The Tribological Behaviors of Self-Lubricating Composites as Filler in Copper Foam

A copper foam-based (CFB) self-lubricating composite was developed as a friction pair material. The composite consists of copper foam with three-dimensionally interpenetrated pores and solid lubricant fillers (polytetrafluoroethylene [PTFE] and MoS2). The thermal and electrical conductivity, bending strength, and tribological properties of the new composite were investigated. The friction and wear properties were investigated on a M-2000 model ring-on-block test rig. An electric field was imposed between the sample and ring to monitor the tribochemical reaction and formation of transfer film by means of contact resistance. Measurement of friction temperature was carried out by means of three thermocouples embedded in the material. The friction coefficients of the CFB composite decrease slightly, and the wear rate substantially decreased overall compared with that of the homologous polymers. The optical and scanning electronmicrographs (SEM) of the frictional surfaces show the worn surface of the CFB composite. The main wear mechanism was three-body abrasion, caused and promoted by plastic deformation, abrasive wear, and fatigue spalling. X-ray photoelectron spectroscopy (XPS) analysis showed that the reactions of MoS2 with Cu accompanied by their respective oxidation reactions are involved in the identifiable copper area.