Effect Of Nano-additives Or Micron-additives On The Microstructure And Properties Of Cu-C Composites

In this paper, four kinds of specimens of Cu-C composites added by nano-copper , nano-silver, micron-copper , micron-nickel were obtained by powder metallurgy technology. Each kind of specimens with 3% additives was sintered under the temperature of 770℃, 800℃, 830℃, 860℃. The important properties are tested according to the state standard of test method for physical-chemical properties of electrical carbon product in order to study the influence of sintering temperature on the specimens. The result shows that as the sintering temperature increases, the density, bending strength and hardness are all larger while the resistivity reduces. The optimum sintering temperature is 830℃. When the sintering temperature exceeds 830℃, the strength increases slowly and the hardness even becomes smaller.Secondly, nano-copper , nano-silver, micron-copper , micron-nickel with different contents were added into the Cu-C composites . After having been sintered under the optimum sintering temperature, density, electrical resistivity, hardness and bending strength of specimen were tested, then microstructure and fracture surface were observed by metallographic microscope, SEM and EDS. The relationship between the content of additives and static properties was researched. The investigation shows that nano-silver could significantly improve properties of composite. But the effect of nano-copper is not ideal. The micron-copper doesn't have obvious effects on the properties of composite. The micron nickel will reduce electric conductivity.Finally, friction and wear properties of four kinds of composite brush with 0% additives, 3% additives and 5% additives were tested for 36 hours on dry friction test with the sliding speed of 10m/s and the load of 4.9N. The weight loss of mechanical wear and friction coefficient were measured. The microstructure and wearing surface were observed by the metallographic microscope. The result shows that the friction coefficient of composite brush with additive is larger than that of composite brush without additive. With the increasing of additive, the wear loss of Cu-C composites added by micron-nickel increases while the wear loss of the other three kinds of composites first increases then decreases.