Wear Properties and Effect of Molds on Microstructure of Graphite Reinforced Copper Alloy Composites Made by Centrifugal Casting

摘要

Graphite reinforced copper alloy composites were cast using gravity and centrifugal casting techniques to identify the effect of graphite particles on microstructural formation and the effect of the casting techniques on the distribution of the particles. Melt containing either 5 or 120 um size graphite particles were gravity cast in both steel and graphite molds. Melts containing 5 mu m graphite particles were also cast in a horizontal centrifugal casting machine. Samples cast in the graphite molds exhibited much greater pore size than that found in the samples cast in the steel molds. Graphite particles moved to the inner periphery when influenced by centrifugal force, resulting in the formation of graphite-rich and graphite-free zones. The volume fraction of graphite particles near the inner periphery was 13 percent, which is higher than the initial volume fraction of graphite particles (7 vol. percent) added into the melt. The results of wear testing showed that the friction coefficient of the pin from the graphite-rich zone is 0.49 and 0.69 for the pin from the graphite-free zone. The size of the machining chips from the graphite-rich zone was much smaller than those from the graphite-free zone. These results suggest that this composite may be an attractive substitute for copper alloys containing