Research On The Anti-Friction Properties And Corrosion Resistance Of MoS₂/Al₂O₃ Micro-Arc Oxidation Self-Lubricating Coatings Based On Electric Parameter Modulation

Aluminum alloy has been widely used in industry as a material with light weight,high strength and good processing performance,especially in the automotive manufacturing field,which provides important support for the development of automotive lightweighting.However,its further popularization and application were restricted due to its disadvantages such as low surface hardness,poor wear resistance,difficulty in lubrication and susceptibility to corrosion.Hence,surface modification of aluminum alloys is required to improve their friction and corrosion resistance.Accordingly,this research is based on the previous study of in-situ synthesis of MoS₂ self-lubricating coating to regulate the composition,morphology,pore structure,anti-friction properties and corrosion resistance of the MoS₂/Al₂O₃coating by regulating the electrical parameters.The MoS₂/Al₂O₃ self-lubricating coating was in-situ synthesized successfully on the surface of aluminum alloy by adding sulfur and molybdenum sources.With the increase of voltage,it shows an increase of MoS₂ content in the coating.Meanwhile,the porosity of the coating has the tendency to increase,then decrease and finally increase again,and the roughness shows an increasing trend.And the thickness and hardness and coating-substrate adhesion of the coating layer all show a trend of increasing first and then decreasing.In particular,the coating prepared at 450 V showed a reduction in porosity with the best thickness,hardness,and coating-substrate adhesion.At this time,the coating exhibits the best anti-friction properties and corrosion resistance,with the lowest coefficient of friction（about 0.2）and abrasion loss,as well as the smoothest abrasive surfaces without visible abrasive grains and grooves.Moreover,it has the most positive corrosion potential and the lowest corrosion current density.An effective lubricating function was provided by MoS₂ during the wear process,which enhanced the anti-friction properties of the coating and transformed the wear state from abrasive wear to adhesive wear.The pore structure of MoS₂/Al₂O₃ self-lubricating film layer can be optimized by regulating the duty cycle.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 power supply provides more energy in each cycle as the duty cycle increases,resulting in the formation of larger discharge channels and the ejection of more molten material,which causes the increase in surface porosity and overall porosity of the coating and tends to form connected pores.In contrast,the narrowing of the discharge channel and the filling of MoS₂ by decreasing the duty cycle led to a change in pore shape from connected to isolated pores and a decrease in porosity.The MoS₂/Al₂O₃ self-lubricating coating showed the best performance at 15%duty cycle with the lowest surface porosity（4.3%）and overall porosity（8.5%）,and the highest hardness and coating-substrate adhesion.Meanwhile,it had the best anti-friction properties with the lowest coefficient of friction（0.13）and abrasion loss,and its wear scar surface was smooth with no visible furrows or flaking.In addition,the pore structure with low porosity and isolated pores also contributed to improved corrosion resistance by inhibiting the propagation of corrosive media,thus the coating at 15%duty cycle has the best corrosion resistance.