Effect of nanoboron carbide particles on properties of copper-matrix/graphite composite materials

In this study, a new type of copper (Cu)-matrix self-lubricating composite was successfully prepared, which was based on nanoboron carbide (n-B4C) particles, Cu-coated graphite, and Cu powders, combined by powder metallurgy. These composites contained 2 wt% graphite as the lubricating phase and 0.2, 0.3, 0.5, 0.8, and 1.2 wt% n-B4C as the reinforcing phase. The effects of different amounts of n-B4C particles on composite properties and the composite wear mechanism were examined. All composites were characterized in terms of microstructure, density, porosity, hardness, compressive yield strength, and friction wear. The results showed that, with n-B4C particle addition, the hardness, compressive strength, friction, and wear properties were improved. With >0.2 wt% n-B4C, composite porosity gradually increased, and hardness, compressive strength, and friction and wear properties sharply decreased. With n-B4C addition, the main wear mode of the composites changed from adhesive to abrasive wear, then to adhesion and peeling wear with increased n-B4C particle content.