A Study On The Fabrication Of Gradient Cu-Ti₃SiC₂ Electrical Material And Its Electrical Property

Electrical contact material is a special electrical conductive material, which not only requires good electrical and thermal conductivity, lower contact resistance and resistance welding, etc, but also requires more stringent requirements according to the conditions, such as arc erosion resistance for the contact material and friction and wear properties for slide contact material. As a new material, FGM can achieve a continuous transition from metal to ceramic and combine the properties of metal and ceramic well. Ti3 Si C2 has both metallic and ceramic properties and can be used as reinforced phase of copper matrix for electrical contact materials. The Cu-Ti3 Si C2 gradient composites are made one end of which, working as the working face, contains more Ti3 Si C2 and the other end, working as the conductor, contains more copper. After the preparation of the Cu-Ti3 Si C2 composite materials and the Cu-Ti3 Si C2gradient materials, the erosion behavior under vacuum and the friction and wear behavior with current of Cu-Ti3 Si C2 composites are studied in this paper.The thermal stability at high temperatures of Cu/Ti3 Si C2 is researched by DSC and diffusion couple. It was found that Copper and Ti3 Si C2 are stable at 800℃ and they react at higher temperatures. Ti3 Si C2 decomposes into Ti C and the released Silicon and Copper form Cu-Si phase or Cu(Si) solid solution and the Ti Si2 and Ti5Si3 Cx are generated at the same time.The Cu-Ti3 Si C2 composites and Cu-Ti3 Si C2 gradient composites are prepared by SPS after pressing. The effect of pressing pressure and sintering temperature on material properties is studied. The results show that density, hardness and bend strength of Cu-Ti3 Si C2composites are optimal at 1000 MPa; Copper reacts with Ti3 Si C2 and generates Ti C and Ti5Si3 while sintering temperature is exceed 800℃. The pure Cu-Ti3 Si C2 composites are prepared by warm compaction at 145℃ and SPS at 700℃ and the Cu-Ti3 Si C2 gradient composites are prepared by SPS at 750℃ after warm compaction or high-speed stamping. The microstructure of gradient composites showed that no clear boundary but good combination exists between the layers, and no obvious defects and agglomeration are founded in gradient composites.The erosion behavior under vacuum of Cu-Ti3 Si C2 composites is studied. The study results show that Ti3 Si C2 particles in Cu-Ti3 Si C2 cathode surface decompose under vacuum arc and C and Ti C are the decomposition products. The roughness of Cu-Ti3 Si C2 cathodesurface increases while the second phase Ti3 Si C2 content increases and the granular droplets bulge. The boiling-like morphology which agrees with the typical model for the development of erosion craters on clean cathodes is clearly seen from the longitudinal section of Cu-Ti3 Si C2 cathode. The boiling-like morphology decreases with the increase of Ti3 Si C2content and the erosion degree of contact aggravates at the same time. Taking Cu-20 mass%Ti3Si C2 for example, Ti3 Si C2 decomposes under high temperature of arc at beginning and Cu-Ti3 Si C2 cathode is covered by the substance composed with Cu, C and partly decomposed Ti3 Si C2; decomposed Ti3 Si C2 and pores(leaving by the gasification of Silicon or Silicon compound) increase while the breakdown times increase and the molten drop become melt;With breakdown times further increasing, the decomposition of Ti3 Si C2 substantially complete and most Silicon is escape, pores are filled with Copper. The melt become melted layer under the repeated impact of plasma after 2000 breakdown times and the morphology agrees with the model for cathode arc spot on surfaces. This shows that the erosion mechanism of Cu-Ti3 Si C2 composites and metallic materials is basically the same, with a excess decomposition process of Ti3 Si C2. The decomposition of Ti3 Si C2 consumes a lot of energy which can reduce the surface temperature of the cathode and reduce the loss of Cu. The results of mass loss testing show that the relationship between Ti3 Si C2 content and the mass loss rate of Cu-Ti3 Si C2 composites is linear and the mass loss rate increases with the increase of Ti3 Si C2 content.The friction and wear behavior of Cu-Ti3 Si C2 composites is studied. The comprehensive properties and friction and wear properties of Cu-based composites can be effectively improved while the Ti3 Si C2 content appropriate increases in material; purity rather than density is the key factor which influences friction and wear properties of Cu-Ti3 Si C2composites; the friction coefficient and wear volume with current are higher than that with no current. Similarly, the friction coefficient and wear amount with heating are higher than which without heating. Wear scar in the surface is lighter without current; Wear scar in the surface isdeeper with current and the adhesive wear is more serious. The adhesive wear is reduced while the Ti3 Si C2 content increases.