Study On Friction And Wear Properties Of Copper Matrix Of Cu-based Powder Metallurgy Friction Materials

The six major speed-ups of China's trains have brought China into the high-speed rail era.As the speed of trains increases,safety issues have attracted public attention.As an important part of the brake safety system,brake pads play a decisive role in braking performance.The domestic brake pads for trains cannot meet the requirements of high-speed rails.At present,they still rely on imports.In order to break the current status of brake-plate-dependent imports,scholars in the field of domestic materials have invested in improving the performance of brake pads.This research mainly studies the influence of matrix type on the friction and wear properties of copper-based powder metallurgy friction materials.By optimizing the formulation and preparation process of the materials,the braking performance of copper-based powder metallurgy friction materials is improved.Comparing the effects of copper matrixes of different types(air atomized copper,water atomized copper,tin bronze,brass)on the structure and frictional wear properties of the material,the best type of copper matrix was determined.The influence of different particle sizes(50 mesh,100 mesh,200 mesh,and 300 mesh)on the copper matrix as the copper matrix were investigated,and the best copper matrix particle size was determined by the effect on the microstructure and friction and wear properties of the material.The V-type mixer was used to mix the components uniformly,and the copper-based powder metallurgy friction material was prepared through a cold press forming and hot press sintering process to test the physical and mechanical properties and friction and wear properties of the material.The effect of copper matrix type on the braking performance of copper-based powder metallurgy friction materials was obtained.The results show:(1)copper-based powder metallurgy friction materials were prepared using gas atomized copper,water atomized copper,tin bronze and brass as the matrix.By comparing and analyzing the hardness,density,porosity,microstructure,friction and wear changes of the four specimens.The gas atomized copper particles have a spherical shape,which increases the bulk density of the material and has good diffusivity during sintering.Therefore,the material has high density and hardness,low porosity,and uniform structure.In the frictionand wear test,the material with a matrix of gas-atomized copper has the highest and the most stable average coefficient of friction,it also has the lowest wear.(2)Using different particle sizes of gas atomized copper powder as the matrixs and preparing the friction materials.With the decrease of particle size,the material density tends to decrease,the continuity of the matrix becomes more and more uniform,and the hardness generally decreases.The friction and wear test was conducted at an initial speed of 7000r/min.As the particle size decreases,the friction coefficient and the wear rate tend to decrease as a whole.However,due to the difference in particle size between the specimens with the copper matrix particle size of 200 mesh,the effect of filling each other's voids was good during the forming and sintering process,and an optimal ratio was formed between the copper particles and the other component particles,and each group was increased.The contact area between the elements increases the density of the green compact,reduces the porosity,and increases the sintered density and hardness.Therefore,the sample with 200 mesh copper matrix has the highest stability of friction coefficient,the lowest wear rate,the best comprehensive performance.