The Effect Of Sintering Process On Properties Of Cu-Based P/M Friction Materials

With the development of train transport, the requirements are stiffer and stiffer in the properties of the braking materials by the speed improvement. Because of the high mechanical strength, high conductibility and excellent friction and wear properties, Cu-based P/M friction materials have been the leading material for friction brake of high-speed train.Cu-based P/M friction material has been made by different sintering process. The effect of sintering temperature and atmosphere on the micro-structure, physical and mechanical properties and friction and wear properties of material have been investigated, and the friction and wear behavior and mechanism in the different braking conditions have been discussed. The results show:(1) Scaly graphite and SiO2 are well-distributed in Cu-based P/M materials. With the increasing of sintering temperature, the pore volume between different components decreases gradually till reached a certain degree. Sintering atmospheres have no effect on the micro-structure of materials.(2) Sintering process have important effects on the physical and mechanical properties of materials. With the increasing of sintering temperature, the densities of materials sintered in N2 andN2+H2 atmosphere increases firstly and decreases then, but the densities in H2 trends to decrease; the compressive strength of materials sintered in N2 and N2+H2 are higher than that in H2.(3) On the same braking pressure, with speed increased, the frictional coefficient increases firstly and decreases then, but the wear volume increases gradually. The slipping speed changes, the wear mechanism changes also. At low speeds, adhesion wear is the main mechanism, but oxidation and fatigue wear takes on priority at high speeds. The materials sintered in the N2+H2 atmosphere have the best frictional property at low speeds, besides, the wear volumes are the lowest and decreases with the increasing sintering temperature. The materials sintered in the N2 atmosphere have the best frictional property at high speeds, and with high frictional stability and lower wear volume at the same time.(4) At the certain speed, with braking pressure increased, the frictional coefficient trends to decrease, frictional stability increases firstly and decreases then, but the wear volume increases greatly. On low pressures, the main wear mechanism is adhesion wear, but fatigue and flake wear are the main mechanism on high pressures. The materials sintered in the N2+H2 atmosphere have the best frictional property on high pressure, the highest frictional stability and the lowest wear volumes, besides, with sintering temperature increased, the wear volume decreases firstly and increases then, and has the lowest value in the sintering temperature of 1000℃.