Development of Production Technique for Ultrafine Tungsten Carbide and Ultrafine Grain Cemented Carbide.

Fine grain cemented carbide having high hardness and toughness is used in various kinds of precision procecing industries such as semiconductor, electronic device, machine work. In order to make clear grain growth mechanism of WC phase for fine grain cemented carbide, a lot of studies have been done. However, there have been a few studies on formtion mechanism of ultrafine WC powder. We succeeded in manufacturing of ultrafine WC powder by direct carburizing method (direct reaction of W oxide powder with C). Particle diameter of WC powder made by direct carburizing method is mainly determined by the nucleation generated by the reaction from WO2.72 to WO2. Direct carburizaing method is advantageous to the manufacturing of ultrafine WC powder, and cemented carbide made from ultrafine WC by direct carburizaing method has higher hardness, strength and toughness than conventional cemented carbide.