采用XRD、SEM和TEM等研究了650 ℃长时时效对12Cr-4W-3Co耐热钢显微组织及650 ℃高温强度的影响。结果表明: 650 ℃时效0~5 000 h后, 该钢的析出相为M23C6相和Laves相, 高温屈服强度逐渐下降; 在0~100 h区间, 屈服强度降低主要是由于马氏体板条回复较快; 在100~1 000 h区间, M23C6、Laves相析出增加, 板条回复减弱导致屈服强度基本不变; 在1 000~3 400 h区间, M23C6、Laves相的长大和板条的继续回复均导致屈服强度降低; 在3 400~5 000 h区间, 板条的回复基本停止, M23C6、Laves相少量析出和长大的共同作用导致屈服强度基本不变。

The effect of long-time aging at 650 ℃ on microstructure and high temperature strength at 650 ℃ of the 12Cr-4W-3Co heat-resistant steel was studied by XRD, SEM and TEM. The results show that the precipitates were M23C6 and Laves phase when the tested steel aged at 650 ℃ for 0-5 000 h, the yield strength at high temperatures gradually decreased. The reduction of the yield strength was mainly resulted from the martensite lath recovery during 0-100 h. The yield strength was basically unchanged for the increase of M23C6 and Laves phases precipitation and the decrease of martensite lath recovery during 100-1 000 h. The growth of M23C6 and Laves phases and recovery of the martensite lath led to the decrease of yield strength from 1 000 h to 3 400 h. During 3 400-5 000 h, the lath recovery stopped, and the yield strength basically unchanged for some precipitation and growth of M23C6 and Laves phases.