in a scratch test of coatings based on the ZrN system with the introduction of Ti, Nb and Hf, which were deposited on a titanium alloy substrate. The coatings were deposited using Controlled Accelerated Arc (CAA-PVD) technology. The comparison was carried out according to two parameters: adhesion strength to the substrate and overall coating strength. The (Zr,Hf)N coating showed better resistance to destruction, but had worse adhesion to the substrate. As a result, although the coating is retained directly in the scribing groove, a large area of delamination and destruction is formed around the groove. The (Ti,Zr,Nb)N coating, with its somewhat lower strength, has high adhesion to the substrate; no noticeable delamination is observed along the groove boundary.

In polymer-based dental composites, wear is a three-body wear system mainly abrasive, because of the food particles and wear products suspended in the oral cavity, which are transferred to the microcavities of the surface of the replacements. Due to this fact, the incorporation of nanodiamond as reinforcement in these polymer matrix composites, which promotes the creation of a solid lubricant tribofilm surface could be advantageous. When nanodiamond is added in contents of 0.8, 1.6 and 3.2 wt %, an increase in microhardness from 95 up to 420 %, compared to the one of neat BisGMA/TEGDMA, is observed. Additionally, the incorporation of a content of 1.6 wt % is enough to cause a diminution of ~78 % in the friction coefficient and a reduction of the specific wear rate and Archard’s coefficient of ~50 %. Nevertheless, the addition of relatively high contents reduces the effectiveness of photoinitiation and UV-curing, which is related to the scattering and absorption of UV radiation by ND.

The paper provides a discussion on the results of studies of the effect exerted by combined degradation factors typical of four types of wear: abrasion, impact-abrasion, tribocorrosion, and impact-abrasion-corrosion, conducted for chain wheels made of Ni-Cu alloyed Austempered Ductile Iron. The studies consisted in determining the content of retained austenite in the structure of the cast irons in question, establishing the measures of wear following wear testing, and identifying basic surface degradation mechanisms observed in the chain wheels tested following multifactorial wear processes. The chain wheels made of ADI were found to have sustained the greatest damage under the impact-abrasion-corrosion (three-factor) wear scenario, while the wear was least advanced in the abrasion (one-factor) wear case. Another observation derived from the studies is that the combined effect of dynamic forces, corrosion, and quartz sand-based abrasives causes increased surface degradation in the cast iron grades taken into consideration compared to processes characterised by a reduced number of degradation factors (i.e. one- or two-factor wear processes). Additional hardness tests and XRD analyses have revealed a distinctive effect attributable to combined degradation factors on the surface hardness increase value and implied that bench testing was followed by phase transition.

In order to improve the wear resistance of copper contacts in high-voltage switches and improve the abnormal discharge phenomenon caused by wear gaps, laser remelting technology was used to strengthen the surface of copper contacts. The surface morphology, microhardness, and wear resistance of the remelted samples were tested and characterized using scanning electron microscopy (SEM), microhardness tester, and friction and wear tester. The test results indicate that laser frequency, pulse width, and current parameters can directly affect the surface morphology and wear resistance of the sample, but their influencing processes vary. The laser frequency is achieved by the variation of the superposition relationship between the impact points, while the pulse width and current are achieved by the variation of the laser intensity at the impact points. When the pulse frequency is 10Hz, the pulse width is 10ms, and the current is 100A, the sample exhibits a more balanced surface morphology, microhardness, and wear resistance.

In this study, the potential of Fe3Al coating material as an environmentally friendly alternative to coatings containing critical elements for brake discs was investigated. A buffer layer of Cr-Mo steel (Ferro 55) was applied to enhance coating quality and prevent the formation of hot cracks during solidification. Microstructural analysis of the cross-section of the coating showed that the buffer layer diffused into the Fe3Al coating, forming a combination of Fe3Al, Fe, and Fe3AlC0.5 phases. The tribological properties of the Fe3Al coating were evaluated by pin-on-disc tests using two different copper-free friction materials extracted from commercial brake pads. The wear results showed a coefficient of friction comparable to that of an uncoated disc, but with a reduction in Particulate Matter (PM) emissions, an interesting aspect that is gaining increasing importance in view of the upcoming international standards..

Magnetron sputtering was used for producing Titanium Vanadium Nitride (TiVN) coatings on a variety of substrates. In this research, we investigate how changing the sputtering power and nitrogen: argon (N2:Ar) gas ratio affects the structural and tribological properties of TiVN coatings. Scanning Electron Microscope (SEM) technique was used to examine TiVN coating surface morphology. Both variants showed a gradual increase in the intensity of the TiVN coating's (111) and (222) peaks. TiVN coating's tribological properties were examined using a pin-on-disc tribometer with varying loads, speeds, and sliding distances. The wear rates of TiVN-coated brass pins were in the range of 2.5×10-4 to 9.14×10-4 mm3/Nm depending on load, sliding distance, and gas ratio variation, when compared to the wear rates of TiVN-coated brass pins deposited at various power, which ranged from 1.76×10-3 to 5.87×10-3 mm3/Nm.

Inspired by nature's examples such as lotus leaves and insect wings, superhydrophobic surfaces have been extensively studied and engineered. However, achieving superoleophobic surfaces, which repel oils, has proven to be more challenging due to the oils' lower surface tension than water. This article presents a novel, cost-effective technique for fabricating superoleophobic surfaces with enhanced durability. We demonstrate the effectiveness of this technique by using Perfluorooctyltriethoxysilane (PFOTES) and silicon dioxide nanoparticles on stainless steel mesh substrate. The resulting surfaces exhibit remarkable superoleophobic properties by incorporating re-entrant structures, low surface energy, and high surface roughness, making them ideal for oil-repellency applications.

The paper investigates experimentally the influence of the Fused Filament Fabrication (FFF) pre-processing strategy on the tribological properties of parts made of PEI (polyetherimide), investigating the difference in the weight loss of the samples caused by abrasive wear before and after the test. The samples were tested for abrasive wear resistance on a tribometer constructed according to ASTM G65/16 (dry sand). Two types of specimen printing orientation along X-axis (lengthwise) and along Z-axis (heightwise) were tested in the study. Three types of path generation strategies were used for manufacturing "X" and "Z" specimens and totally 18 samples were made and tested. Path deposition strategy was carried out with path deposition width of 0.5mm and parallel paths in all slicing layers. In order to reduce the voids in volume, deposition path axes in subsequent layers were shifted by 0.25mm offset. Garnet abrasive Fe3Al2(SiO4)3 was used for this test. The analysis of the experimental data shows the relationship between the samples building direction (X, Z), applied deposition strategies (1X - 3X and 1Z - 3Z) on the resulting resistance to abrasive wear.Keywords: PEI, FFF, path generation strategy, abrasive wear

The concept of friction damper is widespread technique and used to reduce the structural vibrations in many industrial applications. These friction dampers are generally coated with low wear rate materials to reduce the fretting wear. This paper investigates the use of physical vapor deposition (PVD) nitride based AlTiN coating material applied over the stainless steel friction damper to enhance the damping capacity and to reduce the fretting wear. A friction test rig has been developed to measure the dynamic hysteresis characteristics of friction damper at high temperature (700 °C). The damping capacity and fretting wear analysis is carried out at room temperature, 300 °C and 600 °C. The force versus displacment characterisitcs curve is used to predict the damping capacity and fretting wear analysis is carried out at microscopic level for the comparision. It is observed that at room temperature AlTiN coated friction damper has not much influence to improve the damping capacity and to reduce the fretting-wear. However, at high temperature it has better damping capacity and less wear in comparision to uncoated friction damper. Wear behaviour in coated and uncoated damper is different at room temperature and at elevated temperature.

A review of the surface ablation of hominin teeth by attrition, abrasion and erosive wear. The occurrence of these lesions is explored in a sample of South African fossil australopithecine dentitions revealing excessive wear. Interpretation of the nature of the dietary components causing such wear in the absence of carious erosion provides insight into the ecology of the Plio-pleistocene epoch (1-2 million years ago). Fossil teeth inform much of the living past by their retained evidence after death. Tooth wear is the ultimate forensic evidence of lives lived.

This study explored the effects of cryogenic treatment on the microstructure, hardness, and wear-resistance of diamond-like carbon (DLC) by cryogenically treating NAK 80 mold steel coated with DLC. Raman spectroscopy analyzed the structure of the DLC film. Nanoindenter analyzed the hardness and Young’s modulus of the film, and their relationship determined the wear resistance. Wear test assessed the wear rate and friction coefficient of the DLC film. The results showed that cryogenic treatment increased the rate of carbide precipitation and refined the grain structure. Raman spectroscopy indicated that the Raman intensity rate (I_D/I_G) of treated DLC films was smaller than those without cryogenic treatment. When the sp3 bond increased, the hardness and wear-resistance of the DLC film also increased.

The tribological performance of metalwork steel tools is of vital importance in both cold and hot working processes. One solution for improving metal tool life is the application of coatings. This paper investigates the effect of CrAlSiN thin-film PVD-deposition on the tribological behaviour of tool steel K340. The sliding wear performance of the coated K340 steel is analysed in relation to both the uncoated K340 steel and a range of tool steels dedicated to hot- and cold-working, such as X155CrVMo12-1, X37CrMoV5-1, X40CrMoV5-1, 40CrMnMo7 and 90MnCrV8. The investigated tool steels were heat-treated, while K340 was subjected to thermochemical treatment and then coated with a CrAlSiN hard film (K340/CrAlSiN). The hardness, chemical composition, phase structure and microstructure of steels K340 and K340/CrAlSiN are examined. Tribological tests were conducted using the ball-on-disc tester in compliance with the ASTM G99 standard. The tests were performed under dry unidirectional sliding conditions, using an Al2O3 ball as a counterbody. The wear factor and coefficient of friction are estimated and analysed with respect to hardness and alloying composition of the materials under study. SEM observations are made to identify the sliding wear mechanisms of the analysed tool steels and PVD-coated K340 steel. In contrast to the harsh abrasive-adhesive wear mechanism observed for uncoated tool steels, the abrasive wear dominates in case of the AlCrSiN. The deposited thin film effectively prevents the K304 substrate from harsh wear severe degradation. Moreover, thanks to the deposited coating, the K304/CrAlSiN sample has a COF of 0.529 and a wear factor of K=5.68×10−7 m3 N−1 m−1, while the COF of the reference tool steels ranges from 0.702 to 0.885 and their wear factor ranges from 1.68×10−5 m3 N−1 m−1 to 3.67×10−5 m3 N−1 m−1. The CrAlSiN deposition reduces the wear of the K340 steel and improves its sliding properties, which makes it a promising method for prolonging the service life of metalwork tools.

The parallel connection of multiple flexible rings in raceways can significantly improve the electrical conductivity of rolling conductive devices. Multiple flexible rings are generally separated by idlers to form ring-idler rolling pairs. In the present work, alumina (Al2O3), polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), and polyimide (PI) were used as idler materials. Rolling tests for four types of ring-idler contact pairs were carried out in the air at a rotating speed of 10 rpm and a current of 60 A. It was noticed that the voltage drop was the lowest when Al2O3 was incorporated as the idler material. The energy spectrum analysis indicated material transfer between the organic idlers and the flexible ring. Especially on the flexible ring surface, the transferred organic thin film covered the gold-plated layer of the flexible ring and affected the electrical contact of the flexible ring. The transfer of Al2O3 was not obvious, and the mass fraction of Au on the flexible ring surface after the rolling test was 93.1%. The above results could help in selecting the best idler material for high-power conductive rotary joints.

Double-walled carbon nanotube-yttria-stabilized ZrO2 nanocomposites are prepared by a mixing route followed by Spark Plasma Sintering. Incorporation of carbon at contents higher than 2 wt.% results in significantly lower friction coefficients, both against alumina and steel balls. Double-walled carbon nanotubes improve wear resistance and reduce friction without severe damage, contrary to multi-walled carbon nanotubes.

One route to reducing CO2 emissions is to improve the energy efficiency of machines. For example, conventional combustion engines are being downsized (and down-speeded), are now running on lower viscosity engine lubricants (such as SAE 0W-20 or lower viscosity grades) and often also have stop-start systems fitted (to prevent engine idling when the vehicle is stopped). Some of these changes result in higher levels of mixed and boundary friction, and so accurate estimation of mixed/boundary friction losses is becoming of increased importance, both for estimating friction losses, and also for estimating wear volumes. Traditional approaches to estimating mixed/boundary friction, which employ real area of contact modelling such as the Greenwood-Tripp model [1] are widely used, but recent experimental data suggests that these approaches underestimate mixed/boundary friction losses [2-5]. A new model has been developed, based on experimental data, which estimates the proportion of mixed/boundary lubrication, X, as a function of the value (where is the ratio of the oil film thickness separating the surfaces to the combined root mean square surface roughness of the interface surfaces). The precise equation that describes the way in which X varies with takes the form of a “reverse S-curve”, which makes physical sense since S-curves arise naturally in growth processes, and in mixed/boundary lubrication, the real area of contact of rough surfaces grows as the load (and 1/) increases. Numerical estimates of mixed/boundary lubrication losses in internal combustion engines are presented here and compared with published data [2,6]. In addition, the improved method described here is used to estimate both the financial cost of mixed/boundary lubrication for today’s passenger car fleet, and the CO2 emissions associated with these friction losses.

Hypoeutectic Al-Si-Cu-Mg alloys are promising candidates for use in automobile parts. Therefore, various attempts have been made to develop alternative casting technologies to improve the mechanical properties of cast alloys. In this study, the effects of modification with different levels of strontium (Sr) on primary and eutectic silicon (Si) in hypoeutectic Al-Si-Cu-Mg alloys were investigated. Using a gravity cast process, the Sr-modified samples were prepared from melts with four levels (100, 200, 300, and 400 ppm) of Sr. In addition, the wear properties of the cast samples were studied using a block-on-ring wear-testing machine. The sizes of the primary Si phases increased with increasing Sr content in the alloys. Moreover, more finely dispersed eutectic Si was observed with higher Sr content. In frictional wear tests, the specific wear rates of the test specimens decreased as the Sr content increased from 200 to 400 ppm. Coarse Si phases are considered to act as solid lubricants in the contact region during sliding.

Airborne micro- and nanoplastics are widely spread and pose a risk to human health. The effects of virgin (v) and home oxidised (ox) nano- and micropolystyrene (nPS/mPS) (0.1 and 1 µm) were studied on the human alveolar cells (A549). Ox-nPS/mPS, simulating photoaging, allowed effects due to environmental wear to be assessed. Cellular uptake was quantified using FITC-functionalised nPS/mPS, while cytotoxicity, changes in the acidic compartment, ROS production, mitochondrial function and DNA damage were assessed to study the effects of internalised v- and ox-nPS/mPS. The uptake was dose-dependent and very fast, since, at the lowest dose, 20.8% and 21.8% of nPS and mPS, respectively, were internalised after 1 h. Compared to v-, significant ROS increases, DNA damage and mitochondrial impairment were observed after exposure to ox-nPS/mPS. The enhancement of effects due to environmental aging processes highlighted the true potential impact on human health of these airborne pollutants.

Nitriding has long been used to engineer the surfaces of engineering steels to improve their surface and subsurface properties. The role of the surface compound layer (’-Fe4N and/or -Fe2-3N) in improving the tribological and corrosion resistant properties of nitrided steels has been established. However, there have been very few studies on the response of the compound layer to tribocorrosion in corrosive environments. In this work, the tribocorrosion behaviour of a 5 m thick ’-Fe4N nitride layer produced on mild steel (MS) by plasma nitriding has been studied in a NaCl containing solution under various electrochemical conditions. The results show that at a cathodic potential, where mechanical wear is predominant, the total material removal (TMR) from the ’-Fe4N layer is 37% smaller than that from the untreated MS, and at open circuit potential, TMR from the layer is 35% smaller than that from the untreated MS, while at an anodic potential, the ’-Fe4N layer can reduce TMR from mild steel by 87%. The beneficial effect of the ’-Fe4N nitride layer in improving the tribocorrosion behaviour of mild steel is derived from its high hardness and good corrosion resistance in the test solution and its ability to resist both mechanical wear and chemical wear.

One of the modern methods of improving operating characteristics of titanium and titanium-based alloys under conditions of friction and increased contact loads is the method of ion-plasma nitriding. The effect of nitriding of VT5 alloy (Al 4,5-6,7 %, V to 1,2 %, Mo to 0,8 % − analogue 3.7115) in the plasma of a glow discharge excited in a hollow cathode on its tribological characteristics in pairs with different materials in T-1 fuel and under dry friction conditions has been studied. For research and tribological tests, samples of VT5 alloy were nitrided in the plasma of a glow discharge excited in a hollow cathode at a temperature of 975 ± 15°C and a pressure of 58 ± 2 PA in a nitrogen-argon gas mixture with a nitrogen content of 78 %. Studies of samples of VT5 alloy after nitriding showed that the surface roughness Ra was in the range of 0.58-0.64, and the surface hardness HV5 was 525 ± 20 kgf/mm² at a base hardness of 325 ± 15 kgf/mm². Tribological tests were performed on a friction machine 2070 SMT-1 according to the scheme "cube - roller". Tests under conditions of friction with oil were performed at a load of 200 N. The sliding speed during the tests was 1.3 m/s, the test time was 75 sec. The test under dry friction conditions was carried out at a load of 100 N and a sliding speed of 0.785 m/s, the test time was 30 minutes. Low wear ability in relation to the nitrided titanium alloy VT5 (<2.4x10^-4 mm³/s), as well as friction coefficients at the level of 0.08 to 0.12 in the order of their growth had bronze VB-23NTS (Pd 18–22 %, Ni 3–4 %, Zn 3–4 %, Sb 3–4 %, P 0.15–0.3) r.O10C2N3, VB-24 (Sb 4.7–6, 2 %, P 0.4–0.9), steel 1.3505, cast iron GGG80, cemented steel 20Cr3MoWV.

In the manufacturing industry, cutting tool failure is a probable fault which causes damage to the cutting tools, workpiece quality and unscheduled downtime. It is very important to develop a reliable and inexpensive intelligent tool wear monitoring system for use in cutting processes. A successful monitoring system can effectively maintain machine tools, cutting tool and workpiece. In the present study, the tool condition monitoring system has been developed for Die steel (H13) milling process. Effective design of experiment and robust data acquisition system ensured the machining forces impact in the milling operation. Also, ANFIS based model has been developed based on cutting force-tool wear relationship in this research which has been implemented in the tool wear monitoring system. Prediction model shows that the developed system is accurate enough to perform an online tool wear monitoring system in the milling process.

The aim of this work is evaluation of corrosion behavior of SS 304 coated through TIG process. In this work, Ti tube cored with graphite powder was applied. Experimental processes were shown that the optimum parameters for coating procedure are voltage of 15V, current density of 120A and the speed of 2.1mm/s. Investigations on corrosion resistance of coating are shown that not only this composite coating can improve the tribological behavior of this type of stainless steel, but also there is an improvement in its deteriorative property. Moreover, it is observed that mass reduction in coating is 5 times lower than the base metal.

Nickel electrodeposition is a widely utilized method for creating thin films on various substrates with various desirable attributes. Recently, there has been a growing interest in developing nickel composite coatings that incorporate additional elements or particles into the nickel matrix to enhance their properties. These composite coatings offer superior wear resistance, corrosion resistance, hardness, and other functional benefits compared to pure nickel coatings. Some of the recent advancements in electrodeposited nickel composite coatings include improved wear resistance, enhanced mechanical properties and better corrosion resistance. Researchers have discovered that adding Al, Si, Zr, C, W, and Ti particles to nickel coatings can significantly enhance wear resistance. The uniform distribution of these particles within the nickel matrix acts as a barrier to wear and tear. Studies have also shown that nickel composite coatings with Al, Si, Zr, C, W, and Ti particles exhibit superior mechanical properties, including increased hardness. These particles refine the grain size of the nickel matrix and hinder defect movement, leading to greater mechanical strength. Moreover, nickel composite coatings offer improved protection against corrosion compared to pure nickel coatings. This review provides a detail discussion of nickel composite coatings with regard to their comparative advantaged compared to pure nickel coatings on different substrates.

Based on some experiments, the paper describes with the help of polarization the physic-chemical processes that take place in the contact area of friction pairs, during the selective transfer as a result of the change in the input speed of the lubricant (glycerin), as well as how it influences their wear. Through polarization, the quantitative and qualitative transformations of glycerin are studied during frictional stress with selective transfer, the determination of the properties of the selective solution, and the damage to the metals and alloys of the friction pairs, but also after frictional stress.

Wear-resistant steel/carbon steel composite plate not only has the double performance advantage of high strength and wear-resistance, but also can reduce energy consumption and production cost. Based on 50% reduction rate, the wear resistance of BTW1/Q345 composite was studied at different annealing temperatures, and the dry friction and wear tests of BTW1/Q345 composite at different annealing temperatures were carried out by using RETC MFT-5000. The macro-micro morphology and wear mechanism of wear marks at different annealing temperatures were analyzed by using white light interference three-dimensional surface profiler, Scanning electron microscope scanning electron microscope (SEM) and backscatter electron diffraction (EBSD) . The results show that with the increase of annealing temperature, the grain size near the scratch of BTW1 in the wear-resistant layer of the composite plate is refined, and the wear-resistant property is higher than that of the original sample.When the annealing temperature is 860℃,the wear resistance is the best.

Blisks subjected to rough machining for channel creation must undergo finishing processes, and such processes must achieve the required tolerance limits. A high-quality surface finish and predictable long tool life are critical for the finish milling of blisks. Accordingly, the aim of this study was to optimize parameters for the finish machining of an Inconel 718 alloy monolithic blisk. Ball-cone mills were used to machine the blade surface at a constant depth. A sensory tool holder was used to collect cutting force signals during machining, and a digital microscope was used to examine tool wear. The surface texture measuring instrument was used to measure blisk blade surface roughness to evaluate processing quality. This study manipulated two cutting parameters, namely cutting speed and feed per tooth, and investigated their effects. The relationship between cutting conditions and machining efficiency was analyzed. According to the experimental results, we identified a set of optimal parameters for marginal tool wear and fast cutting speeds and then estimated the corresponding tool life by using the derived parameters.

This study presents the computational model to determine the wear behaviour of polymer gears. Using PrePoMax finite element numerical calculation software, a proposed computational model was built to predict wear behaviour based on Archard's wear model. This allows the calculation of the wear depth in each loading cycle with constant mesh updating. The developed computational model has been evaluated on the spur gear pair, where the pinion made of POM has meshed with a support gear made of steel. The computational results that were obtained were compared with the analytical results according to the VDI 2736 guidelines. Based on this comparison, it was concluded that the proposed computational model could be used to simulate the wear behaviour of contacting mechanical elements like gears, bearings, etc. The main advantage of the model, if compared to the standardised procedure according to the VDI 2736 guidelines, is the geometry updating after a chosen number of loading cycles, which enables a more accurate prediction of wear behaviour under rolling/sliding loading conditions.

In this study, nano-diamond (ND) and MoS2 powder are used as additives in a carbonyl iron based magnetorheological fluid (MRF) to improve its tribological performance. MRFs are prepared by dispersing 35 wt.% of CI particles in silicone oil, and adding different proportions (0, 1, 3 or 5 wt.%) of ND and MoS2 additives. Seven kinds of MRFs are made and tested using reciprocating friction and wear tester under different normal loads, and then the friction characteristics are evaluated through analyzing experiment results. The morphology properties of MRFs and contacting surfaces before and after tests are also observed using a scanning electron microscope and analyzed by energy-dispersive X-ray spectroscopy. The results show that the appropriate weight percentage of MoS2 additives may decrease friction coefficient and wear zone. It is also demonstrated from the detailed analyses of worn surfaces that the wear mechanism is influenced not only by additives but also by applied normal load and magnetic field strength.

Tungsten carbide (WC) was well known as a wear-resistant material. Iron-based pow-der was suitable for remanufacturing of cast iron engine parts. To improve the wear resistance of the remanufactured iron-based cast iron engine parts, WC-Co was intro-duced into iron-based powders to prepare composite coatings for cast iron engine components. In this work, FeAlC-x(WC-Co) composite coatings were prepared by plasma transfer arc on compacted graphite cast iron. The influences of WC-Co con-tents in the Fe-AlC-x(WC-Co) composite coatings on the microstructure and properties of the composite coatings were investigated. The composite coatings contained γ-Fe, α-Fe, WC and Fe3W3C mainly. The microhardness of FeAlC-x(WC-Co) composite coatings had the highest hardness of 814 HV0.2, the-lowest coefficient of 0.5 and the lest wear mass loss of 1.3mg when the weight content of WC-Co in the composite coating was 20wt%. As compared with the FeAlC coating, FeAlC-x(WC-Co) composite coating achieved the effect of reducing friction and wear resistance simultaneously, which resulted from the self-lubricating effect of graphite and high wear-resistance of carbides in the claddings.

The (Ti, Nb)(C, B)/IN625 composite coating with both homogeneous and defect-free microstructure were successfully prepared by in situ on the surface of 42CrMo steel using the coupling of the ultra-high-speed laser cladding (EHLA in German) technology with the direct reaction synthesis (DRS) technology, and were comparatively analyzed with the IN625 coating prepared by the EHLA. The microstructure of the fused cladding layer was investigated by selected scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and double spherical aberration transmission electron microscopy (DSA-TEM). The residual stress distribution on both sides of the fused cladding interface was characterised by nanoindentation stress test based on the modified O&P method and the G&S energy method. The results show that the interface of (Ti, Nb)(C, B)/IN625 composite coatings is affected by about 670 kJ Joule heat released from the in-situ reaction, and the interfacial width reaches 24 μm, so that it is 6 times higher than that of IN625 coating prepared by EHLA, which effectively reduces the stress gradient in the interfacial region and alleviates the stress mismatch on both sides of the interface. However, the surface hardness of (Ti, Nb)(C, B)/IN625 composite coating is lower than that of the IN625 coating, with a value of about 240 HV0.2, and the average wear weight loss was only 10% of that of the IN625 coating, which is on the one hand attributed to the in-situ authigenic TiCB, TiC, NbMo3B4, and NbMo2B2 phases supporting the (Ti, Nb)(C, B)/IN625 composite coating substrate to achieve the abrasion reduction and wear resistance. On the other hand, it is attributed to the formation of nano-equiaxial ultrafine grains in the depth range of 250 nm below the wear surface area by the coupling of the three fields of plastic rheology-heat-force, which dynamically strengthens the wear surface.

The effect of plasma electrolytic nitrocarburizing on the wear resistance of carbon tool steel in friction couples with hardened steel and lead-tin bronze is considered. The microgeometry of friction tracks and its change with increasing duration of friction tests are analyzed. The equilibrium roughness is determined, which is optimal for the friction couple and ensures minimal wear. The type and mechanism of wear of carbon tool steel after plasma electrolytic nitrocarburizing has been determined. The optimal values of the plasma electrolytic nitrocarburizing parameters, which provide the lowest values of the friction coefficient and weight wear, have been determined. The phase and elemental composition of the surface layer was studied using X-ray diffraction analysis and EDX analysis. The relationship of the microstructure of the nitrocarburized layer of tool steel with the friction coefficient and weight wear is established.

The paper analyzes the phenomenon that condition the durability and reliability of a type of dental bur based on the wear of the active part and with effect on its quality. For the experimental study, a conical-cylindrical dental bur and a sample dental material in cobalt-chromium alloy, cylindrical shape, tested on a specially made experimental installation were used. The paper was limited to the consideration of a single parameter (loss of mass, mw by wear of the active part of the dental bur tested) for the establishment the durability and reliability, useful for the extension of the lifetime or even optimization of its operation. The wear phenomenon of the active part of dental bur is studied based on the results and experimental data obtained in the work process that was validated by interpolation and led to polynomial functions which approximate very well the dependent parameter, mw, considered in the experimental program. The results of the interpolation showed that in the first 11 h of work, the dental bur works with high efficiency, after which it can be easily decommissioned (optimizing operation, possibly constructive solutions); i.e., it should be replaced with a new one (criterion for replacing of worn dental bur).

Rotor blade bearings enable the rotor blades to pivot about their longitudinal axis and thus control the power output and reduce the loads acting on the wind turbine. Over a design period of 20 years, rolling bearings are exposed to frequent oscillating movements with amplitude ratios of x/2b>1, especially due to new control concepts such as Individual Pitch Control, which can lead to wear and a reduction in service life. The objective of the paper is to identify the dominant wear mechanisms and their consequences for the operation of oscillating bearings. Oscillating experiments with increasing number of cycles on angular contact ball bearings of two different sizes (type 7208 and 7220), show that the damage initiation starts with adhesive and corrosive wear mechanisms, which result in a sharp increase of the torque as well as the wear volume on the bearing raceway. As the number of cycles increases, an abrasive mechanism occurs, resulting in a lower slope of the wear curve and a smoothing of the resulting wear depressions. The wear and torque curves are evaluated and classified using an energy-wear approach according to Fouvry.

The paper contains the results of the 100-hour test campaign of the Additive Manufactured (AM) spare part (retainer – slipper) dedicated for an exact axial piston pump. The material of the retainer-slipper has been identified by using energy dispersive spectroscopy and replaced by other – with similar material properties as the original one. The obtained spare part had been subjected to only one postprocessing type (sandblasting) to analyze the influence of the rough part after the AM process. The whole test campaign has been divided into stages, where after each stage microscopic measurements have been made. During microscopical investigation roughness and geometrical measurements were conducted. The results revealed that it is possible to replace parts in hydraulic pumps with the use of AM. 100-hour test campaign caused about 500% increase in the surface roughness of the pump’s original part which was cooperated with the AM spare retainer-slipper, without any damages to the test system.

The lack of knowledge on the link between the manufacturing process and performances constitutes a major issue of brake lining development. This study focuses on the effect of mixing duration on properties and tribological behavior of organic friction composite materials. The adopted methodology is based on efficient simplified formulations to limit synergic effects by the reduction of number and size distribution of constituents. Microstructural characteristics are analyzed and correlated to thermo physical and mechanical properties. Wear mechanisms and tribological behavior are studied in relation with the given microstructure and material properties. In the elaboration process, mixing duration has an impact on particle distribution and fibre arrangement. Distribution and size of fibre entanglements are found to cluster carbonaceous particles, which creates bulk thermal bridges improving thermal conductivity. Moreover, rockwool fibre arrangements affect density, porosity and thermo-physical properties. In addition, mixing duration disrupts cohesion of fibre bundles with the matrix, affecting compressive modulus and wear behaviour. This microstructural defect fosters an abundant third-body source flow, which results in a high wear flow. Porosities induced by fibre entanglements, presenting large and irregular size and distribution on the friction surface, lead to a low wear resistance and change the stability of friction.

Often, engineers with machining experience often judge machining state and tool life according to chips’ features. Engineers' experience is digitized in this study. During the cutting process, the cutting tool coming in contact with the workpiece produces a shear zone, which causes plastic deformation and shear slip. The chips closest to the shear zone can directly show the state of the tool and workpiece when the material is SKD61. This study used chip color, vibration, and current signal integration for prediction of machining state and cutting tool life. When the cutting tool wears increased, the chip surface color changed in the following way: purpleè purple blueè blue ècyan, or even green and yellow. When the cutting tool was in the accelerating wear phase, the color change was particularly obvious. The Back-Propagation Levenberg–Marquardt (BP-LM) predictive methodology was used to compare the predictive ability of voltage, vibration signal, and chip color. The Mean Absolute Percentage Error (MAPE) for the voltage signal was 12.28%, for the vibration signal it was 11.38%, and for the chip color combined with multi-sensor characteristics it was 7.85%. The MAPE of the chip color was the smallest. Using the General Regression Neural Network (GRNN) methodology, the MAPE for the voltage signal was 10.74%, for the vibration signal 7.96%, and for the chip color combined with multi-sensor characteristics was 6.59%. The MAPE of the chip color was the smallest. Obviously, the chip color combined with multi-sensor signals provided better predictive results than the vibration signal or voltage signal alone. There is currently no research on the usefulness of monitoring chip color for tool life prediction.

In the mold machining process, the cutting tool is worn with machining time, thereby affecting the surface accuracy, leading to poor workpiece dimensions, even fracture. At present, many studies have used multiple sensors to detect the machining conditions of cutting tool and workpiece, including indirect measurement method and direct measurement method. The indirect measurement method, which has been studied widely, mainly uses sensors to capture signals for subsequent data analysis; the direct measurement method mainly analyzes the state of cutting shear zone. Due to the cut-in of cutting tool in the machining process, the workpiece is dislocated rapidly, generating considerable amount of heat, which is transferred to the chips, inducing color change on the surface of chips. Many engineers with machining experience often judge the machining state and tool life according to the chips. The engineers' experience is digitized in this study, and indirect measuring sensors are used to predict the tool life, so as to attain the objective for smart manufacturing, the average percentage error of MAPE using single vibration and voltage eigenvalues as input features is 10%, the voltage signal characteristic values and vibration signal characteristic values are combined. Finally, the chip surface chromaticity eigenvalue is combined with signal characteristic value. The average prediction error of BP-LM method is 7.85%, the average prediction error of GRNN method is 6.59%. Therefore, when the eigenvalue of chip surface chromaticity is added to the prediction result, it can enhance the accuracy of cutting tool wear value prediction more effectively than single sensor signal characteristic value.

TThe paper presents the results of research on the influence of the settings of lubrication and cooling system parameters (solenoid valve opening time and lubricant feed pressure in terms of its quantity) in order to select the optimal lubricating conditions and thus reduce the wear of the dies used in the first forging operation of the valve forging made of high-nickel steel. Based on the observation of lubrication in the industrial process, it was found that a significant part of the lubricant fails to reach the die cavity, reaching the outside of it, which causes die wear due to seizure resulting from adhesion of the forging material to the tool surface, as well as high lubricant consumption and dirt in the press chamber. The authors proposed their own mobile lubricating and cooling system, which allows for a wide range of adjustments and provided with automatic cleaning procedures of the entire system, unlike the fixed lubrication system used so far in the industrial process. First, tests were carried out in laboratory conditions to determine the highest wettability and the lubricant remaining inside the tool cavity. These tests determined the lubrication system parameter settings which ensured that the greatest amount of lubricant remains in the cold die cavity without the forging process. Then, to verify the obtained results, tests were carried out in the industrial process of hot die forging of valve forgings, for short production runs of up to 500 forgings. The results were compared with the measurement of changes in the geometry of tools and forgings based on 3D scanning and surface topography analysis with the use of SEM. For best results (the variant of the setting of the dose and the time of exposure to lubricant), the forging process was carried out with the use of a new tool, up to the maximum service life.

In the process of metal cutting, the anti-wear performance of the tool determines the life of the tool and affects the surface quality of the workpiece. The finite element simulation method can directly show the tool wear state and morphology, but due to the limitations of the simulation time and complex boundary conditions, it has not been commonly used in tool life prediction. Based on this, a tool wear model was established on the platform of a finite element simulation software for the cutting process of titanium alloy TC4 by end milling. The key technique is to embed different types of tool wear models into the finite element model in combination with the consequent development technology. The effectiveness of the tool wear model is validated by comparing the experimental results with the simulation results. At the same time, in order to quickly predict the tool life, an empirical prediction formula of tool wear was established, and the change course of tool wear under time change was obtained.

When a railway vehicle moves on a curved rail, sliding contact occurs between the rail head side and wheel flange, which wears the wheel flange down. The thinned flange needs to be restored above the required minimum thickness for structural safety. In this study, a new process and welding wire for restoring worn-out railway wheels by submerged arc welding was developed. To characterize the properties of the restored wheel, dilatometric analysis of phase transformation, SEM/EDX analyses, hardness measurement, and residual stress measurement using the X-ray diffraction method were performed. Finally, wear tests with full-size wheel/rail specimens were carried out. It was confirmed that the weld metal was composed of bainitic microstructures as intended, and welding defects were not observed. The wear amount of the restored wheel was greater than that of the base material, but it was less than half of the wear depth of the weld-repaired wheel with ferritic–pearlitic microstructures. The developed process seems applicable to industry.

Polymer materials are increasingly being used for sliding machine elements due to their numerous advantages. They are used even where they are deformed and in such a state they interact frictionally e.g. in machine hydraulics or lip seals. Few publications deal with the influence of deformation, which is the effect of e.g. assembly on tribological properties of polymeric material. This deformation can reach up to ε ≈ 20% and is achieved without increasing the temperature of the polymer material. The paper presents the results of investigations in which high-density polyethylene (PE-HD) was maintained in deformation by means of a special grip (holder). The wear of the sample was significantly higher than that of the undeformed sample. This effect persisted even after partial relaxation of the stress in the sample after 24 hours. Additional investigations were carried out to explain the obtained results. There were the microscopic observations of the surface after friction, measurements of microhardness and free surface energy. Changes in the value of surface free energy and a significant decrease in microhardness with deformation under tension were observed. Strained material had a different surface appearance after friction and a different size and form of wear products. It was indicated that it is probable that the cohesion of the material will decrease and that the character of the wear process will change as a result of tension. Tension without heating of polymeric material (PE-HD), e.g. as a result of assembly, has been qualified as a hazard to be taken into account when designing and analysing polymeric sliding elements.

Gray cast iron is one of the most important engineering materials that has many applications in various industries including automotive and machinery manufacturing due to its mechanical properties, wear resistance, machining potentials and low price. In this research effect of adding aluminum and silicon to composition of gray cast iron on microstructure and wear resistance was studied. Moreover, it was investigated the role of formation of Fe-Al-Si intermetallic compound in final properties of the alloy. For studying wear resistance of samples pin-on-disc method was carried out. The results showed that addition of aluminum to gray cast iron causes formation of ferrite matrix, which leads to a decrease in hardness value. Increasing silicon content up to 2 wt. % in cast iron with 4 wt. % aluminum intensifies the formation of ferrite matrix, while further increase to 3 wt. % causes emerging a Fe-Al-Si intermetallic phase. Improvement in hardness value was achieved by increasing silicon content from 3 wt. % to 4 wt. % due to the increased percentage of intermetallic phase. Effect of intermetallic phase on decreasing wear rate was showed by studying microstructure and hardness values, however the lowest wear resistance was observed in aluminum bearing cast iron containing 2 wt. % silicon.

Gray cast iron is one of the most important engineering materials that has many applications in various industries including automotive and machinery manufacturing due to its mechanical properties, wear resistance, machining potentials and low price. In this research effect of adding aluminum and silicon to composition of gray cast iron on microstructure and wear resistance was studied. Moreover, it was investigated the role of formation of Fe-Al-Si intermetallic compound in final properties of the alloy. For studying wear resistance of samples pin-on-disc method was carried out. The results showed that addition of aluminum to gray cast iron causes formation of ferrite matrix, which leads to a decrease in hardness value. Increasing silicon content up to 2 wt. % in cast iron with 4 wt. % aluminum intensifies the formation of ferrite matrix, while further increase to 3 wt. % causes emerging a Fe-Al-Si intermetallic phase. Improvement in hardness value was achieved by increasing silicon content from 3 wt. % to 4 wt. % due to the increased percentage of intermetallic phase. Effect of intermetallic phase on decreasing wear rate was showed by studying microstructure and hardness values, however the lowest wear resistance was observed in aluminum bearing cast iron containing 2 wt. % silicon.

The diameter of a H13 steel tool with M6 threads and a pin diameter of 5.9 mm and a pin length of 5 mm was measured after each 25.4 mm length of friction stir processing (FSP) of 6061-T6 extrusions. The change in pin diameter with FSP time or distance did not exhibit any steady state and was found to have two distinct regions. Metallographic analysis of two tools subjected to FSP for 60 and 120 seconds showed that (i) threads fractured in early stages of FSP, (ii) a built-up layer formed between the threads, and (iii) threads progressively wore with processing time. The metallographic analysis of an embedded tool showed the presence of a fractured piece of the tool in the stir zone. These points are discussed in detail in the paper.

Macrophages are cells involved in the primary response to debris derived from wear of implanted CoCr alloys. The biocompatibility of wear particles from a high carbon CoCr alloy produced under polarization in physiological hyaluronic acid (HA) solution was evaluated in J774A.1 mouse macrophages cultures. Polarization was applied to mimic the electrical interactions observed in living tissues. Wear tests were performed in a pin-on-disk tribometer integrating an electrochemical cell in phosphate buffer solution (PBS) and in PBS supplemented with 0.3% HA, physiological synovial fluid concentration, used as lubricant solution. Wear particles produced in 0.3% HA solution showed a higher biocompatibility in J774A.1 macrophages in comparison to those elicited by PBS. A considerable improvement in macrophages biocompatibility in the presence of 0.3 % of HA was further observed by the application of polarization at potentials having current densities typical of injured tissues suggesting that polarization produces an effect on the surface of the metallic material that leads to the production of wear particles that are macrophages biocompatible and less cytotoxic. The results showed the convenience to consider electric interactions together with other particles parameters, as are size and composition, to get a better understanding of the biological effects of the wear products.

The aim of this paper is to develop a composite coating on St 304 steel employing TIG process. Ti wire cored with graphite powder is used as the means of coating material. The process parameters are varied in order to develop coating with optimum characteristics (i.e., hardness and wear resistance). The microstructure of the coating is analyzed with SEM and XRD. It is found that both of the hardness and wear resistance increase as the current increases while both of these properties decrease as the travelling speed increases. It is found that the coated samples with composite layers have more hardness than the substrate and it could range up to 1100 HV being almost 4.5 times higher than the hardness of St 304. Likewise, the wear resistance of coating is observed to be 4.5 times higher than that of substrate. The high performance of coating, as revealed by microstructural analysis, is due to formation of TiC and Cr₂₃C₆ .The optimum conditions to produce the coating are proposed to be 120 A current and 3.17 mm/s travel speed.

Communication pathways are an underestimated source of synthetic particles in the environment. This study investigated the impact of traffic volume on microplastics (MPs) and tire wear particles (TWPs) pollution in road snow. An examination was conducted in a medium-sized city situated in northeastern Poland, known for being one of the cleanest regions in the country. MPs and TWPs were found at all 53 sites, regardless of the intensity of traffic. The average concentration for all samples was 354.72 pcs/L. Statistically significant differences were found between the average values of particles concentration on low, medium, and heavy traffic roads amounted 62.32 pcs/L, 335.97 pcs/L and 792.76 pcs/L respectively. Within all three studied groups of roads, MPs and TWPs with the smallest size, ranging from 50 to 200 μm, were prevalent. In all studied groups of roads, 4 analyzed shapes of particles were found, with irregular fragments being the most abundant form (89.23%). The most frequently recorded color among the collected samples was black (99.85%), and the least frequently recorded was blue, constituting only 0.01%. This study suggests that snow cover on the roads may act like temporary storage of pollutants during winter in the temperate climate zone and after thaw can significantly increase the concentration of MPs and TWPs in surface waters. Possible measures to decrease the release of MPs and TWPs into the environment in the city may include reducing traffic volume and speed, implementing street sweeping, utilizing filtration chambers, and installing stormwater bioretention systems or settling ponds.

Aloe vera is well known for its biological properties as a bioflavonoid-anti-inflammatory, antibacterial agent. It has been used frequently in the food sector as food coating for its hygroscopic properties and as an ingredient in the lucrative industry. Studies have also included Aloe vera as an eco-friendly green solution based on these properties. The current research focuses on the use of Aloe vera gel in printing pastes as an alternative sustainable solution to synthetic thickeners, evaluating its wet performance and ease of fabric stitching, and has been inspired by studies that similarly used this substance measuring its effect on the fabric's coefficient of friction and antimicrobial action. In the current study, printing pastes with natural colourants and Aloe vera gel thickener derived from natural leaves from Crete increased the fabric's mechanical resistance to abrasion compared to the untreated pastes. The measured performance did not differ substantially from prints with traditional synthetic pastes, hence tolerating the substitution with the non-contaminant variant. The enhanced resistance to abrasion and wear prolongates the fabric's serviceable life and resulting garments, decreasing the need for high industry processing volumes and, as a result, reducing pollution. The resistance to wear was evaluated using the dominant method in textile testing of the Martindale apparatus, which measured the cycles to failure, weight loss, and general appearance deterioration using the official photographic standards.

The principal main of this research work was the study the influence of Cu addition on the wear behavior (WB) of eutectic Al-12.6Si alloy developed by spray forming (SF) method and compared with as-cast (AC) alloys. The phases of chemical compositions and microstructure were studied by optical microscopy, energy dispersive spectroscopy (EDS) and Scanning Electron Microscopy (SEM). The microstructure of SFAl-12.6Si (SF1) alloy reside — of fine primary and eutectic Si phases evenly distributed in the equiaxed α-Al matrix and SF Al-12.6Si-2Cu (SF2) alloy lie of uniformly distributed fine eutectic Si particulates and spherical form θ-Al2Cu precipitates in α-Al matrix. On other hand, the AC Al-12.6Si alloy (AC1) alloy involve of eutectic Si needles in the dendrite α-Al matrix, whereas AC Al-12.6Si-2Cu (AC2) alloy consisted of eutectic Si needles and Chinese script form θ phase distributed randomly in the α-Al matrix. The microhardness and wear properties were analyzed using Vickers hardness (VH) and dry sliding WT. The SF alloys exhibit superior hardness compared to the AC alloys. The wear properties of SF alloys exhibited significantly superior compared to the AC alloys. The SF2 alloy showed high wear resistance (WR) than the SF1 alloy in the entire sliding velocities and applied loads. The results indicate that the spray deposited alloys have a lower coefficient of friction (CF(µ)) than the AC alloys under varying load and sliding velocity conditions. The high WR in the SF alloy was due to microstructural modification during SF and precipitation of fine Al2Cu intermetallic and solid solubility effects. The SF2 depicts increased transition from oxidative to abrasive. In other ways, AC alloys demonstrate wear mechanisms that change from oxidative to abrasive and delamination with an increase in sliding velocity and load.

The effects of co-addition CeO2 and SiC particles on the morphology, surface cracks, microstructure, precipitated phases and wear property of plasma beam spraying Fe55-based coatings on 1025 steel were investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDS), ultra-deep field microscope and wet sand rubber wheel friction tester, respectively. The results showed that the dendrite exhibited a directional growth pattern perpendicular to the substrate and the transitional states of microstructure with the co-addition CeO2 and SiC particles. With addition of CeO2 or SiC affected the flowability of molten steel at macro level, leading to a reduction in the liquid phase diffusion coefficient DL of Cr and C and resulted in a decrease in the G/R ratio. The dendrites changed into equiaxed grains. The main phase composition of Fe55 welding layer is Cr7C3, γ-Fe. The grain boundaries consisted mainly of a reticular eutectic structure. The worn-out uniformly surface of the Fe55+1.5 wt% SiC+0.01wt% CeO2 with Ra was 0.28 μm was smoother than that of other samples. The sub-wear mechanisms during the friction process were microploughing and microcutting. The hardness and toughness of Fe55+1.5 wt% SiC+0.01wt% CeO2 were well-matched, avoiding excessive microcutting and microplastic deformation.

Tungsten carbide inserts (TCI) and polycrystalline diamond compact (PCD) cutters used in two types of drill bits for drilling oil and gas wells were evaluated by a pin-on-disc test. The morphology of the worn surface was characterized by scanning electron microscopy (SEM). The behavior of corrosion resistance was evaluated with the electrodynamic polarization technique. The polycrystalline diamond compact cutter has a higher hardness, better corrosion, and wear behavior compared to tungsten carbide.

The three-dimensional morphology of frictional sub-surfaces holds significant importance for studying tribological issues. However, the uniformity of horizontal datum in 3D scanning is limited for curved surfaces, resulting in the inability to obtain accurate contour characterization parameters from the scanning results. This study aims to address this issue by constructing regular surface equations and normalizing the 3D profiler scanning results. By fitting the data, a "plane" surface representative of the surface features is obtained, and the paper demonstrates this approach on the surface morphology of different worn parts in the frictional area of spherical bearings located in the specific environment of the Three Gorges gate. The results indicate that the obtained "plane" effectively reconstructs the three-dimensional morphology map of the regular surface. Moreover, this reconstructed plane not only clearly illustrates the surface characteristics but also provides the foundation for analyzing the wear mechanism.

The paper focuses on two unconventional magnetic field-based treatment regimes applied to an alloyed steel before applying a thermochemical treatment. This study was conducted in order to improve the behavior of the chosen material during the wear process. Increasing the wear resistance and the micro-hardness of the superficial layer obtained from the treatments are a priority, as well as improving the mechanical properties of a Cr-Mo alloyed steel. Thermomagnetic treatment, applied before plasma nitriding treatment, improves the mechanical properties of the base material, especially in the case of a steel with a considerable chromium content (1,02%). This paper is a review of my own researches in the last years.

Wear usually occurs in the loaded part of hydrodynamic bearings and leads the bearing geometry imperfections. This paper investigates the effects of wear-induced geometric imperfections of tilting pad journal bearings (TPJBs) on the dynamic behavior of the system. Furthermore, the effect of wear on the journal-bearing rub-induced contact pressure severity is investigated. A novel tribo-dynamic model is proposed for a flexible rotor-worn TPJB which integrates a mixed elastohydrodynamic model with a rotor-worn TPJB thermal and dynamic model to assess the effects of the bearing wear progression on the rotor-TPJB behavior. Based on the results, wear changes the temperature distribution of the pads and oil film as well as the dynamic behavior of the system. Dynamic simulations reveal a higher vibration level and contact pressure for the worn TPJBs near the system's critical speed and service speed. Finally, thermal and dynamic condition indicators are suggested to detect TPJB wear severity at its early stages.

The application of metal-matrix composite coatings for protecting and improving the service life of sliding components has demonstrated to have the potentials of meeting the requirements of a diverse range of engineering industries. Recently, a significant body of research has been devoted to study the mechanical and tribological performance of dispersion-strengthened MCrAlY coatings. These coatings belong to a class of emerging wear-resistant materials, offering improved properties and being considered as promising candidates for the protection of engineering structural materials exposed to tribological damage, especially at elevated temperature regimes. This paper attempts to comprehensively review the different reinforcements used in the processing of MCrAlY-based alloys and how they influence the mechanical and tribological properties of the corresponding coatings. Further, the major fabrication techniques together with their benefits and challenges are also reviewed. Discussion on the failure mechanisms of these coatings as well as the main determining factors are also included. In addition, a comprehensive survey of studies and investigations in recent times are summarized and elaborated to further substantiate the review.

In the present paper, Co-B/SiC composite coatings were obtained via electrodeposition from colloidal suspensions with different concentrations of SiC particles and subsequent heat treatments at 350 °C. The composition, morphology and structure of the Co-B/SiC composite coatings were analyzed using glow discharge spectrometry (GDS), scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Hardness and tribological properties were also studied. The results showed that an increase in the SiC concentration in the colloidal suspensions resulted in both an increase in the SiC content and a decrease in the B content in the obtained Co-B/SiC coatings. The Co-B/SiC coatings were adherent, glossy and soft and exhibited a homogeneous composition in all thicknesses. By contrast, an increase in the SiC particle content of the Co-B/SiC composite coating from 0 to 2.56 at.% SiC reduced the hardness of the film from 680 to 360 HV and decreased the wear volume values from 1180 to 23 mm³ N^-1 m^-1, respectively (that is, the wear resistance increased). Moreover, when the Co-B/SiC coatings with SiC content ranging from 0 to 2.56 at.% SiC were subjected to a heat treatment process, the obtained coating hardness values were in the range of 1200 to 1500 HV and the wear volume values were in the range of 382 to 19 mm³ N^-1 m^-1.

Face milling is a well known commercial process highly used in heavy industries that consumes high amount of power. Besides power issue, modern manufacturing industries are aiming for per part cost reduction keeping the product quality unimpaired. Unexpectedly if the part is rejected in any stage of manufacturing, the cost of manufacturing dramatically increases. Major cause of part rejection is excessive tool wear that imparts poor surface profile or catastrophic tool failure that causes adherence of broken tool debris onto machined surface. Furthermore, the tool wear is associated with sliding distance (frictional distance) and the tool life quantifies the cost of tools. As such, from the perspective of manufacturing industries it is imperative to optimize the surface quality parameter, cost of part, power consumption, and material removal – this is exactly what is accomplished here. By this work, it is possible to conserve power consumption, produce parts with lower cost, manufacture with uncompromising surface quality and enhanced material removal rate. Moreover, as intermediate factors of interest, the influences of sliding distance, tool life and tool flank wear on the overall machining performance are evaluated. The multi-objective optimization by Grey Relational Analysis (GRA) revealed that for improved product performance and fast manufacturing (case 1) optimum results are: feed per tooth fz = 0.25 mm/tooth, cutting speed vc = 392.6 m/min and cutting length l = 0.5 mm; for resource conservation (case 2) the optimum results are: feed per tooth fz = 0.125 mm/tooth, cutting speed vc = 392.6 m/min, cutting length l = 0.5 mm.

True contact between solids with randomly rough surfaces tends to occur at a large number of microscopic contact patches. So far, two scaling regimes have been identified for the number density n(A) of contact-patch sizes A in elastic, non-adhesive, self-affine contacts. At small A, n(A) is approximately constant, while n(A) decreases as a power law at large A. Using Green’s function molecular dynamics, we identify a characteristic (maximum) contact area Ac above which a superexponential decay of n(A) becomes apparent if the contact pressure is below the pressure p_cp at which contact percolates. We also find that A_c increases with load relatively slowly far away from contact percolation. Results for A_c can be estimated from the stress autocorrelation function G_σσ (r) with the following argument: the radius of characteristic contact patches, r_c, cannot be so large that G_σσ (r_c) is much less than p_c². Our findings provide a possible mechanism for the breakdown of the proportionality between friction and wear with load at large contact pressures and/or for surfaces with a large roll-off wavelength.

Iron powders having average particle sizes of ~40µm are mechanically mixed thoroughly with aluminum powders ranging from 1 to 10 in wt.% with an average particle size of ~10µm. Two different powder metallurgical techniques cold and hot pressing are used to study the effect of the additive element powder on the mechanical properties, wear properties and the microstructure of the iron based alloys. The hot pressing technique was performed at a temperature up to 500°C at 445.6 MPa. The cold pressing technique was performed at 909 MPa in room temperature. By increasing the Al content to 10 wt. % in the base Fe-based matrix, the hardness was decreased from 780 to 690 MPa and the radial strength was decreased from 380 to 202 MPa with reductions of 11.5% and 40%, respectively. Improvement of the wear resistance with the increase addition of the Al powder to the Fe matrix up to 5 times was achieved compared to the alloy without Al addition for different wear parameters namely; wear time and sliding speed.

A new type of laminated flooring decorated by resin impregnated paper was designed, with the advantages of high stability, low deformation, natural and beautiful surface texture, comfortable foot feeling, low formaldehyde emission, improved flame retardant, high surface hardness and high wear resistance. The structure of this engineered wood flooring is based on the ordinary laminated flooring, followed by a decorative layer of thin wood pieces, and then the transparent improved flame retardant, wear-resistant paper is added to the top. After main influencing factors analysis, the surface unevenness was seriously affect the flame-retardant performance. The wear-resistant paper pressing technology commonly affects the decorative effect of laminated flooring. The hot-pressing temperature is the most important factor affecting the adhesion of resin impregnated. The optimal hot-pressing parameters are selected as the hot-pressing pressure of 3.5 MPa, hot-pressing temperature of 180 ℃, and hot-pressing time of 40 s. The new laminated flooring was improved with high flame retardant, high wear-resistant, combined with the conventional advantages of both solid wood composite flooring and reinforced wood flooring. The new laminated flooring decorated by resin impregnated paper has broad application prospects.

Silicon carbide particle-reinforced aluminum matrix (SiCp/Al) composites are significant lightweight metal matrix composites extensively utilized in precision instruments and aerospace sectors. Nevertheless, the inclusion of rigid SiC particles exacerbates tool wear in mechanical machining, resulting in a decline in the quality of surface finish. This work undertakes a comprehensive investigation into the problem of tool wear in SiCp/Al composite materials throughout the machining process. Initially, a comprehensive investigation was conducted to analyze the effects of cutting velocity vc, feed per tooth fz, milling depth ap, and milling width ae on tool wear during high-speed milling under SCCO2-MQL (Supercritical Carbon Dioxide Minimum Quantity Lubrication) ultrasonic vibration conditions. Furthermore, a prediction model for tool wear was developed by employing the orthogonal test method and multiple linear regression. The model's relevance and accuracy were confirmed using F-tests and t-tests. Ultimately, through the utilization of a genetic algorithm, the milling parameters were optimized, resulting in the identification of the most optimal combination of parameters. Empirical findings suggest that the careful selection of milling parameters can significantly mitigate tool wear, extend the lifespan of the tool, and enhance the quality of the surface. This work serves as a significant point of reference for the processing of SiCp/Al composite materials.

High entropy alloys have excellent wear resistance, so they have great application prospects in the fields of wear resistance and surface protection. In this study, the wear resistance of FeNiCrCoCu high entropy alloy coating was systematically analyzed by molecular dynamics method. FeNiCrCoCu high entropy alloy was used as a coating material to adhere to the surface of Cu matrix. The friction and nano indentation simulation of this coating material were carried out by controlling the ambient temperature. The influence of temperature on its friction properties was analyzed from five aspects: lattice structure, dislocation evolution, friction coefficient, hardness and elastic modulus. The results show that with the increase of temperature, the disorder of the lattice structure increases, which leads to the increase of the tangential force and the friction coefficient in the friction process. At 300K and 600K, the ordered lattice structure of the high entropy alloy coating material is basically the same, and thus their hardness is basically the same. However, the dislocation density at 600K is significantly reduced compared with that at 300K, resulting in the increase of the elastic modulus of the material from 173GPa to 219GPa. At the temperatures of 900K and 1200k, lattice disorder take place rapidly, and dislocation density also decreases significantly, resulting in a significant decrease in the hardness and elastic modulus of the material. When the temperature reaches 900K, the wear resistance of the FeNiCrCoCu high entropy alloy coating decreases sharply. This work is of great value to the analysis of wear resistance of high entropy alloy at high temperature.

17-4PH steel is a widely used grade for precipitation hardening. The growing demand for modern materials with high corrosion and tribological resistance has led to its increased use for the production of medical devices. With additive manufacturing (AM), complex functional shapes can be achieved for medical applications. Direct laser metal sintering (DMLS) technology makes it possible to obtain products with complex architectures, but it also faces various challenges, including imperfections in the surface layer of products due to the use of 3D printing technology itself. This study analyzed the abrasive wear resistance in 0.9% NaCl solution of 17-4PH steel produced by DMLS technology. In order to improve the properties of the surface layer after 3D printing and to improve the tribological wear resistance of the steel, a shot peening (SP) process using CrNi shot and ceramic beads (based on ZrO2) was applied. The chemical and phase composition of the materials obtained, Vickers hardness, surface roughness, and microscopic and SEM imaging were investigated. Tribological tests were carried out using the ball-on-disc method, and the surfaces that showed traces of abrasion to identify wear mechanisms were subjected to SEM analysis. The chemical composition was in accordance with the EOS manufacturer's declarations, and the presence of austenite and martensite was found in the post-production state, while a higher content of martensitic phase was found in the case of peened samples due to phase transformations. The surface hardness of the peened samples increased more than twice, and the post-treatment roughness increased by 12.8% after peening CrNi steels and decreased by 7.8% after peening ZrO2 relative to reference surfaces. Roughness has an identifiable effect on sliding wear resistance. Higher roughness promotes material loss. After the SP process, the coefficient of friction increased by 15.5% and 20.7%, while the wear factor (K) decreased by 25.9% and 32.7% for the samples peened with CrNi steels and ZrO2, respectively. Abrasive and adhesive mechanism were dominant featured with slight fatigue. The investigation showed a positive effect of SP on the tribological properties of DMSL 17-4PH.

To address friction and wear challenges in dry contacts, manufacturers often employ self-lubricating materials. Graphite and its derivatives stand out as particularly suitable due to their exceptional tribological properties. However, under intense friction conditions, graphite can experience a decline in lubricating efficiency due to severe abrasive wear. This abrasive damage results in elevated activated carbon surfaces with increased surface energy, fostering greater adhesion between sliding surfaces. The low friction coefficient of graphite is not an inherent property but rather a consequence of water vapor adsorption by the material. Beyond 150°C, desorption of the vapor occurs, leading to a transition in the friction coefficient from µ=0.1 to µ=0.6. To address this issue, impregnation solutions for self-lubricating materials have been developed, with various compositions tailored to specific objectives. Common types include molybdenum disulfide, soft metals, or polymers. In this predominantly experimental study, the impact of polymer impregnation on the evolution of friction force and wear rate in graphite material bearings subjected to a dry fretting contact under severe thermal stresses at 270°C was investigated. Additionally, the mechanical stresses in the bearings throughout different phases of our tests were analyzed using a numerical model.

The aim of this investigation is to offer a data-based scheme for predicting electrode wear in resistance spot welding. Electrode wear and alloying is one of the most significant factors that affect the mechanical properties of spot welds and the variation in weld quality. In this study, Rogowski coils and twisted pairs attached to the top and bottom electrodes were used to obtain the welding current and the inter-electrode voltage in the welding process, thereby calculating the dynamic resistance value during the welding process. The electrode diameter was obtained from the pressure exerted by the upper and lower electrodes on the carbon paper when the current was cut off and was regarded as an indicator of electrode wear. By continuously welding 0.5mm thick BH 340 steel plates until the electrode failed, the dynamic resistance signal was recorded in real time. Simultaneously, the electrode diameter after every 4 welds was also recorded. On this basis, the correlation between electrode diameter and dynamic resistance is studied. In order to quantitatively study the mapping relationship between dynamic resistance and electrode wear, 11 characteristic values were extracted from the dynamic resistance, and the stepwise regression method was used to obtain the regression formula between the characteristic values and the electrode diameter. Using new data to verify the effectiveness of the regression model, the acquired results display that the maximum error between the predicted value of the electrode diameter and the measured value obtained by the regression equation with the interactive quadratic term is 0.3 mm, and the corresponding relative error is 7.69 %. This result demonstrates that the method proposed in this paper can effectively monitor the electrode wear and failure process.

Structural evolution, mechanical and tribological properties of Al-Mg alloy admixed with 5, 10 and 15 vol.% of iron powder using multi-pass friction stir processing (FSP) have been studied. Homogeneous distribution of intermetallic compound (IMC) particles were achieved after 4 FSP passes what resulted in increasing the stir zone hardness and ultimate tensile stress with simultaneous loss in the ductility. The reinforcement of the aluminum alloy matrix with IMCs allowed reducing wear at the same magnitude of friction. Subsurface composite tribological layer was formed on the FSPed samples as a result of rubbing against a steel counterbody.

The possibility of increasing the resource of steel fingers working in tandem with bronze bushings by plasma-electrolytic nitrocarburizing of the surface of medium carbon steel is shown. The phase composition, microhardness, morphology and surface roughness were studied. Tribological tests were carried out under dry friction conditions according to the shaft-pad scheme. It has been established that plasma-electrolytic nitrocarburizing of the surface of medium carbon steel at a temperature of 700 °C for 5 minutes leads to a decrease in a friction coefficient by 2.3 times, weight wear of steel by 24.9 times, and bronze counterbody by 5.9 times. At the same time, the contact stiffness increases 2.6 times. The type of wear is fatigue with dry friction and plastic contact. Changes in tribological characteristics are associated with the high hardness of the hardened steel surface together with the influence of dispersed nitrides and iron carbonitrides distributed in it.

Nickel base superalloy GH4169 is a material with strong mechanical properties and is difficult to process. In order to reduce tool wear during material processing and improve workpiece surface processing quality, based on the finite element simulation software DEFORM, the influence of n, ap, and fz parameters on tool wear during carbide tool milling GH4169 was studied, and a simulation orthogonal experimental model was established, The prediction model of tool wear is obtained; The ultrasonic vibration milling is compared with ordinary milling, and the improvement degree of different coating materials on carbide tool wear is explored. The results show that the ultrasonic vibration signal is helpful to reduce tool wear, improve the surface quality of the workpiece, and improve the stability of the milling process. TIALN/TIN (WC) composite coated tools have good cutting performance, help to reduce tool temperature, reduce tool wear, and improve tool life.

This article focuses on the issue of motor oils used in the engines of off-road mobile machinery (NRMM), more specifically tractors. The primary goal of the paper is to determine the appropriate replacement interval for these oils. The physical properties of the examined samples were first determined by conventional instruments. Furthermore, the concentration of abrasive metals, contaminants, and additive elements were measured using an optical emission spectrometer. Lastly, the content of water, fuel, glycol, and the products of oxidation, nitration, and sulphation were determined by using infrared spectrometry. The measured values were compared to the limit values. Based on the processing and evaluation of these analyses, the overall condition of the oils was assessed and subsequently the optimal exchange interval of the examined oils was determined. In addition, a risk analysis of the outage was performed. Due to the high yields of crops, farmers can lose a significant amount of product when a tractor is not functioning during the harvest period. This loss for calculated in the paper.

This manuscript deals with the cavitation erosion resistance of low-velocity oxy-flame (LVOF) sprayed Al2O3–40%TiO2/NiMoAl cermet coatings, a new functional application of cermet coatings. The aim of the study was to investigate the cavitation erosion mechanism and determine the effect of feedstock powder ratio (Al2O3–TiO2/NiMoAl) of LOVF cermet coatings on their cavitation erosion resistance. As-sprayed coatings were investigated for roughness, porosity, hardness, Young’s modulus. Microstructural characteristics of the cross-section and the surface of as-sprayed coatings were examined by light optical microscopy (LOM) and scanning electron microscopy (SEM) equipped with the EDS and XRD methods. Coatings cavitation tests were conducted in accordance with the ASTM G32 standard with usage of reference samples made from steel, copper and aluminum alloys. Cavitation erosion resistance was measured by weight and volume loss, and normalised cavitation erosion resistance was calculated. Surface eroded due to cavitation was examined in successive time intervals by LOM and SEM-EDS. On the basis of coating properties and cavitation investigations, a phenomenological model of the cavitation erosion of Al2O3–40%TiO2/NiMoAl cermet coatings was elaborated. General relationships between their properties, microstructure and cavitation wear resistance were established. The Al2O3–40%TiO2/NiAlMo composite coating containing 80% of ceramic powder has a higher cavitation erosion resistance than the reference aluminium alloy.

Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and heat treated powder metallurgy. Cr addition ranged between 5 to 10 wt. % while Zn was added in an amount between 0 to 20 wt. %. Heat treatment processes were performed during powder metallurgy process at different temperatures followed by water quenching. Similar alloys were extruded, with an extrusion ratio of 4.6 to get proper densification. Optical microscopy was used for microstructure investigations of the produced alloys. The element distribution microstructure study was carried out using the Energy Dispersive X-ray analysis method. Hardness and tensile properties of the investigated alloys have been examined. Wear resistance tests were carried out and the results were compared with these of the Al-based bulk alloys. Results showed that the aluminum base alloys containing 10wt. % Chromium and heat treated at 500°C for one hour followed by water quenching exhibited the highest wear resistance and better mechanical properties.

This paper presents and demonstrates the development of a new lightweight coating for aluminium alloy using a novel multicomponent alloy based on the AlSiMgCu system. This coating was applied using a newly designed approach that combined High-Velocity Oxy-Fuel (HVOF) and Plasma Spraying processes. This hybrid technique enables the deposition of coatings with enhanced performance characteristics. The microstructure was studied using optical microscopy (OM) and scanning electron with energy dispersive X-ray spectroscopy (SEM+EDS) microscopy, revealing good adhesion and compaction between the multicomponent coating and the A6061 substrate with 50 to 150 µm thickness. Vickers indentations were performed on the substrate and the new coating material, revealing a 50% improvement in the material's hardness compared to the casted alloy. Additionally, electrical conductivity measurements showed approximative x3.3 times values compared to the alloy in as-cast condition due to high solidification rates altering the morphology of the phases. Corrosion tests demonstrated a lower corrosion rate compared to other multicomponent aluminium alloys and similar to thermal treated A6061 alloy. Finally, tribological results obtained using ball on disc (BOD) test and laser scanning confocal microscopy, confirmed that the new multicomponent coating exhibited reductions in both friction coefficient and wear rate by more than 20% and 50%, respectively. This study demonstrates that using multi-component aluminium coatings could lead to developing of new automotive parts with enhanced properties for corrosion resistance, electrical conductivity, and wear conditions. Optimizing the thermal spraying parameters could further enhance the coating, achieving greater and more homogeneous thicknesses and yielding even higher performance properties.

Effective oral care is important to maintain a high quality of life. Therefore, plaque control can prevent the development and recurrence of periodontitis. Brushing with a toothbrush and toothpaste is a common way to remove plaque; however, excessive brushing or brushing with abrasive toothpaste can cause wear and tear on the dental crown. Hence, we aimed to quantitatively compare the plaque-removal efficiency and tooth wear of toothbrushes using bioelectric effect (BE) with those of mechanical electric toothbrushes. To generate the BE signal, an electronic circuit was developed and embedded in a toothbrush. Further, typodonts were coated with cultured artificial plaques and placed in a brushing simulator. A toothpaste slurry was applied, and the typodonts were eluted with tap water after brushing. The plaques of the typodonts were captured, and the images were quantified. For the tooth wear experiment, polymethyl methacrylate disk resin blocks were brushed twice a day, and the thickness of the samples was measured. Subsequently, statistical differences between the experimental toothbrushes and typical toothbrushes were analyzed. The BE toothbrush had a higher plaque-removal efficiency and could minimize tooth wear. This study suggests that the application of BE may be a new solution for oral care.

The up-to-date challenge towards clean road transport are non-exhaust emissions. Important advances regarding measurement systems, including well defined characterisation techniques, as well as regulation, will happen in the next few years. In this work we present detailed results of particle emissions from a test bed for wheel suspension and brakes, consisting of aerosol (size distribution, particle number (PN) and mass (PM)) and electron microscopy measurements (EM) under different load conditions. Standard tyres and brakes from series production were tested with a high-load driving cycle while particle measurements were conducted by gravimetric measurements and with a TSI SMPS, a TSI APS and a GRIMM OPS. Furthermore, samples were analyzed by electron microscopy. A bimodal particle size distribution (PSD) was obtained with the SMPS, with peaks at 20nm and around 400nm. EM analysis of &gt;1400 single particles from the electrostatic sampler matches the PSD results. EM analysis also showed ultrafine particles, mainly from O, Fe, Si, Ba, Mg and S and also fractal particles with high C fractions. Our results suggest, in agreement with previously published literature, that particulate emissions are related to brake disc temperature and occur in significant amounts above a threshold temperature.

The transportation of feed pellets via pneumatic conveying plays an improtant role in feed industry. In recent years, many efforts are made both exprimentally and numerically to gain a better understanding of the underlying mechanism for pneumatic conveying. Though few of those research is directly related to feed pellets, it can be beneficial to draw a full picture of rencent development in pneumatic conveying, with emphasis on aspects extendable to feed transportation. This paper reviews first the major factors concerning feed pellets pneumatic conveying, such as particle breakage, pipe wear and electrostatic. Building on that, new advancement including emerging new technologies in experiments and simulations are discussed, with a focus on the experimental measurements and mathematical models, repectively. The needs for future research and the analogy to feed pellets tranportation is given lastly.

In this study, cotton fabric reinforced phenolic resin (CPF) composites were modified by adding four two-dimensional fillers: graphitic carbon nitride (g-C3N4), graphite (Gr), molybdenum disulfide (MoS2), and hexagonal boron nitride (h-BN). The tribological properties of these modified materials were investigated under dry friction and water lubrication conditions. CPF/ Gr composite exhibits significantly better tribological performance than the other three fillers modified CPF composites under dry friction, with a 24% reduction in friction coefficient and a 78% reduction in wear rate compared to unmodified CPF composite. Under water lubrication conditions, all four fillers did not significantly alter the friction coefficient of the CPF composite. However, except for an excessive amount of Gr, the other three fillers can reduce the wear rate. Particularly, in the case of 10% MoS2 content, the wear rate decreased by 56%. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed for the analysis of the morphology and composition of the transfer films. Additionally, molecular dynamics (MD) simulations were conducted to investigate the adsorption effects of Gr, MoS2, and PF on the counterpart surface under both dry friction and water lubrication conditions. The difference in the adsorption capacity of Gr and MoS2 on the counterpart, as well as the resulting formation of transfer films, accounts for the variation in tribological behavior between CPF/Gr and CPF/MoS2 composites. By combining the lubrication properties of MoS2 and Gr under dry friction and water lubrication conditions, using them as co-fillers can achieve a synergistic lubrication effect.

At present, in the field of aviation industry, titanium alloy is mainly used to manufacture parts such as compressor disc, blade and casing of aircraft engine. When working, titanium alloy parts produce high temperature due to high-speed running friction, which makes the high temperature oxidation resistance and friction resistance of titanium alloy greatly reduced. When their working environment contains salt, titanium alloys are subjected to thermal corrosion, which limits their wider practical applications. This paper introduce the aluminide coating and its preparation methods. The characteristics and functional mechanism of three functional coatings for service environment, such as high temperature resistant alumina-based coating, thermal corrosion resistant alumina-based coating and wear-resistant alumina-based coating are summarized. Finally, the development direction of composite coatings of titanium and titanium alloys for complex service environment is prospected.

The possibility of increasing wear resistance of the CP-Ti surface using a duplex surface treat-ment combining plasma electrolytic nitrocarburizing in a solution of ammonia, acetone and ammonium chloride and subsequent plasma electrolytic polishing is shown. Morphology and surface roughness, structure and microhardness of the modified layer were studied. The correla-tion of weight wear with hardness of diffusion layer at a low processing temperature and thick-ness of oxide layer is established – the largest decrease in weight wear occurs after nitrocarbu-rizing at 750 °C for 5 min (by 4.3 times). The possibility of an additional increase in wear re-sistance by subsequent polishing of the nitrocarburized CP-Ti surface at a voltage of 275–300 V for 3–5 min in chloride and fluoride electrolytes and 5–10 min in a sulfate electrolyte was re-vealed. Under these conditions, the hardened layer is preserved when the porous outer oxide layer is removed. According to the microtopology of the friction tracks, the wear mechanism is estimated as fatigue in dry friction and plastic contact.

In this paper, Fe-Cr-C-N-Al-Y wear-resistant surfacing alloy was prepared by open arc surfacing with self-shielded flux-cored wire. The wear properties of the surfacing alloy were analyzed by MLS-23 rubber wheel wet sand wear tester. The phase composition and microstructure of the surfacing alloy were analyzed by XRD, SEM, EBSD and TEM, and the strengthening mechanism and wear mechanism of the alloy were discussed. The results show that the microstructure of Fe-Cr-C-N-Al-Y surfacing alloy is composed of M + γ-Fe + M7C3 + AlN. When the content of nano-Y2O3 is 0.456wt. %, the formability of the surfacing alloy is the best and the wetting angle is the smallest, which is 50.8°, AlN and M7C3 precipitate the most, and the microstructure grain is the smallest. At this time, the hardness value of the surfacing alloy is up to 62.3 HRC, which is 11.8 % higher than that of the unmodified surfacing alloy. The minimum wear weight loss is 0.125 g, and the wear resistance is increased by 41.86 %. The wear mechanism of surfacing alloy is mainly plastic deformation mechanism, and the material removal process is micro cutting and furrow wear.

Comminution is a very important and result-determining step in mineral processing. This is because further downstream processes in the beneficiation chain depend entirely on it. Comminution includes the blasting, crushing, and grinding of ore to liberate valuable mineral particles. It consumes most of the energy used in mineral processing plants with grinding using up to 50% of the provided energy. Tumbling mills are an old technology that is still commonly used for grinding. One of the most used tumbling mills is the ball mill. This paper reviews different types of grinding media that have been developed and improved over the years and their properties. Also reviewed are the effects of grinding media on various aspects such as energy consumption, mill efficiency, minerals liberation and grinding rate. A comparison of the grinding media is given together with the knowledge gaps that still need to be bridged to improve the quality and performance of grinding media used in ball mills. Despite various research conducted on ball mills, the grinding process is still a very energy inefficient process. This creates a great opportunity for further research to improve the process because just a slight improvement in the process efficiency significantly reduces the production costs and provides a lot of environmental benefits.

The article describes the study of the properties of polytetrafluoroethylene, modified using natural layered silicates—serpentinite. It is shown that the introduction of a small amount of layered silicates significantly increases the tribological characteristics of the material. The additional introduction of magnesium nano-spinels facilitated the formation of an intercalated polymer-silicate nanocomposite.

In order to enhance the efficiency and combined performances of nitriding layer, aluminum-modified plasma nitriding (Al-PN) was developed in this research by adding some FeAl particles around the samples during plasma nitriding (PN) for 42CrMo steel. The results show that the efficiency is dramatically enhanced almost 6 times comparing with traditional PN, with the effective hardening layer increasing from 224 μm to 1246 μm at 520℃/4h. More importantly, the compound layer increased just a little bit from 11.64 μm to 14.32 μm, which remarkably reduces the ratio of the compound layer thickness to effective hardening layer thickness, thus being quite beneficial to decrease the brittleness level, making the brittleness level decreasing from Level 4 to Level 1. Meanwhile, ultra-high surface hardness and excellent wear behaviors are obtained by aluminum-modified plasma nitriding (Al-PN) due to the formation of dispersed strengthening phased of AlN and FexAl in the nitriding layer, with the surface hardness increasing from 755 HV0.025 to 1251 HV0.025, wear rate decreasing from 8.15 x10-5g N-1 m-1 to 4.07 x10-5g N-1 m-1. In other words, comparing with PN, the wear resistance has been almost doubled by Al-PN. Therefore, the research can provide comprehensive insights into the surface characteristics and combined performances of the aluminum-modified plasma nitriding layer.

Micro-arc oxidation (MAO) is an emerging technology employed to produce high hardness or anti-corrosion ceramic coatings on lightweight metals such Al, Ti, Mg and their respective alloys. However, under non-lubrication conditions, such coatings exhibit relatively high friction coeffi-cients. To enhance the friction reduction properties of the MAO coatings, we employed a one-step MAO process with varying concentrations of graphene oxide (GO) in an aluminate sys-tem electrolyte to create composite coatings on the surfaces of Ti-6Al-4V alloy. The effect of concentrations of GO particles on microstructure, composition, and wear behavior of the result-ing composite coatings was investigated. Measurements of the coating's thickness, hardness, and roughness have also been conducted. Ball-on-disk friction test under dry condition were carried out to reveal tribological behavior of the MAO coating. The addition of graphene oxide in the electrolyte reduces the friction coefficient, with the composite coating containing 5 g/L of GO particles displaying the most effective friction reduction. Moreover, coating thickness increases with higher GO concentration. This friction reduction can be attributed to the particles in the coating acting as lubricants during friction, while GO also reduces adhesive damage, shifting the wear mechanism from adhesive to abrasive.

Carbon fiber reinforced polymers (CFRPs) are being used extensively in modern industries that require high strength-to-weight ratio such as aerospace, automotive, motorsport, and sports equipment. However, although reinforcement with carbon fibers improves the mechanical properties of polymer, this comes on the expense of abrasive wear resistance. Therefore, to efficiently utilize CFRPs in dry sliding contacts, solid lubricant is used as a filler. Further, to facilitate fabrication of objects with complex geometries, selective laser sintering (SLS) can be employed. Accordingly, in the present work, graphite-filled carbon fiber-reinforced polyamide 12 (CFR-PA12) specimens were prepared using SLS process to explore the dry sliding friction and wear characteristics of the composite. The test specimens were aligned along four different orientations in the build chamber of SLS machine to determine the orientation-dependent tribological properties. The experiments were conducted using pin-on-disc tribometer to measure the coefficient of friction (COF), interface temperature, friction-induced noise, and specific wear rate. In addition, scanning electron microscopy (SEM) of tribo-surfaces was conducted to specify the dominant wear pattern. The results indicated that the steady state COF, contact temperature, and wear pattern of graphite-filled CFR-PA12 are orientation-independent, and that the contact temperature is likely to approach an asymptote far below the glass transition temperature of amorphous PA12 zones, thus eliminating the possibility of matrix softening. Additionally, the results showed that the Z-oriented specimen exhibits the lowest level of friction-induced noise along with the highest wear resistance. Moreover, SEM of tribo-surfaces determined that abrasive wear is the dominant wear pattern.

Stainless steel grade AISI 304 is one of the most widespread modern structural material, alas its sliding wear and cavitation wear resistance are limited. Thus, AlTiN and TiAlN coatings can be deposited for increasing the resistance to wear of stainless steel components. The aim of the work was to investigate the cavitation erosion and sliding wear mechanisms of magnetron sputtered AlTiN and TiAlN coatings deposited on SS304 stainless steel. Films surface morphology and structure were examined using a profilometer, light optical microscope (LOM) and scanning electron microscope (SEM). The mechanical properties (hardness, elastic modulus) were tested by nanoindentation tester. The adhesion of deposited coatings was determined by means of the scratch test and Rockwell test. Cavitation erosion tests were performed according to ASTM G32 (vibratory apparatus) with stationary specimen procedure. Sliding wear tests were conducted using a nano-tribo testes i.e. ball-on-disc apparatus. Wear mechanisms are strongly contingent upon the structure and morphology of the tested materials. In relation to stainless steel substrate, the PVD films present a superior resistance to sliding wear and cavitation erosion. Higher resistance was noticed for AlTiN than for TiAlN film, mainly due to its superior hardness and elastic modulus. Cavitation erosion mechanism of both, AlTiN and AlTiN coatings is prone to embrittlement, imputable to fatigue processes that result in coating rupture and spallation that consist in coating fragmentation, formation of pits and finally detachment from the substrate. Additionally, films nanoindentation results measured before and after cavitation testing indicate changes in coatings structure, that acknowledged wear mechanism that starts with coating internal delamination in flake spallation mode. In contrary to PVD coatings, steel substrate is characterized by developed cavitation erosion wear with roughened surface and plastically deformed, semi-brittle, eroded surface. Sliding wear of thin films is based on micro-ploughing mechanism. For stainless steel adhesive sliding wear mode and plastic deformation with smearing, material transfer and grooving were observed. It was confirmed that various fluid machinery components made from austenitic stainless steel that undergo cavitation erosion, can be prevented by deposition of AlTiN and TiAlN films.

This study deals with the turning of AISI O2 steel, which has high machinability and dimensional stability in heat treatment and is used in the manufacture of many machine elements, with cryogenically treated and untreated and coated and uncoated cutting tools. In the first phase of the study, along with the determined cutting parameters, Fc and Ra output parameters were also optimized using the RSM method. In addition, numerical significance was obtained with ANOVA analysis, and estimated values were calculated by preparing regression equations. In the second phase, the wear performance of cutting tool tips with and without deep cryogenic treatment was explained with the support of SEM images, EDX, XRD, and microhardness analyses. Feed (F) was found to be the most influential parameter on Fc at 78.89%. The lowest optimized Fc value found with the RSM method was 339.99 N. In order to obtain this value, Vc 252.525 m/min and F 0.16 mm/rev should be selected. In addition, CVD-coated and cryogenic heat-treated cutting tools should be preferred for ideal Fc. It was shown that the most effective parameter on Ra was F, with 69.38%. For both heat treatment and coating conditions, Ra increased significantly as the feed rate increased. In the case of selecting Vc as 243.434 m/min and F as 0.16 mm/rev, the smallest Ra value optimized with the RSM method is 1.04 μm. In addition, a cutting tool without coating and cryogenic heat treatment is also needed for ideal Ra. According to the results of the analysis confirming the effect of deep cryogenic heat treatment on the wear performance of cutting tools in the second stage, coated and uncoated cutting tools had at least 16% longer life compared to the others.