Comparison of the Effects of Shot Peening, Surface Mechanical Attrition Treatment and Laser Shock Peening on a 316L Stainless Steel

Abstract : Conventional shot peening (SP), Surface Mechanical Attrition Treatment (SMAT) and laser shock peening (LSP) are three processes that are widely used to induce prestresses at the surface of materials in order to improve their hardness, wear resistance and fatigue life. SP and SMAT are quite similar since, in both treatments, the specimen is hit by shots with the aim to induce severe plastic deformation. The main differences reside in the size, velocity and impact direction of the shots. In LSP the surface of the treated part is modified with shock waves. These waves propagate into the material and induce local plastic deformations. In this study, we are comparing the effects that these three treatments have on the hardness, residual stresses and microstructure of a 316L stainless steel. Experimental investigations have been conducted to determine the micro-hardness profiles, to measure the in-depth residual stress fields using X-ray diffraction and the hole drilling method and to characterise the microstructure of the specimens after treatment using electron backscatter diffraction (EBSD) and Transmission Kikuchi Diffraction (TKD).