Converting calcium tungstate to tungsten, tungsten carbide and cemented tungsten carbide

What is it about?

Tungsten is conventionally made by the reduction of tungsten oxide with hydrogen, tungsten carbide by the reaction of tungsten with carbon and cemented tungsten carbide by the sintering together of tungsten carbide with a metal, usually cobalt. This paper reports the electrochemical preparation of tungsten, tungsten carbide and cemented tungsten carbide starting with calcium tungstate, carbon and cobalt oxide, depending upon the desired end product. The starting materials were mixed and pelletised, and the pellets then made the cathode in a calcium chloride based melt. On the application of a modest potential (∼3 V), the calcium tungstate was reduced to tungsten, the mixture of calcium tungstate and carbon to nanosized tungsten carbide and the mixture of calcium tungstate, cobalt oxide and carbon to cemented tungsten carbide, all in ∼1 h. The products were characterised and the reaction path determined.

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Why is it important?

This paper describes an alternative method of treating tungsten ores.