Abrasive tool making process – material – or composition – With inorganic material – Clay – silica – or silicate
Patent
1990-05-15
1992-04-21
Dixon, Jr., William R.
Abrasive tool making process, material, or composition
With inorganic material
Clay, silica, or silicate
51293, 51307, 51309, B24D 302
Patent
active
051063930
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to diamond compacts for use in the cutting, turning, drilling and similar working of hard materials.
Many different kinds of diamond compacts and diamond composites have been described in the literature and their properties vary widely. Generally speaking, a diamond compact is understood to mean a polycrystalline body possessing substantial abrasiveness and hardness and low or negligible porosity, comprised of more than 50 percent by volume of diamond crystals, in which a large proportion of diamond-to-diamond contacts occur.
U.S. Pat. No. 4,151,686 (Lee et al.) discloses a method for producing a diamond compact comprising diamond particles bonded by silicon carbide. According to this process, a mass of polycrystalline diamond powder is placed in juxtaposition with a body of silicon. The diamond-silicon assembly is placed in a high pressure-high temperature apparatus and subjected to a pressure of about 55 kilobars. The diamond-silicon assembly is then heated to about 1200.degree.-1500.degree. C. whilst subjected to pressure. This causes the silicon to melt and to infiltrate the mass of diamond powder. The temperature and pressure are maintained for a sufficient time to cause most of the silicon to react with the diamond to form silicon carbide which forms a strong bond between the diamond crystals, thereby producing a compact typically containing about 80-90 volume percent of diamond particles and 10-20 volume percent of silicon carbide. The product may possess high strength and hardness. A commercial product "SYNDAX-3" (Tomlinson et al., Ind. Diamond Rev. 45,299-304, 1985) is produced according to this process and is marketed as a cutting element for rock drills.
In order to practically utilize compacts produced by the process of U.S. Pat. No. 4,151,686, it is necessary to shape them into desired forms. This is difficult because of the hardness of the diamond compacts. Currently, when these kinds of compacts are used in industry they are shaped by laser-cutting and drilling. This is a rather inflexible technique in its mode of operation and cannot readily make cuts deeper than 3 about mm into diamond compacts. It is also limited in the range of shapes which can be produced. Moreover, laser cutting damages the surfaces of the compacts, necessitating removal of the damaged layer by a diamond-lapping process which is relatively expensive.
A technique which is widely employed in the shaping, working and machining of hard materials is Electrical Discharge Machining (EDM) also known as "spark erosion" and "wire-cutting". This technique can cut, drill and shape samples with much larger dimensions than can be worked by laser-cutting and is much more versatile in the range of shapes it can produce. However, in order to machine materials successfully, they must possess a low electrical resistivity. The EDM techniques cannot be applied successfully to machine diamond compacts of the type produced according to U.S. Pat. No. 4,151,686 because of the relatively high electrical resistivity displayed by these samples - typically between 0.3 and 5.0 ohm cm.
A method for producing a compact consisting of diamond bonded by silicon carbide possessing improved abrasive properties as compared with the compact of U.S. Pat. No. 4,151,686 is described in our pending International Patent Application No. PCT/AU85/00201. The improvements include pre-mixing of silicon with diamond prior to hot-pressing, which is carried out at lower pressures using a pressure-temperature-time cycle which causes an extensive degree of plastic deformation of the diamond crystals. More specifically, there is disclosed a process for producing a diamond compact for cutting, turning, drilling, and otherwise working ultra-hard ceramics, carbides and rocks which comprises (i) intimately mixing a mass of particulate diamond crystals with a bonding agent comprising silicon in the proportions 60-95 volume percent of diamond to 40-5 volume percent of bonding agent; (ii) subjecting the mixture within a confining space to a
REFERENCES:
patent: 4142869 (1979-03-01), Vereschagin et al.
patent: 4151686 (1979-05-01), Lee et al.
patent: 4260397 (1981-04-01), Bovenkerk
patent: 4311490 (1982-01-01), Bovenkerk et al.
patent: 4534773 (1985-08-01), Phaal et al.
patent: 4874398 (1989-10-01), Ringwood
Australian National University
Dixon Jr. William R.
Thompson Willie J.
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