Structure And Tribological Properties Of VN-based Composite Coatings Prepared By Arc Ion Plating

With the rapid development of aerospace field,more requirements are put forward for high temperature,high speed and heavy load operations.It is urgent to develop excellent performance,high efficiency and durable solid lubricating materials at elevated temperature,especially to design and produce materials with low friction coefficient and high wear resistance over a wide temperature range.As a preliminary intelligent lubricating material,temperature self-adaptive lubricious coating provides a good design idea and feasible process method.In this paper,a series of VN-based coatings were deposited in N₂ and C₂H₂ atmosphere by multi-arc ion plating.The chemical composition and microstructure of the coatings were characterized and the hardness of the coatings was measured by nanoindentation.In addition,the tribological properties of the coatings under different temperatures were evaluated by multi-functional friction and wear tester.Based on the high temperature and oxidation backgrounds,a new way to design self-lubricating composite coatings for creating VAlCN/VN-Ag coating was put forward,and a specific process plan for deposition of VAlCN coatings was formulated.By adjusting the flow rate of C₂H₂,the effects of carbon contents on the microstructure,mechanical and tribological properties of VAlCN coatings were explored.The VAlCN coatings annealed under various temperatures showed different microstructures and properties.The coating possessed the smallest friction coefficient after annealing at 550?due to in situ V₂O₅ oxidized lubricating phase,which provided excellent antifriction and wear resistance.By multicomponent doping into coatings,four kinds of VN-based composite coatings were prepared,including Ag and Al elements,which can improve lubricating behavior and enhance mechanical properties of coatings,respectively.The effects of introducing C,Ag and Al element on the properties of the composite coatings were detected.The results revealed that Al element can strengthen the hardness,elastic modulus and wear resistance of the coatings.Doping Ag lowered the hardness and load-carrying capacity of the VAlCN-Ag coating.The amounts of sp² hybrized carbon were closely correlative with reducing the friction coefficient of the coating.Thermodynamically driven Ag diffusion and high temperature oxidation products AgVO₃ and Ag₃VO₄ greatly reduced the friction coefficient due to the synergistic lubrication,and achieved the generation of low friction reaction film induced by high temperature tribochemistry reaction.The VAlCN/VN-Ag multilayer coatings were designed and deposited in a Flex-coat850 system.The mechanical and tribological properties were evaluated.The tribochemical effects of multilayer VAlCN/VN-Ag and composite VAlCN-Ag coatings on wear surfaces at different temperatures were investigated.It was found that multilayer VAlCN/VN-Ag coatings had better mechanical properties than composite VAlCN-Ag coatings.The silver slow-release effect and oxygen barrier mechanism of multilayer interface were analyzed.The friction reduction and wear resistance mechanisms of multilayer and composite coatings at different temperatures were revealed.