Synthesis of WC-0.67wt.%Cr3C2 nanopowders by a one-step reduction-carbonization method and their characterization

Abstract

Nano WC powders containing uniformly dispersed grain growth inhibitors are high-quality raw materials suitable for the fabrication of ultrafine grade WC-Co alloys. In this study, nano WC and WC-0.67wt.%Cr3C2 powders were prepared by a one-step reduction-carbonization method from WO3 and WO3-0.72wt.%Cr2O3 powders prepared via a spray drying-calcination process. The effect of Cr2O3 on the phase composition and microstructural evolution during the one-step reduction-carbonization of WO3 was investigated through X-ray diffraction, transmission electron microscopy, and scanning electron microscopy studies. When the reaction temperature was lower than 800 °C, WO2 and nano W phases were formed because Cr2O3 dispersed uniformly around the WO3 particles effectively hindered their reduction and inhibited the growth of W. With a further increase in the temperature to greater than 800 °C, Cr2O3 was gradually converted into Cr3C2 distributed on the surface of WC, leading to the formation of smaller WC grains. Additionally, Cr2O3 promoted the carbonation reaction due to the existent of smaller W with higher activity. Finally, the nano WC-0.67wt.%Cr3C2 powder with a narrow grain size distribution and high specific surface area of 4.58 m2/g−1 was obtained under a hydrogen gas flow rate of 50 L/min at 1100 °C in 0.5 h.