Study On Preparation And Tribological Behavior Of Layered Graphite-Copper Composites Materials

Graphite-copper composite materials have widely applications because of excellent tribological properties and other properties as electrical conductivity, thermal conductivity, oxidation resistance and corrosion resistance. However, the physical property is different from each other, at 1100℃the wetting angle is up to 140°, there is neither chemical reaction nor diffluence between graphite and copper, after mechanical mixing and PM sintering, when graphite combine with graphite, many pores exist, which seriously affect the strength of the material and the friction and wear properties. Investigate and development of high-performance graphite-copper composite materials is ideal electrical contact materials which can solve friction and wear problems under special conditions. In this paper, we use electroplating to prepare layered graphite-copper composite materials, systematically study friction and wear behavior and mechanism of composite materials under different conditions and explore academic rule of reducing friction, which is of great significance for the development of new graphite-copper composite material to provide a theoretical basis and technical support.Before electroplating, we put graphite in vacuum, high temperature environment to desulfurization, then reaming treatment, the diameter of the hole is 0.3mm, and the hole-pitch is 5mm. The plating method adopts constant-current, the current is 10A and current density is 7A/mm2. Plating solution, which is composited by acid(35g/L) and coppersulfate(100g/L). After plating, put the coppered graphite in high temperature and vacuum environment to deoxidize. Then using HIP to stiner coppered graphite, the HIP condition is 800℃×70MPa×3h. The stinered sample is compact, and there is no crack in it. Microstructure shows that the copper is connected in three-dimensional form.Using stereology quantitative methods to analyse the volume fraction of copper. The density of composite increase with the increasing of volume fraction of copper. When the volume fraction is 52%, the density, impact toughness, bending strength and brinell hardness are 5.159g/cm3,11.5J/cm2,53.72MPa and 14.31HB, respectively.The wear and frictional test of different working environments were invested, the grain produced by the wear process and the structure of the wear surface were studied by means of microstructure analysis, something more, the wear and frictional properties and mechanisms of the compound materials were discussed in this paper. The results shows that when the friction direction perpendicular to the layer, the friction performance of composite is the best. The wear rate increases with the increasing of volume fraction of copper, load, sliding speed, but the friction coefficient shows the opposite result. The wear form of the Compound materials under different situation is mainly particle attrition, with the increasing of volume fraction of copper, load, sliding speed, the degree of adhesive wear, oxidation wear is aggravating.