Transactions of Nonferrous Metals Society of China
JOURNAL OF RAILWAY SCIENCE AND ENGINEERING
|Vol. 19 Special 3 December 2009|
（XIE Chen-hui(谢晨辉)2, PI Zhi-ming(皮志明)2, HU Mao-zhong(胡茂中)2, XU Tao(徐 涛)2,
WU Guo-gen(吴国根)2, YU Zhi-ming(余志明)1, YI Dan-qing(易丹青)1）
Abstract:Crystal growth of tungsten during hydrogen reduction of tungsten oxide (WO3) to prepare coarse grain tungsten powder at high temperature (950 ℃) was studied. The phase composition and morphologies of products were investigated by means of XRD and SEM. The results show that the reduction sequence of hydrogen reduction of WO3 is WO3→WO2.9→W18O49→WO2→W. The step of WO2→W is the critical step which determines the grain size of tungsten powder. The partial pressure (pH2O/pH2) of H2O within powder layer shows strong effect on the nucleation and grain growth of tungsten. By increasing the pH2O/pH2 within powder layer, well-developed coarse grain tungsten powder with particle size above 15 μm is obtained. After carburizing, the powder can be used to produce ultra-coarse grain cemented carbide with grain size above 5 μm.
Key words: coarse grain tungsten powder; hydrogen reduction of tungsten oxide; crystal growth; partial pressure