Reaction sintering of diamond using a binary solvent-catalyst of the Fe-Ti system

Reaction sintering of diamond was investigated using a starting mixed powder of purified natural graphite and a binary solvent-catalyst of the Fe-Ti system under high pressure (7G Pa) and temperature (1700°C) conditions for e treatment time of 1 to 15 min. Diamond sintered compact of about 100% conversion ratio from graphite todiamond was obtained with the binary solvent-catalyst content: 11.4 to 17.0 vol% (30 to 40wt%) Fe and 6.6 to 7.7vol% (10wt%) Ti. The sintered compact having the bulk density of 4.1 to 5.5g cm^–3, consisted of diamond phase and metal carbide (Fe₃C and TiCx) phase. The Vickers microhardnesm (under 1000 g load) mfthesintered diamond phase was >8OO0, while that ofthe metal carbide phase was 1000 to 2000. The transformation from graphite to diamond proceeded in a short time (< 1 min), which was followed by a particle joining between the formed diamond grains, when the densification would be attained at the reaction time of 15 min by pooling out the melt of carbon and solvent-catalyst.