Enhanced tribological properties of copper metal-matrix composites reinforced with fluorinated graphene oxide nanosheets

Applications of copper coatings on metal components are abundant owing to their high conductivities, corrosion resistance and anti-bacterial properties. However, applications of these coatings on moving parts are limited due to their poor tribological properties; tendencies to generate high friction and susceptibility to degradative wear. In this study, we have fabricated a fluorinated graphene oxide-copper metal matrix composite (FGO-CMMC) on a bearing steel substrate by a simple electrodeposition process in water. The FGO-CMMC coatings exhibited excellent lubrication performance under pin-on-disk (PoD) tribological sliding, which reduced CoF by 63 and 69%, compared to the GO-CMMC and pure copper coatings that were also prepared. The lubrication enhancement of the FGO-CMMCs is attributed to the tribochemical reaction of FGO with the AISI 52100 steel counterface initiated by sliding load. The formation of an asymmetric tribofilm structure on the sliding track is critical; the performance of the FGO/Cu tribofilm formed in the track is boosted by the continued fluorination of the counterface surface during PoD sliding, passivating the tribosystem from adhesion-driven breakdown. Other influences include the improved interlaminar shear strength of the FGO-containing composite. The excellent lubrication performance of copper coatings by FGO incorporation makes the CMMC a promising solid lubricant candidate for use in mechanical engineering applications.