长期服役对316L不锈钢HAZ组织及性能的影响

采用金相分析的方法，对服役15年后发生应力腐蚀失效的箱式储罐用316L不锈钢焊接接头热影响区（heat-affected zone，HAZ）组织进行观察分析.探讨了HAZ富Cr相的析出行为及其对耐蚀性的影响，并对服役前后的焊接接头HAZ进行了应力腐蚀敏感性对比试验.结果表明，经长期服役的316L不锈钢HAZ内析出相主要是富Cr碳化物和σ相，平均腐蚀54 h后HAZ出现应力腐蚀裂纹；未经服役的焊接接头试样腐蚀200 h后未发生应力腐蚀开裂；表明HAZ内富Cr碳化物及σ相在焊接过程中形核，服役期间在残余应力等因素的促进下持续长大，焊接接头应力腐蚀敏感性显著增加.

Effect of long-time service on microstructure and properties of weld HAZ of 316L stainless steel

Metallographic analysis was used to investigate the microstructure of heat-affected zone (HAZ) of 316L stainless steel weld in which stress corrosion failure occurred after 15-year service. The precipitation behavior of Cr-rich phase in HAZ and its effect on the corrosion resistance of welded joints were discussed. Comparison test of stress corrosion susceptibility was conducted on welded joints before and after service respectively. The results showed that in HAZ the main precipitates inside HAZ were Cr-rich carbides and σ phase after long-time service. On average, SCC occurred in HAZ after 54 hours etching of the sample after long-time service, but for the raw sample, SCC would not occur even after 200 hours etching. It is suggested that Cr-rich carbides and σ phase nucleated inside HAZ during welding and then is coarsened continuously during the operation service due to the effect of residual stress, leading to prominently increasing stress corrosion susceptibility of welded joints.