PTFE填充铜网复合材料损伤过程研究

Study of Damage Processes in PTFE-filled Copper Mesh Composites

为了研究聚四氟乙烯(PTFE)填充铜网复合材料的摩擦磨损性能以及细观损伤机制,使用往复摩擦磨损试验机对其进行全寿命磨损测试,并用扫描电子显微镜、光学显微镜和三维形貌仪对材料摩擦面及磨屑进行表征。结果表明:PTFE填充铜网复合材料全寿命(202 h)磨损过程主要分为磨合、稳定磨损和严重磨损3个阶段;在前20 h磨合阶段,摩擦因数逐渐升高,高载荷下大量的PTFE被挤出导致磨损率较大,同时转移膜生成,失效形式主要为机械剪切力下的剥落。在20~190 h稳定磨损阶段,摩擦因数先降低再升高且波动较大,磨损率趋于稳定,磨损机制主要为磨粒磨损,磨屑由层片状向粉末状转变,材料摩擦面粗糙度逐渐降低且磨损不均匀。通过微观表征,发现铜网编织结点与凸峰处磨损严重,通过受力仿真分析,发现铜网编织结点与凸峰处有应力集中现象,与试验中磨损严重的区域正好相对应,试验与数值模拟相关联。在190~202 h严重磨损阶段,摩擦因数和磨损量进一步升高,材料的耐磨性能与润滑性能急剧下降,最后材料被磨穿失效。

In order to investigate the frictional wear performance and fine damage mechanism of polytetrafluoroethylene(PTFE)-filled copper mesh composites,full-life wear tests were conducted using a reciprocating friction and wear tester,and the material friction surface and wear chips were characterized by scanning electron microscopy,optical microscopy and three-dimensional morphometry.The results show that the full-life(202 h)wear process of PTFE-filled copper mesh composites is mainly divided into three stages:wear-in,stable wear and severe wear.In the first 20 h wear stage,the friction coefficient gradually increases,and a large amount of PTFE is extruded under high load,resulting in a large wear rate,while a transfer film is generated,and the failure is mainly in the form of spalling under mechanical shear.In the 20 h to 190 h stable wear stage,the friction coefficient first decreases and then increases and has a large fluctation,and the wear rate tends to be stable.The wear mechanism is mainly abrasive wear,and the abrasive chips change from lamellar to powder.The roughness of the friction surface gradually decreases and the wear is not uniform.Through microscopic characterization,it is found that the copper mesh weave junction and the convex peak are seriously worn.Through force analysis,it is found that the copper mesh weave junction and the convex peak have stress concentration phenomenon,which corresponds to the area of serious wear in the test,the test and numerical simulation correlate.In the 190 h to 202 h severe wear stage,the friction coefficient and wear amount further increase,and the wear resistance and lubrication performance of the material decrease sharply,and finally the material is worn through and failed.