Plasma Activated Sintering (PAS) of Tungsten Powders

Plasma Activated Sintering (PAS) is a short time, high temperature densification process based on three main contributions: resistance sintering, pressure application, and plasma generation. PAS was applied to the densification of untreated tungsten powder at temperatures between 2050 and 2685 K for 2 to 8 minutes in air or vacuum. The density values ranged between 80.2 and 91.5 % of theoretical density. The initial micron grain size was retained after consolidation at temperatures of 2350 and 2400 K. Net shape consolidation of a cutting tool was achieved by PAS densification of WC-Co powders. The clean grain boundary observed by high resolution electron microscopy in some of the PAS consolidated specimens suggests that activation of the powder surfaces may take place to enhance the densification process. This physical surface activation may be responsible for enhanced sintering of tungsten particles with no need for additives. The major benefits from this new non-conventional technique include an unusual short densification time (minutes as compared to hours for conventional densification), retention of unique initial microstructures and properties, as well as sintering in one single step with no requirements for binders, prior cold compaction or controlled atmospheres.