Preparation And Property Of Powder Metallurgy Copper-matrix Composite Friction Materials

In the21Century, technology develops highly and the requirements for the performanceof the material get more and more high. Metal matrix composite comes into being because ofthis demand. Metal matrix composite is a combination of metal matrix of metal andreinforcement properties with high dimensional stability and high specific strength and otherexcellent performance. Compared with the traditional metallic material, metal matrixcomposite has higher stiffness and strength; Compared with the resin matrix composite,metal matrix composite has better heat resistance and electrical conductivity; Compared withthe ceramic material, metal matrix composite has higher impact resistance and hightoughness. The excellent performances of metal matrix composite make it win a largenumber of extensive research and development when it appears in the world. In recent years,various countries of the world have developed in high-speed railway rapidly, and havecontributed to the pace of China’s high-speed railway industry towards forward. With thecontinuous improvement of the running speed, requirements for brake material and brakedevice get more highly. On one hand, the fast running speed of the high-speed trains updatesthe concept of the traditional train basic brake equipment and braking system technologies,and provides an objective requirement for the introduction of new materials and newadvanced preparation and new production technology; On the other hand, it also requires theperformance and preparation of the brake shoe, brake disc, brake pads more strictly. Thefollowing is the main work of this paper.Preparation of high-speed train Brake: Cu-Sn alloy powder by mechanical alloying10h isthe matrix, after10h mechanical activation of the Ti-C powder is increasing grinding phase,graphite is the lubrication phase, and add the alloy powder of Fe, Ni, Cr, the ball to powderratio is10:1, milling time is1h and the milling speed is200r/min. Cold mold those mixedpowder of the above mechanical alloying by hydraulic universal machine, choosing600MPato suppress and pressuring1min dwell time, and the sample mass is pre-computed15g afterthe molding. Sinter the sample contained in the container into the sintering furnace, and thesintering temperature are780°C and830°C, and holding time reaches the set temperature for1h, followed by furnace cooling. In the sintering process of Brake materials ofhigh-speed train, after the mechanical activation Ti-C powder form of TiC, and synthesisreaction will release a lot of heat to raise the surrounding Cu-Sn matrix phase transition ormelting, thereby forming the heat-affected zone. Heat-affected zone can improve the matrixand enhance the interface between the phase, thereby increasing the strength of the materialof the brake film. The three-body abrasion is the main wear mechanism of brake padmaterial, and part of the abrasive wear under high load is the delamination. With theincreasing experimental load, the brake pad friction coefficient gradually reduce. When thetest load is increasing, friction coefficient and wear rate of materials adding Ni, Cr has notthe obvious inflection point, indicating that the addition of Ni, Cr, help to reduce the test loadfor the friction and wear properties of composites.Preparation of TiC reinforced Cu matrix composites used in cold pressing-sinteringmethods is similar to the high-speed train brake for cold pressing of the composite material.Mixed the prepared activated Ti-C powder used planetary ball mill mechanical alloying5hand10h prior and Cu powder at mass ratio of1:9, ball to powder ratio of10:1, and millspeed200r/min and500r/min ball mill powder mixed for1h and2h. Add90%of Cu powderafter10h mechanical activation of the TiC powders using cold pressing-sintering methodcan be homogeneous TiC reinforced Cu matrix composites. Can see the heat-affected zone inthe sintering temperature of800°C, with the increasing sintering temperature, the Cu matrixcomposites gradually become thick, heat-affected zone is a gradual return to disappear.Using different milling intensity on the microstructure of the composites, with the increase inthe intensity of mixed milling, grain size has been reduced in the copper matrix composites,content of TiC decreases, and the organization gradually refined. In the process of frictionand wear of Cu-TiC composites the three-body abrasion is the form of wear performance, aswell as a small amount of abrasive wear and delamination wear. The friction coefficient andwear rate of the copper matrix composites with the increase of the experimental load decline.The increase content of TiC in the composites helps to improve the wear resistance of thematerial.