The Influence Of The Components Of High Copper Carbon Brush On The Microstructure And Performance

The influence of alloy elements (such as Lead and Tin) and graphite content on the microstructure and basic performance such as bulk density, porosity, strength, hardness, conductivity and wear resistance of high copper carbon brushes were studied. The wear mechanism of carbon brush was analyzed. At the same time, the effect of the defects of the dual material on the wear performance of high carbon brush was conducted.The influence of alloy elements and Graphite content on the microstructure of carbon brush was studied by Microscope observations, SEM scanning, EDS and XRD analysis. The results showed that it was a simple mechanical combination between copper and graphite without chemical reaction. And graphite divided the continuity of copper matrix by flocculent mass distribution around the copper substrate. Lead and Tin elements didn’t change the state of the combination of copper and graphite, lead and tin existing in the form of oxide in carbon brush partially.Different tests of carbon brush were conducted, such as density test, specific surface area test, hardness test, crushing strength test and conductivity test. It turned out that adding lead greatly increased the density of carbon brush to 5.374 g/cm3, but decreasing other parameters. Adding tin reduced its conductivity, but improving its strength and hardness, their value as much as 34.5MPa and 54.07 HBW. The performance of carbon brush reduced with the increase of graphite content. When graphite content was 15% wt, the resistivity was 1.32×10-1Ω·m, and the ability of conduct was best.The wear experiment was carried on the carbon without current. It turned out that the friction coefficient was minimum and the wear resistance was worst of carbon brush of adding lead. Carbon brush of adding tin expressed better wear resistance during the short time. The friction coefficient and the wear resistance of carbon brush constantly decreased with graphite contents increasing, when graphite content was 15%wt, it was the best wear-resisting. The wear mechanism of carbon brush was adhesive wear, with abrasive wear and peeling wear. Defects in friction pair led to the friction coefficient and wear resistance decreasing after 60min. Number of defects didn’t change the wear mechanism of carbon brush, but increasing the friction coefficient and wear volume.The wear experiment was carried on the carbon with current. It turned out that after wearing 30min, the wear volume of carbon brush of adding lead was maximum (0.645cm3), carbon brush of adding lead being 0.175cm3, and when graphite content was 15% wt, carbon brush expressed best wear-resisting, the wear volume of 0.146cm3. The friction coefficient of carbon brush didn’t present regularity because of current existing. And the wear mechanism was altered because carrying current. Carbon brush of adding lead presented adhesive wear, with abrasive wear and ablation. The wear mechanism of other carbon brush was adhesive wear and ablation.