One-step fabrication of wear resistant and friction-reducing Al2O3/MoS2 nanocomposite coatings on 2A50 aluminum alloy by plasma electrolytic oxidation with MoS2 nanoparticle additive

Wear resistant and friction-reducing Al2O3/MoS2 nanocomposite coatings were fabricated in-situ on 2A50 aluminum alloy substrate using one-step plasma electrolytic oxidation in silicate electrolyte solution with MoS2 nanoparticle addition. The effect of MoS2 incorporation on microstructure and wear resistance of the obtained ceramic coatings was investigated by regulating the concentration of MoS2 nanoparticle. Phase structure, microstructure, composition and wear resistance of the ceramic coatings were characterized by XRD, SEM, EDS, profilometer and ball-on-disc friction and wear tester. The results show that the anodic voltage of micro-arc discharge stage increased with the increasing of MoS2 concentration and the prepared ceramic coatings were mainly composed of alpha-Al2O3, gamma-Al2O3, MoS2, and mullite phases. The EDS mapping results show Mo and S elements were evenly distributed in the ceramic coatings indicating the formation of Al2O3/MoS2 nanocomposite coatings. Friction performance evaluation shows that the ceramic coatings obtained at the MoS2 nanoparticle concentration of 4 g/L exhibit the best wear resistance and antifriction property. During the friction and wear test, the protective lubricant film formed between ceramic layer and grinding parts is the largest and the average friction coefficient is the lowest, as low as 0.1. The wear rate was the lowest (about 5.28 x 10-4 cm3 center dot N-1 center dot m- 1). It can be concluded that MoS2 can play a good antifriction and lubrication effect in ceramic layer, optimize the microstructure of ceramic layer, and improve the wear resistance of ceramic layer.