Research On Frtting Wear Behavior Of CuMg0.4 Alloy

Relatively stationary mating surfaces are susceptible,which leads to micron-level relative motion.This relative motion is called fretting,and component damage caused by fretting is called fretting wear.The existence of fretting wear will greatly reduce the normal service life of the component,and in severe cases may also lead to the premature failure of the component.The integral dropper is an indispensable part of the overhead contact system which is a crucial component in the high-speed railway system.As a result,the researches on the fretting wear behavior of integral dropper,which aims to extend the service life of dropper under the conditions that the safety of service is ensured,have significant impact on the operation of high-speed railway system.Cu Mg0.4 alloy,the integral dropper material for high-speed railway overhead contact system,is used as the research object of this thesis,and the fretting wear test under different working conditions is carried out using a self-designed fretting wear test equipment.Combined with characterization analysis methods such as Scanning Electron Microscope(SEM),Energy Dispersive Spectrometer(EDS),Electron Microprobe(EPMA),X-ray Photoelectron Spectrometer(XPS)and White Light Interferometer(WLI),to reveal the response of the tribo-chemical state on the fretting wear mechanism and fretting wear resistance.The main conclusions can be draws as follows:(1)By classifying the trend of the real-time F_t-D curve shape during the fretting wear test of Cu Mg0.4 alloy,the fretting running characteristics can be divided into three fretting regime:partial slip regime(PSR),mixed fretting regime(MFR)and slip regime(SR).The wear mechanism in the partial slip regime is dominated by adhesive wear,while the slip regime is dominated by abrasive wear and oxidative wear.The wear mechanism in the mixed fretting regime is the coexistence of elastic and plastic deformation,and cracks are likely to occur in the mixed fretting regime.(2)Observed during the different frictional operation stages of the slip zone,it is found that the friction coefficient of the worn surface rises rapidly within a short number of cycles after the start of the test.After rising to the maximum value,the friction coefficient drops rapidly,and finally tends to gradually Stable value.With the continuous increase of the number of cycles,the delamination and wear debris on the worn surface and the O element content of the worn surface gradually increases,and the O element content of the worn surface gradually increases,and its abrasion resistance gradually deteriorates.(3)The variation of crossing angle within a certain range will not change the fretting regime if other parameters are consistent.But as the crossing angle increases,the abrasion resistance of Cu Mg0.4 alloy will become worse.In the mixed fretting regime,when the crossing angleα=15°,there are only small cracks on the worn surface.As the crossing angle gradually increases toα=30°or 45°,obvious cracks appear in the center of the worn surface.With the increase of the crossing angle,the content of O element in the worn surface gradually increases,the degree of oxidation gradually deepens,and the amount of wear also increases linearly.(4)After the Cu Mg0.4 alloy is corroded for a period of time in a high-humidity environment containing Cl~-,a corrosion product film different from the matrix will be formed on the surface of the sample,which shows a different wear performance from the matrix in the fretting wear test.In the mixed fretting regime,because the corrosion products are easy to peel and refine,the time of direct contact between the samples will be shortened,and the occurrence of surface cracks on the worn surface will be avoided.However,as the corrosion time increases,the Cu O content in the center of the worn surface gradually increases,which will increase the amount of wear and make the abrasion resistance worse.