Anisotropic effect of pre-strain on hydrogen embrittlement susceptibility in a stable austenitic stainless steel

Different pre-strain of uniaxial tensile deformation or cold rolling were applied to 0.02C–18Cr–11Ni-0.15 N austenitic stainless steel to investigate the effect of pre-strain stress modes on hydrogen embrittlement (HE). The susceptibility to HE was negligibly affected by tensile pre-strain, but it increased with the degree of pre-strain by cold rolling. This resulted from differences in strain distribution, twinning behavior, and changes in H diffusivity arising from the two deformation methods. Homogeneous strain distribution was observed after uniaxial tensile deformation, whereas the deformation was locally concentrated after cold rolling. This led to localized H adsorption to assist crack propagation. While twinning was the main deformation mechanism in the present steel, only the twins formed during cold rolling were vulnerable to stress localization owing to their crystallographic orientation. These twins acted as initiation sites for H-induced cracking and degraded the HE resistance. Finally, H diffusion was less active in tensile-strained samples, and high HE resistance was effectively maintained despite the increase of strength by pre-straining as a consequence.