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核电站凝汽器海水室主体材料为奥氏体不锈钢和钛材,用于保护不锈钢和钛合金凝汽器的铁合金阳极在服役过程有个别铁脚断裂发生脱现象。通过失效断口部位腐蚀形貌分析、断口裂纹金相分析和腐蚀晶界扫描电子显微镜(SEM)分析、晶间腐蚀产物X射线能谱(EDX)分析,研究确定铁阳极脱落失效原因。研究结果表明,铁阳极脱落的主要原因是其304不锈钢铁脚受到严重的敏化,在一定的条件下产生晶间型应力腐蚀而导致腐蚀断裂,并据此制定了处理方案。
The main material of the seawater condenser of nuclear power plant condenser is austenitic stainless steel and titanium. The ferroalloy anode for protecting stainless steel and titanium alloy condenser has some iron foot breakage occurring during service. The failure causes of the iron anode anodization were studied through the analysis of the corrosion morphology at the failure fracture site, the metallographic analysis of the fracture crack, the scanning electron microscopic (SEM) analysis of the grain boundary and the EDX analysis of the intergranular corrosion products. The results show that the main reason for the iron anode to fall off is that its 304 stainless steel iron foot is severely sensitized, and under certain conditions, intergranular stress corrosion is caused to lead to corrosion cracking, and the treatment scheme is worked out accordingly.