SYNTHESIS AND SINTERABILITY OF COMPOSITE POWDER OF THE TIB2-B4C SYSTEM

Composite powders of composition TiB2-xB4C (x = 0.3, 0.5, 0.7 and 1.0) were synthesized by a solid state reaction between TiCxN1-x and amorphous boron. The formation of TiB2 and B4C occurs by a stepwise process: (1) the formation of TiB2 by the substitution of boron for carbon or nitrogen atoms in TiCxN1-x; (2) the simultaneous or subsequent formation of B4C by the reaction between unreacted boron and free carbon released from TiCxN1-x. The formation reaction of a well-dispersed composite powder of the TiB2-xB4C system was completed by heat treatment of the starting powder mixed in the mole ratio TiCxN1-x: B = 1:(4x + 2) under a flowing argon atmosphere at 1500-degrees-C for 60 min. The synthesized powder, which was densified at 4 GPa and 1600-degrees-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.