Microstructures and tribological properties of MoS2 overlayers on MAO Al alloy

To improve tribological properties of micro-arc oxidation (MAO) coating, MoS2 overlayers with self-lubricating effect were prepared by hydrothermal synthesis. The results showed that MoS2/MAO coating was mainly composed of MoS2, γ-Al2O3 and mullite phases. With an increase of hydrothermal temperature, crystallinity, thickness and continuity of the MoS2 overlayer were increased. E2 g/A1 g ratio in the Raman spectra experienced a decrease from 0.738 to 0.493. XPS and TEM analysis discovered that oxygen was incorporated into the MoS2 at lower hydrothermal temperature from incomplete decomposition of MoO42-. Wear tests evidenced a lower average COF and better self-lubricating effect in the MoS2 synthesized at lower temperature. It was concluded that oxygen-incorporation into the MoS2 improved self-lubricating effect due to alignment to basal-plane orientation.