针对甲基丙烯酸甲酯装置C22哈氏合金换热器盘管的泄漏事故, 采用化学成分、SEM和EDAX等分析手段进行了详细分析。结果表明, C22哈氏合金换热器盘管的泄漏原因是由于焊接不当, 在母材和焊缝之间热影响区的晶界上析出了高钼的碳化物。高钼碳化物析出相使周围贫铬, 钼区在含硫酸的氧化性介质下在晶界上优先腐蚀, 导致合金的腐蚀泄漏。通过固溶处理和快速冷却可以消除高钼碳化物在晶界上析出, 从而避免硫酸引起的晶间腐蚀泄漏。

Aiming at the leaking accident of coil of Hastelloy C22 heat exchanger in methyl methacrylate equipment, we analyzed the reason in detail by means of chemical composition analysis, SEM, EDAX and so on. The results show that the leaking accident of coil of Hastelloy C22 heat exchanger was caused by improper welding. On the grain boundary of heat affected zone between base metal and precipitated phase, high Mo content carbide which will cause the priority corrosion of low Cr, Mo material surrounding it was precipitated, leading to intergranular corrosion and leakage. The precipitation of high Mo content carbide on grain boundary can be eliminated by solution treatment and fast cooling, sequentially, intergranular corrosion leakage induced by sulfuric acid will be avoided.