Internal hydrogen supersaturation produced by dislocation transport

A quantitative model is presented for the generation of internal supersaturations of hydrogen by kinetic rather than thermodynamic means. The maximum brittleness and slow strain rate limit is treated. The process invoked assumes hydrogen transport to deposition sites by dislocation drag, and reemission of the hydrogen by diffusion. The kinetic supersaturation is calculated from a balance between hydrogen arrival and departure rates, for internal and external hydrogen sources, and for smooth section and crack geometries. When applied to ferritic and austenitic steels, the model predicts that the kinetic supersaturations are extremely small in all realistic situations.