Mechanical properties of Mo-Nb-TiC in-situ composites synthesized by hot-pressing

Mo-40 mol%TiC and Mo-20 mol%Nb-40 mol%TiC in-situ composites were synthesized by hot-pressing mixed Mo, Nb and TiC powders. Both composites consist of two phases, Mo solid solution (A2) and TiC (B1), after hot-pressing at 2073 K and 70 MPa for 2 h followed by annealing at 2073 K for 24 h. Porosity of hot-pressed compacts decreased by Nb addition to Mo-40 mol%TiC. The composites have different microstructural features. Clusters consisting of fine bcc particles are observed in sizes similar to original Nb powder in Mo-20 mol%Nb-40 mol%TiC, while there are no clusters in Mo-40 mol%TiC. These composites show excellent strength superior to monolithic TiC at high temperatures. The addition of Nb to Mo-40 mol%TiC suppresses effectively intergranular fracture above 1473 K. Furthermore, fracture toughness of these composites is higher than that of monolithic TiC. Fracture toughness of Mo-20 mol%Nb-40 mol%TiC is slightly lower than that of Mo-40 mol%TiC. The obtained results are discussed in relation to microstructural characteristics.