Crack growth rate in hydrogen pre-charged martensitic steels during slow strain rate tests

Crack growth rate in two high strength martensitic steels with the Mo contents of 0.43 wt.% and 1.06 wt.% was investigated by means of slow strain rate tests (SSRT) on compact tensile specimens after hydrogen pre-charging. It was found that the crack growth rate increased and the values of stress intensity factors KIH and KImax decreased with the increase of pre-charged hydrogen concentration. The steel with higher Mo content showed much lower crack growth rate than the steel with lower Mo content. It could be attributed to more nano-sized precipitates that can act as the hydrogen trapping sites and mitigate hydrogen deleterious effects on crack growth rate and the KIH and KImax values.