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采用光学显微镜(OM)、能谱仪(EDS)、X射线衍射仪(XRD)、高温显微镜原位观察等实验手段,分析了ZG40Cr25Ni20奥氏体耐热钢烧损原因。结果表明,随着温度升高,奥氏体晶粒不断长大,碳化物Cr23C6不断形成和长大,碳化物中的Cr含量和碳化物硬度不断增加,奥氏体基体中的Cr含量不断减少。温度过高,碳化物溶解,形成孔洞,促进微裂纹沿晶界的扩展,奥氏体晶粒间的结合力逐渐减弱,基体发生过烧,钢的结晶组织遭到破坏,失去金属原有的塑性和强度,造成高温耐热管失效,孔洞和微裂纹的形成及扩展是材料失效的主要原因。此外,高温显微镜原位观察和热处理实验结果表明,ZG40Cr25Ni20耐热钢中碳化物的溶解温度为1030~1250℃。高温显微镜原位观察为碳化物溶解观察和耐热钢失效分析提供了一种新的方法。
The reason of burning loss of ZG40Cr25Ni20 austenitic heat-resisting steel was analyzed by optical microscope (OM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and in situ observation with high temperature microscope. The results show that as the temperature increases, the austenite grain grows continuously, the carbides Cr23C6 continue to form and grow, and the Cr content and carbide hardness in the carbides increase continuously, and the Cr content in the austenite matrix decreases . When the temperature is too high, the carbides dissolve to form holes that promote the propagation of micro-cracks along the grain boundaries. The bonding force between austenite grains gradually weakens, the matrix burns out, the crystal structure of the steel is destroyed, and the original metal Plasticity and strength, resulting in high temperature heat pipe failure, the formation and expansion of holes and micro-cracks is the main reason for material failure. In addition, the results of in-situ observation and heat treatment of high temperature microscope showed that the dissolution temperature of carbide in ZG40Cr25Ni20 heat-resisting steel was 1030 ~ 1250 ℃. High-temperature microscopy in situ observation provides a new method for the observation of carbide dissolution and failure analysis of heat-resistant steels.