Formation of the (Ti,V)(C,N) solid solutions by HPHT sintering of mechanically alloyed TiC–VN powder mixtures

Abstract

Nanocrystalline solid solutions of Ti_1−xV_xC_0.5N_0.5 (x = 0.4–0.6) were synthesized by HPHT sintering (7.7 GPa, 2150 °C) of TiC–VN powder mixtures (molar ratios 2 : 1, 1 : 1, and 1 : 2), which had undergone preliminary 9-hour mechanochemical processing in a high-energy planetary ball mill until the formation of (Ti,V)C and (V,Ti)N solid solutions. The resulting compacts possess homogeneous microstructure, which was confirmed by XRD, SEM and EDS studies. Composition of the sintered solid solutions corresponds to the original TiC–VN blends, while their lattice parameters fit well into the linear dependence of Vegard's law. The Ti_1−xV_xC_0.5N_0.5 solid solutions remain stable after annealing for 2 hours at 800 °C. The Vickers microhardness measurements were carried out, with the hardness values monotonically varying between those typical for TiC and VN phases. The proposed two-step method (mechanochemical activation followed by high-pressure sintering) enables the synthesis of composites containing nanocrystalline solid solutions of a predetermined composition.