Analysis of WC with increased Ta doping

WC powder with increased Ta doping has been produced. Tungsten and tantalum metal powders were cocarburized to yield a mixture of cubic and hexagonal carbide. The carburization was made through a two-step carburization process with (W,Ta)(2)C powder as an intermediate product. X-ray diffraction analysis showed that the lattice parameters of the hexagonal phase in the fully carburized powder were larger than those of pure WC indicating the formation of a mixed crystal carbide, (W,Ta)C. The powder with the largest lattice parameters was investigated in detail. A method to produce atom probe tomography specimens of this powder was developed. The largest Ta solubility, expressed as Ta/(Ta + W), was 0.086 which is more than four times higher than what previously has been observed. In addition, it was found with electron backscatter diffraction that the (W,Ta)C grains had a large fraction of Sigma 2 grain boundaries as well as a small fraction of what was suggested as Sigma 4 grain boundaries. (C) 2015 Elsevier Ltd. All rights reserved