The Study On Preparations And Friction And Wear Behaviors Of Copper-based Brake Material

With the gradual increasing in the speed of high-speed rail, higher and higher demands have been put forward. In order to obtain high-performance brake lining, the six kinds of materials which consisted of Cu-graphite-Fe-Sn-Cr-SiO2-MoS2, were produced by powder metallurgy technology. In the test,300-600μm large-size graphite small-size iron which is smaller than 38μm and small size SiO2 which is smaller than 28μm are used. The purpose of this paper is to investigate the influence of the graphite and iron on sintered microstructure and friction and wear properties, without any other compositions changing. As a result,(1) Density, compressive strength and friction coefficient of the friction material can be well controlled by the porous design which consists of the large-size graphite and small-size hard particles. The sintered organizations in this composition show high friction coefficient and low wear rate. In the test, the friction coefficient is in the range of 0.53-0.81.At a different friction speed, with increasing content of graphite the friction coefficient of material is reduced. When the content of graphite is between 6-8%, due to the lower graphite as the speed increases the wear rate of the material increases dramatically. When the graphite contents are over 10%, strengths of materials are reduced, so wear is intensified.(2) In the test, the continuity and compactness of materials can effectively improved by using the large-size flake graphite. The smaller atomized iron particles we used in materials for strengthening component can be better wetted by the matrix structure and well combined with copper, to improve the density and compressive strength. In the test, the material densities are higher than 5g/cm3,and the relative densities are close to 85%,and the hardness of materials are between 100-130HV, and compressive strengths are higher than 77Mpa which reach the brake friction material performance requirements.(3) Within 8-18%Fe, the wear resistance of materials enhances, along with the increase in iron content. When the iron content is 20%, excessive iron increases the division of iron in the matrix, result in wear resistance decreasing.(4) In a word, the content of the friction and wear brake lining with the optimum performance we have obtained in the test is 10%C,18%Fe,57%Cu,7%Sn,5%Cr,2% SiO2,1% MoS2 material. The performance of the brake lining shows that density is 5.307g/cm3, compressive strengths are 116.32MPa, friction coefficients are over 0.7, the micro-hardness are 120.91HV.