钝化膜应力导致不锈钢应力腐蚀

FILM-STRESS INDUCED STRESS CORROSION CRACKING OF AUSTENITIC STAINLESS STEEL

用恒位移加载台,在透射电镜（TEM）中原位观察应力腐蚀前后裂尖前方位错组态的变化以及微裂纹的形核和扩展.结果表明,310不锈钢在沸腾的25％MgCl2水溶液中应力腐蚀时腐蚀过程能促进位错发射、增殖和运动;当腐蚀促进的位错发射和运动达到临界状态时,应力腐蚀裂纹形核和扩展.测量表明,304不锈钢在沸腾MgCl2中自然腐蚀时表面钝化膜会产生一个附加拉应力,它可能是腐蚀促进位错发射和运动的原因.

A constant deflection device set up within a transmission electron microscope (TEM) was used to investigate the change in dislocation configuration ahead of a crack tip during stress corrosion cracking (SCC) of type 310 austenitic stainless steel in a boiling MgCl2 solution, and the initiation process of stress corrosion microcrack. Results showed that the corrosion process during SCC enhanced dislocation emission, multiplication and motion. Microcracks of SCC initiated when the corrosion-enhanced dislocation emission and motion reached a certain condition. A passive film formed during corrosion of austenitic stainless steel in the boiling MgCl2 solution generated a tensile stress. During SCC, the additive tensile stress generated at the metal/passive film interface assists the applied stress to enhance dislocation emission and motion.