Tribological behavior of copper-molybdenum disulfide composites

The dry sliding friction and wear behavior of Cu-MoS2 composite pins against bearing steel (AISI 52100) discs were investigated in order to determine the optimal additive content. The MoS2 content ranged from 0-40 vol%. The microstructure and composition of the worn surface, wear debris and transfer layer were observed and analyzed in detail to reveal the dominant friction and wear mechanisms. It is confirmed that MoS2 is an effective lubricant for copper matrix composites against steel because the friction coefficient decreased from 0.67 to 0.18 when adding 20 vol% of the MoS2. The wear rates of the composites tended first to increase then decrease as the MoS2 content increased. The high wear rates of Cu-5 vol% MoS2 and Cu-10 vol% MoS2 composites are mainly attributed to the cracks associated with the MoS2 particles, and the decrease of wear rate for composites with MoS2 above 20 vol% is derived from the formation of a nearly continuous lubricating film on the worn surface. The formation mechanism for MoS2 lubricating film has been clarified by observing its microstructure and characterizing its distribution in the worn surface.