Study On Friction And Wear Properties Of Fretting Transition Zone Of TC4 Alloy

Titanium alloys are widely used in equipment manufacturing and engineering because of their advantages of high specific strength and strong corrosion resistance.However,the poor friction and wear properties of titanium alloys limit its expansion in industrial applications to a certain extent.Therefore,it is of great significance to study the friction and wear properties of titanium alloys.The research on the fretting transition zone of TC4 alloy can explore the difference of wear mechanism in different states,which provides a certain basis for selecting appropriate wear reduction measures.This work has enriched the research of the friction and wear properties of TC4 alloy and the fretting transition zone.In this paper,the friction and wear characteristics of fretting transition zone of TC4 alloy are studied.Using SRV-IV fretting friction and wear tester,the wear tests of different displacement amplitudes of ball/plane contact steel ball GCr15/TC4 alloy friction pair under 100 N normal load were carried out.The curves of volume wear,wear coefficient and friction coefficient,the profile of wear mark,the surface and subsurface morphology of wear mark were analyzed under different states.The displacement amplitude range of fretting transition region under fixed conditions is obtained.The friction and wear characteristics of TC4 alloy in fretting,fretting transition zone and reciprocating sliding state are studied.The main research results of this paper are as follows:1.Under the experimental conditions,the amplitude range of the fretting transition zone which obtained from the curve of wear coefficient change is from 100?m to 175?m.2.The wear volume in the fretting state is much smaller than that in the reciprocating sliding state,and the wear volume increases rapidly in the fretting transition zone.The depth and width of wear mark increase abruptly in the fretting transition zone,the damage of TC4 alloy increases sharply in the fretting transition zone,and the profile of wear mark changes from zigzag to smooth.3.The curves of friction coefficient of fretting,fretting transition zone and reciprocating sliding state have different characteristics.In the fretting state,the coefficient of friction curve changes in stages and increases with the increase of displacement amplitude.In the reciprocating sliding state,the friction coefficient fluctuates violently and the friction coefficient curves of different displacement amplitudes are almost coincident.The curve of friction coefficient in the fretting transition zone is between fretting and reciprocating sliding.4.In different states,the wear mechanism has quiet different.Under fretting condition,the wear mechanism is adhesive wear and fatigue stripping,accompanied by certain oxidation wear and plastic deformation.Surface fatigue damage is the main cause of material damage.In reciprocating sliding state,the wear mechanism is mainly abrasive wear,oxidation wear and serious plastic deformation of the surface.The adhesion wear is weak,and the serious plastic deformation of the surface is the main cause of material wreck.The wear mechanism changes in the fretting transition zone from severe adhesion wear to abrasive wear and surface plastic deformation.The oxidation wear is increasing and made the matrix damage more serious.5.In the initial stage of the fretting transition zone,the third body layer covering the surface of the wear mark can effectively reduce the friction and wear.With the increase of the displacement amplitude,the third body layer can only cover part of the wear mark and form a bulge on the surface.This third body layer not only fails to reduce friction and wear,but even causes more serious matrix damage.