The Micro-Tribological Behavior and Friction Mechanism of the Graphite/Cu Composites and Copper-coated Graphite-graphite/Cu Composites

Abstract The ring-block tribological behavior of the graphite/Cu(G/Cu) composites and copper-coated graphite-graphite/Cu(CCG-G/Cu) were studied by observing the friction coefficient,wear rate,microstructure and morphogoly of the composites after friction experiments.SEM and TEM were used to character the micro-morphology and micro-structure of debris,friction surface and friction cross section of the composites.The results show that adding 20wt% copper-coated graphite could reduced the friction coefficient and wear rate of the composites.The micro-morphology and micro-structure show that the copper phase are undergo oxidation and plastic deformation under cyclic stress,results in abundant deformation area in copper-rich zones.Interlaminar shedding and intramolecular tearing occurs in graphite phase,and then laid flat on the friction surface,forming a friction film with higher integrity and reducing the friction coefficient of the composites.The TEM images of the friction cross section show that deformation zone is mainly composed of accumulation zone,drag zone and carbon film.The simulation of the friction process shows that the initial stage is mainly dominated by abrasive wear and adhesive wear.With the progress of the experiment,the exposed copper phase is oxidized and oxidative wear occurs,graphite is shed and transferred to the contact surface.In the later stage of the experiment,a complete friction film with high graphite content is formed on the contact surface,which is mainly dominated by fatigue wear.