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对热处理态的高温Cr-Co-Mo-Ni齿轮轴承试验钢在500℃下进行不同应力的持久试验,采用内插法得到500℃,500h的断裂强度为1 022MPa;借助金相显微镜、扫描电镜和透射电镜等仪器观察试验钢持久试验前后的微观组织变化。结果表明:500℃条件下,随着加载持久应力由1 150MPa降低至950MPa,试验钢断裂时间由96.4h延长至845.8h,基体中碳化物平均尺寸由0.3μm长大到0.5μm以上,所占面积分数由1.65%上升至3.85%;随着持久应力的降低及断裂时间的延长,马氏体板条束发生剪切变形—碎化—重新排列的变形过程,位错密度呈下降趋势;持久断裂前后,试验钢基体中析出相均为M6C型碳化物。
The heat-treated high-temperature Cr-Co-Mo-Ni gear bearing test steel was subjected to different stress lasting tests at 500 ℃. The interfacial method was used to obtain the breaking strength at 500 ℃ for 500h. The breaking strength was 1022MPa by metallographic microscope, scanning electron microscope And transmission electron microscopy and other equipment to observe the microstructure changes of the test steel before and after the long-term test. The results show that the fracture toughness decreases from 1 150 MPa to 950 MPa at 500 ℃, and the fracture time increases from 96.4 h to 845.8 h. The average carbide size in the matrix increases from 0.3 μm to 0.5 μm, accounting for The area fraction increased from 1.65% to 3.85%. With the decrease of the lasting stress and the extension of fracture time, the martensite lath bundle shear deformation - fragmentation - rearrangement deformation process, the dislocation density showed a downward trend; lasting Before and after fracture, the precipitated phase in the test steel matrix was M6C type carbides.