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用Auger电子能谱分析技术、光学和电子金相法,对经过高温持久试验的加与未加稀土Cr18Ni18Si2奥氏体钢试样进行了晶界化学成分和碳化物等组织结构观测。结果表明,Cr18Ni18Si2钢在高温持久试验过程中,硫、磷和锑等杂质元素产生严重的晶界偏聚。添加0.15%混合稀土能够显著降低硫的偏聚程度,消除磷和锑的偏聚。稀土对Cr18Ni18Si2钢高温持久试验过程中析出的第二相类型及其与基体的位向关系没有影响,但稀土能够延缓M_(23)C_6型碳化物沿晶界析出过程,改变碳化物粒子的分布形态。根据实验观测结果讨论了稀土改善Cr18Ni18Si2奥氏体钢高温持久断裂性能的机制。
Using Auger electron spectroscopy, optical and electronic metallographic methods, the grain boundary chemical composition and the structure of carbides were observed on the specimens with or without addition of Cr18Ni18Si2 austenitic steel after long-term high temperature test. The results show that Cr18Ni18Si2 steel during the long-term high temperature test, sulfur, phosphorus and antimony and other impurity elements have serious grain boundary segregation. Addition of 0.15% mixed rare earth can significantly reduce the segregation degree of sulfur and eliminate segregation of phosphorus and antimony. The rare earths have no effect on the type of second phase precipitated during the high temperature long-term test of Cr18Ni18Si2 steel and its orientation relationship with the matrix. However, rare earth can delay the precipitation of M23C6 carbides along grain boundaries and change the distribution of carbide particles form. Based on the experimental observations, the mechanism of rare earths to improve the permanent rupture properties of Cr18Ni18Si2 austenitic steel under high temperature is discussed.