Improvement in the tribological behaviour of surface-nanocrystallised 304 stainless steel through supersonic fine particle bombardment.

[Display omitted] • Nanocrystals were introduced into the surface layer after SFPB. • Wear resistance of the treated samples was improved. • The mechanism of SFPB on the wear properties of 304 stainless steel was provided. The effects of supersonic fine particle bombardment (SFPB) on the wear properties and surface integrity of 304 stainless steel were investigated. Moreover, the impact of different air pressures (1, 1.5, and 2 MPa) on the microstructure, microhardness, and tribological behaviour of the material was explored. The results indicated that SFPB significantly refined the surface grains and transformed the austenitic phase into the martensite phase. The subsurface microhardness of 304 stainless steel increased with air pressure, with maximum increases of 58%, 90%, and 98% at 1, 1.5, and 2 MPa, respectively. However, higher air pressures resulted in increased microdefects, which adversely affected the wear rates. Notably, the sample with the highest microhardness (2 MPa) exhibited the highest wear rate, whereas the best tribological performance was observed at 1.5 MPa. Surface integrity analysis revealed that the tribological performance of 304 stainless steel was influenced by both surface defects and surface nanocrystals. This study provides insights into the mechanism by which SFPB affects the wear properties of 304 stainless steel. [ABSTRACT FROM AUTHOR]