Research On New Material For Pantograph Slide Plates

Railroad's electrification and the high speed are the tendencies which the present world railway transportation develops. With the speed of the continuous improvement of our trains, developed excellent performance pantograph slider material has become a goal pursued by researchers. Carbon slider is prone to arouse accidents for its high electrical resistivity and low strength. Immersed metal carbon slider need complicated producing process which leads to high cost. And common pantograph slider prepared by powder metallurgy technology usually causes serious abrasion of the conducting wire. To solve these problems, this thesis will attempt to preduce excellent copper matrix composites reinforced by ceramic particles. Ti3SiC2 is a kind of novel structural-functional ceramics material, it combines the merits of both metals and ceramics. It has outstanding properties, such as low density, high melting point, nice electrical and thermal conductivity, high elastic modulus, high fracture toughness and machinability. And more significantly, it has very low friction coefficient and nice self-lubricating property. Copper matrix composites reinforced with TiB2 particles have been widely used as electrical contact materials because of its high strength, high electrical conductivity, and excellent high temperature. Therefore, this paper will try to combine the TiB2 reinforced copper and Ti3SiC2 dispersion strengthened copper, prepared the TiB2/Ti3SiC2 reinforced Cu composites. This material may integrate the excellent properties of TiB2, Ti3SiC2 and copper. So it becomes to a new material for pantograph slide plates worthy of study.In this thesis, we main studied electroless plating copper on TiB2 and Ti3SiC2. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) were utilized to investigate the phase composition and the morphology characteristics of the products. This paper resolved the problem of wettability through electroless plating copper on TiB2 and Ti3SiC2. Mixture through the ball milling method to make it uniform dispersion.In this thesis, In order to find the ideal TiB2/Ti3SiC2 reinforced copper composite material, various raw materials ratios in volume fraction, different sintering temperatures, unequal pressing pressure and granularity of Ti3SiC2 were investigated. Under the three temperature points 850℃,950℃and 1050℃, Molding pressure ranges from 0 to 40MPa, granularity of Ti3SiC2 ranges from 100 to 400mesh, the performance of composite material which prepared by pressureless sintering, content Ti3SiC2 for 10% and 20%, TiB2 for 0-30%, the rest of the powder is copper were especially studied. Affer determining the optimum process and the best ratio, the performance of composite material which prepared by hot pressing compared with which prepared by pressureless sintering. Four-probe resistivity meter, HB-3000 Brinell hardness tester, the MTS-810 material testing machine and the JB-5 impact testing machine were utilized to investigate the electrical properties of composite materials and mechanical properties, the application of scanning electron microscopy(SEM) coupled with energy-dispersive spectroscopy (EDS) study of microstructure and fracture mechanism of composite materials.Results indicated that composite materials has best performance when pressureless sintering temperatures of 950℃, molding pressure of 30MPa, soaking time of 2.0h, Ti3SiC2 average granularity of 75μm, Ti3SiC2 volume content of 10%, TiB2 volume content is 6%. Resistivity, hardness, tensile strength of the composites respective is 7.437μΩ·cm,67.5HBS,71.597MPa. Wherein the other processes were same for the experiment, integrated performance of composite materials which prepared by hot pressing were better than the samples which prepared by pressureless sintering. And resistivity, hardness, tensile strength, toughness of the composites respective is 5.337μΩ·cm,95HBS,258.94MPa,3.47J/cm2. We can find each reinforcement phase in the matrix is more uniform dispersion by Metallographic photos when the content of TiB2 is lower. The microstructure of the composites was investigated by using SEM. And the fracture mechanism of the composites was analyzed. The breakage is due to tearing of matrix near Cu-TiB2 interface, in addition, the interfacial debonding and Ti3SiC2 cleavage crack have a prominent effect on the failure mechanism of composite under tensile and impact loads.