Study on friction and wear of 9Cr18 steel with composite treatment of laser shock processing and surface texturing

The composite treatment of laser shock processing (LSP) and laser-induced surface texturing was employed to enhance the tribological performance of 9Cr18 steel. LSP was conducted with energies of 5–7J, while surface texturing was achieved by controlling laser parameters to produce micro-pits with depths ranging from 9.9 to 32.5 μm and surface densities of 21–37%. The results demonstrated that LSP significantly improved surface hardness to 820HV 0.1 at 7J, induced −876MPa residual compressive stresses , and refined grain size by 10.20%, as revealed by EBSD analysis. The synergistic effect of LSP-6J and surface texturing reduced the friction coefficient by 57% and wear loss by over 90% under boundary lubrication, with optimal performance observed at a texture depth of 18.0 μm and surface density of 37%. Under dry friction, the composite treatment achieved a 57% reduction in friction coefficient and over 90% reduction in wear loss, with the best results at a texture depth of 14.6μm and surface density of 37%. The wear mechanism transitioned from abrasive and adhesive wear to slight abrasive wear, attributed to the combined effects of surface hardening, lubricant retention, and debris trapping by textures.