Tribological behaviors of graphite/epoxy two-phase composite coatings

To obtain a composite coating possessing both good conductivity and high wear resistance, a series of coatings with conductive graphite and epoxy resin were designed. The seepage critical value (SCV) of conductive coatings was used to identify the transformation between continuous phase and dispersed phase for graphite/epoxy composite coatings. Before SCV, the coatings were insulated with epoxy resin as continuous phase and the wear behavior was primarily characterized of adhesive wear with local adhesive spalling of epoxy resin. After SCV, the coatings appeared conductivity and the surface resistance decreased monotonically with the increase of graphite content. Both the curves of friction coefficient vs. graphite content and wear rate vs. graphite content showed the same model with two valleys at graphite content of 30% and 50%, respectively. At graphite content of 50%, an optimal solid lubricant film was obtained which leaded to the lowest friction coefficient and wear rate, due to a possible dynamic equilibrium between the transfer and spalling of debris. The tribological behaviors of these coatings were evaluated using a ring-on-block tribo-tester under dry sliding friction.