Thermally stable diamond compacts

(54) DESCRIPTION Diamond Press Body (56) QUOTES PUBLICATIONS: EP A 104 063 B24D 3/06, GB A 1,588 483 B24D 3/10 (57) SUMMARY:

A heat-stable diamond compact having an alloy having a liquidus temperature above 700 ° C bonded to a surface thereon. The alloy contains at least 40 weighted silver or gold or a combination thereof and 1-10% by weight of an active metal consisting of tungsten, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium and / or molybdenum and has a liquidity temperature above 700^eC.

PRV 328 ALLF 138 9 132 AA

The numbers in parentheses indicate the international identification code. INID code Letter within k.ammer indicates international document code

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Diamond compact

The present invention also relates to heat-stable diamond compacts which comprise a polycrystalline mass of diamond particles present in an amount of at least 70 volumes * bound to a hard conglomerate and which can withstand a temperature of 1200 ° C in vacuum without any appreciable structural degradation of the compact.

Soap press bodies are well known in the art and are widely used in the industry for grinding various workpieces. They consist essentially of a mass of abrasive particles present in an amount of at least 70 volume, preferably 80-90 volume * of the compact and which are bonded to a hard conglomerate. Compacts are polycrystalline masses and can replace large single crystals. The abrasive articles in the press bodies always consist of extremely hard abrasives, such as diamond and cubic boron nitride.

Siip press bodies may contain a second phase or a bonding matrix containing a solvent (also known as a catalyst) useful in synthesizing the particles, for diamond being examples of suitable Group VIII solvent metals in the periodic system, such as cobalt, nickel or iron , or an alloy containing such a metal. The presence of these solvents in the diamond compact makes them heat sensitive at temperatures above 700^eC. In other words, diamond degradation is likely to occur at temperatures above 700 ° C. This, together with differences in the coefficient of thermal expansion of the diamond and solvent respectively, causes structural degradation in the compact. The result is that the compact is substantially weakened or becomes unusable as abrasives.

U.S. Patent No. 4,224,380 discloses a method of leaching a substantial amount of solvent

461 771 from a diamond cutting body. The resulting product is therefore substantially free of catalyst and is more heat stable than the non-leached product. Such a compact is capable of withstanding temperatures of up to 1200 ° C under vacuum without any noticeable structural degradation occurring in the compact. The compact is referred to as a heat-stable compact.

Other heat stable diamond press bodies are described in the literature and are used commercially. For example, European Patent Publication 0 116 403 discloses a heat-stable diamond cutting body comprising a mass of diamond particles present in an amount of 80-90 volumes of the body and a second phase present in a amount of 10-20 volume» of the body, the mass diamond particles essentially contain diamond-diamond bonds to form a coherent skeletal mass and the second phase contains nickel and silicon, wherein the nickel is in the form of nickel and / or nickel silicide and the silicon is in the form of silicon, silicon carbide and / or silicon silicide.

A further example of a heat stable diamond cutting body is described in British Patent Specification 2158086. The heat-stable diamond compact includes a mass of diamond particles present in an amount of 80-90 volumes of the compact and a second phase present in an amount of 10-20 volumes of the insert, the mass of diamond particles containing substantially diamond-diamond bonds to form a continuous skeletal mass and the second phase mainly contains silicon, the silicon being in the form of silicon and / or silicon carbide.

European Patent Publication 0 104 063 discloses a method for bonding a cubic boron nitride compact to a cemented carbide substrate. The method comprises the steps of metallizing a surface of the cubic boron nitride compact by bonding a layer of gold, silver or a gold or silver-based alloy to the surface and bonding of the metallized surface to a surface of the cemented carbide over a brazing alloy having a liquidity temperature above 700 ° C.

The preferred brazing alloy contains at least 40

461 771 wt.% Silver, gold or a combination thereof and 1-10 weight of an active metal consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium and / or molybdenum. The description in this patent publication is expressly limited to bonding of a cubic boron nitride compact to a cemented carbide substrate.

The descriptions in the four above-mentioned scriptures are hereby incorporated by reference.

The present invention relates to a polycrystalline mass of diamond particles present in an amount of at least 70% by volume. which are bonded to a hard conglomerate and can withstand a temperature of 1200 ° C in vacuo without any appreciable structural degradation of the compact, with an alloy layer bonded thereon, containing at least 40 weighted silver or gold or an alloy combination thereof and 1-10 by weight of an active metal consisting of tungsten, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium and / or molybdenum, and having a liquidus temperature above 700 ° C.

Thus, the diamond compact is a heat stable diamond compact which is exemplified in the above descriptions and is well known in the art. These compacts can withstand a temperature of 1200 ° C in vacuum, e.g. a vacuum of 10 ~⁵ mbar or bite, without any noticeable structural degradation of the die body. In particular, such compactors can be used in grinding tools where high temperatures are generated during their use, such as in trimming or fine-preparation tools, or where high temperatures are required during the manufacture of the tool, as in^tbetraded or impregnated drill bits.

As mentioned above, heat-stable diamond compactors are used in applications where high temperatures are generated during use or during manufacture of the tool. Such compacts are not easily wetted by conventional brazing and this is one of the reasons why they are generally kept mechanically as a rule.

461 771 fixed to the tool workspace. For example, in a surface-hardened drill bit, the individual press bodies, which may have a triangle shape, a cubic shape, a hexagonal shape or some other useful shape, will be held mechanically in the matrix in the drill bit work surface. It is desirable to supplement the mechanical bond by a bond of chemical or brazing nature.

It has been found that the above-mentioned alloy binds extremely strongly to the surface of the diamond compact, upon which it is applied. Furthermore, it is evident that the alloy binds readily to a plurality of commercially available brazers and forms a brazing bond with the matrix on conventionally surface treated or impregnated cutouts.

The alloy coated surface can be easily bonded to a cemented carbide substrate either directly or through another commercially available brazing solder. When another commercially available brazing is used, a high temperature brazing such as a silver / copper / zinc / nickel / manganese brazing or a copper / manganese / nickel / indium / tin brazing, both of which have a liquidity temperature above 700 ° C, is preferred. The diamond compact, when heat stable, can withstand such temperatures and the resulting brazing bond is extremely strong. Thus, the invention enables brazing of a heat-stable diamond compact at a tool or tool holder in contrast to uncoated heat-stable diamond compact according to the prior art.

The alloy preferably contains 40-70 weight * gold or silver or a combination thereof. Examples of suitable alloys are as follows:

1st Gold and the active metal.

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

3rd A ternary silver / copper / palladium alloy containing the active metal, especially titanium.

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

The heat-stable diamond compact can be used in the form of small fragments with any of a number of useful shapes, such as cube, triangle or hexagon. For such compacts, it is convenient that the alloy layer is bonded to at least 75t of its surface.

The heat-stable diamond compact can also be in the form of a disc or segment of a disc with a flat main surface on each of opposite sides thereof. For such compacts, it is convenient that at least one of the planar main surfaces has the alloy layer bonded thereto. The coated flat surface can be bonded to a cemented carbide surface.

The alloy can be bonded to the surface of the diamond compact by contacting the surface with the alloy, e.g. in the form of a foil, followed by increasing the temperature of the coated compact to a temperature above the liquidity temperature of the alloy in a non-oxidizing atmosphere. An example of a suitable 4 non-oxidizing atmosphere is vacuum of 10 mbar or better. In order to improve the wettability of the surface of the diamond compact, it is advisable to first apply an expansion vaporization of gold or silver to the surface of the compact before bonding the alloy thereto. The gold or silver expansion vapor may generally have a thickness of at most a few micrometers. A process for applying a gold or silver expansion vapor before bonding the alloy to the surface is fully described in European Patent Publication 0 104 063.

The heat-stable diamond compact can be any known in the art, but is preferably one of the type disclosed in British Patent Specification 2158086.

The invention is further described with reference to the following examples.

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Example 1

A diamond compact in disc form is prepared using the method described in British Patent Specification 2158086. The compact consists of a mass of diamond particles containing a substantial amount of direct diamond-diamond bonds to form a coherent skeletal mass, and a second phase consisting essentially of k of elemental silicon and silicon carbide. The compact was a heat stable diamond compact according to the above discussion.

A flat main surface of the diamond compact was degreased in alcohol.

A 100 micron thick foil of silver-based alloy was placed on the degreased and etched surface of the diamond compact. The silver-based alloy contained 62% silver. 19% copper, 14% palladium and 5% titanium, all percentages being calculated by weight. A cemented tungsten carbide slab was placed on the alloy foil to form an unbound stack. A load of 50-100 pounds was applied to the unbound stack. The loaded stack was then heated in a vacuum better than 10 mbar to 1100 ° C and kept at this temperature for 10 minutes. The bar was then allowed to cool to ambient temperature. It was found that an excellent bond was obtained between the heat-stable diamond compact and the cemented carbide.

A similar bonded compact was prepared using the same procedure except that an expansion vaporizer (0.1 mm thick) of gold was applied to the surface of the compact after degreasing. Here, too, an excellent bond was obtained between the compact and cemented carbide.

Example 2

A heat stable diamond pressing body as described in Example 1 exhibited a flat main surface which was degreased in alcohol. On this degreased and etched surface was applied a 100 micrometer thick foil of the same silver / copper / palladium / titanium alloy. The compact and foil were heated to 1100 ° C in a vacuum better than 10 ° C.⁴ mbar and kept at this temperature for 5 minutes. The compact was cooled to ambient temperature. The alloy was found to bind strongly to the diamond compact during the production of a metallized surface.

The metallized compact was placed in place on a cemented tungsten carbide disk with the metallized surface facing down. Between the metallized surface and the cemented carbide was placed a 100 micron thick sheet of Nicuman - 36 - alloy (56Cu - 36Mn - 2Ni - 3ln - 3Sn) with a melting range of 771-825 ° C. A load of about 50-100 pounds was applied to the unbonded press / carbide stack.

The stack was heated to 1000 ° C in a vacuum better than 10 ° C.⁴ mbar and kept at this temperature for 10 minutes, the bar was allowed to cool to ambient temperature.

It turned out that the diamond compact was firmly bonded to the cemented carbide.

Example 3

A heat-stable diamond compact as described in Example 1 was broken into several cubes. The cubes were degreased in alcohol. Then, on the clean surfaces of the cubes, an expansion vaporizer, about 0.1 microns thick, of gold was applied using standard sputtering coating procedures.

All but one surface of each cube was then enclosed in a foil of an alloy as described in Example 1. The wrapped cubes were heated to a temperature of 1100^eC in a vacuum of lO^-4 mbar. This caused the alloy to melt and bind to each cube. The gold coating facilitated the wetting of the surfaces of the cubes and facilitated the bonding of the alloy to these surfaces. The alloy was found to be very firmly bonded to the cubes, exhibiting shear strength above 15 kp / mm.

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