Dry sliding wear behavior of plasma-sprayed aluminum hybrid composite coatings

Al-SiC _p composite and Al-SiC _p -C _p hybrid composite coatings were produced by plasma spraying of premixed powders onto A356 alloy substrates. Four composite coatings, Al+20 vol pct SiC _p , Al+20 vol pct SiC _p +C _p , Al+40 vol pct SiC _p , and Al+40 vol pct SiC _p +C _p , were obtained. The dry sliding wear behavior of these coatings and pure aluminum have been studied at a sliding velocity of 1 m/s in the applied-load range of 25 to 150 N (corresponding to a normal stress of 0.5 to 3 MPa). The composite coatings had a significantly improved wear resistance over pure Al. The composite coatings with a higher SiC _p content of 40 vol pct exhibited superior wear resistance than those with a lower SiC _p content of 20 vol pct. The presence of graphite particles had different influences on the wear resistance, depending on the applied load. At lower loads, graphite improved the wear resistance considerably. At higher loads, the wear resistance of the hybrid composite coatings was similar to that of the composite coatings without graphite particles. At lower loads, an oxidative wear mechanism was dominant. At higher loads, delamination was a major wear mechanism. Graphite particles did not change their wear mechanism at the same applied loads.