Preparation And Friction Performance Of MoS₂/Y Composite Coating For Piston Ring

Piston ring is one of the core components of the internal combustion engine.The piston ring suffered the severest wear due to the very harsh and complex working conditions.The MoS₂ self-lubricating coating with low friction coefficient and good wear resistance can be prepared on the surface of the piston ring,which can improve the friction and wear performance of the cylinder-piston ring tribo-pairs.However,pure MoS₂ coating prepared by the existing technology generally not limited by complex preparation process but also exhibits the loose structure,low hardness and adhesion and poor adaptability to different tribology environments.Chemical vapor deposition?CVD?technology has the advantages of simple process,strong film-based binding force,and good handling of complex shape.It is widely used in the preparation of anti-wear,corrosion resistance and oxidation resistance coatings.Rare earth element yttrium?Y?can enhance the coating's density,refine the crystal particles and enhance the film-based bonding force and improve the wear resistance of the coating.Therefore,in this paper MoS₂ lubricating coating and modified MoS₂/Y composite lubricating coating were deposited by CVD method,to study the influence of deposition parameters on the coating performance.This article focuses on analysis the tribological properties of the MoS₂/Y composite coatings in difference friction environments?atmospheric environment,deionized water,grease and lubricants?,and difference applied load,and analyze the factors that affect the friction coefficient and service life of the MoS₂/Y composite lubricating coating,to provide theoretical and experimental support of the prepared and application of MoS₂/Y composite lubricating coating.First,during the deposition of MoS₂ coating on the stainless steel substrate,it is found that a brittle iron-sulfur compounds layer will generate earlier,and the iron-sulfur compounds layer will not only hinder the formation of MoS₂ but also deteriorate the performance of stainless steel.On the surface of stainless steel pre-deposition of a TiN inter-layer can solve this problem.The effects of deposition parameters on the properties of the coatings were investigated.It was found that the temperature had significant effects on the surface morphology,composition and tribological properties of the coatings.The experimental results show that the MoS₂ coating deposited at 820 ? has better surface structure and less intermediates,and has better tribological properties than coatings that deposited under other temperatures.Subsequently,the modified MoS₂/Y composite lubricating coating was prepared by adding the rare earth element Y to the MoS₂ coating.The results showed that the addition of Y could make the surface particles of the coating smaller and eliminate the columnar crystals of the coating and make the coating structure more compact.The change of coating structure not only enhance the hardness and adhesion of the coating,but also improve the friction and wear properties of MoS₂ lubricating coating in the atmospheric environment.The MoS₂/Y composite coating not only has a lower friction coefficient,but also wear time up to 6 times longer than pure MoS₂ coating.It is also found that the tribological behavior of the MoS₂/Y composite lubricating coating is affected by the friction environment.When the friction is in the water environment,the composite coating is eroded by water and the wear process is intensifies.Under the lubricating oil condition,coating and lubricants form a composite lubrication effect,MoS₂/Y composite coating exhibit excellent tribological properties.When test the friction properties in a variety of applied load conditions,at the initial of friction process,the friction coefficient decreases with the load increases since the friction surface is elastoplastic contact,and the coating will occur peeling off after a long time friction,eventually leading to lubrication failure,and the load increase will accelerate this process.