Effect of shot peening coverage on hardness, residual stress and surface morphology of carburized rollers

Shot peening is currently becoming a widely used surface strengthening technique that can refine the material grain, increase the hardness and introduce a certain depth of residual compressive stress layer. At the same times it changes the surface topography which may have a deleterious effect on the contact fatigue life. A fully understanding on the mechanism of shot peening for high-strength steels is to be explored. In this paper, the effect of shot peening coverage on residual stress, surface roughness, microhardness and microstructure of rollers are experimentally investigated. Experimental results show that the shot peening leads to a slight increase of surface and near-surface hardness from 690 HV to 740 HV, and an appreciably increasing of the subsurface maximum compressive residual stress. Moreover, some retained austenite in the the near-surface layer are transformed to martensite after shot peening, and wherein the grain refinement occurs.