Experimental Research On Producing Tungsten Carbide By Using Sodium Tungstate As Materials

Tungsten carbide is a kind of material with special physical and chemical properties like high strength, high toughness, high hardness and good wear resistance, heat and corrosion resistance etc., it has become a good substitute for noble metals in material processing, cutting tools, mining, military and other fields. At present, tungsten carbide is produced by tungsten powder as raw materials in the high temperature reaction with carbon production. However, tungsten is all made by tungsten oxide, through a very complex chemical process with long process and high cost. Sodium tungstate is an intermediate product in the production process of APT to produce tungsten trioxide, using sodium tungstate as raw material for preparing tungsten carbide powder can shorten the process, reduce the production cost.In this paper, the process of producing tungsten carbide by using sodium tungstate as raw material, calcium carbide as reductant were studied, and the two main process-reduction and two time high temperature carbonization process were analyzed using TG-DTA analysis, X ray diffraction, scanning electron microscopy and chemical analysis testing. The formation process of tungsten carbide was explored, and a better technical conditions of using sodium tungstate as raw material, calcium carbide as reducer to prepare tungsten carbide was obtained.The results of reduction process show that it is good at the formation of tungsten carbide and the growth of grain and the decreasing of crystal defect with the increasing of reduction temperature, the ratio of calcium carbide and reduction time. The content of oxide of reduction product which leached by hydrochloric acid is about 1%. The transformation process of tungsten from sodium tungstate to tungsten carbide should pass the way Na2WO4â†'WO3â†'WO2â†'W-W6C2.54â†'W2Câ†'WC with the reduction temperature rising.The W2C in the reduction product can be transform to WC by high temperature carbonization. In the high temperature carbonization process, the particle size of tungsten carbide increasing with the increase of heating rate and holding time, and decreasing with the decrease of cooling rate. It also can remove the most of lattice defects. The tungsten carbide with grain size of 100 nm could be obtained.The results of the paper show that it is feasible to produce tungsten carbide through two main process-reduction and two time high temperature carbonization process by using sodium tungstate as raw material and calcium carbide as reductant. The process can not only shorten process but also decrease the cost of production. It has significance for practice reference.