Effect of different heat-treatment processes on corrosion resistance of 17-4PH steel

The heat-treatment process exerts a substantial influence on both the quantity and morphology of reversed austenite in 17-4PH stainless steel. In this study, the effects of different ageing treatment methods on the microstructure and corrosion resistance of the steel were investigated. Through the observation of microscopic morphology, it was found that adjustment and ageing treatment and double ageing treatment were more conducive to the migration of elements in the steel than single ageing treatment, and they also improved the microstructure. In addition to improving the uniformity of alloy element distribution, uniformity also controls the reversed austenite content. By controlling the content and distribution of reversed austenite, the stability of the corrosion film formed at the interface can be improved, thereby improving the corrosion resistance of stainless steel. The stainless steel, after adjustment treatment and ageing treatment, has better corrosion resistance. The electrochemical corrosion resistance in a high-temperature and high-pressure underground environment was evaluated based on parameters including passivation current density and passivation potential. The results revealed a significant improvement of 50.5% in electrochemical corrosion resistance and a remarkable increase of 45.96% in pitting corrosion resistance. Furthermore, the FeCl₃ pitting test demonstrated a substantial decrease of 63.16% in pitting density and a reduction of 27.96% in the uniform corrosion rate.