In-situ Synthesis of Nano Tungsten Carbide Composite Powder

Tungsten carbide is an important part of cemented carbide and cermet. It has high hardness, high wear resistance and excellent fracture toughness. It is known as "industrial teeth". It has been widely used in drilling tools, cutting tools, precision moulds, mining tools, printing needles, military armour piercing projectiles and other fields.

The preparation methods of nano tungsten carbide composite powder mainly include spray drying fluidized bed technology, chemical gas phase carbonization and mechanical alloying. The common problems of these methods are that the prepared tungsten carbide composite powders contain cobalt, and most of them use gas phase carbonization, which makes the cost high, and the preparation process complex, difficult to control, and unsuitable for industrial production.
Based on the exploration and research of the process, some scholars have proposed a method to prepare nano-tungsten carbide composite powder by in-situ synthesis. The implementation scheme is as follows:

The powdered ammonium tungstate, 18% activated carbon, 0.6% powdered vanadium acetate and 0.4% powdered chromium acetate were dissolved in 1000ml distilled water (70-100 ℃). After stirring, a uniform solution was obtained. The solution was heated for 1-2 h at 100-300 C and dried for 1-5 h at 50-100 C. Finally, the precursor powder was obtained. Nano WC-V₈C₇-Cr₃C₂ powders with average particle size less than 100 nm and uniform particle size distribution were prepared by placing precursor powders in a high temperature reactor under vacuum conditions at 1000-1200 C and 30-60 min.

Tungsten carbide composite powders containing vanadium carbide or chromium carbide grain growth inhibitors were prepared by in situ synthesis. Because of the absence of cohesive phase cobalt, the production cost is greatly reduced. Moreover, the production process can be completed by one-time carbonization, the process is simple and the operation is convenient. The particle size of the produced tungsten carbide powder is less than 100 nm, the particle size distribution is narrow, the particle size is uniform and the impurity content is small, which can fully meet the application of tungsten carbide powder in the field of ultra-fine cemented carbide.

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