Production of copper based electrical motor brushes and investigation of properites

This study was carried out on the examination of the production and properties of electric motor brushes which act as electrically conductive and wear elements in direct contact with the moving part (rotor) of electric motors. Within the scope of the study, electric motor brushes were produced and their characteristics were investigated in six different groups consisting of copper matrix composites containing graphene, hexagonal boron nitride, alumina, boron carbide and silicon carbide reinforcements in varying proportions. The composite powders were compacted with a cold and single-acting hydraulic press under a pressure of 500 MPa (±5 MPa) following 8 hours of mechanical alloying process. The molded samples were sintered at 900 ° C for 1 hour in a reducing gas atmosphere. Each sample was tested three times at 100 kPa spring pressure, 8, 16, 24, 32 m/s rotational speeds and current densities of 4, 8, 12, 16 A/cm2. In addition to that, the electrical conductivities, porosities, hardness, wear losses, surface roughness and temperature changes (oC) during testing were investigated for each sample. It was determined that the electrical conductivity decreased with increasing reinforcement ratio. In terms of electrical conductivity, it was determined that SiC is the most negative reinforcement material. When the electro-mechanical abrasion tests were examined, the lowest friction force (N) was measured with 0.083 N on a brush containing 5 wt. % graphene with 1 wt. % Al2O3. The lowest voltage drop (V) was measured with 0.03 V on a sample containing 10 wt. % Gr. with 0.5 wt. % Al2O3. When the weight loss of the brush samples were evaluated, it was determined that the most weight loss was achieved with a sample of 20 wt. % h-BN reinforced copper-based brush, at the rotation speed of 32 m/s with a current density of 16 A/cm2. It was also found that the average weight loss for this sample was 152.4 mg. When the hardness values were examined, it was seen that the general tendency in the hardness of samples decreased with the increasing of reinforcement ratio. The highest hardness value was found on the copper based composite brush (20 HB) containing 5 wt. % Gr.