The Preparation And Tribological Properties Of MoS₂/Ti(Zr) Composite Coatings

Molybdenum disulfide,as a kind of excellent solid lubricant material has been used widely,but MoS2 coatings are easily oxidization and failure in humid environment,thus limiting its applications.For improving the oxidation resistance of MoS2 coatings,mainly by doping metals to improve its performance at present.Doping Ti in MoS2 is currently the most widely used,not only improve the oxidation resistance of MoS2 coating in humid environment,but also keep the composite coatings has lower friction coefficient.The purpose of this study is to find a kind of metal doped in MoS2 coating not only improve the oxidation resistance of MoS2 coatings in humid environment but also has lower friction coefficient than MoS2/Ti composite coatings.In this study,MoS2/Ti?MoS21Zr and MoS2/Ti/Zr composite coatings have been deposited by closed field unbalanced magnetron sputtering system.The content of Ti and Zr in composite coatings was controlled by varied the currents of Ti and Zr targets applied to targets.The phase composition and micro-structure of all MoS2/Ti(Zr)coatings were examined by X-ray diffraction,Atomic force microscope and Transmission electron microscope.The hardness,adhesion to substrates and friction coefficient of MoS2/Ti(Zr)composite coatings were characterized by nano-indentation test,scratch tests and the friction and wear tests.The X-ray diffractometry,Transmission electron microscope analyses revealed the nature of MoS2 coating was crystalline and the layered structure on the direction parallel to the substrate.MoS21Ti/Zr composite coatings as a whole were amorphous,but a small quantity of nanocrystalline has been found inset into amorphous.The hardness and modulus of MoS2/Ti(Zr)composite coatings have been increased obviously.With the increasing of the target currents applied to Ti target or Zr target,the hardness and modulus of MoS2/Ti and MoS2/Zr composite coatings increased.The adhesion to substrates of these composite coatings has been improved after doped Ti and Zr in MoS2 at the same time.The surfaces roughness of MoS2/Ti(Zr)composite coatings is smaller than pure MoS2 coating.In addition,the surface roughness of MoS2/Zr composite is smaller than MoS2/Ti and MoS2/Ti/Zr composite coatings.MoS2/Ti(Zr)composite coatings not only show low friction coefficient but also show long endurance life under the same load.With the increasing of the load,the friction coefficient of MoS2 and MoS2/Ti(Zr)composite coatings both increased.Similarly,MoS2/Zr composite coating showed the lower friction coefficient compared to MoS2/Ti and MoS2/Ti/Zr composite coatings in air condition.While MoS2/0.3Ti/0.4Zr and MoS2/0.4Ti/0.4Zr composite coatings showed excellent tribological behavior compared to other MoS2/Ti(Zr)composite coatings in humid environment.