Effects of nickel addition on properties of Ag-W electrical contact materials

Tungsten and silver powders doped with small amounts of nickel were milled in a heavy duty attritor for 150 min to constitute the W-35 wt-% Ag composition. Milled powders were compacted, sintered, furnace cooled, and re-sintered using industrial conditions. Scanning electron microscopy (SEM) investigations revealed homogeneous dispersions of silver and tungsten regions both in the as milled powders and the as milled compacts. The X-ray results taken from the milled powders and the as milled compacts showed the presence of the characteristic W and Ag peaks. Bulk hardness values of the sintered compacts increased with increases in nickel additions. The arc erosion characteristics of the W-35 wt-%Ag compacts indicated that the erosion rate of the contact material declined with nickel additions. Contact life expectancy increases about 10 fold for the W-35 wt-%Ag compact containing 1 wt-%Ni from the one with no Ni content.