Healing of hydrogen attack in austenite stainless steel under heat treatment

The specimens of 304 austenite stainless steel with the hydrogen attack bubbles or cracks were heat treated at 600°C for 6h. The SEM and TEM observations on the specimens before and after the heat treatment showed that the bubbles or cracks could be healed completely by heat treatment. The healing of hydrogen attack bubbles of cracks is closely related to heat diffusion of Fe and C atoms in austenite. The driving force of crack healing results from the plastic deforming energy Es induced by the growth of hydrogen attack bubbles or cracks. The critical condition of healing of bubbles or cracks is Es≥2γ/r (where γ is the surface tension, r is the radius of bubbles or half length of crack). During healing of the hydrogen attack bubbles or cracks, the recovery, polygonization and recrystallization of the sub-grain also occurred.