Hydrogen Softening in the Thin Plate of Microcrystalline 316L Stainless Steel

The thin-plate specimen of 316L austenite stainless steel was charged with hydrogen using a cathodic charging technique. Despite the short diffusion distance of hydrogen predicted by the diffusion-controlled model for a semi-infinite sheet, the Vickers hardness measurements revealed the full effect of hydrogen in the center of the cross-sections of thin-plate specimens as well as in the vicinity of the outer surfaces, which appears to be due to the short-circuit diffusion mechanism along the grain boundaries. The room-temperature tensile properties of both undeformed and deformed (20, 40%) samples were examined and compared. Hydrogen softening was apparent in both types of samples. For example, the 40% deformed sample showed an approximately 17 and 7% lower yield and tensile strength, respectively, after H charging at a strain rate of 2 × 10−4 s−1 with a concomitant decrease in ductility compared to that without H.