The specimens of 304 austenite stainless steel with the hydrogen attack bubbles orcracks were heat treated at 600℃ for 6h. The SEM and TEM observations on thespecimens before and after the heat treatment showed that the bubbles or cracks could behealed completely by heat treatment. The healing of hydrogen attack bubbles or cracksis closely related to heat diffusion of Fe and C atoms in austenite. The driving forceof crack healing results fram the plastic deforming energy Es induced by the growthof hydrogen attack bubbles or cracks. The critical condition of healing of bubbles orcracks is Es ≥ 2γ/r (where γγ is the surface tension, r is the radius of bubbles or halflength of crack). During healing of the hydrogen attack bubbles or cracks, the recovery,polygonization and recrystallization of the sub-grain also occured.
X.G.Li,C.F.Dong and H.Chen School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China State Key Laboratory of Corrosion and Protection, Institute of Metal Research, The Chinese Academy of Sciences, She
The healing mechanism of hydrogen-attacked cracks in low carbon steel and Cr-Mo steel and its influencing factors during the healing process were studied by recovering heat treatment of split specimens in vacuum. The result showed that crack pacing tums much smaller under the condition of pure heating, especially for crack tips. The healing effect is well related to the length of cracks with the shorter in priority. By the primary mechanism of thermal diffusion, iron and carbon atoms must diffuse at the high speed in steel to realize that plasticity deformation energy exceeds and overcomes surface tensile force energy. In addition, phase transformation and stress-stain relationship also have positive effects on the process.
