The effects of CdO on the static gap arc erosion of silver-based contacts

Homopolar static gap electrical tests are used to evaluate the effects of adding cadmium as a metal to form an alloy, or as an oxide to form a composite on the erosion behavior of silver-based contacts. Pure silver tends to have anode-dominated erosion with little cathode disruption. Adding cadmium as either a metal or as oxide changes the erosion to cathode dominated. The cadmium tends to transfer from the cathode to the anode surface where it agglomerates in the form of an oxide regardless of its initial form (i.e. metallic or oxide particles). Material changes indicate reduction at the cathode surface and oxidizing at the anode surface. It is deduced that the deposited layer with its CdO agglomerates and porosity provides a weld-inhibiting interface between the contacts. The transferred material can also cover or heal areas weakened by prior arc erosion.<>