Susceptibility of different crystal orientations and grain boundaries of polycrystalline Ni to hydrogen blister formation

The effects of crystallographic orientations, grain boundaries (GBs) and the possible contribution of dislocations to the diffusion of hydrogen were studied. Our experimental results show that the (001) crystal orientation has the minimum number of hydrogen induced blisters compared to other crystal orientations. We observed formation of blisters along the slip traces after plastic deformation and along special GBs. It shows that the interaction between dissolved hydrogen and lattice defects (e.g. dislocations and GBs) could cause void formation and ultimately induce intergranular and/or transgranular cracks in nickel. In this work we analyzed hundreds of GBs mostly with a misorientation of less than 60°. It was observed that the random GBs with a misorientation between 30 and 40° have the fastest hydrogen diffusion rate and are very sensitive to hydrogen segregation. In contrast, random GBs with a misorientation below 25°, low angle GBs and the coincidence site lattice (CSL) GBs are much less prone to blister formation.