Contact Load on the Current-Carrying Tribological Performance of Copper–Graphite Composites

This study investigates the current-carrying tribological properties and wear mechanisms of copper-graphite composites under varying contact loads. Two copper-graphite composites with different graphite content were prepared using the pressure sintering method. Current-carrying tribological tests were conducted at three distinct contact loads. Scanning electron microscopy, X-ray diffraction, laser confocal microscopy, and pin-on-disk tribological testing were utilized to examine the current-carrying tribological properties and the worn morphologies of the materials. The results indicate that, under the three contact loads, the friction coefficient of the copper-graphite materials ranged from 0.3 to 0.5, the wear rate was on the order of 10^-13 m³/(N·m), the average voltage drop varied between 0.7 and 1.6 V, and the average electrical noise ranged from 0.2 to 0.9 mV. The wear mechanism included delamination wear and a minor amount of abrasive wear, and the lubricating film formed on the surface was mainly composed of C, PbO, and CuO. Notably, copper-graphite composites with lower graphite content exhibited superior hardness, electrical conductivity, and relative density compared to those with higher graphite content. At a contact load of 0.31 N, the copper-graphite composite containing 30wt% graphite demonstrated the most favorable current-carrying tribological performance, characterized by the lowest wear rate (1.09 × 10^-13 m³/(N·m)), voltage drop (0.943 V), and electrical noise (0.234 mV).