Characterization and Tribological Properties of Graphene/Copper Composites Fabricated by Electroless Plating and Powder Metallurgy

Self-lubricating copper matrix composites reinforced with graphene were prepared by electroless plating and powder metallurgy. The morphology and structure of graphene, Cu@graphene powder, and Cu@graphene/Cu composites were characterized and the tribological properties of Cu@graphene/Cu composites were investigated. The X-ray diffraction pattern of Cu@graphene confirms the coexistence of characteristic peaks of both copper and graphene, with a weakened characteristic peak of carbon impurity. The obtained morphology of Cu@graphene reveals that the surface of the graphene is completely covered with a uniform and compact copper layer with lots of copper nanoparticles. Raman and Fourier transform infrared spectroscopy analyses show that the oxygen functional groups and defects on the surface of the redox graphene can be reduced through the electroless plating process. The tribological results indicate that the coefficient of friction of Cu@graphene/Cu composites initially decreases and then increases with an increase in Cu@graphene content. The lowest coefficient of friction, which is about 29.47% lower than that of pure Cu, is achieved in the Cu@graphene/Cu composites with 3.0 wt% Cu@graphene. The chemical composition and topography of the wear tracks for Cu@graphene/Cu composites infer that the formation of a well-consolidated graphene-rich lubricious tribolayer at the contact surface and a higher microhardness work together to enhance the tribological performance of Cu@graphene/Cu composites.