Effect Of Submicron Tungsten Copper Composite Powder On The Current-carrying Wear Performance Of RMCBCs Composites

Resin matrix carbon brush composites(RMCBCs)are the mainstream materials for carbon brushes for medium and high-power electric tools.However,the current-carrying wear performance of existing RMCBCs is difficult to meet the requirements of complex service conditions.Therefore,how to improve the current-carrying wear performance of RMCBCs has become one of the research hotspots in the industry.The binder is an important part of the carbon brush material.The performance of the binder is the key to the matching degree of the carbon brush/commutator friction pair,but the research on the effect of the composites on the anti-wear performance comes from the resin curing temperature and resin deformation resistance have hardly been reported.So,this paper takes RMCBCs for medium and high-power electric tools as the research object.Based on the study of epoxy resin modification,the study of the effect of the submicron tungsten copper composite powder and modified epoxy resin on the performance of RMCBCs was carried out.The focus was on the effect of curing temperature and structural evolution on the performance of RMCBCs.On this basis,the effect of the submicron tungsten copper composite powder on the current-carrying wear performance of RMCBCs was systematically studied.Furthermore,the regulation mechanism of the sparseness-effect of the stress dispersion and transmission in the composite material system was clarified,also,the blocking-effect of the passive particle reinforcement of the resin to inhibit microcracks to improve the anti-wear performance of the carbon brush was demonstrated.The main research contents are as follows:(1)The effects of different curing temperatures on the performance of RMCBCs were systematically compared.It was found that with the increase of curing temperature,the resistivity,Shore hardness,flexural strength and compressive strength of RMCBCs all increased first and then decreased,reaching the maximum value of618.20??·m,22.6HSD,37.44MPa and 42.88MPa respectively,when the curing temperature was 200?.When the curing temperature of RMCBCs is 200?,the current-carrying wear rate reaches the minimum value of 3.18mm³·h^-1,and the wear surface is mainly fatigue wear.(2)The RMCBCs(RMCBCs-W@Cu)with uniformly dispersed tungsten-copper composite powder was prepared by using the electrostatic adsorption method.The study found that when adding 3.75wt.%tungsten copper composite powder to RMCBCs,the flexural strength and compressive strength of RMCBCs-W@Cu reached the maximum values of 39.6MPa and 48.32MPa,respectively,and the current-carrying wear rate reached to the minimum value is 1.64 mm³·h^-1.Compared with RMCBCs reinforced with tungsten powder(RMCBCs-W)and RMCBCs reinforced with copper powder(RMCBCs-Cu),RMCBCs-W@Cu had the best overall performance.Among them,the average friction coefficient of RMCBCs-W@Cu was 0.243,which was decreased by 17.34%compared to the control.Also,the thermal conductivity of RMCBCs-W@Cu was 1.76 times than that of the control.After adding tungsten-copper composite powder,the fatigue wear of RMCBCs was effectively suppressed.(3)Based on experimental results and theoretical calculations,the effect of the change of curing temperature on the current-carrying wear mechanism of RMCBCs was studied.The analysis showed that the adhesive wear of RMCBCs was attributed to the cut of the hydrogen bond formed by the hydroxyl group between the wear surface and the friction film.The fatigue wear of RMCBCs is attributed to the poor resistance to deformation of the wear surface.Through nanoindentation,finite element analysis and theoretical calculations,it was confirmed that after the tungsten-copper composite powder was introduced into RMCBCs,the reduction in friction coefficient was consistent with the experimental results.The special"planetary structure"of the tungsten-copper composite powder builds a"sparse-blocking combination"structure inside the RMCBCs,which"sparses"the interfacial stress,"blocks"the cracking caused by the deformation of the resin,and reduces the fatigue wear,thereby significantly improving the current-carrying wear performance of RMCBCs,this research provides a reliable theoretical support for the industrial development of high-performance RMCBCs.