Effect of Micro-Arc Oxidation on Friction–Wear Behavior of Cold-Sprayed Al Coating in 3.5 wt.% NaCl Solution

Abstract

A cold-sprayed Al coating on S355 steel was processed using micro-arc oxidation (MAO). The friction–wear behavior of the obtained coating in 3.5 wt.% NaCl solution was investigated using a wear test, and the effects of wear loads and speeds on the friction–wear performances of the MAO coating were analyzed. The results show that the MAO coating is primarily composed of Al2O3, with no other phases. The average coefficients of friction (COFs) of the MAO coating under the wear loads of 0.5, 1.0 and 1.5 N are 0.48, 0.62, and 0.76, respectively, and the corresponding wear rates are 4.20 × 10−5, 4.21 × 10−5 and 4.27 × 10−5 mm3 m−1 N−1, exhibiting the higher wear resistance. Under the wear load of 1.0 N, the average COFs of the MAO coating at the wear speeds of 5.0, 6.7 and 8.3 Hz are 0.32, 0.45 and 0.62, respectively; and the corresponding wear rates are 3.21 × 10−5, 3.49 × 10−5 and 4.21 × 10−5 mm3 m N−1, respectively, which increase with the increase in wear speeds. The wear mechanism of the MAO coating is fatigue wear and abrasive wear, and its wear resistance was better than the cold-sprayed Al coating.