Preparation And Friction And Wear Properties Of Al₂O₃/C/MoS₂ Composite Coatings

MoS₂lubricating anti-wear coating has the advantages of low friction coefficient,low shear strength and strong surface adhesion,which is widely used in industrial production and mechanical parts.However,the single component MoS₂coating has poor wear resistance and thermal conductivity,which limits its application in high load and high speed conditions.At present,the introduction of hard particles and thermal conductive agent has become one of the important ways to improve the tribological properties of MoS₂-based composite coatings.In this thesis,MoS₂-based composite coating was prepared on the surface of ductile iron by spraying method,and phosphating film was introduced to improve the adhesion between film and substrate.The morphology of the composite coating and the friction and wear properties under different service conditions were studied.The friction and wear properties of MoS₂-based composite coating were improved by introducing hard particle alumina（Al₂O₃）and thermal conductive graphite（C）,and the wear resistance mechanism of Al₂O₃filler and the synergistic lubrication mechanism of C and MoS₂were further clarified.The main research contents are as follows:By introducing the’four in one’phosphating film,the adhesion between the composite coating and the substrate was significantly improved.The friction and wear properties of single component MoS₂composite coating under different service conditions were studied.It was found that under high load conditions,the microhardness of single component MoS₂-based composite coating was low,and the wear volume and wear rate were high.The coating had a large area of spalling and poor wear resistance;At high speed,due to the poor thermal conductivity of the composite coating,a large number of friction heat generated by high speed friction aggravates the wear of the coating,and the wear rate of the composite coating is higher and the wear resistance is poor.In view of the shortcomings of low microhardness and poor wear resistance of MoS₂-based composite coating,the microhardness of the composite coating was significantly improved by doping hard particle Al₂O₃,thereby improving the wear resistance of the composite coating at low speed and high load.The particle size and doping amount of Al₂O₃were investigated,and the results showed that 3%-8μm Al₂O₃/MoS₂composite coating had the best wear resistance.In view of the poor thermal conductivity and high wear rate of MoS₂-based composite coating under low load and high speed conditions,the thermal conductivity and wear resistance of the composite coating were significantly improved by C doping,and the C particle size and doping amount were explored.The results show that 3%-10μm C/MoS₂composite coating has the best tribological properties,and C and MoS₂can play a good synergistic lubrication mechanism.The Al₂O₃/C/MoS₂composite coating co-doped with Al₂O₃and C has the best wear resistance under high load and high speed conditions.The wear mechanism of the composite coating is mainly adhesive wear and contains abrasive wear.This paper innovatively through Al₂O₃and C co-doping,significantly improved the wear resistance of MoS₂based solid lubrication coating under high load and high speed conditions,and the lubrication and wear reduction mechanism of hard particles and thermal conductivity/solid lubricant doped MoS₂based solid lubrication coating was discussed.