THE APPLICATION OF ULTRA-FINE PARTICLES IN TUNGSTEN POWDER METALLURGY

摘要

Ultra-fine tungsten powder (3.7 m2/g surface area), in amounts up to 25％, was mixed with commercial tungsten powders of 2, 4.5, and 6.8 micron average particle size. When compacted at 60 tsi, the densities varied from 69％ (of theoretical) for the 2 micron admixture to 76％ for the 6.8 micron admixture. Upon sintering in hydrogen for three hours at 1700°C, the corresponding values were 92％and 80％. The highest sintered densities were obtained in every case with the largest addition of ultra-fine powder.nThe radial/axial shrinkage ratio of the compacts was found to correlate with the density increase during sintering. This ratio (varying from 0.80 to 1.86 for all the mixtures) decreased with increasing amount of densification for each series of specimens.