The Influence of Parameters on Surface Properties and the Optimization of HVOF-Sprayed NiCr/WC-Co Coatings

This work focuses on parametric optimisation and the prediction of performance for NiCr/WC-Co coatings prepared using high-velocity oxygen fuel (HVOF) spraying. An L18 orthogonal experimental design based on the Taguchi method and the response surface method (RSM) was adopted to examine how key process parameters affect the microstructure, phase composition and hardness of the coatings. A total of eight controllable factors were selected and the hardness, microstructure and phase characteristics of the coatings were evaluated using a Vickers hardness tester, scanning electron microscopy and X-ray diffraction. Analysis of variance (ANOVA) revealed that travel velocity, methane flow rate, powder feed rate and spraying distance were the dominant parameters affecting coating hardness, accounting for altogether 76.25% of the total variance.The model established in this study demonstrates remarkably high predictive accuracy, with a coefficient of determination (R²) of 0.985 and an average prediction error of just 1.16%. This model accurately reflects the nonlinear relationship between process parameters and coating hardness. Meantime, verification experiments were conducted under optimal conditions. The measured hardness was 1352.7 ± 75 HV, in close agreement with the predicted value of 1365 HV. This result has a relative error of 0.98%, which validates the reliability of the second-order model, and a dense layered structure, low porosity, and minimal decarburization of tungsten carbide are exhibited by the coating. Adding a NiCr intermediate layer improves interfacial bonding and reduces structural defects. It is demonstrated by the results that the Taguchi-RSM method is reliable for the optimization of HVOF spraying parameters and the prediction of coating hardness. Overall, this study provides technical support and industrial application for the preparation of high-performance NiCr/WC-Co ceramic-metal composite coatings.