Mechanochemical Synthesis of Nanocrystalline Tungsten Carbide Powders

Abstract

Nanocrystalline tungsten carbide powder mixtures of WC, W₂ C, and cubic WC_1–z were prepared by the mechanochemical method of reactive high energy ball milling WO₃–Mg mixtures containing graphite as a source of carbon for the W phase. The synthesis is completed in two steps, namely the explosive reactive synthesis of α-W by the reductive reaction of Mg with WO₃ and the diffusion reaction of high activity α-W with C. The chemical regularities of mechanochemical synthesis of the refractory compounds are given. After grinding for 50 h at a milling rate of 250 rev min⁻¹, all WO₃ and C diffraction peaks disappeared and only diffraction peaks of tungsten carbides and MgO remained. The final product, with an average grain size of about 4–20 nm was obtained after MgO was removed by HCl solution. PM/0795