The effect of pre-strain on hydrogen embrittlement in 310S stainless steel

The effect of pre-strain on hydrogen embrittlement (HE) was investigated using STS 310S, considering its application to a ferrous cylinder liner for hydrogen storage. Whereas tensile strength was insignificantly influenced by hydrogen charging, elongation was decreased due to a ductile to brittle fracture transition. However, the degree of the reduction in elongation by hydrogen charging was decreased with increasing pre-strain, indicating that pre-straining improved the resistance to HE by suppressing the fracture transition. The cause for suppression of the fracture transition by pre-strain was investigated through the analyses of strain hardening behavior and thermal desorption of hydrogen. The strain hardening rate curves of annealed and pre-strained specimens was divided into several stages, which were greatly affected by primary and secondary twinning, regardless of hydrogen charging. This strain hardening analysis showed that pre-straining suppressed mechanical twinning during tensile deformation. The thermal desorption analysis revealed that the migration of diffusible hydrogen atoms to twin boundaries was hindered by pre-strain. Therefore, the reason why pre-strain suppressed the fracture transition to improve the resistance to HE was because pre-strain hindered both mechanical twinning during tensile deformation and hydrogen delivery to twin boundaries not to form highly hydrogen-concentrated twin boundaries.