Comparison of physical properties of Ta-Cu-X contact materials with mixing of additives

Abstract

W-Cu materials dominate the high-current electrical contact material market despite their limited machinability. This study investigates a potential alternative contact material, tantalum-copper-X (Ta-Cu-X; X = tungsten carbide (WC) or cerium oxide (CeO2), in which Ta imparts excellent machinability and thermal resistance while the oxides and carbides impart excellent mechanical properties. CeO2 and WC were selected as additives owing to their favorable chemical stability. Ta-Cu-X powder mixtures were prepared in order to facilitate the incorporation of different ratios of additives into molded and sintered Ta-Cu composites with a Ta: Cu wt% ratio of 40:60. The electrical conductivity, arc resistance, and hardness of the resultant composites were investigated. The electrical and thermal conductivities of the composites decreased with increasing additive content; however, their hardness increased. An optimum combination of electrical conductivity (52.8% IACS (International Annealed Copper Standard)), thermal conductivity (194.2 W/m center dot K), and hardness (163.5 HV) was demonstrated by the composite containing 0.5% CeO2; these properties compare favorably with those of commercially available electrical contact materials.