【摘要】 为研究火电站主蒸汽管道用首批国产P91钢长期运行后的组织性能变化规律，文中利用光学显微镜（OM）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、布氏硬度计及万能试验机对国内某电厂主蒸汽管道用首批国产P91钢服役50 000 h前后的微观组织和力学性能进行测试与分析。研究结果表明：P91钢服役前组织为回火板条马氏体，板条界、原奥氏体晶界及晶内分布细小弥散的M₂₃C₆碳化物，板条内分布有高密度的位错；服役50 000 h后，P91钢中的M₂₃C₆型碳化物发生了粗化，同时有Fe₂Mo型Laves相析出，布氏硬度降低，微型杯突力学性能下降，断裂机理仍为以韧窝为主的微孔聚集型断裂；马氏体板条形态变化、M₂₃C₆粗化以及Laves相的析出是造成P91钢性能下降的主要原因。该结果可为评定国产P91钢管道安全运行提供一定的理论参考。更多还原

【Abstract】 The study is intended to examine the evolution of the microstructures and properties of the first batch of domestically produced P91 steel for the main steam pipelines in thermal power stations after long service.Optical microscopy（OM）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,Brinell hardness test and a universal testing machine attached small punch test（SPT） jig were used to investigate the microstructures and mechanical properties of P91 steel in a thermal power station before and after 50000 hours of service.The results show that the microstructures of P91 steel before service consisted of the tempered lath martensite with high-density dislocation and the fine M₂₃C₆ carbides distributed along both the lath boundary.After 50 000 hours of service, M₂₃C₆ carbides has become coarsening, and Fe₂Mo Laves phase precipitated, the dislocation density in martensite lath decreased, and both Brinell hardness and SPT properties decreased.Moreover, the SPT fracture mechanisms of P91 steel before and after 50 000 hours of service remains a microporous aggregation type fracture dominated by tough nests.The change of martensite lath morphology, M₂₃C₆ coarsening and the precipitation of Laves phase are the main reasons for the performance degradation of P91 steel.These results can provide a theoretical basis for evaluating the safety of domestically produced P91 steel pipes.更多还原