Study On Fretting Wear Behavior Of Tc4 Alloy At Different Temperatures

Titanium alloys have been widely used in aerospace,petrochemical and other fields attributed to its excellent properties such as lower density,higher specific strength,good machining and weldability.However,titanium alloys have low hardness,poor wear resistance,and are extremely sensitive to fretting damage,which leads to premature failure of mechanical components,and greatly threatens the safe operation of the equipment.Therefore,it is necessary to carry out research on the fretting wear behavior of titanium alloys.Laser shock peening(LSP)is a modern technology for surface modification of materials by using the effect of shock waves,which can improve the wear resistance of titanium alloys.Studying the effect of LSP on fretting wear behavior of titanium alloys have great significance to carry out fretting damage protection.In this paper,the SRV-IV fretting wear tester is used to study the fretting wear behavior of TC4 alloy and LSP-TC4 alloy under different temperature conditions.Analysis methods such as optical microscope,laser scanning confocal microscope and scanning electron microscope are used to characterize the friction coefficient,wear volume and wear scar morphology.The damage mechanism of TC4 alloy and LSP-TC4 alloy under different fretting conditions are analyzed,and the influence mechanism of laser shock peening to improve the wear resistance of TC4 alloy is discussed.The main research contents and conclusions of this paper are as follows:1.According to the experimental data,the TC4 alloy operating conditions fretting map and material response fretting map were drawn.It was found that with the increase of the displacement amplitude or with the decrease of the normal force,fretting running condition changed from partial slip region to mixed slip region,and finally to gross slip region.The transition of the fretting running condition has little correlation with temperature.2.Ambient temperature and displacement amplitude have significant effects on the friction coefficient and wear volume of TC4 alloy and LSP-TC4 alloy.When the temperature is constant,the friction coefficient and wear volume increase with the increase of the displacement amplitude;when the displacement amplitude is constant,the friction coefficient gradually decreases and becomes more stable as the temperature increases,and the wear volume shows the same trend as the friction coefficient.3.At room temperature,the wear debris layer formed by fretting is thin,looseand porous,and is not tightly bonded to the substrate.while at high temperatures,the wear debris layer formed by fretting is thicker and denser,and is more firmly bonded to the substrate.The wear debris layer blocks the direct contact of the fretting sample,which is beneficial to slowing the loss of material,so the material shows better wear resistance with increasing temperature.4.Compared with TC4 alloy,LSP-TC4 alloy has better wear resistance.On the one hand,laser shock peening can cause high-density dislocations on the surface of titanium alloy,forming a nano-gradient structure,which greatly improves the hardness of the material surface and helps to reduce adhesive wear.On the other hand,laser shock peening can also introduce a large amount of residual compressive stress,effectively reducing fatigue wear caused by cracks.5.In the partial slip region,the friction coefficient is small and stable,and the obvious adhesion zone and micro-slip zone structure can be seen on the wear scar surface.Fretting damage mainly occurs in the micro-slip zone,and the damage mechanisms are mainly oxidative wear,adhesive wear and fatigue wear.As the fretting running condition shift to the mixed slip region,the adhesion zone disappear,the micro-slip region occupies the entire wear scar surface,and the frictional dissipation energy increases significantly.The main damage mechanism is oxidative wear and fatigue wear.In the gross slip region,the friction coefficient fluctuates sharply,and the wear volume increases rapidly.The wear mechanism becomes oxidative wear,abrasive wear,fatigue wear and slight adhesive wear.With the increases of temperature,the degree of oxidative wear is more and more serious.