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采用扫描电镜(SEM)及透射电镜(TEM)分析,并结合常温及高温力学性能试验,研究了火力发电厂汽轮机12%Cr马氏体耐热钢高温螺栓长期运行后的组织与性能。结果表明,12%Cr钢长时间运行后硬度、强度指标下降趋势明显,高温螺栓长期运行后(35万小时)冲击功显著降低,表现出明显的脆化倾向。高温螺栓长期运行后微观组织中的碳化物聚集长大,并沿晶界与亚晶界网状析出,这是造成12%Cr马氏体耐热钢高温螺栓材料强度、韧性降低的主要原因。
The microstructure and properties of 12% Cr martensite heat-resisting steel high temperature bolts for thermal power plant after long-term operation were studied by scanning electron microscope (SEM) and transmission electron microscopy (TEM) The results showed that the hardness and strength of 12% Cr steel decreased obviously after long-term operation, and the impact energy of the high-temperature bolt decreased significantly after long-term operation (350,000 hours), showing obvious tendency of embrittlement. After long-term operation, the carbides in the microstructure grew up and reticulated along the grain boundaries and subgrain boundaries, which was the main reason for the decrease of the strength and toughness of the 12% Cr martensitic steel.