Genetic Structure Of Tungsten Powder In The Reduction And Carbonization And Its Role In The Preparation Of Nano-tungsten Powder And Tungsten Carbide Powder Applications

As one of the most important resource, tungsten-based materials have natures of high melting point, high elastic modulus, high hardness, good thermal conductivity and excellent fracture toughness, etc. The products have been widely used in many industrial areas. Hydrogen reducing tungsten oxide powder has its own characteristics, it become one of the main methods of industrial production of tungsten powder.The phase structure, morphology and particle size evolutions of tungsten oxide reduced by hydrogen process were studied by X-ray diffraction, high-temperature metallurgical microscope, scanning electron microscope and specific surface area meter. It is shown that the phase structure evolution is WO3-WO2.90-WO2.72-WO2-W. The surface morphology of powders changes from a smooth grain to a rough grain and eventually the powder turn to several small grains. The specific surface area increases in WO3hydrogen reducing is also researched, the results show that the powder’s BET will increase when WO3reduced to WO2.72, then decrease in the left reaction.Influence of Preparation of tungsten carbide powder was studied. The result shows that the most important factor to affect the grain size of tungsten carbide powder tungsten powder size and size distribution. Carbonization process mainly depend on the surface of tungsten particles and carbon gas reaction and solid silica diffusion within the tungsten powder to achieve. Therefore, the influence of carbonization temperature, carbonization time, materials and carbon content of tungsten carbide powder size is relatively small, but the tungsten carbide grain size, the rate of carbonation and performance, the general rule is:at a certain temperature range, the higher the temperature of carbonization holding time is longer the more completely, carbonation; raw purple tungsten and tungsten yellow, after reduction, carbonation, the purple tungsten, tungsten carbide grains smaller, single phase, uniformly dispersed particles, size distribution, purple tungsten is ideal for the production of tungsten powder, tungsten carbide raw materials; the carbonization process of the tungsten powder:W powder→the W2C→WC sequence, rely mainly on the surface of tungsten particles and carbon gas reaction and solid silica diffusion within the tungsten powder. Tungsten powder with carbon formed due to the toner with the hydrogen reaction of hydrocarbons and volatile, so when the ratio of toner to the number of moles of tungsten powder, the number of moles is greater than1, about1:1.07for the best value. Preparation of BET2.44m2/g WC powder.The morphology of tungsten powder was observed by W-Cu alloys. It shows that tungsten powder can be clearly observed by W-Cu alloys under SEM. This method can be use to observed the morphology of tungsten powder.By the method of preparation of the W-Cu alloy metallographic observation of the morphology, the two-dimensional morphology and particle size of the clear characterization of the tungsten particles of tungsten powder can be used as a characterization of tungsten powder morphology and particle size approach.