Sliding contact characteristics between self-lubricating composite materials and copper

Previous investigations of a composite material (CM-1) containing 20% of MoS₂ and 20% of WS₂ showed that whereas the coefficient of friction was reduced to that between pure copper metals by the incorporation of solid lubricants, contact resistance was increased by 1-2 orders of magnitude due to the presence of copper oxide film. Coefficients of friction and contact resistivities of two types of composite materials CM-4 (WS₂ 8%) and CM-5 (WS₂ 45%), with low resistivities were measured simultaneously using an experimental tester. It was found that the contact resistances were reduced to as low as 1/10 that of CM-1. Although coefficients of friction of 0.4-0.5, which were slightly higher than that of CM-1 (0.3), were obtained, it was found that those composite materials could be applied to the sliding electric contacts where occurrence of welding must be prevented by lowering frictional force and wear rate. It was further found that CM-5 showed better lubricating performances than CM-4 and was more suitable as the material for sliding electric contacts