Effect of Temperature on Tribological Properties of Cu-12.5Ni-5Sn-Graphite Self-Lubricating Composites

Cu-12.5Ni-5Sn-graphite self-lubricating composites were prepared by powder metallurgy. The mechanical properties and tribological properties of the composites with different graphite contents at elevated temperatures were investigated. The worn surfaces were analyzed by using scanning electron microscopy and Raman to investigate the friction, wear and lubricating mechanism. The results show that the hardness and yield strength of composites decreased with the increase of the graphite content. The temperature had a remarkable impact for the friction and wear properties of composites. At room temperature, the friction coefficient and wear rate of composites with 1% or 3% graphite were obvious lower than that of composite with 5% graphite. At 300 ℃, the composite with 3% graphite had the best friction and wear properties. At 500 ℃, the composite with 5% graphite content had the optimal tribological properties. At room temperature, the composite with the better self-lubricating properties were mainly attributed to the formation of almost smooth and continuous graphite lubricating film. At 300 ℃ and 500 ℃, the mixture lubricating film of some metallic oxides and graphite was responsible for self-lubricating performance of composites.