Effect Of Cr On Friction And Wear Properties Of Cu-based Powder Metallurgy Material

Copper-based powder metallurgy material is used widely for making brake of high speed train because of its high friction coefficient and good wear resistance. The material is made of Multiple-component, material properties is regulated by adding different elements. This paper is prepared by powder metallurgy for Cu-Cr based materials which is made of copper, chromium, graphite and SiO2, making constant speed and simulation of inertial test by friction tester, and making the analysis the change of friction and wear properties for diffenent content of Cr (5～20%wt) under different pressure, different order, dry or wet condition and friction speed. The results show:Under constant speed friction, with the chromium content increased, the friction coefficient decreased, but the change was slightly. Dry friction coefficient was significantly higher than the wet rubbing, when speed friction velocity below1000r/min, with the raise of the friction velocity, dry and wet friction coefficient difference is not obvious. At the same time, moisture accelerated the loss of the third body, resulting in increased wear quality. Friction coefficient is reduced as the friction pressure increases, when the chromium content is high, as the pressure increases, the friction coefficient is significant fluctuation, showing unstable characteristics. The effect on the friction performance of the friction order is with the relevant of the third body, overall, friction coefficient did not differ much.Under inertia friction condition, the results show that the friction coefficient reduced and wear resistance increased with increasing chromium content. The reason is that the high hardness of chromium strengthen the matrix, which reduced the damage and roughness of material surface, so that the friction coefficient and the wear rate decreased. With friction velocity increased, the friction temperature increased, temperature effects on the friction coefficient played a leading role, reduce the coefficient of friction materials, the reduce degree of the chromium content of15%and20%materials is more obvious. When the friction velocity is3000r/min, wet friction coefficient is higher than that of dry friction, this is due to the high speed friction is formed at high temperature and centrifugal effect is not conducive to the moisture on the surface of the residence, weakened the lubrication, the water film at the same time, the cooling effect of water on the surface avoid the reducing of base metal strength on the surface, this is helpful to improve the friction coefficient.Together, with the increase of chromium content, the friction coefficient reduced, the two materials of the chromium content of15%and20%have better abrasion resistance.