Influence of laser peening on the hydrogen embrittlement resistance of 316L stainless steel

The effects of laser peening (LP) on the surface micro-structure and hydrogen embrittlement behavior of 316L stainless steel specimens were investigated. 316L stainless steel samples were treated by LP first, and then hydrogen charged electrochemically in 0.5 mol/L dilute sulfuric acid solution in the presence of 1.25 g/L sodium phosphate. Surface residual stress and microhardness of the specimens were recorded before and after hydrogen charging, while the surface microstructures of the specimens were also observed by means of optical microscope (OM) and scanning electron microscope (SEM). Furthermore, a slow rate tensile test was conducted by an electronic universal testing machine to study the toughness loss during the hydrogen charging process. The results showed that the LPed areas were less influenced by hydrogen atoms than the base metal. Also, susceptibility to hydrogen embrittlement was decreased after LP, and the strengthening mechanism of LP on hydrogen embrittlement resistance was subsequently revealed and analyzed on the basis of compressive residual stress, grain refinement and dislocation changes.