焊缝蠕变强度对马氏体/贝氏体异种钢接头界面蠕变损伤的影响

Influence of creep strength of weld on interfacical creep damage of welded joint of martensitic heat-resistant steel and bainitic heat-resistant steel

采用脉冲氩弧焊接工艺、高温加速模拟、扫描电镜观察研究了不同焊缝蠕变强度匹配条件下,马氏体耐热钢(9Cr1MoVNbN)与贝氏体耐热钢(12Cr2MoWVTiB)焊接接头的界面蠕变损伤、破坏特征及早期失效倾向。结果表明,焊前预热250℃,焊后回火750℃×1h条件下,加速模拟运行500,1000,1500h后低匹配接头中焊缝/贝氏体钢界面的蠕变损伤最严重,发生了界面蠕变断裂,早期失效倾向较大;而高匹配接头中焊缝/贝氏体钢界面的蠕变孔洞几乎连成裂纹,蠕变损伤和早期失效较大;而中匹配接头的界面蠕变损伤程度最轻,仅发现少量孤立蠕变孔洞,早期失效倾向最小。

The creep damage and characteristics of interfacial failure and early failure of welded joints of martensitic heat-resistant steel (9Cr1MoVNbN) and bainitic heat-resistant steel(12Cr2MoWVTiB) with different creep strength of weld have been investigated by means of argon tungsten pulsed arc welding and high temperature accelerated simulation test. And the microstructure was rescarched by scanning electron microscope. The results show that the interfacial creep damage of undermatching welded joint is very serious, and the interfacial failure occurred, and the early failure tendencies are higher than those of overmatching and equalmatching welded joints after accelerated simulating operation 500 h, 1 000 h and 1 500 h, respectively, on condition that preheat temperature is 250 ℃,and postweld heat treatment is 750 ℃×1 h. The creep damage and early failure tendency of overmatching welded joint is higher than that of equalmatching joint, and the creep cavities of weld/bainitic heat-resistant seel interface nearly link to form creep cracks. The creep damage and early failure tendency of equalmatching joint are the lowest among the three joints, and few isolated cavities are found in the test.