DIAMOND TOOLS FOR ROCK DRILLING AND MACHINING

Abstract: A polycrystalline diamond tool comprising a diamond layer (A) is bonded to a support body (B) having a complex, non-plane geometry by means of a thin more than 3 µm continuous layer (C) of a refractory material applied by PVD or CVD technique.

Description: Field of invention The invention relates to wear and impact resistant material which is comprised of polycrystalline diamond and cemented carbide or of other combinations of hard materials. On the market there has already been introduced a number of different high pressure-high temperature sintered tools containing polycrystalline diamond as the main ingredient. The tools are used for different purposes, among which the most important ones are rotating rock drilling (oil drilling), metal cutting and wire drawing. The production of such polycrystalline diamond tools using high pressure-high temperature (HP/HT) technique has been described in a number of old patents, e.g.: US 2,941,248, US 3,141,746, US 3,239,321 and US 3,407,445. All these patents disclose the use of a pressure and a temperature during the sintering within the diamond stable phase area. Tools are described having more than 50 vol % diamond and a binder metal, e.g. Co or Ni, but no support bodies are mentioned. In some later patents e.g. US 3,745,623 and US 3,767,371 high pressure-high temperature sintered polycrystalline diamond tools are described where the superhard body, containing more than 70 vol % diamond, is bonded to a body of cemented carbide. US 4,311,490 describes a high pressure-high temperature sintered body comprising at least two layers of diamond (or cBN) on top of each other and bonded to a body of cemented carbide. US 4,403,015 describes the use of intermediate layers consisting of cubic boron nitride (below 70 vol %) and one or more carbides, nitrides, carbonitrides or borides between the superhard polycrystalline diamond layer and the support body. With such layers the thermal conductivity will be reduced. A number of other patents describe the use of intermediate layers applied as powder or foils between the diamond (cBN) layer and the support body e.g. US 4,063,909, US 4,108,614, US 4,228,942, US 4,229,186, US 4,293,618 and US 4,411,672. DE-A-0 180 243 discloses a sandwich structure in which a diamond compact is bonded to a compact body by a diffusing blocking bonding layer of a refractory material made from a powder mixture. Summary of the invention The invention relates to high pressure, high temperature sintered bodies of diamond on a support body of cemented carbide or of other combinations of hard materials with a non-plane contact surface. Between diamond or other superhard material and support body a thin layer of preferably titanium nitride (TiN) has been applied by PVD or CVD. The invention is defined in claim 1. A preferred embodiment is shown in claim 2. Brief description of the drawings A number of examples of composites with support body with non-plane contact surfaces are given in Figs 1 - 3 in which A refers to the diamond body, B to the support body and C to the titanium nitride layer. Detailed description of the invention According to the invention there is provided a composite body comprising more than 50 % by volume of polycrystalline diamond bonded to a support body of cemented carbide or of other combinations of hard materials in which there is an intermediate layer of titanium nitride applied by CVD or PVD. The contact surface of the support body is non-plane. Said surface can be spherical or cylindrical or be provided with depressions, recesses or grooves in a more or less regular pattern. Such a non-plane surface can not easily be provided with an intermediate layer of a foil or a powder between the support body and the polycrystalline diamond or other superhard material. It has now surprisingly been found that a thin continuous layer of titanium nitride (TiN) thickness >3 µm, preferably about 10 µm on the support body of non-plane surface geometries (cemented carbide or another P/M material or metallic material) by use of the PVD or CVD coating techniques, preferably techniques operating at moderate substrate temperatures (below 700 °C) is sufficient to prevent diffusion into the polycrystalline diamond layer and embrittlement of the surface layer of the support body close to the diamond layer. After coating the support with the titanium nitride layer in a PVD or CVD equipment, support body and diamond powder are sintered at high pressure (> 40 kbar) and high temperature (>1000 °C) to a composite compact. The intermediate layer technique according to the invention for sintered diamond bodies has been found to be especially valuable for support bodies with complex surface geometries where the previous thin metal foil and powder techniques are limited for technical reasons, e.g. coating of vertical and negative surfaces on support bodies with narrow strips - Figs 1-2 or coating of support bodies with curved surfaces - Fig. 3. In spite of the small thickness of the intermediate titanium nitride layer obtained it has been found that its continuity and stability during sintering is acting as an effective diffusion barrier of the metallic components preventing depletion of bindermetal, especially cobalt, from the support and in connection to that preventing brittleness in the underlying support material. This is particularly valid when the surface region of the support body is surrounded by diamond on three sides such as for example support bodies with narrow strips or rectangular teeth - Figs 1-2. Another great advantage with the intermediate titanium nitride barrier layer between diamond and support is the effective control obtained of the quantity and composition of catalyst (Co, Ni, Fe, etc) added to the diamond because the whole catalyst quantity must be added to the diamond powder before sintering quite independently of the composition of underlying support material. Hammer tests of diamond/cemented carbide specimens according to the invention has shown an excellent bonding in the interfaces between support and titanium nitride layer as well as between titanium nitride layer and diamond. The cracks pass through diamond and the cemented carbide support but never in or adjacent to the titanium nitride layer. It has also been shown that with this thin titanium nitride layer possible with the present invention, no adverse effects on the brazing properties are obtained. Example 1 Cemented carbide buttons of WC-Co type (WC - 13 weight-% Co) with a contact surface of complex geometry ("Claw Cutter"-type, US Pat. No. 4,592,433) were coated with a 10 µm continuous titanium nitride layer by use of PVD-technique. The titanium nitride coated buttons were then sintered at high pressure, high temperature (65 kbar/1400 °C) with a powder mixture of 94 % by volume diamond and 6 % by volume of cobalt. Hammer tests of the diamond/cemented carbide composites obtained showed an excellent bonding in the interface between cemented carbide and titanium nitride layer as well as between titanium nitride layer and diamond body. The cracks passed through diamond or the cemented carbide body but never in or adjacent to the titanium nitride layer. Brazing tests indicated no adverse effects on the brazing properties due to the presence of the intermediate titanium nitride coating.

Claims: A polycrystalline diamond tool comprising a layer of more than 50 % by volume of diamond compact bonded to a support body by means of a thin, more than 3 µm continuous, metal diffusion-blocking, intermediate bonding layer of a refractory material characterized in that said refractory material is titanium nitride applied by PVD- or CVD- technique and that the coated surface of said support body has a non-plane geometry, at which said surface is spherical or cylindrical or provided with depressions, recesses or grooves. A polycrystalline diamond tool according to claim 1 characterized in that the support body consists of cemented carbide.

Inventors: ARONSSON, SVEN BERTIL, WALDENSTROEM, MATS GEORG, DR., Waldenström, Mats Georg, Dr.
Applicants: SANDVIK AKTIEBOLAG
Application year: 1988
Main classification: B22F7
IPC codes: C23C16, E21B10, B23B27, B22F7, B24D3, C30B29, C23C14, C23C28