Experimental analysis of the tribological behavior of electroless nickel-coated graphite particles in aluminum matrix composites under reciprocating motion

Pure graphite particles and graphite particles coated with an electroless nickel (EN) film were introduced into an aluminum alloy via powder metallurgy to form two kinds of 6061 aluminum alloys. Tribological performances exhibited in unlubricated frictional contacts and in oil lubricated contacts were compared for both alloys. Variations in seizure resistance, friction behavior, wear mechanism, wear particle size, and wear loss were studied related to variations in graphite content of the aluminum composite material. A wear test machine equipped with an electrical contact resistance (ECR) function, in combination with the measurement of wear displacement, was used to investigate friction and wear performances and the wear mechanism. Wear rates and friction coefficient for the two kinds of alloys were compared to evaluate the tribological effect of the coated particles. The optimum graphite content in the alloys under both lubrication regimes was also determined.