Effect of normal load on damage mechanism of gradient copper-graphite composites under electric current

A gradient design of material is an effective way to solve the inhomogeneity of current-carrying damage. However, service conditions have a great influence on the current-carrying damage of gradient composites. To promote the development and application of current-carrying friction materials, it is necessary to elucidate the current-carrying damage mechanism of gradient composites with different service conditions. To this end, the gradient copper-graphite composites were prepared by hot pressing and sintering, and the variation in the current-carrying properties of the composites with loads were investigated in this study. The results showed that with increasing load, the wear rate of the composites initially decreased and then increased, while the currentcarrying properties initially improved and then deteriorated. The composite exhibited better current-carrying tribological performance at the load of 55 N, and the wear rate of the composite was 1.59 x 10-4 mm3 N- 1 m- 1. Meanwhile, the current carrying efficiency and current carrying stability was 98.5 % and 2.2 %, respectively. The main wear mechanism of the composite at 55 N was plastic deformation.