Synthesis of the WC and Mo2C carbides by mechanical alloying of metal powder and carbon nanotubes

Abstract

Nanoscale WC and Mo2C carbides are synthesized from the elemental metal powder (with particle size of about 40 um; purity is not less than 99.6% wt.) and the carbon nanotubes (CNTs, with average diameter of 10-20 nm) by mechanical alloying in a high-energy planetary ball mill for the first time. Nature of interaction of the charge components at processing in a ball mill is studied on test samples (selected at each 1-2 hours of synthesis) using a complex of x-ray techniques. These techniques include: a full-profile analysis for the primary processing of diffractograms obtained with DRON-3M apparatus; qualitative and quantitative phase analysis for determining the phase composition of the products of synthesis; x-ray structural analysis to verify and refine the structural models; Williamson-Hall method for determining the grain sizes of synthesized carbides and microdistortions of their crystal lattice. Four hours of charge processing result in a formation of the high-temperature W2C and Mo2C carbides, the crystal structure of which is related to the ζ-Fe2N structure type with vacancies within the metal sublattice. Further milling of W-CNT mixture (up to 10 hours) is accompanied by the W2C + CNT → WC transformation, while processing of the Mo-CNT mixture leads to its dispersion. The effect of CNTs on mechanochemical synthesis of the WC and Mo2C carbides is considered. As shown, the mechanical alloying of W/Mo-CNT is a highly effective method for the fabrication of the WC and Mo2C carbides. Due to their unique mechanical characteristics (high hardness, wear resistance, and strength), these materials are widely used in making materials for the abrasive and metal cutting tools.