Recovery of tungsten carbides for preparing ultrafine WC-Co composite powder using core-shell structured precursor synthesized by CVD

The oxidation-reduction method is widely used in the recycling of cemented carbides because it offers advantages of a relatively low production cost, high recovery rate, and easy control of particle size. In this work, WC and Co in waste YG8 hard alloy were converted into WO3 and CoWO4 by oxidation. Subsequently, anhydrous alcohol, which was used as the reductant as well as the carbon source, was injected into the reaction system. A core -shell structured precursor synthesized by chemical vapor deposition method from pyrolyzed anhydrous alcohol was directly subjected to reduction and carbonization. Through thermodynamic calculations, the possible reactions in the carburization process were proposed. The influences of the reaction temperature and reactive time during the formation of WC Co powder were investigated. The effects of temperature on the particle morphology and size were also analyzed. Further, the possible reaction mechanism involved in the reduction and carburization processes was proposed on the basis of transmission electron microscopy and X-ray diffraction analyses. The results showed that the waste YG8 hard alloy was completely oxidized at 850 degrees C for 1 h. Pure WC -Co composite powder was synthesized at 800 degrees C with a holding time of 10 h, and the average particle size was similar to 190 nm. The coarsening rate of particles increased markedly with relatively high activation energy when the carburization temperature was higher than 850 degrees C.