Tribological behavior of cobalt/graphene composite coatings

Abstract Pure cobalt and cobalt/graphene composite coatings were fabricated on St37 steel substrates by using the electrodeposition method. The morphology and microhardness of the coatings were investigated. The tribological behavior of the specimens was evaluated under the normal loads of 5, 10, and 15 N and through the sliding distances of 300, 600, and 900 m at the ambient temperature. SEM images revealed that the graphene particles had been appropriately distributed within the cobalt matrix. Both the cobalt and cobalt/graphene composite coatings had a nodular-pyramidal morphology. However, the morphology of composite coating was finer than that of the pure cobalt film. According to the wear results, both the cobalt and composite coatings exhibited a much better wear behavior compared to the steel substrate. The co-deposition of graphene particles decreased the volume loss and friction coefficient of pure cobalt film. The volume loss increased by the increment of the applied load and sliding distance. However, increasing the normal load decreased the average coefficient of friction in all the samples. The main wear mechanism of all the samples was abrasion, except for the substrate at the high normal loads.