Electro Spark Synthesis of α-WC Powder and Study of Its Phase Transformations upon Annealing

We propose in this paper a method for the synthesis of α-WC powder by the method of electric spark discharge, where WC–8% Co (anode) and W (cathode) are used as electrode materials, and deionized water is used as a dielectric liquid. The synthesized powder was subjected to thermal annealing after drying in an air atmosphere at temperatures of 250, 400, and 600°C for 2 h in order to analyze its thermal stability and identify possible temperature-dependent phase transitions. The phase composition, morphology, and particle sizes of the synthesized powder and powders subjected to thermal annealing were studied by powder X-ray diffraction and scanning electron microscopy. The synthesized powder contained two phases: the dominant α-WC phase and the α-W₂C phase. Both α-WC and α-W₂C phases almost completely transformed into the CoWO₄ phase at an annealing temperature of 600°C. The processes of formation of the phase components of the synthesized powder and the transition of these components to the CoWO₄ phase as a result of thermal annealing are discussed.