Tribological behaviors of foamed copper/epoxy resin composites augmented by molybdenum disulfide and multi-walled carbon nanotubes

A novel foamed copper/epoxy (FCE) composite possessing improved wear resistance was developed as a rubbing pair material. The composites consist of an open-cell foamed copper skeleton and an epoxy resin and auxiliary additives, such as molybdenum disulfide (MoS₂) and multi-walled carbon nanotubes (MWCNTs). A universal UMT-2 friction and wear tester was utilized to study the tribological properties of the FCE composites under dry lubrication conditions. We found that the amount of MoS₂, the porosity of the copper foam, and the presence of the MWCNTs all have an effect on the friction and wear properties of the composite materials. The friction coefficient of the composite material gradually decreases as the amount of MoS₂ increases; however, the wear rate initially decreases and then increases. When the MoS₂ content is 30%, the wear rate reaches a minimum. The wear rate decreases as the porosity of copper foam decreases, but porosity has little effect on the friction coefficient. As the rotation speed of the grinding steel plate and the applied load on samples increase, the wear becomes more significant. The presence of MWCNTs also increases the strength and wear resistance of the epoxy resin matrix. Depth-of-field microscopy and scanning electron microscopy were employed to observe the worn-surface morphologies and wear mechanism. The worn surface of the FCE composite matrix is divided into three parts: the hollow metallic copper skeleton region, the polymer zone, and the transition zone copper skeleton that contains some polymer material. It is important to note that the wear mechanism of the various compositions is adhesive wear and slight abrasive wear, and the fatigue crack that runs perpendicular to the direction of movement begins to form at higher speeds, which results in a higher wear rate.