In-situ synthesis of WC and WC-17Co powder under hydrogen atmosphere by solid carbothermic reduction method

WC ceramic is considered one of the advanced engineering ceramics due to its favorable properties. The weakness of this ceramic is, however, its brittleness, which can be tackled by composite making and addition of compounds such as Co to the structure of WC. In this research, WC and WC-17Co powders were synthesized by the in-situ carbothermic reduction from active carbon raw materials including WO3 and Co3O4. The main goal of this research was to determine the appropriate amount of carbon in the composition of raw materials. For this purpose, the raw materials were mixed in different ratios of excess carbon as the primary variable. All the samples were heat treated with a heating rate of 10°C.min−1 to a temperature of 1200°C for 3 h in a hydrogen atmosphere. Thermodynamic studies showed that cobalt and tungsten were regenerated from Co3O4, and WO3 at the temperature of 250°C and 700°C, respectively; by raising the temperature to about 1200°C, the formation of tungsten carbide was complete. According to the results, a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) and X-ray diffraction pattern (XRD) were obtained. The main reason for the lack of carbon in the total production of the WC phase was the reaction of carbon with hydrogen in the furnace atmosphere at temperatures less than 500°C, which could be solved by adding further carbon to the raw materials. The combinations (118.37gr WO3-147.06gr C) and (56.95gr C-23.15gr Co3O4-98.25gr WO3) created the best conditions for the production of WC and WC-17Co powders. The results of microstructural studies also showed that the size of grains in the WC-17Co composite powder was larger (less than 200 μm) than that in the WC ceramic powder (less than 20 μm). This was related to the presence of Co3O4 in the raw materials and cobalt in the WC-17Co cermet powder.