Improvement of cavitation erosion resistance of lean grade austenitic stainless steels by friction surfacing

Cavitation erosion (CE) and pitting characteristics of the friction-surfaced (FSed) AISI 201 austenitic stainless steel (ASS) coatings were investigated. FSed 201 coatings were successfully fabricated on AISI 304 substrate via FS with different spindle speeds. The FSed 201 coatings exhibited superior CE resistance as compared with both 304 substrate (approximately 1.3-fold) and as-received 201 ASS (approximately 1.8-fold), attributed to the reduced density of ∑3 twin boundaries and increased hardness achieved through FS. Moreover, FSed coatings underwent ε- and α′-martensite transformation, a process that absorbed more impact energy, thereby mitigating crack propagation and CE damage. The presence of martensite in the vicinity of cracks impeded their growth, further contributing to the enhanced CE resistance. Additionally, SEM-EDS and SKPFM results showed the mechanism for the improvement of CE resistance by FS. FS process effectively fragmented the strip shaped MnS inclusion into substantially sub-micron sizes. It reduced the micro-galvanic effect between inclusion and surrounding matrix and synergistically suppressed pitting and CE susceptibility. Improvement in pitting and CE resistance of FSed coatings induced by varying spindle speeds was less pronounced. This work enhanced the pitting and CE resistance of AISI 201 via FS method, which is a low-cost and environment-friendly method with broad industrial applications.