Influence of refractory particle size on sintering of electrical contacts with high volume fraction of liquid phase

摘要

This work deals with different processes for Ag-based electrical contacts fabrication. The Ag-based contacts had 22 vol.% WC and W (Ag-30WC and Ag-35W, in wt.%). With this high llquid volume content (78%), the use of infiltration process isimpossible because there are no conditions to make pre-sintered skeleton with this volume of open and interconnected porous. In this work, samples of Ag-30WC and Ag-35W were sintered using the conventional sintering method: mixing, pressing and heattreating above Ag's melting point. The objective was to establish the Influence of WC (and W) particle size and the influence of Ni coating on final porosity. Three different WC and W particle sizes have been used, all chemically Ni-coated. The wettingphenomenon is discussed to explain the difference between Ag-W and Ag-WC wetting behavior. The results showed that it is necessary to have minimum WC and W powder particle sizes, both chemically Ni-coated, to obtain sintered samples with less than 5%final porosity.