Properties of Cu–Mo Materials Produced by Physical Vapor Deposition for Electrical Contacts 

Abstract

New Cu–Mo composite materials were produced by physical vapor deposition (PVD) using an L5 electron-beam unit. They were proposed as an alternative to silver-containing materials for the manufacture of electrical contacts. The electrical (resistivity), mechanical (hardness, shear strength), and chemical (oxidation resistance in long-term operating conditions, high currents and temperatures, weldability of contact pairs at peak loads) properties of the PVD Cu–Mo composites were studied against the properties of serial electrical contact materials manufactured from AgC5 and Ag–CdO pseudoalloys. The developed materials were found to be competitive with silver-based composites in terms of output resistivity and resistance to welding of contact pairs at currents up to 3000 A, exceeding the rated value by more than 10 times. The resistivity increased by two to three times, but no signs of seizure (welding) were found on any contact. The strength of the brazed joint with a copper contact holder provided with the Cu–Mo alloys was higher than with the AgC5 alloys by more than two times and the hardness by four times. At the same time, the developed copper-based alloys were inferior to the silver-based alloys in oxidation resistance, in turn leading to an increase in resistivity and heating of the contacts. The corrosion resistance of the Cu–Mo alloys strongly depends on the presence of droplet inclusions (with corrosion processes being intensified around them), operating environment, and operating temperature of the contacts. In operating conditions with minimal oxidation processes (low humidity, room temperatures), the use of copper-based contacts is much more expedient because they are less costly compared to silver-based contacts.