Synthesis and sintering of TiB2 and TiB2-TiC composite under high pressure

TiB2 and TiB2-TiC composite compacts with 98-99% density are prepared by hi gh-pressure sintering (HPS) of premixed powders and by high-pressure self-c ombustion synthesis (HPCS) from the elemental constituents. The sintering a nd synthesis experiments are carried out at 3 GPa in the temperature and ti me ranges 2250-2750 K and 5-300 s, respectively. A high sintering temperatu re (2750 K) is required to obtain dense monolithic TiB2 compacts (98% densi ty) by HPS. Compacts with a similar density are obtained at lower sintering temperature (2250 K) when 15 mol% TiC is added to TiB2. The composite comp acts have marginally better fracture toughness than that of monolithic comp acts. TiB2 and TiB2-TiC compacts (99% density) are also prepared by HPCS fr om elemental constituents. A minimum ignition temperature of 2250 K is requ ired to make the reaction self-sustaining, The compacts prepared by HPCS ha ve superior fracture toughness to those prepared by HPS. The microstructure s and the properties of the compacts prepared by HPS and HPCS are compared. possible sequence of reaction during the HPCS of TiB2-TiC is proposed. (C) 2000 Elsevier Science S.A. All rights reserved.