Effect of grain size on hydrogen embrittlement sensitivity in stable austenitic stainless steel 316L

Austenitic stainless steels are renowned for their exceptional resistance to hydrogen embrittlement, making them promising candidates for fabricating liquid hydrogen storage tanks. However, their relatively low tensile strength limits their applicability in high-pressure hydrogen environments. This study investigates the effects of hot rolling treatment on 316L stainless steel, with solid solution treatment serving as the baseline control. The HE sensitivity of the steel was evaluated using in-situ hydrogen-charged uniaxial slow strain rate testing. The results indicate that the grain size of the solid-solution-treated 316L was 69 μm, while the hot-rolled specimens exhibited a refined grain size of 30 μm. Consequently, the tensile strength increased to 410.5 MPa, and HE sensitivity decreased by 11.2%. It clarifies the dual-beneficial effect of hot rolling – simultaneously enhancing strength and HE resistance. It uncovers the underlying mechanism: grain refinement increases grain boundary density to accommodate hydrogen, while the formation of more deformation twins under stress disperses dislocation-transported hydrogen at grain boundaries, thereby delaying crack initiation. This dual mechanism provides new insights into the synergistic regulation of strength and HE resistance, providing a high-performance material solution for high-pressure liquid hydrogen storage tanks, pipelines, and other critical components in hydrogen energy systems.