Microstructure And Properties Of Ti₃SiC₂/Carbon Fibre Dispersion-strengthening/Cu-graphite Composites

With the motor on the current density and speed of the circle becoming higher and higher,the requirement for the quality of the brush materials is also rising,which the previously used copper-graphite material can not meet.In this paper a fact is elaborated that the performance of the composite materials can be improved when the part of graphite is replaced by copper coating Ti₃SiC₂ and carbon fiber.The interfacial adhesion between Ti₃SiC₂,carbon fiber and copper matrix of the composite coating can be increased by copper coating processing. Ti₃SiC₂ particle surface was coated with copper by electroless plating method without sensitization and activation.The influenece of temperature,pH value, CH₂O and loading capacity on copper coating were studied.In doing so we finally got the appropriate copper process.The result indicates that smooth and compact layer can be gained when the temperature is 55～60℃,pH value about 12.5, initial concentration of CH₂O 16 ml/L,loading capacity of 3 g/L and time for electroless plating 20～30min.In order to embody the strengthening function between copper coating processing and copper matrix;copper-coated-Ti₃SiC₂-Cf-Cu-graphite matrix composites which were obtained by powder metallurgy process was compared with Ti₃SiC₂-Cf-Cu-graphite matrix composites,and its mechanical properties were tested.The results show that with the increase of the content of Ti₃SiC₂ and carbon fiber the composite materials' density,the conductive rate,hardness,the bending strength are increased;In the same components,when copper-coated -Ti₃SiC₂-Cf-graphite-Cu matrix composite is compared to the Ti₃SiC₂-Cf-graphite-Cu matrix composite,the performance of the former is superior to that of the latter. It is clear that copper coating Ti₃SiC₂ and carbon fiber helps to promote the interfacial adhesion of both of the elements with the copper matrix,thus strengthening the property of the composites.The frictional wear tests were carried out on six composites with different components.The results show that whether the line speed be 5m/s or 10m/s,in the same components,the frictional wear of copper-coated-Ti₃SiC₂-Cf-graphite- Cu matrix composite is superior to that of Ti₃SiC₂-Cf-graphite-Cu matrix composite. The friction coefficient of the composite material is decreased with the increase of the line speed.When six groups of composite materials are compared,it is found that the wear resistance of composite materials and the performance are excellent when the part of graphite is replaced by 2%copper coating Ti₃SiC₂ and 1%carbon fiber.