Effect of Bimodal Structure on the Frictional Properties of Copper-Graphite Composites

In this study, we prepared Cu-graphite composites with a bimodal structure by spark plasma sintering using CuO, nickel-plated graphite (Ni-Gra) and Y2O3 with different particle sizes. The presence of the bimodal structure was demonstrated by EBSD. The copper-graphite composites with bimodal structure effectively suppress strain localization of friction and wear, while graphite has a lubrication effect, which can greatly reduce the friction coefficient of the material. The microstructure of the material surface as well as the abrasion marks were analyzed by SEM and 3D profiling. The microstructure results show that the Cu2O generated during the sample preparation process can improve the bonding effect between Ni-Gra and Cu matrix. The frictional wear results show that the bimodal structure of the copper-graphite composite is excellent frictional wear performance, mainly due to which the ultrafine grains (UFGs) bear most of the load during the friction process, while the plastic deformation of the coarse grains (CGs) plays the role of supporting the UFGs.