Pore structure optimization of MoS2/Al2O3 self-lubricating ceramic coating for improving corrosion resistance

Abstract

As light alloys have inherent friction and corrosion problems, an appropriate ceramic coating is often needed to resolve these problems in tribological and corrosive environments. In this work, the optimized pore structure of MoS2/Al2O3 self-lubricating ceramic coating was designed by in-situ synthesis of MoS2 combined with plasma electrolytic oxidation (PEO) and regulating the duty cycle. The evolution of pore structure was investigated by X-ray computed tomography. It is found that the power supply delivers more energy in each cycle as the duty cycle increases, resulting in larger discharge channels and ejecting more molten material. The change of the pore shape from connected to isolated and the decreasing of porosity through decreasing the duty cycle, which was caused by the narrowing of discharge channel and reduction of molten oxide ejection are acquired. The isolated pores structure is conducive to superior corrosion resistance, which can blocks the penetration of corrosive medium. Additionally, MoS2/Al2O3 coating exhibit a 75% reduction in coefficient of friction over traditional PEO coatings. This coating preparation approach is expected to provide a newly strategy to optimize the pore structure of the self-lubricating ceramic coating by regulating electrical parameters.