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AssigneesMitsubishi Materials Corporation, Japan New Metals Co., Ltd.
InventorsHiroshi Yaginuma, Susumu Morita
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A process is provided for producing a fine tungsten carbide powder, which comprises the steps of drying a slurry, which is obtained by mixing an aqueous ammonium tungstate solution with a carbon powder, at low temperature, to form a precursor, mixing a reduction and carburization product, which is obtained by reducing and oxidizing the precursor in an inert gas, with a carbon powder in a proportion required to substantially carburize the entire tungsten component into tungsten carbide (WC), and carburizing the mixture; and a high-performance fine tungsten carbide powder produced by the process, which has an average particle size of 0.8 μm or less and is free of a coarse power having a particle size of more than 1 μm, and which also contains less metal impurities and contains oxygen and nitrogen in a predetermined amount.
A tungsten carbide powder comprising (a) an average particle size as measured by the Fischer Subsieve Sizer process of 0.8 μm or less, (b) a maximum particle size in a particle size distribution as measured in accordance with ASTM B430-79 of 1 μm or less, (c) the content of tungsten based on the component excluding a non-metal component being at least 99.9% by weight, (d) the content of nitrogen and that of oxygen in crystal lattices being respectively within a range of 0.08-0.30% by weight and 0.10-0.60% by weight and (e) a lattice constant of an a-axis and that of a b-axis being respectively within a range of 0.29020-0.29060 nm and 0.28380-0.28420 nm.
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