Study On Preparation And Wide Temperature Range Tribological Properties Of NiCrAlY/NiCrAlY-Ag-MoS₂ Multilayer Films

Nickel-based self-lubricating film has excellent mechanical properties,oxidation resistance and tribological properties in a wide temperature range,which is of great significance to improve the service life and properties of friction parts in a wide temperature range.In this paper,nickel-based self-lubricating films were prepared based on the theory of in-situ reaction formation of lubricating phase and multi-lubricating phase cooperative lubrication.The effects of multiphase coupling on the microstructure and tribological properties of the films in a wide temperature range were studied,and the friction and wear mechanisms of the composite films at different temperatures were analyzed.In this paper,NiCrAlY-MoS₂ films with different MoS₂ content and NiCrAlY/NiCrAlY-Ag-MoS₂multilayer films with different modulation ratios were prepared on the surface of GH4169superalloy by ion source composite magnetron sputtering technique.The chemical composition,microstructure and mechanical properties of different films were analyzed by EDS,SEM,XRD,Raman,microhardness tester and Rockwell hardness tester.At the same time,the friction and wear testing machine was used to study the tribological properties of the film in a wide temperature range,and the friction and wear mechanism of the film at different temperatures was studied by detecting and analyzing the wear marks after friction tests at different temperatures.The effect of MoS₂ doping on the properties of NiCrAlY-MoS₂ thin films was studied.The results show that the density and microhardness of the NiCrAlY-MoS₂ films are decreased by MoS₂ doping,but the tribological properties of the NiCrAlY-MoS₂ films are improved by MoS₂ doping.The friction coefficient of the films is reduced to 0.038～0.09,and the minimum wear rate reaches 2.14×10^-6 mm³/Nm.The NiCrAlY-MoS₂ films still exhibit good wear resistance after high temperature oxidation.The NiCrAlY-MoS₂ films show good comprehensive properties when the MoS₂ doping amount is 48.1%.NiCrAlY/NiCrAlY-Ag-MoS₂ multilayer films with different modulation ratios were prepared.The effects of modulation ratio on the structure and properties of NiCrAlY/NiCrAlY-Ag-MoS₂ multilayer films were studied.The results show that the compactness and mechanical properties of the film are improved by the multi-layer structure,and the maximun hardness of the multilayer film can reach to 426 HV.At low temperature,the friction coefficient of multilayer films increases with the increase of modulation ratio.At500℃,the friction coefficient of multilayer films are in the ranges of 0.3～0.35,and the wear rate of the films decreases to 5.08×10^-5 mm³/Nm with the increase of modulation ratio.The multilayer films with modulation ratio of 1:2 show good tribological properties at room temperature to 500℃.It is found that MoS₂ lubricated the multilayer film at low temperature,while Ag and Mo₄O₁₁ lubricated the film at 500℃.The NiCrAlY/NiCrAlY-Ag-MoS₂ multilayer films were oxidized at high temperature.The results show that the structure density and mechanical properties of the multilayer composite films are greatly improved by oxidation treatment,and the hardness reaches580～630HV.The multilayer films with modulation ratio of 1:4 after oxidation treatment show good tribological properties at 25～700℃.The friction coefficient is between 0.3～0.34 and the wear rate is at order of 10^-5 mm³/Nm in the whole test temperature range.At 700℃,synergistic solid lubrication is provided by the formed Mo O₃ and Ag₂Mo O₄.