Sliding friction and wear of Cu-graphite against 2024, AZ91D and Ti6Al4V at different speeds

Cu-graphite composite fabricated by powder metallurgy art is no longer novel material. However, it might be a versatile self-lubricating material sliding against different metals and alloys. In this connection, understanding towards its tribological behavior and wear mechanism is very important. Sliding tribological behaviors of Cu-graphite composite against different counterparts, specified as 2024 aluminium alloy, AZ91D magnesium alloy, and Ti6Al4V titanium alloy, were investigated over varied sliding speeds at room temperature in air. The friction and wear tests were conducted on a pin-on-disk tribo-meter. Tribological performance of Cu-graphite composite strongly depended on its counterpart materials. Cu-graphite composite could provide friction reduction in sliding against 2024 and Ti6Al4V. Cu-graphite composite was a good self-lubricating material in sliding against AZ91D at low speeds but not at 0.25 and 0.50 m/s. Wear mechanism of Cu-Gr composite was related to the transfer, counter-transfer, mechanical mixing and tribo-oxidation at tribo-interface. Sliding speed had influences on tribo-interface and thereby wear mechanism. Finally, the effects of naturally occurred oxide film and sliding speed were discussed.