Powder metallurgy material composition selection of powder metallurgy friction materials is general by base metal, such as friction and lubrication group yuan of multivariate composite materials. Among them the main function of it is combined with mechanical metal matrix way keep ceramic composition and lubricant in it, form has a certain strength of the whole. Attribute matrix with gold, and its organization structure, physical and chemical properties to a great extent, decides the domestic company of powder metallurgy brake piece of metal ceramic friction and wear properties and thermal stability, mechanical properties and thermal conductivity.

Matrix elements in iron base matrix generally add a certain amount of alloy elements Cu, W, Ni, P, Cr, Mo and Si, to improve the performance of the matrix. Adding alloy elements in conjunction with the matrix of Fe alloy pearlite formation, and formation of carbide phase or intermetallic phase, so as to improve the high temperature strength of the substrate and antioxidant ability, and can reduce the wear of the materials. Base copper base powder metallurgical brake materials adding alloy elements zinc, Ni, Al, Ti, Mo, and Sn, etc. Friction yuan is commonly used in friction materials friction group yuan have SiO2, Al2O3, and SiC, B4C, join the friction components of main purpose is to improve the substrate material of friction coefficient, enhance the strength of the substrate. It is generally believed that the Cu base friction materials adding SiO2 as abrasive relatively appropriate. SiO2 to improve the coefficient of friction, reduce wear and tear have certain effect, but there are also studies have shown that SiO2 caused by reduction and dissolved iron and reduced iron carbide content reducing friction properties.

SiC high hardness, high melting point, high temperature does not react with the matrix. Studies show that with the increase of the content of SiC friction coefficient increases, the appropriate content can lower the amount of wear and tear, excessive SiC will destroy the strength of the matrix, prone to peeling off, thus aggravate the wear and tear of material. When sintering Al2O3 can stable friction coefficient, no crystal shape shift, can improve the thermal stability of materials.

Lubrication components in order to improve the scratch resistance and abrasion resistance of material, need to add lubrication components in material composition, usually add lubrication components are: low melting point metals (Pb, Sb, Bi), non-metallic solid lubricant (graphite, MoS2), hexagonal BN and BaSO4, etc. Graphite solid lubrication role is powder metallurgy materials, one of the main components of material wear and the braking stability plays a very important role. Graphite in the material by combining state and free two forms exist, and Fe carbide or intermetallic compound formation, parts and other alloy elements to form compounds; With layered six-party flake free graphite crystal structure of interlayer bonding between atoms bond energy is low, easy to slip, the layer within a strong interatomic bonding force, slip plane layer not peeling off, because the graphite to form transfer film on metal surface, so it has excellent lubricity. Don't miscibility between graphite and Cu, Fe, Sn, its basic evenly distributed between the metal substrate. Sintering process of graphite block of metal atom diffusion between, hinder the formation of sintering neck, increase the porosity of materials. Pore often occur at the interface between graphite and metal, and a narrow flat hole, easy cause stress concentration.

Conclusion according to current situation of China's railway and the urgency of the development of high-speed trains, as well as China's national conditions, at the present stage except imported vehicle vehicle response is given priority to with powder metallurgy friction materials of brake piece of systematic study on brake material, comparable to or developed to replace imported brake products, and realizing industrialization as soon as possible. At the same time, the C/C composite materials and ceramics can be in-depth study of friction materials, to further speed up and to the high speed development of railway in our country, make sufficient technical preparation.