Tool insert

Abstract: A tool insert such as a nozzle is produced by providing a former (10) depositing a diamond layer (12) on at least a portion of a surface (14) of the former (10), bonding a polymer-based support (18) to a surface (16) of the diamond layer (12) and removing the former (10) to expose a wear-resistant diamond surface (24). The top portion (22) may be removed to produce a nozzle. The diamond layer is preferably a CVD diamond layer.

Description: This invention relates to a tool insert and more particularly to such an insert which presents a wear-resistant surface. There are many tool inserts in use commercially which present a wear-resistant surface. Examples of such inserts are nozzles and bearings. In the case of nozzles, wear-resistant surfaces may be provided by cemented carbide or by a metal. Such surfaces tend to have short working lives when exposed to hostile and corrosive environments. GB-A-1 012 529 discloses a method of coating a plastics material with a strongly-adhering non-metallic inorganic film such as a titanium dioxide film, comprising coating a heated solid chemically inert support material such as gold with a non-metallic inorganic film by a vapour phase technique involving a chemical reaction, e.g. hydrolysis of TiCl₄ vapour, bonding said film to said plastics material, and separating said support from said film. According to the present invention, there is provided a tool insert comprising a diamond layer presenting major surfaces on each of opposite sides thereof, the one major surface of the diamond layer providing a wear-resistant surface for the insert and the other major surface of the diamond layer being bonded to a polymer-based support which has sufficient strength to withstand the forces to which the tool insert is subjected in use. Further according to the invention, a method of producing a tool insert as described above includes the steps of providing a suitable former, depositing a diamond layer on at least a portion of a surface of the former, bonding a polymer-based support as described above to a surface of the diamond layer, and removing the former to expose a wear-resistant diamond surface on the layer. The drawings illustrate schematically the various steps in the embodiment of the invention. The wear-resistant surface of the diamond layer is preferably shaped to define a passage which will typically be of closed configuration in section. Examples of suitable passages are cylindrical and conical passages. Examples of such tool inserts are nozzles. The tool insert may also be a bearing. The polymer will have sufficient strength to withstand the forces to which the tool insert is subjected during use. It will, therefore, vary according to the nature of the insert. The polymer may be a thermoplastic polymer or a thermosetting polymer. Generally, thermoplastic polymers are preferred. The polymer may, for example, have the following characteristics: Density: 0,90 - 1,23 g/cc Heat capacity: 1,916 - 2,100 kJ/kg/k Tensile strength: 12 - 200 N/mm² Softening temperature 88 to 155°C. Rockwell hardness 44 - 60 C Scale Coefficient of Thermal Expansion 5 - 710 ppm Examples of polymers which have these characteristics are polyethylene, polypropylene, polycarbonates, neoprene and polybutadiene. Such polymers are particularly useful for tool inserts which are nozzles. Other examples of suitable thermoplastic polymers are polyether ether ketone, polyether ketone, polyaryl ether ketone, poly (amide-imide), and polyphenylene sulphide. The polymer may be strengthened by including or embedding therein fibres or powders. These powders may be metallic or ceramic in nature and a particularly suitable example is graphite powder or fibre. An example of suitable metal particles are copper particles. Typically the powder or fibre will be provided in a amount of up to 40% by mass of the polymer. An example of a suitable polymer is a high performance poly (amide-imide) resin such as that sold under the trade name Torlon. A particularly suitable resin of this type is that numbered 7130 which contains 30% by mass of graphite fibre and 1% by mass fluorocarbon. The diamond layer may be produced or deposited on the former by methods known in the art such as chemical vapour deposition (CVD) and ion implantation (also known as ion beam deposition). The preferred method is CVD which produces a CVD diamond layer on the former. CVD involves the synthesis of diamond from the gas phase. The process generally involves providing a mixture of hydrogen or oxygen gas and a suitable gaseous carbon compound such as a hydrocarbon, applying sufficient energy to that gas to dissociate the hydrogen or oxygen into atomic hydrogen or oxygen and the gas into active carbon ions, atoms or CH radicals and allowing such active species to deposit on a substrate to form diamond. Dissociation of the gases can take place by a variety of methods. One such method is the use of a hot filament. In this method, the gas temperature at the filament is about 2000°C and the substrate on which diamond growth occurs is at 800 to 1100°C. A second commonly used method is a plasma assisted method. The hydrogen or oxygen and gaseous carbon compound are excited into a reaction state in a plasma region. The energy of excitation may be microwave, RF or DC plasma, or UV light or heat. The substrate is heated by the plasma. The former will be made of a material which is suitable to allow a diamond layer to be produced thereon using the particular method chosen. Examples of suitable materials, particularly for CVD, are silicon, titanium, hafnium, tantalum, molybdenum and carbides and nitrides thereof. The former may be removed from the diamond layer by methods such as etching, machining and milling. An embodiment of the invention will now be described with reference to the accompanying drawings. Referring to these drawings, in a first step I a silicon former in the shape of a cone 10 is provided. In step II the cone 10 has a layer of diamond 12 deposited over the entire sloping side surface 14 using any known chemical vapour deposition method. The diamond layer 12 will have a rough outer surface 16. The diamond-coated cone of step II is then placed in a suitable mould and a polymer support 18 produced around the cone (step III). The moulded polymer support 18 has a threaded portion 20. In the final step IV, the silicon cone 10 is removed, for example by etching, and the top section 22 of the unit produced in step III removed, for example by milling, to produce a polymer-based pre-threaded nozzle with a diamond lining. The inner surface 24 provides a highly abrasive resistant surface for the passage 26 of the nozzle. The surface 24 has a fine finish replicating that of cone 10 and not a rough finish of a normal CVD diamond film or layer.

Claims: An article comprising a layer (12) presenting major surfaces (24, 16) on opposite sides thereof, the one major surface (24) of the layer providing a wear-resistant surface for the article and the other major surface (16) of the layer being bonded to a polymer-based support (18) which has sufficient strength to withstand the forces to which the article is subjected in use, characterised in that said article is a tool insert and said layer (12) is a diamond layer. A tool insert according to claim 1 wherein the wear-resistant surface (24) of the diamond layer (12) is shaped to define a passage. A tool insert according to claim 2 wherein the wear-resistant surface (24) of the diamond layer (12) is shaped to define a passage (26) of closed configuration in section. A tool insert according to claim 3 wherein the passage (26) is a cylindrical or a conical passage. A tool insert according to any one of the preceding claims wherein the diamond layer (12) is a CVD diamond layer. A tool insert according to any one of the preceding claims wherein the polymer has the following characteristics: Density: 0,90 - 1,23 g/cc Heat capacity: 1,916 - 2,100 kJ/kg/k Tensile strength: 12 - 200 N/mm² Softening temperature 88 to 155°C. Rockwell hardness 44 - 60 C Scale Coefficient of Thermal Expansion 5 - 710 ppm A tool insert according to claim 6 wherein the polymer is selected from polyethylene and polypropylene. A tool insert according to any one of claims 1 to 6 wherein the polymer is selected from polyether ether ketone, polyether ketone, polyaryl ether ketone, poly (amide-imide) and polyphenylene sulphide. A tool insert according to any one of the preceding claims which is a nozzle. A process of producing an article according to any one of the preceding claims which includes the steps of providing a suitable former (10), depositing a layer (12) on at least a portion of a surface (14) of the former (10), bonding a polymer-based support (18) to a surface (16) of the layer (12) and removing the former (10) to expose a wear-resistant surface (24), characterised in that said article is a tool insert and said layer (12) is a diamond layer. A process according to claim 10 wherein the former (10) is made of a material selected from silicon, titanium, hafnium, tantalum, molybdenum and carbides and nitrides thereof.

Inventors: JONES BARBARA LYNN, JONES, BARBARA LYNN
Applicants: DE BEERS IND DIAMOND, DE BEERS INDUSTRIAL DIAMOND DIVISION (PROPRIETARY) LIMITED
Application year: 1991
Main classification: B05B1
IPC codes: B21C3, C23C16, B05B1, B24C5