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 alpha-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 degrees 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 alpha-WC phase and the alpha-W2C phase. Both alpha-WC and alpha-W2C phases almost completely transformed into the CoWO4 phase at an annealing temperature of 600 degrees 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.