Role of Cr-carbide Coating on Graphite Particles in the Mechanical and Wear Behavior of Graphite/Copper Composites

Graphite/Cu composites have attracted intensive attention for engineering applications under dry sliding conditions due to their excellent thermal, electrical and self-lubrication performances. However, their mechanical and anti-wear properties are usually restrained by the fragility of graphite as well as the poor interfacial bonding between graphite and copper. Herein, Cr-Carbide coatings, synthesized on graphite particles by molten salt method, were introduced as interfacial layers to prepare graphite/Cu composites by vacuum hot pressing process for improving the mechanical and wear properties of the composites. The coating was composed of Cr 3 C 2 and Cr 7 C 3 phases with an average thickness of several micrometers. The flexural strength, electrical conductivity, and friction and wear behaviors of the composites were evaluated. Dry-sliding friction tests were performed at room-temperature using a reciprocating ball-on-disc tester. The results showed that the carbide coating was beneficial for the improvement of interfacial bonding, so that the flexural strength and electrical conductivity of the composites increased. Moreover, the carbide coating could maintain the load carrying capacity of the contact plane and stability of the friction films, proving helpful in keeping the wear mode as mild abrasive wear, rather than severe delamination wear that occurred on the uncoated composite. Comparing the performance of the composites containing 70 vol.% coated and pristine graphite, the coated graphite/Cu composite had an appropriate friction coefficient, particularly at high normal loads, and its flexural strength and electrical conductivity were increased by 160 and 85%, respectively, and the specific wear rate was decreased by 70%. Graphical Abstract