渗碳轴承钢的显微组织和疲劳性能分析

Analysis of microstructure and fatigue performance of carburizing bearing steel

利用旋转弯曲疲劳实验机研究了一种高温渗碳轴承钢在对称循环应力下表现出的高周疲劳性能,测量了S-N曲线,绘制了疲劳升降图,计算了该实验钢的疲劳极限。利用光学显微镜观察,该实验钢的渗碳层组织是由隐晶马氏体+残留奥氏体+少量碳化物构成;心部组织是由细小板条马氏体+少量残留奥氏体+大量弥散碳化物构成。用扫描电镜观察了该实验钢的疲劳断口,分析了断裂特点。对疲劳断口的研究表明:旋转弯曲疲劳起裂主要是由钢表层或次表层的复合氧化物夹杂引起,从而导致断裂的发生。

The high cycle fatigue performance of carburizing bearing steel which was used in the field of aviation under symmetrical cycle stress condition was investigated by using rotating-bending fatigue testing machine. The S-N curves and fatigue up-down graph were obtained. The fatigue limit stress was calculated. Utilization of OM,the microstructure of carburized layer consists of crystal martensite,residual austenite and a few carbides,the microstructure of the center is lath martensite,a few residual austenite and a lot of carbides.The fatigue crack feature was analyzed by observing crack profile under SEM. The study of fatigue crack reveals that most of the fatigue cracks initiates at surface or sub-surface non-metallic inclusions of composite oxide,and then crack growth results in fracture eventually.