Hydrogen-enhanced plasticity of 310S stainless steel

Transient creep of hydrogen-austenitic stainless steel solid solutions at 55 C was studied to determine the effects of hydrogen on plastic deformation. Thin specimens at AISI 310S stainless steel were slowly cathodically charged to uniform hydrogen contents, and no significant damage was introduced. A constant load was then applied, while the charging current density remained the same, so as to prevent outgassing of the hydrogen during the tests. It was found that at short times the creep rate of a hydrogenated specimen was lower than that of specimen without hydrogen. However, the creep rate decreased at a slower rate thereafter, so that the transient creep stage was longer, and in some cases the creep was even larger than in a hydrogen-free specimen. This is clear evidence of hydrogen-enhanced plasticity. Elasticity interactions between hydrogen atmospheres and moving dislocations were used to explain the observed phenomenon. Hydrogen enhancement and localization of plasticity have been cited as fundamental causes of hydrogen embrittlement. The prolongation of the transient creep stage has significance for propagation of stress corrosion cracks. (orig.)