Effect of laser peening on microstructure evolution and hydrogen damage sensitivity of 316L stainless steel

Laser peening has emerged as a promising technique to reduce hydrogen damage in 316L stainless steel (316L SS). This study investigated the effects of laser peening on the hydrogen damage mechanism of 316L SS with varying microstructures. Microstructural characterization revealed that untreated 316L SS exhibited annealing twins and original austenite grains, whereas laser-peened samples demonstrated a composite microstructure containing retained austenite, martensitic phases, deformation twins, and distinct slip bands. Electrochemical results showed that laser-peened samples at 6.4 GW/cm2 displayed the lowest passivation current density (ipass) and the highest total resistance (Rsum) after hydrogen charging. This phenomenon is attributed to the enhanced grain refinement by the laser peening process. Additionally, the samples laser-peened at a power density of 6.4 GW/cm2 showed the lowest sensitivity to hydrogen damage. This is because a more excellent passivation film was formed, resulting from the reduction in the content of OH- /O2- in the passivation film.