Depth-profiling of residual stress and microstructure for austenitic stainless steel surface treated by cavitation, shot and laser peening

While the general characteristics of various peening techniques have been established, there have been few comparative studies. Here we compare the variation of the residual stresses and microstructural characteristics with depth for 316L austenitic stainless steel treated by cavitation peening (CP), shot peening (SP) and laser peening (LP) all peened to similar intensity levels. While the plastically affected depths were similar in all cases (similar to 400 mu m), the SP specimen showed the most extensive near surface plastic deformation, deformation twinning, dislocation density and compressive residual stress. To counterbalance this, the compressive residual stresses extended deeper for the LP and CP. Across the three treatments, a similar dependency was found between diffraction peak broadening and hardness. The dislocation density at the surface determined by the diffraction line profile analysis (LPA) for the SP specimen (4.9 x 10(15) m(-2)) was approximately 2.5 times that for the CP and LP specimens (2.0 x 10(15) and 2.1 x 10(15) m(2)). Electron backscatter diffraction (EBSD) shows that the extensive work introduced by the SP had generated planar defects near to the surface. The increase in yield stress estimated from the hardness corresponded with the increase in dislocation density obtained by the LPA.

Automated summary

A comparative study was conducted on the effects of different peening techniques on 316L stainless steel, indicating that peening treatment results in surface plastic deformation, residual compressive stress, and increased dislocation density, with varying degrees of impact depending on the peening method used.