Sliding electrical contact behavior of brass fiber brush against coin-silver and Au plating

Abstract

Sliding electrical contact behavior of the brass fiber brush with 23% packing fraction was investigated as sliding against coin-silver and Au plating under vacuum and air conditions. The friction coefficient, contact resistance and electrical noise of the brushes were analyzed. The microstructure and worn surfaces of the brass fiber brush and counter discs were observed to discover the involved wear mechanisms. The friction coefficients in vacuum are much higher than those in air. The contact resistances and electrical noises of the brush against both discs in vacuum are extremely low. The contact resistance against coin-silver quickly increases as the sliding condition varies from vacuum to air, which is much higher than that against Au plating. Sliding speed has an insignificant effect on the contact resistance and electrical noise of fiber brush. Formation of oxide film and loose oxide particles on the worn surfaces of fibers and the coin-silver disc leads to the increase of contact resistance and electrical noise. The transfer of gold from Au plating to worn surfaces of brass fibers is used to prevent the oxidation of fibers and keep the contact resistance and electrical noise in a relatively low level. The multi-contact mechanism of brass fiber brush has been also discussed.