The diffusion and trapping of hydrogen along the grain boundaries in polycrystalline nickel

Grain misorientation is accommodated by dislocations that are capable of hydrogen trapping. However, it is often reported that in face-centered-cubic materials, grain boundaries may also act as preferential paths for hydrogen diffusion. We present a study conducted on polycrystalline nickel where we coupled several techniques to distinguish trapping and short-circuit diffusion of hydrogen. The results suggest that the hydrogen diffusion is accelerated along the boundaries, and that diffusion may slow down when the dislocation density stored in the boundary is substantial.