中文摘要：

在650℃下对国产T91耐热钢进行了标准拉伸持久试验,采用外推法计算出该钢105h的持久强度极限为55.42 MPa。使用OM、SEM、TEM和XRD对不同应力状态下的蠕变断裂试样微观组织进行分析比较。研究结果显示,随着持久断裂时间的延长,T91耐热钢蠕变断裂状态由韧性断裂向脆性断裂模式改变;材料中出现马氏体板条组织分解、M23C6碳化物粗化、位错密度降低和再结晶等现象。析出相强化作用的下降,马氏体板条的碎化和多边形化以及位错机构的退化是国产T91耐热钢蠕变性能下降的主要原因。碳化物的EDS分析表明,不同形貌M23C6碳化物成分存在差异,含Si元素M23C6碳化物更可能在持久过程中长大。

英文摘要：

Standard creep-rupture tests for domestic T91 heat-resistant steel（T91 HRS）were conducted at 650 ℃/105 h,creep-rupture strength calculated by the extrapolation is 55.42 MPa.The microstructure of rupture specimens under different stress states was observed by OM,SEM,TEM,EDS and XRD.The results reveal that with the increase of rupture time at low stress level,the fracture mode of domestic T91 HRS changes from ductile to brittle;some phenomena such as the coarsening of M23C6 carbides,the decomposition of martensite lath structure,the decrease of dislocation density and the recrystallization appear in T91 HRS.The weakening of precipitate hardening,the fragmentation and polygonization of martensite lath,as well as the degeneration of dislocation structure are the main factors to deteriorate the creep performance.The EDS analysis shows that the M23C6 carbides having different morphology are dissimilar in composition;the rod-shaped M23C6 carbides containing Si are more likely to coarsen during test process.