Tribological Behaviors of Cu/RGO/WS2 Composites in Air and Vacuum Environments

No single lubricant can provide effective lubrication in various environments. In this study, both graphene (RGO) and WS2 were added to the Cu matrix to prepare self-lubricating composites that can adapt to different environments. Three kinds of Cu-based composites containing different volume ratios of lubricants were fabricated by a hot-pressing method. The physical and mechanical properties of the composites were measured. The tribological behaviors of the composites were tested using a ring-on-disc wear tester in air and vacuum environments. Scanning electron microscopy, 3D laser scanning confocal microscopy, and X-ray photoelectron spectroscopy were used to characterize the worn surface of the composites. Monolayer RGO was prepared, and the I-D/I-G ratio of RGO was 0.85. The fabricated composites were mainly a mechanical mixture of Cu/RGO/WS2. The total volume of lubricant was constant in the composites, and the hardness increased and thermal conductivity decreased with increasing volume ratio of WS2 to RGO. In air, Cu-RGO exhibited the lowest friction coefficient and wear rate, and Cu-WS2 showed the highest. In a vacuum, Cu-WS2 demonstrated the lowest friction coefficient and wear rate, whereas Cu-RGO was worn through. RGO played the lead role in wear reduction and self-lubrication in air, whereas WS2 was dominant in a vacuum. Cu-RGO-WS2 had greater potential applications due to its low sensitivity to different environments.