Viability study and mechanical characterisation of copper-graphite electrical contacts produced by adhesive joining

Using pitch as binder additive between copper and graphite during the sintering process of brushes for electrical motors supposes an increment in the fabrication cost due to pitch previous treatment. In this work, mechanical properties for a type of brushes, obtained using two different methods without pitch addition, has been studied. In the first method, a conventional dry mixing of copper and graphite powder has been carried out by ball mill. The selected composition was 60 wt.% Cu and 40 wt.% C. All the samples were compacted at different pressures using uniaxial compacting. The green parts were infiltrated with a polymeric binder by vacuum method. Finally, a heat treatment was carried out to cure the infiltrated parts to improve mechanical strength. In the second method, a mix of copper, graphite and polymeric binder was made to obtain pastes. This raw material was compacted at different pressures by uniaxial pressing to obtain parts. After this, a curing treatment was carried out. Physical and mechanical properties, electrical conductivity, bending strength, porosity and wear behaviour, have been measured. (C) 2003 Published by Elsevier B.V.