Carburization of ammonium paratungstate by methane: The influence of reaction parameters

Tungsten carbide powder is conventionally produced by carburization of tungsten powder by carbon black in a solid–solid reaction. This paper reports the carburization of ammonium paratungstate by methane to yield tungsten carbide at low temperature in short times. The carbide powder is fine grained and has specific surface area around 35 m2/g. This makes the powder interesting for catalysis and fine grained hard metals. The influence of reaction parameters such as temperature, gas flow, composition of the reaction gas and powder charge are investigated by means of gas chromatography and XRD with Rietveld refining. The overall reaction time is the sum of reduction and carburization times of the sequential reactions. Some parameters, like gas composition affects only the carburization rate, other parameters, such as gas flow affects both reactions.