The specimens of 304 austenite stainless steel with the hydrogen attackbubbles or cracks were heat treated at 600 deg C for 6h. The SEM and TEM observations on thespecimens before and after the heat treatment showed that the bubbles or cracks could be healedcompletely by heat treatment. The healing of hydrogen attack bubbles or cracks is closely related toheat diffusion of Fe and C atoms in austenite. The driving force of crack healing results from theplastic deforming energy E_s induced by the growth of hydrogen attack bubbles or cracks. Thecritical condition of healing of bubbles or cracks is E_s >= 2 gamma/r (where gamma is the surfacetension, r is the radius of bubbles or half length of crack). During healing of the hydrogen attackbubbles 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 andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The result showed that crack pacing turns much smaller underthe condition of pure heating, especially for crack tips. The healing effect is well related to thelength of cracks with the shorter in priority. By the primary mechanism of thermal diffusion, ironand carbon atoms must diffuse at the high speed in steel to realize that plasticity deformationenergy exceeds and overcomes surface tensile force energy. In addition, phase transformation andstress-stain relationship also have positive effects on the process.
