三种粘结固体润滑涂层微动磨损性能比较研究

Comparative Study of Fretting Wear Behavior of Three Kinds of Bonded Solid Lubricating Coatings

采用Deltalab-Nene型微动摩擦磨损试验机和UMT-2型通用摩擦磨损试验仪对比考察了42CrMo钢基体表面MoS2基、石墨基、PTFE基粘结固体润滑涂层的微动磨损性能及其同涂层划痕临界载荷的相关性;基于微动损伤表面和截面扫描电子显微分析以及涂层原始表面和微动磨损表面X射线衍射分析,探讨了几种涂层的微动损伤机理.结果表明:3种涂层的减摩抗磨性能并不简单取决于其同基体的结合强度,而是同时与涂层本身的机械力学性能和微结构密切相关;涂层在微动早期经历较轻微的塑性变形和流动,并可沿滑动方向发生晶粒择优取向,进而在偶件磨损表面形成转移膜,从而有效地起到减摩抗磨作用;涂层的失效主要归因于往复疲劳应力作用下的裂纹萌生、扩展以及层状剥落.

The fretting behaviors of MoS2-based, graphite-based (G-based), and polytetrafluoroethylene-based (PTFE-based) bonded solid lubrication coatings were comparatively investigated. The critical loads of the three kinds of coatings were determined on a scratch tester and correlated with the fretting behaviors of the coatings. Moreover, the original surfaces and the fretted surfaces of the coatings were analyzed by means of scanning electron microscopy and X-ray diffraction. It was found that all the three coatings were able to form transfer films on the counterpart steel surface in the presence of mild plastic deformation and flowing, which contributed to significantly decreasing the friction and wear during the fretting process. The three kinds of coatings were characterized by tangential preferential orientation during the early-stage fretting. The critical loads of the three kinds of coatings were ranked as MoS2-based coating > PTFE-based coasting > G-based coating, which was not all the same as that of the friction-reducing and antiwear abilities which were ranked as PTFE-based coasting > MoS2-based coating > G-based coating. This indicated that the fretting friction and wear behaviors of the coatings were not only dependent on their critical loads but also on their mechanical properties and microstructures. Moreover, the lubrication failure of the tested bonded solid lubricating coatings was attributed to the fretting-induced plastic deformation and flow, the initiation and propagation of cracks, and the superficial peeling off in the presence of reciprocal cyclic fatigue stress.