Study On Friction Properties And Wear Mechanism Of The Cu-15Ni-8Sn-0.3Si-0.1Ti Alloys

Cu-15Ni-8Sn alloy is a kind of copper-based alloys with excellent comprehensive properties,which was initially paid attention as an excellent elastic material and a substitute for beryllium-copper alloy.With the rapid development in the fields of aviation,aerospace,electronics,electrical appliances and communications,its application as high-strength wear-resistant materials has also been highly valued,and it is one of the hotspots of the development of advanced copper alloys in recent years.Microalloying is an important way to improve the properties and expand application of Cu-15Ni-8Sn alloy.In this paper,a novel Cu-15Ni-8Sn-0.3Si-0.1Ti alloy was selected as the research object.Based on the comprehensive measurement of the alloy,the friction and wear properties of the alloy under different conditions were systematically tested by ring-block friction and wear test.The analysis technology of Scanning electron microscopy(SEM),electron backscattered diffraction(EBSD),energy dispersive spectroscopy(EDS),transmission electron microscopy(TEM,STEM,HRTEM)and X-ray diffraction(XRD)were used to systematically study the microstructure evolution of the alloy wear debris,wear surface and friction layer.The main conclusions are as follows :(1)The comprehensive performance test of the aging Cu-15Ni-8Sn-0.3Si-0.1Ti alloy prepared by “casting + homogenization + hot extrusion + heat treatment” process test were carried out,including physical properties,tensile mechanical properties and hardness at room temperature,high temperature and low temperature,shear properties,compression properties,impact properties,bearing properties,fatigue properties and corrosion properties.(2)Under dry friction condition,the wear rate of cast Cu-15Ni-8Sn-0.3Si-0.1Ti alloy decreases slightly with the increase of load at low load(below 300 N),and increases significantly at high load(400 N)and high speed(400 r/min).The alloy debris is mainly fine particles,however,the debris is mainly large flakes at high speed(400r/min)and high load(400 N).When the load increases from 100 N to 300 N,the thickness of the oxide layer(OL)and the mechanically mixed layer(MML)increases.When the load increases to 400 N,the thickness of the oxide layer decreases sharply,but the thickness of the mechanically mixed layer changes little at low rotational speed(200 r/min),and increases significantly at high rotational speed(400 r/min).The dominant wear mechanism of the alloy is abrasive wear and adhesive wear under low load,oxidation wear under relatively high load(300 N),and serious delamination under load of 400 N.(3)Under dry friction condition,the average friction coefficient of the as-extruded Cu-15Ni-8Sn-0.3Si-0.1Ti alloy at high speed(400 r/min)is slightly smaller than that at low speed(200 r/min).When the load increases from 100 N to 400 N,the steady-state average friction coefficient of the alloy gradually decreases,but the wear rate changes little.Alloy wear debris is mainly fine particles.The average thickness of oxide layer,mechanically mixed layer and severely plastically deformed layer(SPDL)increases with the increase of load,especially when the load is 400 N,the average thickness of each layer increases sharply.The dominant wear mechanisms of the alloy with load increasing from 100 N to 400 N are all abrasive wear and adhesive wear.(4)Under dry friction conditions,the average friction coefficient of the aged Cu-15Ni-8Sn-0.3Si-0.1Ti alloy is slightly smaller than that of the aged Cu-15Ni-8Sn alloy.The wear rate is the lowest when the load is 300 N,and is significantly lower than that of the Cu-15Ni-8Sn alloy.The debris containing Si and Ti alloys under 300 N load is mainly granular and uniform in size,while the debris without Si and Ti alloys is mainly flake.With the increase of load,the size of debris increases.The total thickness of the tribo-layer of the alloy containing Si and Ti is obviously smaller than that of the alloy without Si and Ti.The main reason for the better friction and wear properties of alloys containing Si and Ti is that Si and Ti significantly refine the original grains of the alloy,inhibit the discontinuous precipitation on the grain boundary,and significantly improve the plasticity of the alloy.Under 300 N load,the wear mechanism of alloy containing Si and Ti changes from abrasive wear and adhesive wear to oxidation wear,mainly because Si and Ti promote the stability of mechanically mixed layer and oxide layer in the alloy friction layer.(5)Under oil lubrication condition,the stability of aged Cu-15Ni-8Sn-0.3Si-0.1Ti alloy and aged Cu-15Ni-8Sn alloy during friction is significantly better than that under dry friction condition.The wear rate under oil lubrication is also above one order of magnitude lower than that under dry friction.The wear rate of Cu-15Ni-8Sn-0.3Si-0.1Ti alloy is significantly lower than that of Cu-15Ni-8Sn alloy and ZBAl 16-3-1.5alloy.It is difficult to distinguish the oxide layer,mechanically mixed layer and severely plastically deformed layer clearly in the friction layers of three kinds of wear-resistant copper-based alloys,however,there is still a different friction layer with both oxidation and plastic deformation characteristics.The main reason for the excellent oil friction properties of aged Cu-15Ni-8Sn-0.3Si-0.1Ti alloy is attributed to its excellent comprehensive mechanical properties,especially its elongation is superior to aged Cu-15Ni-8Sn alloy and as-cast ZBAl 16-3-1.5 alloy.