Reaction interaction in Hf–Nb–B4C and Hf–Nb–B4C–C systems

The reaction interaction in the Hf–Nb–B4C and Hf–Nb–B4C–C systems has been studied at a temperature of 1750 °C, isotherm times of 30 and 60 min and residual argon pressure of 100 Pa. A different sequence of interactions between the reactants was established. In the Hf–Nb–B4C system, the formation of HfB2, NbB2, HfC, and NbC phases is a consequence of the diffusion saturation of Hf and Nb with boron and carbon from B4C. The presence of elemental carbon in the Hf–Nb–B4C–C system conditions the initial synthesis of HfC and NbC carbides. In addition to the formation of carbides, the diffusion and borination from B4C of these carbides occurs, resulting in the formation of borides HfB2 and NbB2. The conclusions are verified by thermodynamic calculations.