Experimental and numerical investigation on residual stress of 316L SS treated by different laser shock peening parameters

Abstract

316 L stainless steel has excellent mechanical properties, but fracture occurs when working in some extreme environments for a long time. As one of the important surface treatment technologies, laser shock peening (LSP) can improve the mechanical properties by inducing compressive residual stress (CRS) within the material, and has been widely used in a variety of fields due to its outstanding capabilities. Since LSP produces significant CRS, the influence of different laser parameters on the residual stress distribution of 316 L stainless steel was studied by numerical simulation, and verified by experiments. The results reveals that with the increase of laser energy, the residual stress in the surface and depth direction of the material increases firstly and then decreases gradually; three LSP cycles were performed on the same material, and it was found that the surface CRS within material had only a slight increase with three LSP cycles compared to the one with two LSP cycles, indicating that the CRS had reached the saturation; the effect of LSP on the residual stress of materials under different spot shapes was also studied, which indicates that the square spot can achieve better strengthening effect for multi-point LSP. Furthermore, the reasons for the improvement of mechanical properties were analyzed through microstructure observation.