Effect of Sintering Temperature and Hydrophobic Treatment on the Microstructure and Properties of Copper-Graphite Composites

Abstract

Copper-graphite composites were prepared by spark plasma sintering (SPS) using copper-coated graphite powder. Hydrophobic surfaces were successfully constructed by chemical etching and surface treatment. The density, metallographic structure, microstructure, Shore hardness, resistivity, water contact angle, and friction/wear properties of the composites were investigated using the Archimedes drainage method, a metallographic microscope, a scanning electron microscope, a hardness tester, a resistometer, a surface science tester, and a friction tester. The results showed that the relative density and Shore hardness of the copper—graphite composites increased slightly from 90.04% and 56 HSD to 92.66% and 59 HSD, respectively, when the sintering temperature increased from 700 to 900 °C. The copper and graphite phases in the copper-graphite composites were uniformly distributed with a continuous and network-like structure at various sintering temperatures. The interface between the copper and graphite was in good condition, without any obvious cracks or voids. The optimum process for hydrophobic surface construction included etching with a 1 mol/L K₂Cr₂O₇-H₂SO₄ solution for 1 min, and soaking in a 0.09 mol/L cetylbenzene sulfonic acid alcohol solution for 1 h. The contact angle of the copper—graphite composite reached 130°. Hydrophobic treatment was beneficial for reducing the friction coefficient (from 0.18–0.19 to 0.13–0.15) and the wear rate (from 4.1–6.2×10⁻³ to 1.1–2.1×10⁻³ mm³/(N·m)), demonstrating obvious antifriction and wear-resisting properties. The resistivities of the hydrophobic-treated samples increased slightly, from (4–8)×10⁻⁷ Ω·m to (5–15)×10⁻⁷ Ω·m, meeting the resistivity requirements of copper-graphite composite pantograph sliders and current receiver sliders in actual working conditions.