IE32229L - Diamond compacts - Google Patents

Abstract

1,240,525. Diamonds. GENERAL ELECTRIC CO. 1 Aug., 1968 [8 Sept., 1967], No. 36801/68. Heading C1A. Polycrystalline diamond compacts containing not more than 2% by wt. of material other than diamond, having a density in excess of 91% of the theoretical and being substantially homogeneous are produced by either: (i) heating fine diamond particles at a temp. of 600-900‹ C., or (ii) bombarding fine diamond particles with +ve ions in an inert atmosphere (as defined) at subatmospheric pressures. After either of these two treatments the diamonds are compacted at a pressure >50 kilobars and a temp. of 1300‹ C. Fig. 1 is a diagram of the equipment required for either of the first two treatments. 1 is a pan of Mo, Co, Ti on which the diamonds are placed. For ion bombardment anode 4 and the pan 1 acting as cathode are wired to a D.C. supply which produces a voltage differential of between 1500 and 1800 volts. Agitation of the cathode can be carried out by a solenoid-actuated vibrator 8. For the heating process, a resistance heater 9 beneath the pan is used. Fig. 2 is a diagram of the reaction vessel for use in the high pressure, high temp., compacting step. The reaction vessel 17 is of the indirectly heated type having a pyrophyllite outer cylinder 18 and a graphite heating tube 19. Another cylinder 20 of alumina is placed inside the heating tube and a liner 21 of graphite is placed inside the alumina cylinder. Matrix materials that may be used to form the compacts are B, Ta, Mo, Ti or their carbides or borides. The compact however should not contain more than 2% by wt. of matrix material. The sintering stage is carried out in an inert atm. or preferably a reducing atm. An inert atmosphere is defined as an atmosphere free from oxygen, nitrogen and water vapour. [GB1240525A]