High Current Brush Material Development, Part II: Metal- Solid Lubricant Coated Wires

The preparation and testing of an electrical contact material, metal-solid lubricant coated copper wires for fabrication of multielement high current brushes, are described. The composite coating consisted of a metal, copper or silver, and an overall 1-5 weight percent (wt %) of a fine solid lubricant powder (graphite, WS 2, or WSe2) evenly dispersed and well oriented in the metal matrix. The coatings were obtained by an electrolytic codeposition technique. By sliding a bundle of the coated wires against a rotating silver or copper slip ring at constant speed of 16.75 m/s, the sliding characteristics-- contact voltage drop and friction of the testing system-were measured as a function of current density up to 12.4 MA/m²in several different gas environments. Several brush life tests were made at 12.4 MA/m 2. Results indicate that the coated wire possesses high currentcarrying capability under a wide range of environmental conditions. The tests also showed that vapor lubrication is applicable to all solid lubricants with lameilar structure for reduction of wear rate. A tribochemical background of the sliding system is discussed.