The effect of stress state on the hydrogen embrittlement of nickel

The ductility of nickel sheet subjected to in situ cathodic hydrogen charging has been investigated over a range of multiaxial stress states including uniaxial, plane-strain, and equibiaxial tension. The data show that the extent of ductility loss due to the presence of hydrogen increases as the stress state tends from uniaxial to equibiaxial tension. In all instances, the hydrogen embrittlement is characterized by intergranular fracture with failure occurring due to microcrack formation, microcrack link-up, and macrocrack growth. The increased susceptibility of nickel to intergranular hydrogen embrittlement with increasing biaxiality of stress state is shown to be a consequence of an enhanced rate of the link-up of strain-induced intergranular microcracks.