Effect of NaAlO₂ Co-Electrical Parameters on the Wear Resistance of MAO/MoS₂ Self-Lubricating Composite Coatings

This study aims to enhance the wear resistance of MAO/MoS₂ composite coatings fabricated on TC4 titanium alloy substrates through a composite process of microarc oxidation (MAO) and hydrothermal synthesis. The MAO treatment experiments were designed according to the L16 (4⁵) orthogonal array to optimize the NaAlO₂ concentration and electrical parameters (oxidation voltage, frequency, duty ratio, and treating time), with four levels for each factor. The optimized MAO process parameters were identified as a NaAlO₂ concentration of 10 g/L, an oxidation voltage of 500 V, a frequency of 200 Hz, a duty ratio of 20%, and a treating time of 30 min. The experimental results indicated a notable reduction in porosity, from 4.45% to 0.30%, in the optimized composite coating. Concurrently, there was a 43.2% increase in microhardness and a 327.9% increase in adhesive strength. Furthermore, the average coefficient of friction (CoF) of the composite coating was observed to be 0.13 at a high load of 20 N and a wear time of 20 min, representing a significant reduction of 68.5% compared to the CoF of the single MAO coating.