Synthesis and sinterability of composite powder of the TiB 2-B 4C system

Abstract

Composite powders of composition TiB 2- xB 4C ( x = 0.3, 0.5, 0.7 and 1.0) were synthesized by a solid state reaction between TiC x N 1− x and amorphous boron. The formation of TiB 2 and B 4C occurs by a stepwise process: (1) the formation of TiB 2 by the substitution of boron for carbon or nitrogen atoms in TiC x N 1− x ; (2) the simultaneous or subsequent formation of B 4C by the reaction between unreacted boron and free carbon released from TiC x N 1− x . The formation reaction of a well-dispersed composite powder of the TiB 2- xB 4C system was completed by heat treatment of the starting powder mixed in the mole ratio TiC x N 1− x : B = 1:(4 x + 2) under a flowing argon atmosphere at 1500 °C for 60 min. The synthesized powder, which was densified at 4 GPa and 1600 °C for 15 min, exhibited favourable sinterability. The sintered compact showed a relative density of 93.7%–97.0% and a Vickers microhardness of 35.3–37.3 GPa depending on the composition.