高温与应力耦合作用下Cr-Co-Mo-Ni齿轮轴承钢微观组织演变

 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1022MPa；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1150MPa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。

Microstructure Evolution Research of Cr-Co-Mo-Ni Gear and Bearing Steel Under Action of Temperature and Stress Coupling

Creep-rupture test was performed under the temperature of 500℃ and different stresses for heat treated high temperature Cr-Co-Mo-Ni gear and bearing steel. The creep-rupture strength obtained by interpolation was 1022MPa at the state of 500℃ for 500h. The microstructure of the samples, before and after creep-rupture test, was investigated by OM, SEM and TEM. The results show that the rupture time extends from 96.4h to 845.8h, the average size of carbides in the matrix increases from 0.3μm to 0.5μm and the area ratio increases from 1.65% to 3.85% with the stresses reduced from 1150MPa to 950MPa at the state of 500℃. With the reduction of stresses and the extension of rupture time, the martensite lath changes with shear deformation, fragmentation and rearranges. And the dislocation density decreases. The precipitated phase is always M6C before and after creep-rupture test.