Electric current effects in wear phenomena at a rotating Cu-Ag interface

Abstract

Two silver wire brushes were held in contact with a rotating copper slip ring in an ultrahigh vacuum system. After initial sputter cleaning of the copper slip ring, the vacuum system was backfilled with humidified CO 2 to a pressure of 1 atm. A d.c. electric current was passed across the silver brushcopper slip ring-silver brush assembly and the resulting wear particles were analyzed using scanning electron microscopy and electron probe microanalysis. The slip ring surface was analyzed using Auger electron spectroscopy to determine the amount of silver transferred. Currents ranging from 0 to 50 A were used. In each case the numbers of pure copper, pure silver, copper-rich and silver-rich particles were recorded as a function of the current. The Auger signal from the slip ring and the concentrations of the elements in the wear debris were plotted versus the current to determine the role of current in the present Cu-Ag system.