The Use of Ceramic Matrices Infiltrated with Silver for Electric Contact Applications

Results are presented of experiments that compare the performance of three ceramic-Ag contact materials (TiC-Ag, TiB2-Ag and NbC-Ag) with the well known WAg contact material. The conductivities of the ceramic-Ag contacts were found to be comparable to that of W-Ag. Erosion measurements in an 880 A 440 V rms circuit showed that the rate of erosion was not a simple function of the ceramic material´s heat of evaporation. The erosion mainly occurred through evaporation with some particle ejection in case of the W-Ag and NbC-Ag materials. The ceramic-Ag materials performed well when subjected to testing in a 100 A low voltage circuit breaker. A microstructural evaluation revealed that the contacts could have been improved by lowering the surface tension between the ceramic and silver to achieve better wet- ting.