In-situ SEM investigation on stress-induced microstructure evolution of austenitic stainless steels subjected to cavitation erosion and cavitation erosion-corrosion

This study investigated the effect of stress on the microstructure evolution of austenitic stainless steels (316L SS and 304 SS) subjected to cavitation erosion and cavitation erosion-corrosion. Results show that continuous accumulation of stress of austenitic stainless steels at the early stage of cavitation erosion was observed from the samples tested in deionised water (DIW) but not in artificial seawater (ASW), which is due to stress release induced by ASW. In addition, a stress-induced phase transformation from austenite to martensite during the cavitation erosion tests in both DIW and ASW was observed in 304 SS, but not in 316 SS. Furthermore, primary cavitation craters formed during the cavitation erosion were not expanded directly but shrank first and then expanded due to re-accumulation of stress. More importantly, this study reports for the first time that pre-existing pores are not initiation points of cavitation erosion damage, possibly because of the ductility of austenitic stainless steels, which resulted in continuous shrinkage of the pores caused by the accumulated stress. Our findings provide new insights into understanding the failure mechanisms of austenitic stainless steels subjected to cavitation erosion, which will inform the development of high-performance cavitation erosion-resistant materials.