Effect of Graphite Content on the Tribological Performance of Copper-Matrix Composites Under Different Friction Speeds

The effect of graphite (Gr) content on tribological performance of copper-matrix composites against H13 steel was investigated using a pin-on-disk test in the range of 3.14-47.1 m/s. The composites with different weight fractions of Gr (up to 18%) were fabricated by powder metallurgy technique. The results showed that the friction coefficient and wear rate generally decreased with the increase in Gr content. However, the friction coefficient and wear rate differ at various speeds. At 200 and 500 r/min, the friction coefficient and wear rate kept lower with the increase in Gr content, because the third body of Cu-Al-3% Gr specimen had strong fluidity and plasticity. By contrast, the particle third body of Cu-Al-12% Gr specimen, which contained higher content of Gr, could roll easily. Increased Gr feeding to the third body was reasonable for the decreasing of friction coefficient and wear with the increasing of the amount of Gr content at the speed in the range of 1000-2000 r/min. Under the high-speed, the friction coefficient showed slight change because the friction temperature induced all the third bodies to extend and flow effortlessly without componential influence. However, wear decreased significantly because the third body possessed more metal, which favored attachment to the counter disk.