The paper presents a method for testing transport of composite contacts materials under electrical arc conditions at high currents and for polarized electrodes. Tests and the discussion of results were carried out for silver-metal, silver-metal oxide and silver-tungsten carbide contact materials. Additionally, tungsten electrode was used as the second contact which was either cathode or anode. Spectrometric analysis of arc erosion components transported onto the second electrode and into the surroundings was carried out.

In this paper, the relationship between contact materials and sticking characteristics, and stability of contact resistance to obtain excellent contacts for telecommunication relays, is studied. The contact switching current for telecommunication relay is low. Moreover, contact force and opening force in these relay are respectively several mN. Nine kinds of contact materials are selected as a experimental factor. They are Ag, Ag-Ni (Ni: 0.03 to 20%), Ag-Cu 10%, Ag-Pd 60% and Pd-Ru 10%, and are overlaid with gold except Pd-Ru 10%. In this study, contact life tests on a commercial ultra-miniature telecommunication relay by mounting above-mentioned contacts are conducted. The sticking and the contact resistance are monitored at each switching operation in the contact life test. After the life test, the contact surfaces are observed, and the depth of crater, the height of pip and projected concave area are measured, then the relationship between the sticking morphologies and the composition of each material are studied. As the result of this study, the contact sticking of telecommunication rely is assumed to be the result of mechanical locking, and the effects of the Ni content in the Ag-Ni contacts is clarified. Moreover, it is confirmed that the effects of opening force on the sticking characteristics are remarkable.