Effects of Thermal Laser Shock Peening on Stress Corrosion Susceptibility of 304 Stainless Steel

As a new surface strengthening technology, laser shock peening (LSP) can effectively improve the stress corrosion resistance of metal surface. However, the martensitic transformation induced by traditional LSP has negative effects on the corrosion resistance of 304 stainless steel. In order to retard the martensitic transformation, the thermal laser shock peening (TLSP) tests of 304 stainless steel were carried out in this work. The residual stress, grain size, microhardness and martensite content of the surface layer of the specimens were measured. The stress corrosion sensitivity of the TLSP 304 stainless steel was studied by slow strain rate test (SSRT). The results show that high residual compressive stress, grain refinement and martensitic transformation occurred on the surface of the specimens after TLSP, and the martensite content is significantly lower than that of the traditional laser peening specimens. The stress corrosion sensitivity index of the specimens treated by TLSP is significantly lower than that of the untreated specimens. With the increase in the TLSP temperature, the stress corrosion sensitivity index of the specimens decreases, especially when the laser shock peening temperature rises above 50 degrees C, the stress corrosion sensitivity index decreases significantly.