Friction and Wear Behavior of Copper‐graphite Composites with Different Compositions in Water Environments

Copper-graphite composites with different copper content are prepared by spark plasma sintering (SPS) at 900 °C using copper-coated graphite powder and ordinary graphite powder as raw materials. Two groups of specimens are used for friction testing, including the original specimens and K2Cr2O7-H2SO4-etched specimens. The density, microstructure, Shore hardness, resistivity and friction and wear properties of the samples were investigated using the Archimedes drainage method, scanning electron microscopy, a hardness tester, a resistance tester, and a friction tester. The results showed that the relative density of the samples with different compositions reached about 90 %, and with an increase of copper content, the density and the relative density of the copper/graphite composites increased. As the copper content increased from 10 wt % to 50 wt %, the Shore hardness of the composites increased from 37 HSD to 59 HSD. Under dry-friction conditions, with an increase of Cu wt %, the friction coefficients and wear rates of the original specimens showed a downward trend, while those of the chemically etched specimens first increased and then decreased. Under water-friction conditions, both the original samples and chemically etched samples show very low friction coefficients, about 0.15 and 0.12, respectively, which are far lower than the friction coefficients (∼0.20) obtained under dry-friction conditions. The wear rates of the original specimens decreased with an increase of copper content, while those of the chemically etched specimens increased first and then decrease. The electrical conductivities of the copper/graphite composites were slightly reduced by chemical etching, but the resistivity of the copper/graphite composites remained at a low level of 10−7 Ω⋅m for a copper content of 40–50 wt %.