Switching performance of W-Ag electrical contacts fabricated by mechanical alloying

Blended elemental W - 35 w/o Ag powders were mechanically alloyed in a heavy duty attritor mill for times up to 15h followed by compaction, sintering, furnace cooling and re-sintering under industrial conditions. Changes in the morphology and microstructure of the as-milled powders and the compacts were characterized by scanning electron microscopy which revealed regions of nominal composition and loose W particles in the as-milled state. X-ray diffraction scans of the milled powders and compacts showed the presence of W and Ag peaks. Higher densities and hardness values were achieved for compacts mechanically alloyed at longer times. The arc erosion characteristics of the W-35w/oAg compacts confirmed that the erosion rate of the contact material decreased with increasing milling time. On the basis of a linear regression estimate, all the compacts were found to be suitable for electrical contact applications. In particular, compacts mechanically alloyed for 10h were estimated to endure more than 3 × 10⁶ operations.