| The spindle bearing is the "heart" of the aero-engine.It is the key and important components of the aero-engine.Because of working under the high speed(14500r/min),high load(50000N)and complex loading conditions,the bearings' service life has a direct impact on the aero-engine working life.In the service process of spindle bearings,there is the possibility of no oil lubrication due to the failure of the lubricating oil system,and the risk of overloading operation,during which the service conditions have exceeded the design service conditions of the spindle bearing.The bearing materials(M50 or M50NiL)and structural design cannot meet bearing service requirements for wear resistance and friction reduction.How to improve the service life of the spindle bearings under such special working conditions,is currently the field of innovation of various technologies.On the premise of not changing bearing materials and the design of structures,this article is doing research on the application of surface coating technology to improve the service life of spindle bearings under special working conditions,and the platform test and verification are carried out.In this paper,the typical structure and service condition of engine spindle bearings are analyzed.It is considered that the reasonable design of low temperature preparation condition of film is the basis of film preparation of high performance bearing surface.In this paper,a composite thin film system has been designed and constructed at low temperature by using multi arc,magnetron sputtering and PECVD composite technology.The anode layer ion source is selected to avoid the defects of low density and weak energy of the gas ion produced by the traditional glow discharge,and prevent the formation of ions bombarding residual droplets on the surface.Moreover,the gas ion source etching will not cause obvious heating effect on the parts,reduce the risk of the workpiece tempering,and improve the adhesion between the film and the substrate.Considering the key factor of the film/substrate adhesion-the internal stress of the film a tungsten(W)doped graded composite multilayer film is designed in this paper It can not only effectively reduce the internal stress of pure carbon based films,improve the toughness of films,but also improve the film/substrate adhesion of carbon based films.Meanwhile,the WC phase formed by W and C enhances the wear resistance of the films.Combined with the gradient composite multilayer structure,the toughness of the film and the film/substrate adhesion are further improved.The carbon based composite multilayer films prepared in this paper is proved to have negligible effect on the plastic deformation and contact fatigue properties of the matrix materials.by the contact mechanics software FilmDoctor Pro.On the basis of the optimized design of the film structure,the preparation process of DLC thin film doped with W,TiN thin flim and other multilayer structures flims has been studied in the following aspects:the effect of plasma etching energy on adhesion of film;the effects of W doping amount on mechanical and tribological properties of DLC thin films;the influence of hard impurity on the tribological properties of the films.the effects of different target current,substrate bias and deposition temperature on mechanical properties and Tribological Properties of TiN thin films;and the influence of bulk roughness on the friction and wear properties of the films.The optimized processing parameters is concluded from the research.Optimized Processing parameters of plasma etching is-400V ion source power,substrate bias 2kW,and processing time 60min.Process parameters optimization for W-DLC thin film is 10A ion source,rotating cathode target 7.5A,substrate bias-80V,and deposition temperature of 180?.Process parameters optimization for TiN film is 100A target current,substrate bias-80V,and the deposition temperature of 300?.The carbon based films were prepared on different roughness substrates and their tribological properties were tested.The effects of matrix roughness on the tribological properties of the films were investigated.The results show that when the substrate roughness is above Ra0.025,the prepared films show the best adhesion and the best friction and wear properties to meet the requirements of the design.In this paper,a low temperature system is designed and bulit to prepare composite functional films.According to the special structure of bearing,the special tooling for bearing and the special tooling for roll(ball)coating are designed and developed.The preparation of gradient composite multilayer film on bearing surface has been realized.The long life W-DLC film and TiN film have been prepared for the key parts of the bearing.the test on the host platform test platform is carried out.The evaluation results are as follows:The TiN film prepared by bearing guiding surface at low temperature has passed 50 hours performance test,while uncoated bearing failed before 8 hours.The W-DLC coating bearing has passed the 30 minute oil break test.The bearing works normally and the film remains intact.The bearing deposited with W-DLC composite film has passed the test of high speed and heavy load(speed 14500r/min and axial load 50000N),and the oil temperature of the coated bearing is always lower than that of the uncoated bearing(10-15 ?).The results show that compared with the bare bearings,the coated bearings have better wear resistance and lower coefficient of friction,reduce the heat generation of friction,effectively improve the service life of the lubricating oil,further ensure the lubrication effect of the bearings,and improve the service life of the bearing under the special working condition.To sum up,through the research work of this paper,a low temperature system is designed and bulit to prepare composite functional films.The designed gradient composite functional film effectively improves the service life of spindle bearings under special service conditions with heavy load and high speed.The research results will provide theoretical support and technical support for the design and development of the main shaft bearing of aero engines. |
PDF Full Text Request