Study On Self-lubricating Modification Technologies And Tribological Properties Of Flame Sprayed Nickel-based Coatings

Nickel-based coatings with high hardness and good wear resistance are widely used in surface protection and performance improvement of mechanical equipment components.However,the lack of lubrication phase limits its application in lubricating components.In order to improve the tribological properties of flame sprayed nickel-based alloy coatings,the flame sprayed Ni60 coatings were firstly modified with three kinds of composite self-lubricating materials,and then the effects of different self-lubricating modification technologies on the microstructure and tribological properties of flame sprayed nickel-based coatings were studied in this paper.Firstly,Ni60/CaF₂ composite coating was prepared by flame spraying Ni60 and CaF₂powder mixture.The microstructure and tribological properties of the composite coating were studied.The results show that,compared with the flame spraying Ni60 coating,although the content of metal bonding phase in the Ni60/CaF₂ composite coating was reduced due to the addition of CaF₂,which lead to a decrease in the hardness and bonding strength of the coating,and an increase in the wear rate,the friction coefficient of the composite coating was significantly reduced.In comparison,when CaF₂ was added at20wt.%,the friction coefficient of the composite coating decreased significantly,while the wear rate increased only slightly,indicating that the composite coating had good anti-friction and wear-resisting performance.Secondly,self-lubricating materials MoS₂ and PTFE were used to seal the pores of the flame sprayed Ni60 coating,and the microstructure and tribological properties of the prepared Ni60/MoS₂ and Ni60/PTFE composite coatings were studied.The results show that MoS₂ and PTFE can be introduced into the surface and internal pores of Ni60 coating by hydrothermal synthesis and impregnation/sintering technology respectively,which can significantly reduce the porosity of Ni60 coating and improve the mechanical properties of the coating.In the process of friction and wear,continuous MoS₂ and PTFE lubrication films were formed on the worn surface of the coating,which reduced the adhesive wear and abrasive wear between the coating and the counterpart,and greatly improved the tribological properties of the coating.Finally,the Ni60/CaF₂ coating was sealed by using the hydrothermal synthesis MoS₂,and the microstructure and tribological properties of the prepared Ni60/CaF₂/MoS₂composite coating were studied.The results show that Ni60/CaF₂/MoS₂ composite coatings with two lubricating phases were successfully prepared by double composite technology,and the lubricating phase CaF₂ and MoS₂ were well combined with the binding phase Ni60.In the process of friction and wear,CaF₂ and MoS₂ played the role of anti-friction and lubrication,while Ni60 alloy phase played the role of wear resistance and load bearing.The synergistic action of these three components significantly improved the tribological properties of Ni60/CaF₂/MoS₂ composite coating.