Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Reexamination Certificate
1999-11-23
2001-08-07
Mai, Ngoclan (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
C423S446000, C117S079000, C428S408000
Reexamination Certificate
active
06270548
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a diamond crystal containing material useful, for example, as a tool component or insert.
The manufacture of diamond matrix composites or tool materials or components, such as saw segments, grinding wheels and polycrystalline diamond (PCD) products, is well established. There are various methods used in their manufacture. For saw segments, pellets, pearls, and the like, diamond powder is mixed with matrix material and the mixture sintered, substantially at atmospheric pressure, to produce the component. Alternatively, the molten matrix material is infiltrated into a bed of the diamond powder, also substantially at atmospheric pressure, to produce the component. For PCD products, diamond powder is sintered under conditions of high temperature and high pressure in the presence of a solvent-catalyst, and the resultant piece shaped afterwards to produce the final component.
In essence, each method and product starts with diamond powder and then the component is fabricated. Some of these methods are conducted at substantially atmospheric pressure, and components produced by them, are restricted to matrices that sinter or infiltrate at relatively low temperature so that graphitisation of the diamond is avoided or minimised.
In the manufacture of PCD products, the solvent-catalyst is restricted usually to the matrices used for the production of the cemented tungsten carbide support, or in the case of the more thermally stable products, the infiltrant is restricted to those elements or compounds which react with the diamond to form a desirable phase, e.g. silicon forming silicon carbide.
SUMMARY OF THE INVENTION
According to the present invention, a method of making a bonded, coherent material comprising a mass of diamond crystals in a matrix, optionally containing another phase, includes the steps of providing a source of diamond crystals, providing a plurality of growth centres defined by diamond crystals, the quantity of source crystals generally being greater than that of the growth centres, producing a reaction mass by bringing the source and growth centres into contact with a solvent/catalyst and the other phase, when used, subjecting the reaction mass to conditions of elevated temperature and pressure suitable for crystal growth in the reaction zone of a high temperature/high pressure apparatus to produce the material and removing the material from the reaction zone, the necessary supersaturation of carbon in the solvent/catalyst being achieved, at least in part, and preferably predominantly, by a selection of particle size difference between the source crystal and the growth centres.
The bonded, coherent material made by the method of the invention has been found to contain a mass of diamond crystals in which at least 40 percent, typically at least 80 percent, and generally substantially the entire mass, consists of synthetic twinned diamonds. The twinned diamond include contact twins, macle twins, including multiple and single macle twins, polysynthetic twins and star twins, i.e. a multiple twin in which at least some of the twin planes are not parallel. Various shapes of twin diamonds are also to be found. These shapes include blocky or cube shape, plate shape and column shape. For the plate and column shaped diamonds, the crystals have a high aspect ratio, i.e. a high ratio of longest dimension to shortest dimension. A bonded, coherent material of this type is believed to be new and forms another aspect of the invention.
The bonded, coherent material of the invention may, for example, be used as a tool component, blank or insert, bearing surface, substrate for further processing, abrasive material, heat sink, biomedical material, catalyst body or the like. These materials in their application all use the properties of diamond, the matrix or a combination of the properties of diamond and matrix.
The material may have zones of different properties. For example, the zones may vary in crystal concentration or size, in matrix, in nature of the other phase, or in a combination thereof. The differing zones may extend in layers or regions which are distributed in a random or ordered way, for example, from one side of the material to an opposite side or may extend in layers from a central point to an outside surface of the material.
The invention has particular application to materials which have a diamond content of less than 80 percent by volume.
The material may be produced in such manner as to provide it with a substrate to which it is bonded. The nature of the substrate may be chosen to complement the properties of the material.
REFERENCES:
patent: 4505746 (1985-03-01), Nakai et al.
patent: 5503104 (1996-04-01), Spiro
patent: 5772756 (1998-06-01), Davies
patent: 0 699 642 (1996-03-01), None
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patent: 2 239 011 (1991-06-01), None
Adia Moosa Mahomed
Campbell James Wilbert
Chapman Raymond Albert
Davies Geoffrey John
Hedges Lesley Kay
Mai Ngoclan
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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