Hydrogen effects on dislocation activity in austenitic stainless steel

Nanoindentation has been used to study the effect of dissolved hydrogen on the deformation of small volumes for the austenitic stainless steel 21Cr–6Ni–9Mn. Hydrogen reduces the load at which dislocations are nucleated and it is further shown that this is likely due to hydrogen reducing the shear modulus. Slip steps around indentations have been imaged and have shown hydrogen increases slip planarity. This is attributed as the cause of the increase in the measured hardness. Additionally, regions in which slip steps resulted primarily from a single slip plane prior to hydrogen charging exhibited slip steps from two different slip planes after hydrogen charging. This suggests that hydrogen may lower the stress necessary for dislocations to glide on the second slip plane. The increase in slip planarity and activation of slip on additional planes are consistent with the hydrogen-enhanced localized plasticity mechanism.