Synthesis of TiB2-Ti(CN) Composites by Reactive Spark Plasma Sintering.

Dense TiB2-TiCxN1-x and TiB2-Ti(C0.5N0.5)y composites were synthesized from powder mixtures of B4C, BN and Ti by reactive spark plasma sintering. The reaction 2xB4C+2(1-x)BN+3(x+1)Ti→(3x+1)TiB2+2TiCxN1-x for TiB2-TiCxN1-x and the reaction B4C+BN+(5/2+2/y)Ti→5/2TiB2+2/yTi(C0.5N0.5)y for TiB2-Ti(C0.5N0.5)y, proceeded during their sintering. The relative density of the TiB2-TiCxN1-x composites increased as the nitrogen content decreased, and the composites had relative densities more than 99 % at higher x than 0.5. The Young's modulus, Vickers hardness and fracture toughness of the composites increased with increasing x. For TiB2-Ti(C0.5N0.5)y composites, the relative density became still higher than 99.1 % at smaller y than 1, i.e., increasing nonstoichiometry. However, the Young's modulus, Vickers hardness and fracture toughness decreased with decreasing y value.