Study On Tangential Fretting Wear Characteristics Of TC6 Titanium Alloy And Coating

The continuous progress of advanced aero-engine development technology marks China Manufacturing transfer from a"manufacturing power"into a"manufacturing power".Among them,as the core component of aero-engine,its quality,performance and application of new materials greatly affect the reliability and service life of the engine.The blade damping boss is a close fitting point between two adjacent blades.Under the normal working conditions of the blades,vertical or horizontal micro-movement is likely to occur here,which affects the structural strength of the blade damping boss and the overall safety of the blade group.Therefore,it is of great significance to study the fretting wear failure of aero-engine blades and their related components.In consequence,the tangential fretting wear of the aero-engine blade damping boss material TC6 is studied,and the fretting wear mechanism of TC6 titanium alloy under different working conditions is also discussed in this thesis which will be instructive and meaningful to the optimization of aero-engine blade body materials and anti-wear coatings.The tangential fretting wear test of TC6 titanium alloy was carried out on the full-mode fretting wear test system which was developed by our research team independently.In the test,a ball/plane contact model was formed between the two contact surfaces of TC6titanium alloy plane sample and sillicon nitride ceramic balls which were used as the upper grinding pair.By changing the displacement amplitude,normal load,contact temperature and substrate surface coating,the fretting wear characteristics of TC6 titanium alloy under different working conditions were investigated.At the same time,scanning electron microscopy(SEM),energy dispersive analysis(EDS),electron probe(EPMA),white light interferometer and other characterization equipments were used to characterize the microscopic morphology of TC6 titanium alloy end-face wear spots,and to analyze the tangential fretting damage mechanism of TC6 titanium alloy and its coatings.The main conclusions are as follows:(1)Displacement amplitude and normal load both have significant effects on the tangential fretting wear of TC6 titanium alloy.When the normal load is constant at room temperature,with the increase of the displacement amplitude,the fretting operation transitions from the partial slip zone to the mixed zone,and finally stabilizes in the complete slip zone.On the contrary,when the displacement amplitude is constant at room temperature,with the increase of the normal load,the fretting operation moves from the complete slip zone to the mixed zone and stabilizes in the partial slip zone.When the fretting operation in partial slip region,the center of the wear scar shows a slight adhesive damage,and a small amount of wear debris accumulates on the edge due to the micro-slip.When the fretting operation in the mixed zone,the degree of wear is increased,the proportion of the adhesive area is reduced,abrasive wear and oxidative wear are generated,and the accumulation of wear debris is caused.When the fretting operation in the complete slip zone,severe plastic deformation occurs on the surface of the contact zone,and the degree of wear is severe.The micro-morphology shows typical characteristics of furrows,delamination,cracks,wear debris accumulation and small-scale adhesion.(2)The increase of temperature has obvious influence on the wear resistance of TC6titanium alloy.When the normal load,displacement amplitude and cyclic number are constant,and as the test temperature increases,the oxidative wear degree,wear scar width,wear depth,wear volume and wear rate all show an increasing trend.Compared with room temperature,high temperature promotes the degree of oxidation wear.After the oxidation of Al element in the sample,an alumina wear-reducing layer is formed,and the contact area of the original two-body contact of the grinding pair is greatly reduced,which inhibits the material wear under high temperature.It can be concluded that TC6 titanium alloy has better wear resistance and wear reduction performance when it is under the high temperature condition of this study.(3)Different coatings have different protective effects on the TC6 titanium alloy substrate.Through the study of tangential fretting characteristics of different coatings in the complete slip zone with the most serious fretting damage in TC6 titanium alloy,the evolution trend of F_t-D-N hysteresis curve and friction coefficient curve,as well as the degree of oxidation of wear scar microstructure.The results show that the T800 coating has less oxygen accumulation in the wear scar and the smallest wear volume,and has the best protection effect on the TC6 titanium alloy substrate.