氢腐蚀裂纹的愈合规律及机理研究

From the present status of hydrogen attack (HA) research and theoretical interpretation, thermodynamic and kinetic models are based mainly on the HA formation process. The goal of this project was to study the decomposition reactions of methane bubbles and the healing mechanism of HA cracks for heat treatment >600℃. Specimens, including carbon steel, alloy steel and stainless steel, with HA bubbles and cracks were obtained in different temperature, time and same pressure. After HA, specimens were subject to various heat treatments. It was observed by SEM, TEM and high-temperature microscopy that HA bubbles and cracks (≤ 10μm length) could be healed completely by heat treatment at 600℃ for stainless steel and at 1000℃ for carbon steel. The studies performed showed that crack healing is controlled by diffusion and that the recovery kinetics depend on the plastic deforming energy Es arising from the growth of HA bubbles or cracks. These findings led to the conclusion that the critical condition for healing of bubbles or cracks is Es ≥2γ/r (where γis the surface tension, r is the radius of bubbles or half length of cracks) provided the atoms of H, C, Fe can diffuse rapidly. During healing of the HA cracks, the dense of dislocation around grain boundaries decreased and the dislocation type transformed from tangle dislocation with high energy to vertical and regular dislocation with low energy. The recovery, polygonization and recrystallization of the sub-grain were also taken place. This work supplied and developed the HA theory, and in addition it provided a new way to assess and treat the HA cracks in the industry.

申请者认为现有的高温氢腐蚀热力学与动力学的理论只包含了缺陷生成的正过程，而对缺陷逆过程的热力学和动力学研究的设想，对氢腐蚀裂纹愈合的临界条件进行探讨.以上的研究郧馑鹕说睦砺塾兴毕住Ｎ⒄剐滦偷母呶虑飧慈毕莸拇矸椒ê驮し拦こ淌鹿实姆⑸峁┬碌乃悸酚胪揪丁