Study Of The Microstructure And Frictional Wear Properties Of Wear-resistant Brass

At present,the aerospace field and military aircraft are developing rapidly,and the requirements for key components such as plunger pumps are getting higher.Among them,it is very important to improve the wear resistance of friction pair slipper material.The domestic sliding shoe parts are characterized by short working life,weak load-bearing capacity,unable to meet the high-speed,high-pressure and high-vibration service environment.The proportion and amount of trace alloying elements of wear-resistant brass(C67300)in service lack of theoretical guidance and the microstructure and mechanical properties of it have a large gap with the international advanced level(US).Thus,it is need to further develop high-performance slide shoe materials with independent intellectual property rights.Therefore,in this work,the composition design method based on the cluster plus connected atom model was used to optimize the trace elements of C67300 copper alloy,and to explore the influence of different heat treatment processes(solution,hot rolling and aging)on the microstructure(especially the particle size and volume fraction of precipitated silicides)and mechanical properties of the designed alloy,to establish process-related tissue regulation guidelines,and to reveal the influence of micro structure on macroscopic properties.Secondly,the frictional wear behaviour of annealed and cold-rolled C67300 copper alloy with counter-abrasive GCr15 steel was further investigated,as the frictional wear mechanism of sliding boots in an oil-lubricated environment has rarely been studied.The experiment first prepares designed alloy ingots in an intermediate frequency induction furnace,then performs solution treatment at 873?1113 K/3 h,rolls between 923?1023 K,and then ages at 673?723 K for 1?2 h;C67300 alloy and the original shoes are from the company.Using a series of characterization testing techniques:optical microscope(OM),scanning electron microscope(SEM),X-ray diffraction(XRD),electron probe micro-analyzer(EPMA),transmission electron microscope(TEM),universal tensile testing device,hardness tester and friction testing machine,etc.,carried out the characterization of phase structure,microstructure,mechanical properties and friction properties.The results show that the wear-resistant copper alloy is mainly composed of ?-Cu(FCC structure),?-CuZn(B2 structure),and three sizes(primary,fine,nano)hard particles ?-M5Si3(D88 structure).Heat treatment has obvious effects on the microstructure and mechanical properties of the designed alloy.Among them,the solid solution and hot rolling treatments both increase the strength of the alloy,and aging improves plasticity.Especially ductility ?=29.4%and the tensile strength is ?UTS=580 MPa at 673 K/2 h,which can meet the strength of the shoe plasticity requirements and as an alternative material.In addition,the strength mechanism of the alloy in different states is discussed,and the calculated strength increment is in good agreement with the measured yield strength.The strengthening mechanism of the aging state is mainly solid solution strengthening,grain boundary strengthening and precipitation strengthening.Under the conditions of a constant load of 300 N and different speeds(400?700)r/min,the friction coefficient of the cold rolled and annealed C67300 alloys decreases with the increase of speed;while at a constant speed of 400 r/min,different applied loads(under the condition of 200?500)N,the friction coefficient of cold-rolled and annealed alloys both increase with the increase of applied load.Under different test conditions,the friction coefficient of the cold-rolled C67300 alloy is lower than the annealed state,and the variation range is smaller,showing better wear resistance.This is mainly due to the fact that the H/E=0.020 of the cold-rolled C67300 is closer to the H/E of the GCr15 steel is 0.035.It is expected to improve the wear resistance of the material through the composition design and heat treatment to improve the microstructure,increase the alloy's H/E,and the mechanical properties to match the alloy of the counter-grinding pair.