Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Long Term Aging Treatment Impact on Ultralow Iron Alloy 625 Intergranular Corrosion Property

Version 1 : Received: 27 September 2017 / Approved: 29 September 2017 / Online: 29 September 2017 (04:13:44 CEST)

How to cite: Zhu, Z.; Sui, Y.; Dai, A.; Cai, Y.; Xu, L.; Wang, Z.; Chen, H.; Shao, X.; Liu, W. Long Term Aging Treatment Impact on Ultralow Iron Alloy 625 Intergranular Corrosion Property. Preprints 2017, 2017090149. https://doi.org/10.20944/preprints201709.0149.v1 Zhu, Z.; Sui, Y.; Dai, A.; Cai, Y.; Xu, L.; Wang, Z.; Chen, H.; Shao, X.; Liu, W. Long Term Aging Treatment Impact on Ultralow Iron Alloy 625 Intergranular Corrosion Property. Preprints 2017, 2017090149. https://doi.org/10.20944/preprints201709.0149.v1

Abstract

This paper investigates the evolution of microstructures and precipitations of an ultra-low iron alloy 625 subjected to long term aging treatment by scanning electron microscope (SEM) and X-ray diffraction(XRD). Use ASTM G28A acid Fe3(SO4)2 erosion to represent intergranular corrosion weightlessness and corrosive morphology. The result shows that alloy at 750C by aging treatment for 40h, precipitated γ'' phase in the grain boundary. In high density area of γ'' phase, occurs γ'' phase to δ phase degeneration transformation by aging treatment for 200h and the needle-like δ phase becomes more with time prolonged. And γ'' phase degenerated to δ phase completely until treated for 1000h. The sample which has aging treatment tends to have intergranular corrosion and mainly because alloy element spreading leads to dilution area and grain boundary precipitated phase, plus interlaced δ phase’s dissolving, which makes sample grain particle fall off and this results in apparent weightlessness. The weightlessness rate(WLR) is related with precipitated volume score. With aging sensitization time change, can be described by Johnson-Mehl-Avrami equation, i.e.: WLR=44.32[ 1exp( t 10.99 ) ]+44.62[ 1exp( t 327.8 ) ]+1.267 ( mm/a )

Keywords

Alloy 625; aging sensitization treatment; intergranular corrosion; ASTM G28A methods

Subject

Chemistry and Materials Science, Metals, Alloys and Metallurgy

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