Consolidation and high-temperature properties of ceramics in the TaC–NbC system

In this study, we explored the consolidation, solid-solution formation, and high-temperature properties of carbides in the Ta–Nb–C system. The tantalum niobium carbide bulks can be consolidated by spark-plasma sintering only at a temperature of 2200°C using a 30-min dwell. The ceramics were homogeneous solid solutions and a linear dependence of the lattice parameters on the NbC content was observed. The average grain size varied between 10 and 30 μm, while the reference monolithic tantalum carbide consolidated under similar conditions had a grain size exceeding 40 μm. The room temperature strength linearly decreased from TaC to NbC. The 75 mol% NbC ceramic showed almost an unchanged strength up to 1600°C (450 ± 20 MPa), following the linear decrease in strength to 290 MPa at 2000°C. The monolithic tantalum carbide had showed the lowest strength at 2000°C among the studied ceramics.