Improvement of the high temperature oxidation resistance and anti-arc erosion of pure Cu with the addition of La and graphite

Abstract

The effect of La and graphite additives on the oxidation resistance and arc erosion behavior of Cu alloys were studied. The pure Cu was completely oxidized to be Cu2O and CuO at 1000° for 1h, whereas the CuLa/C was partially oxidized. The reinforced phase graphite suppressed the formation of continuous copper oxide films. The formation of compact barrier layer of CuLa/C alloy was helpful for preventing the in-diffusion of the oxygen and was very effective in reducing the oxidation rate of the CuLa/C alloy. The resistance of pure copper was lower than that of CuLa/C alloy by EIS analysis. It was due to the electrolyte penetrated into the porous oxide film and decreased the resistance of oxide film of pure copper. Furthermore, The CPE-P of CuLa/C alloy was less than that of the pure copper, indicating the oxide film of CuLa/C alloy is more compact. After 5000 operations, the surface of pure Cu contacts were oxidized and eroded seriously, results in a marked increase in contact resistance and temperature rise. While contact resistance and temperature rise of CuLa/C contacts remained relatively stable. In the presence of an arc, the graphite combined with oxygen in the air or of the CuLa/C contacts, to form carbon oxide and carbon dioxide, emission of which can dissipate arc heat away from the contacts and reduce the surface temperature. Therefore, the addition of La and graphite improve the arc erosion resistance of Cu-based contacts.