Synthesis of tungsten carbide-nickel composites by the field-activated combustion method

The activation of self-propagating combustion reactions in the WC-Ni system was investigated by using an electric field. Self-sustaining combustion in elemental reactants with composition corresponding to WC-x wt.%Ni (0 less than or equal to x less than or equal to 10) composites can be activated only when the imposed field is above a threshold value. The nature of combustion products depended on the magnitude of the field. The products contained the high temperature phase (WC), low temperature phase (W2C) and mixed compounds of type Ni2W4C. WC diffraction peaks in X-ray diffraction diagram shifted right when moving from the reactants region to the final product one or increasing electric field. The effect of the relative density of the reactants compact on the synthesis of WC-Ni was also investigated. Moreover, the reaction mechanism of WC-Ni is proposed. X-ray and microscopic analysis of the quenched combustion front suggests that the synthesis of WC is a process involving the solid diffusion of carbon into a carbide layer. Molten Ni reacts with W and W2C to form intermediate phase, which decomposes into WC and Ni. Molten Ni redounds the transformation from W2C to WC phase. (C) 2003 Elsevier Science B.V. All rights reserved.