铌微合金化重载齿轮钢的疲劳性能

Fatigue properties of niobium-microalloyed case hardening steels for heavy duty gears

利用旋转弯曲疲劳试验方法研究了三种重载齿轮钢渗碳后的疲劳性能。结果表明,添加铌能够细化重载齿轮钢组织,提高渗碳层硬度,从而提高其疲劳强度。同时,疲劳裂纹在渗碳层沿原奥氏体晶界扩展,铌微合金化重载齿轮钢的晶粒细化,从而可以阻碍疲劳裂纹的扩展。此外,扫描电镜观察疲劳断口发现,重载齿轮钢渗碳后疲劳裂纹起源于基体或夹杂物,夹杂物尺寸越小,疲劳性能越好。

Fatigue properties of three case hardening steels for heavy duty gears after carburization were investigated by means of rotating bending fatigue tests. The results indicate that Nb microalloyed steels possess finer microstructure and higher case hardness, resulting in higher fatigue limits. Intergranular fracture is observed in the fatigue crack propagation region of the carburized case, indicating that the finer prior austenite grain size in the carburized case of the Nb microalloyed steels can more effectively suppress fatigue crack propagating. Scanning electron micrographic observations on fracture surface show that fatigue cracks usually initiate from matrix or inclusions, and thus the smaller the size of inclusions is, the better the fatigue properties are.