Cemented carbide WC-Co nanocomposite powders were synthesized through in situ reduction and carbonization of a core/shell precursor in vacuum. Samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The results revealed that WC-Co composite powders can be obtained at 950 degrees C for 1 h and the particle size is in the range from 30 to 50 rim with good dispersion. The formation mechanism of the WC-Co composite by in situ reduction and carbonization reactions was proposed. The preparation process could be divided into three steps: first, the reagents were dissolved and mixed to an aqueous solution; second step is to synthesize a carbon encapsulated core/shell nanostructure precursor using hydrothermal route, and finally, in situ reduction and carbonization of the precursor to the desired nanocomposite powders in vacuum. (C) 2012 Elsevier Ltd. All rights reserved.