Thermally stable diamond compacts

DESCRIPTIVE MEMORY filed in support of a request for

PATENT OF INVENTION formed by

DE BEERS INDUSTRIAL DIAMOND DIVISION (PROPRIETARY) LIMITED for:

Compact, thermally stable diamond products.

Priority of a patent application in South Africa filed August 13, 1984, under No. 84/6272.

Inventor: Noël John PIPKIN.

<img file="BE903052A1_D0001.tif" />

Compact, thermally stable diamond products.

The present invention relates to thermally stable compact diamond products.

Abrasive compacts are well known in the art and are used extensively in industry for the abrasion of various workpieces. They consist essentially of a mass of abrasive particles present in an amount of at least 70%, preferably 80 to 90% by volume of the compact product bound in a hard conglomerate. Compact products are polycrystalline masses and can replace large single crystals. The abrasive particles of compacts are invariably ultra-hard abrasives, such as diamond and cubic boron nitride.

Abrasive compacts may contain a second phase or binding matrix which contains a solvent (also known as a catalyst) of interest in particle synthesis. In the case of diamond, examples of suitable solvents are metals of Group VIII of the Periodic Table, such as cobalt, nickel or iron or an alloy containing such a metal. The presence of these solvents in compact diamond products makes them thermally sensitive to temperatures above 700 ° C. In other words, at temperatures above 700 ° C. we are probably witnessing a degradation of the diamond. This, along with the differences in the coefficients of thermal expansion of diamond and solvent, causes structural degradation of the compact product. The result is that the compact product is significantly weakened or is rendered unusable as an abrasive product.

US Patent No. 4,224,380 describes a process for leaching out a large amount of solvent from a diamond compact. The resulting product is therefore essentially free of catalyst and is thermally more stable than the unleached product. Such a compact product has the ability to withstand

<img file="BE903052A1_D0002.tif" />

t ”··” ft ·· ftft ft »* · ·» • •• ft · “·· · ft • ·· ft ftft ft ··· · • ••• ft ··· ft ft • ft ftft ftft ft ft · • ft ftft ftft ftft ftftft ft ··· at temperatures up to 1200 ° C in a vacuum without any significant structural degradation of the vacuum. The compact product is also known to be a thermally stable compact product.

Other thermally stable diamond compact products have been described in the literature and are used commercially. For example, European Patent Publication No. 0 116 403 describes a thermally stable diamond compact product comprising a mass of diamond particles present in an amount of 80 to 90% by volume of the body and a second phase present in an amount of 10 to 20% by volume of the body, the mass of diamond particles containing a large diamond-to-diamond bond to form a coherent skeletal mass, the second phase containing nickel and silicon, the nickel being in the form of nickel and / or nickel silicide and the silicon being in the form of silicon, silicon carbide and / or nickel silicide.

Another example of a thermally stable diamond compact product is that described in UK Patent Application No. 8508295. This thermally stable diamond compact product comprises a mass of diamond particles present in an amount of 80 to 90% by volume of the compact product and a second phase present in an amount of 10 to 20% by volume of the body, the mass of diamond particles containing a diamond-to-diamond bond important to form a coherent skeletal mass and the second phase consisting essentially of silicon, the silicon being in the form of silicon and / or silicon carbide.

European Patent Publication No. 0 104 063 describes a method of bonding a compact cubic boron nitride product to a cemented carbide support. The method comprises the steps of metallizing a surface of the cubic boron nitride compact product by bonding a layer of gold, silver or a gold or silver-based alloy to this surface and by bonding the metallized surface to a surface of the cemented carbide support through a brazing alloy having a liquid temperature greater than 700 ° C. The preferred brazing alloy contains at least 40% by weight of silver,

<img file="BE903052A1_D0003.tif" />

• v ft ftftft * ftft ftfte »· •» ft ft ft * ·· • · · · ·· ·· “···&gt; · · · ft · • ft ftft ·· ft · • · · · · Ftft ft * * ·· ft of gold or a combination of these elements and 1 to 10% by weight of an active metal chosen from the group comprising titanium, zirconium, hafnium, vanadium , niobium, tantalum, chromium and molybdenum. The description of these patent publications is specifically limited to bonding a compact cubic body nitride product to a cemented carbide support.

The descriptions of the four publications mentioned above are incorporated herein by reference.

According to the present invention, there is provided a polycrystalline mass of diamond particles present in an amount of at least 70% by volume bound in a hard conglomerate and capable of withstanding a temperature of 1200 ° C. in a vacuum without occurring. αε. significant structural degradation of the compact product, this compact product comprising an alloy layer bonded to a surface thereof, this alloy containing at least 40% by weight of silver or gold or a combination thereof and 1 to 10% by weight of an active metal selected from the group consisting of tungsten, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium and molybdenum and having a liquidus temperature above 700 ° C.

The diamond compact product is therefore a thermally stable diamond compact product, examples of which are described in the above description and are well known in the art. These compact products can withstand a temperature of 1200⁰ C. in a vacuum, for example a vacuum of 10 mbar or more, without significant structural degradation of the compact product. These compact products find particular applications in abrasive tools where high temperatures are produced during their use, such as in cutting or grinding tools, or where high temperatures are required during the manufacture of the material. 'tool, as for example in surface or impregnated drilling tools.

As mentioned above, thermally stable compact diamond products are used in applications where elevated temperatures are produced in use or during the manufacture of the tool. These compact products are not easily wetted by the usual welds and this is one of the reasons

<img file="BE903052A1_D0004.tif" />

• · for which they are held mechanically as a general rule in the working surface of the tool. For example, in a surface-fitted drill tool, the individual compact products, which may be triangular, cubic, hexagonal, or any other interesting shape, will be mechanically held in the matrix of the drill tool's working surface. . It is desirable to complete the mechanical bond with a bond of a chemical nature or of the welding or brazing type.

The alloy specified above was found to bond extremely strongly to the surface of the compact diamond product to which it was applied. In addition, the alloy was found to bond readily to a variety of commercially available solders and to form a solder bond with the die of conventional impregnated and surface-adjusted drilling tools.

The alloy coated surface can easily be bonded to a cemented carbide support, either directly or through other commercially available solder or solder. When another commercially available solder or solder is used, it is preferably a high temperature solder, such as a silver / copper / zinc / nickel / manganese solder or a copper / manganese / solder. nickel / indium / tin, both having a liquid temperature greater than 700 ° C. The compact diamond product, being thermally stable, can withstand such temperatures and the solder bond thus obtained is extremely strong. The invention also allows a thermally stable diamond compact product to be welded to a tool or tool holder unlike the uncovered thermally stable diamond compact products of the prior art.

The alloy will preferably contain 40 to 70% by weight of gold or silver or a combination of these elements. Examples of suitable alloys are as follows:

1. Gold and active metal.

2. A binary silver / copper alloy containing the active metal.

3. A ternary silver / copper / pailadium alloy containing the active metal, in particular titanium.

<img file="BE903052A1_D0005.tif" />

<img file="BE903052A1_D0006.tif" />

The thickness of the alloy layer is not critical, but generally will not exceed 200 microns in thickness.

The thermally stable diamond compact can be used in the form of small fragments of any of a number of interesting shapes, such as cubic, triangular or hexagonal. For these compact products, it is preferable that the alloy layer is bonded to at least 75% of their surface.

The thermally stable diamond compact product can also be fed in the form of a disc or a disc segment having a major planar surface on each of its faces. For this type of compact product, it is preferable that the alloy layer is bonded to at least one of its major flat surfaces.

The coated flat surface can be bonded to a cemented carbide backing.

The alloy can be bonded to the surface of the diamond compact product by contacting the surface with the alloy, for example in the form of a sheet, and then raising the temperature of the coated compact product to a temperature of above the liquidus temperature of the alloy in a non-oxidizing atmosphere. An example of a suitable non-oxidizing atmosphere is a vacuum of 10 mbar or more. To improve the wettability of the surface of the diamond compact, it is first preferable to apply a thin layer of gold or silver on the surface of the compact product before bonding the alloy to it. The thin layer of gold or silver will generally have a thickness not exceeding a few microns. A method of applying a thin layer of gold or silver before bonding the alloy to the surface is fully described in European Patent Publication No. 0 104 063.

The thermally stable diamond compact can be any compact product known in the art, but is preferably of the type described in UK Patent Application No. 8508295.

The invention will now be described with reference to the following examples.

Example 1.

A compact diamond product is prepared in the form

<img file="BE903052A1_D0007.tif" />

•4 4444 44

4 · «

4 · 4 ·· · 4 · 4 ι · · 4 · · · 4 · · · · • 44 4 4 · ·

4 4 4 4 4

4 · ·· ·· disc using the method described in UK Patent Application No. 8508295. The compact product is formed from a mass of diamond particles containing a substantial amount of direct diamond-to-diamond bond so as to form a coherent skeletal mass and a second phase formed essentially of silicon in the form of elemental silicon and of silicon carbide. The compact product is a thermally stable diamond compact product as discussed above.

A major flat surface of the diamond compact is degreased in alcohol. A 100 micron thick silver-based foil is placed over the degreased and pickled surface of the diamond compact. The silver-based alloy contains 62% silver, 19% copper, 14% palladium and 5% titanium, all percentages being by weight. A disc of cemented tungsten carbide is placed on the alloy sheet so as to obtain. A load of 50 to 100 g is applied to the loaded stack is then heated in an unbound stack. unbound stacking.

a vacuum of more than 10 mbar up to 1100 ° C. and is maintained at this temperature for 10 minutes, up to room temperature.

The stack is allowed to cool. It is observed that an excellent bond is obtained between the thermally stable diamond compact product and the cemented carbide disc.

A similar bonded compact product was obtained using the same method except that a thin layer (0.1 mm thick silver) was applied to the surface of the compact after degreasing. Again an excellent bond is obtained between the compact product and the cemented carbide disc.

Example 2.

A thermally stable diamond compact product, as described in Example 1, has a major flat surface degreased in alcohol. To this degreased and pickled surface, a sheet with a thickness of 100 microns of the same silver / copper alloy is applied. . / pailadium / titanium. The compact product and the sheet are heated to -4

1100 ° C in a vacuum of more than 10 mbar and they are maintained at this temperature for 5 minutes. The compact product is cooled to room temperature. It can be seen that the alloy is strongly ··· • ft ·· ft ··· β · ft ··· ··, ··· ·· - ”♦ ·· · · ··· · · · · * aft ·· ft · · · ·. * ·· ·· ·· ··· ···· bonded to the diamond compact while producing a metallized surface.

The metallized compact is placed on top of a cemented tungsten carbide disc with the metallized surface facing down. Between the metallized surface and the cemented carbide disc is placed a Nicuman disc of alloy 36 (56% Cu 36% Mn - 2% Ni - 3% In - 3% Sn) with a thickness of 100 microns, with a melting range of 771 to 825 ° C. A load of about 50 to 100 g is applied to the unbound compact product / carbide stack.

The stack is heated to 1000 ° C in a vacuum of more than 10 mbar and maintained at this temperature for 10 minutes. The stack is allowed to cool to room temperature.

It is found that the compact diamond product is strongly bound to the cemented carbide disc.

Example 3.

A thermally stable diamond compact product as described in Example 1 is fragmented into a series of cubes. The cubes are degreased in alcohol. A thin layer, approximately 0.1 micron thick, is then applied to the clean surfaces of the cubes using spray coating techniques.

All except one surface of each cube are then wrapped in a foil of an alloy as described in Example 1. The wrapped cubes are heated to a temperature of 1100 ° C in a vacuum of 10 mbar. . This melts the alloy and binds it firmly to each cube. The thin layer of gold facilitates the wetting of the surfaces of the cubes and facilitates the bonding of the alloy to these surfaces It is found that the alloy is very firmly bonded to the cubes, showing

Z zz -2 a tear resistance exceeding 15 kgmm.

It should be understood that the present invention is in no way limited to the above embodiments and that many modifications can be made thereto without departing from the scope of the present patent.

<img file="BE903052A1_D0008.tif" />

• “ft ft * • · * i • ♦ · · • e · · · • · · ·“ Β ·· * - ** • “• · • ·“ · ”·· ·· ·“ ·· • · • w ·· · «··