Study On Tribological Properties Of Solid Lubricating Films For Aerospace Bearings

As one of key component of aero-engines,aero-engine bearings play a vital role in the safety of aviation aircraft due to their smooth running,service durability and reliability.Aero-engine bearings are often used in severe operating conditions such as variable load,variable speed,high DN value,intermittent service,and oil-breaking.Their short life and poor reliability have become the bottleneck for the improvement of aero-engine bearing performance.In order to prolong the service life of aviation bearings and improve their working reliability,surface modification technology is used to prepare a solid lubricating film with excellent friction properties,low wear rate and high load-bearing capacity on the contact sub-surface.Graphite-like carbon films have attracted much attention from researchers due to their unique structure and excellent tribological properties.In order to explore the tribological behavior of graphite-like carbon films under starved lubrication and oil-breaking conditions,the tribological properties of graphite-like carbon films in the starved lubrication and oil-breaking conditions were studied.In order to improve the service performance of aero-engine bearings under abnormal working conditions,it provides theoretical and experimental basis for meeting the long-life and high reliability requirements of aero engines.The three film were prepared on GCr15 and Si(P100)substrates by magnetron sputtering.They are undoped GLC,GLC/Cr doped with Cr,GLC/WC doped with WC,respectively.The structure and mechanical properties of the three film were analyzed by SEM,Raman,XPS,nanoindenter and scratch tester.It was visible that the doping of Cr and WC increases the sp~2 carbon content of the Graphite-like carbon film,and the elastic modulus and hardness decrease,At the same time,the Cr doping improves the internal structure of the film and the bonding strength of the film to the substrate,However,the WC doping reduces the bonding strength of the film to the substrate.The tribological properties of the three films under the conditions of starved lubrication and oil-breaking were investigated by HSR-2M high-speed friction and wear tester and MFT-5000 multi-functional friction and wear tester,and the tribological adaptability of three films under the condition of starved lubrication and oil-breaking was explored.The results show that the three kinds of films have excellent tribological properties in the starved lubrication and oil breaking environments.but exhibit different anti-wear properties,and the lifes of the three films vary greatly,followed by GLC/Cr>GLC>GLC/WC.As the load and speed increases,the wear rate of the three films increases,The order between them is GLC/WC>GLC>GLC/Cr.and the main form of wear changes.The stress distribution of the three films was analyzed by the finite element software ABAQUS,and the effects of film thickness,material properties and friction coefficient were simulated to analyze the film stress by orthogonal test.The results show that the maximum Von Mises stress of the three films occurs in the working layer.The maximum Von Mises stress of the three films is ranked as GLC/WC>GLC>GLC/Cr.The order of influence of various factors on the film Von Mises stress is the friction coefficient between the working layer and the steel ball,the Poisson's ratio of the working layer material,the elastic modulus of the working layer material,the thickness of the transition layer and the thickness of the working layer.The primary and secondary factors affecting the Mesis stress of the film are the friction coefficient between the working layer and the steel ball,the Poisson's ratio of the working layer material,the elastic modulus of the working layer material,the thickness of the transition layer,and the thickness of the working layer.Appropriately reducing the elastic modulus of the working layer,increasing the Poisson's ratio of the working layer and reducing the surface roughness of the working layer can reduce the stress concentration of the film during the contact process;the design thickness of the film transition layer should be selected at 0.5?m.Left and right,and the thickness of the working layer should be selected to be about 1.5?m.