Plastic Ratcheting and Fatigue Crack Formation in Austenitic Steels with Hydrogen

Load-controlled fatigue-life of 316L austenitic stainless steel was measured using notched and smooth specimens in two hydrogen conditions: with no added hydrogen and after thermal hydrogen charging to saturate the steel with internal hydrogen. The fatigue-life of the smooth specimens increased after hydrogen charging. In contrast, hydrogen decreased the notched fatigue-life; in part due to a reduction in the fatigue crack incubation life. An increase in the yield stress was measured after hydrogen charging which influences plastic strain accumulation during cyclic loading. The measured fatigue results are discussed in the context of hydrogen effects on local deformation conditions.