Other

Moosa Mahomed Adia

Raymond Albert Chapman

Geoffrey John Davies

Aulette Stewart

Lesley Kay Hedges

Klaus Tank

Richard P Burnand

Trevor J Martell

Stephen A Parsons

Stewart N Middlemiss

Roy Derrick Achilles

Bronwyn Annette Roberts

Alan R Jarvis

James Wilbert Campbell

A tool insert comprises a substrate () having a support surface and a support ring extending laterally from the support surface. The support ring is sized to define a recess () within the confines thereof and a shelf about the periphery thereof. A layer () of ultra-hard abrasive material is located within the recess and bonded to the substrate and the support ring (), and presents a primary cutting edge () for the tool insert. A protective layer () is bonded to the shelf about the support ring so as to protect the primary cutting edge. The protective layer provides a secondary cutting edge () for the tool insert, the depth of the protective layer being selected so as to be sufficient to protect the primary cutting edge whilst cutting, milling or drilling through a first substance but to expose the primary cutting edge upon encountering a second substance.

Composite tool insert

A cubic boron nitride cluster comprises a core () and an overgrown region, the overgrown region containing a plurality of cubic boron nitride crystallites () extending outwards from the core (). The majority of the cubic boron nitride crystallites () have a cross-sectional area which increases as the distance from the core () increases. A method of producing cubic boron nitride clusters is also provided.

Cubic boron nitride clusters

An abrasive product which comprises a polycrystalline mass of self-bonded abrasive particles of irregular shape, the product being substantially free of a second phase and containing substantial plastic deformation of the abrasive particles. The abrasive particles are preferably diamond or cubic boron nitride and the plastic deformation of the particles is preferably at least 0.3 percent. The abrasive product may be made by subjecting a mass of the particles to elevated temperature and pressure conditions.

Abrasive product

The invention provides a mass of crystals, particularly diamond crystals, having a size of less than 100 microns and in which mass the majority of the crystals are faceted single crystals. The invention further provides a method of producing such a mass of crystals which utilizes crystal growth under elevated temperature and pressure conditions, the supersaturation driving force necessary for crystal growth being dependent, at least in part, on the difference in surface free energy between low Miller index surfaces and high Miller index surfaces of the crystals. Preferably, the method is carried out under conditions where the Wulff effect dominates.

Crystal growth

A diamond cluster includes a core and an overgrown region containing a plurality of diamond crystallites extending outwards from the core, the majority of the crystallites having a cross-sectional area which increases as the distance of the crystallite from the core increases. Generally, at least 80% of the crystallites have a cross-sectional area which increases as the distance of the crystallite from the core increases. Furthermore, a method of producing a plurality of the diamond clusters includes the stops of providing a source of carbon, providing a plurality of growth center particles, each comprising a bonded mass of constituent particles, producing a reaction mass by bringing the carbon source and growth center particles into contact with a solvent/catalyst, subjecting the reaction mass to conditions of elevated temperature and pressure suitable for crystal growth, and recovering a plurality of diamond clusters from the reaction mass.

Growth of diamond clusters

A method of making a bonded, coherent material comprising a mass of crystals, preferably diamond crystals, in a matrix is provided. The steps include providing a source of the crystals of the type to be grown and which are substantially free of macroscopically faceted surfaces, producing a reaction mass by bringing the source crystals into contact with a suitable solvent/catalyst, 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 conditions of crystal growth being chosen such that the source crystals are converted to crystals having developed macroscopic facets of low Miller index. Preferably the conditions of elevated temperature and pressure used are such that the Wulff effect dominates.

Crystal-containing material

Diamond crystals may be grown by providing a source of diamond crystals, providing a plurality of growth centers defined by diamond crystals, mixing the source and growth center diamond crystals with a solvent/catalyst in particulate form to form a reaction mass, subjecting the reaction mass to conditions of elevated temperature and pressure suitable for crystal growth, and recovering the diamond crystals. The necessary supersaturation of carbon is achieved in the solvent/catalyst, at least in part, and preferably predominantly, by a selection of the particle size difference between the source crystal and the growth centers. The mass of diamond crystals produced by this method has a high concentration of twinned diamonds.

Diamond growth

A method of making a bonded, coherent material comprising a mass of diamond crystals in a matrix, which optionally contains another phase. The method includes the steps of providing a source of diamond crystals, providing a plurality of diamond centers defined by diamond crystals, producing a reaction mass by bringing the source and growth centers into contact with a solvent/catalyst, 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 method is characterized by providing the necessary supersaturation of carbon in the solvent/catalyst, at least in part and preferably predominantly, by a selection of particle size difference between the source crystal and the growth centers. The mass of diamond crystals in the matrix of the bonded, coherent material of the invention has a high concentration of twinned diamonds.

Sintering process for diamond and diamond growth

A method of producing an abrasive product comprises the steps of providing a mixture of diamond and discrete carbide particles, the diamond particles being smaller than the carbide particles and present in the mixture in an amount of more than 50 percent by volume, and subjecting the mixture to diamond synthesis conditions in the presence of a binder metal such as cobalt, nickel or iron. The abrasive product thus produced has a substantial amount of direct diamond-to-diamond bonding and many of the characteristics of a diamond compact, but improved impact resistance due to the presence of the carbide particles. The abrasive product has particular application in the machining of wood products such as natural wood, chipboard, fiberboard and hardboard.

The invention provides a method of making an abrasive product which comprises a layer of bonded ultra-hard abrasive particles bonded to a substrate. The abrasive product is typically a diamond or cubic boron nitride composite compact. The method includes the steps of:

Manufacture of abrasive products

The inventin provides a method of making an abrasive product which comprises a layer of bonded ultra-hard abrasive particles bonded to a substrate. This abrasive product is typically a composite abrasive compact. The method includes the steps of:

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Mondeor, South Africa

Raymond Albert Chapman