Friction behavior of co-continuous alumina/aluminum composites with and without SiC reinforcement

Co-continuous alumina/aluminum composite materials with excellent physical and mechanical properties offer great potentials for lightweight, wear resistant, and high-temperature applications. Composite materials prepared from a liquid-phase displacement reaction present a unique microstructure in which each phase is a continuous network penetrated by the network of the other constituent. The frictional and wear effects of adding SiC particulate to the co-continuous composite, as well as the application of MoS2 coatings were examined. Pin-on-disc experiments were performed between 440C stainless steel balls and composite disc samples of alumina/aluminum at 0.2 m/s sliding velocity, with loads of 0.25 and 0.75 N. Microstructural analysis of the composites, wear scar analysis on the composite discs, and material transfer to the steel balls were examined using a scanning electron microscope equipped with an energy-dispersive X-ray spectroscope. The coefficients of friction obtained from the Al2O3/Al composites with and without the SiC particulate reinforcements were correspondingly 0.9 and 0.7 at 60 m sliding distance. Transfer of aluminum to the steel counterface was not observed and the debris consisted mostly of iron oxide for all tests without the MoS2 coatings. The friction coefficients dropped to 0.1 when the composite surface was burnished with a MoS2 coating. The SiC particulate-reinforced Al2O3/Al ONNEX composites showed higher wear resistance and caused a lower wear rate on the steel counterface than the unreinforced Al2O3/Al ONNEX composite.