Combustion synthesis of tungsten carbides under electric fieldI. Field activated combustion synthesis

The activation of self-propagating combustion reactions in the W–C system was achieved by using an electric field. Self-sustaining combustion in elemental reactants with the composition corresponding to WC can be activated only when the imposed field is above the threshold value of 1V cm−1. The nature of the combustion products depended on the magnitude of the field. The product consisted of two kinds of tungsten carbides, WC and W2C. The effects of tungsten particle sizes and the relative densities of the reactant compacts on the synthesis of tungsten carbide were also investigated. Finally, the reaction mechanism of tungsten carbide was proposed. X-ray and microscopic analysis of the quenched combustion front suggested that the synthesis of WC is a process involving the solid diffusion of carbon into a carbide layer. W2C is the intermediate phase between WC and reactants (W and C).