Pitting resistance of 316 stainless steel after laser shock peening: Determinants of microstructural and mechanical modifications

Abstract Laser shock peening (LSP) was performed on a 316 stainless steel for microstructural and mechanical modifications. To identify the dominant factor controlling pitting corrosion resistance, a single LSP impact was performed and various characterization techniques, such as scanning electron microscopy, X-ray diffraction, transmission electron microscopy, electron backscattered diffraction, microhardness and residual stress analysis were conducted. The results show that a considerable increase in the microdefects, microhardness, and compressive residual stress occurred at a depth of ∼200 μm from the surface, while no evident grain refinement was observed. The compressive residual stress reduced the metastable pitting nucleation rate. However, microdefects after LSP treatment resulted in larger metastable pits, which are more likely to combine to transform into a stable one. It is summarized that the substantial microdefects can deteriorate the superiority of compressive residual stress induced by LSP in the pitting resistance of 316 stainless steel.