The welding tendency of CuCr contact materials in vacuum

Diffusion welding tests of vacuum casting Cu-30Cr, Cu-30CrZr, Cu-30CrTe and Cu-30CrZrTe alloy contact materials as well as sintered CuCr25 p/m contact materials were performed in the vacuum chamber of Gleeble 3500, and the joining forces of the welded pairs were measured by tensile test at ambient temperature. Characteristics of fracture surfaces were analyzed by optical microscope and SEM. It shows that the joining force and strength decrease in the order of Cu-30CrZr, Cu-30Cr, Cu-30CrZrTe, CuCr25 and Cu-30CrTe contact materials; fractographs of these contact materials show different fracture mechanisms. These results show that the joining force of the welded specimen depends mainly on the bonding force of the interface of Cr and Cu phases. Therefore, the modified structure and behavior of the interface of Cu/Cr phases by adding micro-alloying Te to decrease properly the bonding force of interface of Cr/ Cu phases will crucially improve the welding behavior of Cu-Cr alloy contact materials. Thereby, the possibility to improve the anti-welding property of available CuCr contact materials further and the potential fusion-welding problem of some VCB with lower contact force are discussed.