姿控飞轮用陶瓷球轴承失效特性分析

Failure Properties of Ceramic Ball Bearings of the Attitude Control Flywheel

通过氮化硅陶瓷球混合轴承和钢球轴承在干摩擦条件下的高速(5000r/min)运转试验,对比分析了电机驱动电流的变化特性和轴承运行噪声等指标,利用立体显微镜、扫描电子显微镜和X射线光电子能谱仪等分析混合陶瓷球轴承摩擦副的表面形貌,分析陶瓷球轴承的失效特征及其在无润滑条件下的长时间稳定运行机制.结果表明:陶瓷球轴承在临界失效阶段的电机驱动电流波动比普通钢制轴承小,在进入严重失效前可持续运行5h,比普通钢制轴承的运行时间长得多;陶瓷球以表面裂纹和表层剥离为主要破坏机制,滚道破坏机制主要表现为疲劳裂纹、点蚀及犁痕等多种形式;在运转过程中,陶瓷球轴承脱落的片状磨屑因脆性易形成微球体而被排出摩擦工作区,延迟了出现轴承运行卡死等现象.由于氮化硅陶瓷球混合轴承摩擦副的不同材质特性和损伤方式,使得其临界失效性能优于普通钢制轴承.

Currents of driving motor and the noise of bearing in rotating were comparatively analyzed through the experiment that a hybrid ceramic ball bearing and a steel bearing rotates at the high speed of 5 000 r/min without lubricants. In order to study the failure property and long-time stable rotating process, the surface feature of friction pairs of the hybrid ceramic ball bearing was investigated by stereomicroscope, SEM and XPS. Experiment results indicated that the driving current fluctuation of the bearing was weaker than general steel bearing at the stage of critical failure, and the operating life was longer than the steel bearing before the severe wear stage. Surface crack and peeling off of the ceramic balls were the two main forms of fatigue wear. The wear forms of both raceways were cracksing pitting and ploughing, etc. The longer operating life in critical failure states after the lubricating failed was attributed to ceramic exfoliation from the surface of balls at adherence abrasion sites due to its brittleness, and in the meanwhile the ceramic micro-spheres formed from the debris were extruded rapidly. The hybrid ceramic ball bearing in critical failure states after lubricating failure exhibited better than the steel bearing, owing to the differ- ence of the special properties and wear characteristics of the bearing friction-pairs.