Influence of powder granulometry on the sintering of binderless tungsten carbide

In the production of uniaxially pressed components, the powder size, distribution and pressure used are key factors to obtain a high quality product. Several models have been reported to correlate the packing and sintered densities as a function of the compaction pressure but, most of them for spherical-like and wide particle size distributions, In this work, a series of submicron average particle size (0.8, 0.4 and 0.2 mum) commercial WC powder mixes are evaluated for pressures in the range 200-350 MPa. The cobalt binderless samples were vacuum solid state sintered at 1400 degreesC for 1 h. The results indicated that both green and sintered densification (Dr) increased with pressure (p) and that the bimodal and trimodal mixtures studied follow a mathematical expression of the type: Ln(1/(1-Dr)) = 0.428 x 10(-2) p + 0.576 for the green relative density in the whole pressure range evaluated.