Effect of micro-shot peening on the surface integrity of high-speed steel

Micro-shot peening (MSP) is a surface-strengthening technique that improves the mechanical properties of materials. This study investigated the effects of MSP on S790 high-speed steel (HSS). The MSP-treated S790 exhibited a distinctive ridge-like texture with a surface hardness of 689.5 HV and a surface residual stress of −1767.3 MPa. Electron backscatter diffraction (EBSD) analysis revealed that MSP induced significant grain refinement and increased local misorientation near the surface, indicating high dislocation density and severe plastic deformation. Pin-on-disk wear tests revealed that MSP treatment markedly improved wear resistance. MSP reduced the wear width from 624 μm to 224 μm and decreased mass loss from 2.3 mg to 0.2 mg compared to the as-received S790. Post-wear surface characterization revealed that MSP significantly reduced the extent of adhesive and delamination wear observed in the as-received S790 specimen. The superior wear resistance achieved through MSP treatment highlights the synergistic effects of surface hardening and surface texturing in mitigating wear damage and enhancing surface integrity.