A novel core-shell structured ultra-coarse WC-Co composite powders prepared by fluidized bed chemical vapor deposition

The ultra-coarse WC-Co composite powders with a core-shell structure were effectively prepared by fluidized bed chemical vapor deposition (FBCVD) using CoCl2 precursor. An excellent interfacial bonding was formed between WC and the deposited Co. Defluidization was the major barrier to depositing high-Co-content composite powders, which was caused by the adhesion of the deposited Co particles. Decreasing the deposition temperature reduced the cohesion force of the deposited Co particles, which was thus beneficial to preventing the defluidization. Increasing the WC particle size and the gas velocity increased the collision force and benefited the fluidization. The final Co contents were largely dependent on the deposition and fluidization behaviors. For the conditions tested, the optimal deposition temperature was 800 degrees C while the minimum WC particle size suitable for FBCVD was 25 m.