Abstract
In order to control the grain size of submicron grains in cemented tungsten carbides, (1) the relation between the morphorogical properties of W powders and the properties of WO3, and H2WO 4 3(NH 4)2O.12WO3.5H2O, and (2) the transition of particle sizes after the reaction W+C→WC, were studied by measuring the particle size with the permiability, the absorbtion, X-rays, apparent and tap density, and electron microscope. Several results were obtained as follow.
(1) The permiability, the apparent and tap density, and the colour of submicron W powders are subject to the size of aggregated particles.
(2) The size of the unit particles can determined better by using the X-ray, the absorbtion, the electron microscope methods.
(3) The size of the aggregates of fine W powders is subject to the size of WO3 particles, but the size of the unit particles is not subject to it.
(4) The particle size of WC powders is subject to the size of unit particles of W powders, either when the W powders are the weak aggregates that are easily broken into dispersed unit particles or when they are the strongly sintered aggregates of unit powders.
(5) The WC grain size of WC-Co alloy is subject to the size of WC powders, if grain growth does not occur during sintering.
