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研究了T91铁素体耐热钢的相变行为与微观组织。结合热力学计算与差热分析法分析了相变行为;利用光学显微镜、扫描电镜和透射电镜观察了材料的显微组织;用X射线衍射仪检测了材料晶体结构。结果表明,经正火与回火处理的样品,其相变温度Ac1与磁性转变温度分别为856.2、749℃,其中计算的相变平衡转变温度Ae1为820℃,与实验测量的Ac1吻合很好;冷却过程中发生马氏体相变温度为400℃,根据热力学计算,其平衡析出相为MX、M23C6和Z相,MX相和M23C6型碳化物的最高溶解温度分别为1264、866℃。经正火、回火处理的样品基体组织为回火马氏体,析出相为MX、M23C6,由于短时回火与相对较低的Cr含量,所以未发现Z相。
The phase transition behavior and microstructure of T91 ferritic heat-resistant steel were studied. The phase transition behavior was analyzed by thermodynamic calculation and differential thermal analysis. The microstructure of the material was observed by optical microscope, scanning electron microscope and transmission electron microscope. The crystal structure of the material was examined by X-ray diffraction. The results show that the phase transition temperature Ac1 and magnetic transition temperature of the samples after normalizing and tempering are 856.2 and 749 ℃, respectively, and the calculated equilibrium transition temperature Ae1 is 820 ℃, which is in good agreement with the experimental Ac1 The temperature of martensite transformation during the cooling process was 400 ℃. According to the thermodynamic calculation, the equilibrium precipitates were MX, M23C6 and Z phases, and the maximum dissolving temperatures of MX and M23C6 carbides were 1264 and 866 ℃, respectively. After normalizing and tempering, the microstructure of the sample was tempered martensite. The precipitated phases were MX and M23C6. The Z phase was not found due to short-term tempering and relatively low Cr content.