Microstructure Analysis and the Effect of Cr Additive on Electrical Performance of (Cp-Nb)/Cu-Cd Electrical Contact Materials

(C_P-Nb)/Cu-Cd electrical contact material, which contains 1.7 wt.% of Cd, 0.5 wt.% of C_P (man-made diamond particles) and 2.0 wt.% of Nb, is fabricated by powder metallurgy process and is considered to be used as a low cost substitute of silver-based contacts in heavy duty AC contactors. The existing state of each element was analyzed and the improvement of arc erosion resistance was achieved by introducing a small amount of Cr additive. Microstructure investigation revealed that a fine crystal transition layer was formed around the embedded Nb particles to enhance the binding force between Nb particles and Cu-Cd alloy basis, and then improved the arc erosion resistance of this material. The addition of Cr could also reduce the penetration depth of fissures that pierces into contact material during the arc erosion test. Evaluated from of arc erosion duration and temperature rise test results, an optimal 0.7 wt.% Cr content was concluded.