高温应力时效后T91钢组织与性能的演变

Evolution of high temperature and stress time effect on microstructure and properties of T91 steels

为研究电站高温金属部件在高温应力作用下显微组织老化损伤程度的演化规律,设计了高温应力时效老化试验,对供货态T91钢在不同温度不同应力条件下进行高温时效老化.用金相显微镜、扫描电镜、透射电镜、定量金相和显微硬度等试验方法研究组织性能变化.结果表明,T91经不同温度老化后的微观组织随着温度和应力的升高,回火马氏体位向特征分散,晶界和晶内沉淀相粒子尺寸粗化,沉淀相颗粒Feret直径从原始供货态0.200μm增加到0.435μm.在相同温度下应力对组织老化的影响明显,马氏体板条内位错密度降低,板条亚结构退化,马氏体板条特征逐渐消失.随着温度的提高硬度呈现加速下降变化趋势,硬度的下降与析出相颗粒尺寸的增加同步变化,且变化趋势相似.

In order to study the evolution of microstructure damage degree of elevated temperature metal parts in power plant under high temperature and stress environment,the high-temperature and stress time effect aging test was executed for investigating the aging behavior of T91 steel at different temperatures and stresses.The optical microscopy,scanning electron microscopy,transmission electron microscopy,quantitative metallography and microhardness tester and other testing methods were used for studying the structure and performance.The results show that the orientation characteristics of tempered martensite is dispersed;and the size of precipitation phase particles located in grain boundary increased from 0.200 μm to 0.435 μm with increasing temperature and stress at different aging temperatures.The stress exhibited great effect on the organization of aging behavior at same temperature and decreased the density of dislocation in martensite lath,degraded the lath sub-structure and reduced the character of martensite lath.The hardness exhibits a decreased trend which is believed to relate with the increase of precipitation particle.The temperature and stress indicated the similar effect on hardness and the particle size.