Nano-indentation was used to study the effect of dissolved H on the deformation of small volumes for the austenitic stainless steel 21Cr–6Ni–9Mn. Hydrogen reduced the load at which dislocations were nucleated and it was further shown that this was likely due to H reducing the shear modulus. Slip steps around indentations were imaged and have shown H increased slip planarity. This was 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 H charging exhibited slip steps from two different slip planes after H charging. This suggested that H could 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 were consistent with the H-enhanced localized plasticity mechanism.

Hydrogen Effects on Dislocation Activity in Austenitic Stainless Steel. K.A.Nibur, D.F.Bahr, B.P.Somerday: Acta Materialia, 2006, 54[10], 2677-84