Thermally Stable Pointed Diamond with Increased Impact Resistance

Abstract

In one aspect of the present invention, an insert comprises a sintered polycrystalline diamond body bonded to a cemented metal carbide substrate. The diamond body comprises a substantially conical shape with conical side wall terminating at an apex. The diamond body comprises a first region with a metallic catalyst dispersed through interstices between the diamond grains and a second region proximate the apex with the characteristic of higher thermal stability than the first region.

Description

BACKGROUND OF THE INVENTION

This invention generally relates to diamond bonded materials and, more specifically, diamond bonded materials and inserts formed therefrom that are specifically designed to provide improved thermal stability when compared to conventional polycrystalline diamond materials.

U.S. Pat. No. 263,328 to Middlemiss, which is herein incorporated by reference for all it contains, discloses a thermally stable region having a microstructure comprising a plurality of diamond grains bonded together by a reaction with a reactant material. The PCD region extends from the thermally stable region and has a microstructure of bonded together diamond grains and a metal solvent catalyst disposed interstitially between the bonded diamond grains. The compact is formed by subjecting the diamond grains, reactant material, and metal solvent catalyst to a first temperature and pressure condition to form the thermally stable region, and then to a second higher temperature condition to form both the PCD region and bond the body to a desired substrate.

U.S. Pat. No. 266,559 to Keshavan et al., which is herein incorporated by reference for all that it contains, discloses a diamond body having bonded diamond crystals and interstitial regions disposed among the crystals. The diamond body is formed from diamond grains and a catalyst material at high pressure/high temperature conditions. The diamond grains have an average particle size of about 0.03 mm or greater. At least a portion of the diamond body has a high diamond volume content of greater than about 93 percent by volume. The entire diamond body can comprise the high volume content diamond or a region of the diamond body can comprise the high volume content diamond. The diamond body includes a working surface, a first region substantially free of the catalyst material. At least a portion of the first region extends from the working surface to depth of from about 0.01 to about 0.1 mm.

U.S. Pat. No. 7,473,287 to Belnap et al., which is herein incorporated by reference for all that it contains, discloses a thermally-stable polycrystalline diamond materials comprising a first phase including a plurality of bonded together diamond crystals, and a second phase including a reaction product formed between a binder/catalyst material and a material reactive with the binder/catalyst material. The reaction product is disposed within interstitial regions of the polycrystalline diamond material that exists between the bonded diamond crystals. The first and second phases are formed during a single high pressure/high temperature process condition. The reaction product has a coefficient of thermal expansion that is relatively closer to that of the bonded together diamond crystals than that of the binder/catalyst material, thereby providing an improved degree of thermal stability to the polycrystalline diamond material.

U.S. Pat. No. 6,562,462 to Griffin, which is inhere incorporated by reference for all that it contains, disclosed a polycrystalline diamond or diamond-like element with greatly improved wear resistance without loss of impact strength. These elements are formed with a binder-catalyzing material in a high-temperature, high-pressure (HTHP) process. The PCD element has a body with a plurality of bonded diamond or diamond-like crystals forming a continuous diamond matrix that has a diamond volume density greater than 85%. Interstices among the diamond crystals form a continuous interstitial matrix containing a catalyzing material. The diamond matrix table is formed and integrally bonded with a metallic substrate containing the catalyzing material during the HTHP process. The diamond matrix body has a working surface, where a portion of the interstitial matrix in the body adjacent to the working surface is substantially free of the catalyzing material, and the remaining interstitial matrix contains the catalyzing material. Typically, less than about 70% of the body of the diamond matrix table is free of the catalyzing material.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the invention, an insert comprises a sintered polycrystalline diamond body bonded to a cemented metal carbide substrate. The diamond body comprises a substantially conical shape with conical side wall terminating at an apex. The diamond body comprises a first region with a metallic catalyst dispersed through interstices between the diamond grains and a second region proximate the apex with the characteristic of higher thermal stability than the first region.

The second region may comprise a natural diamond. The natural diamond may form the apex. The natural diamond may be covered by a small layer of first region. The metallic catalyst in the small layer may be mixed with the diamond grains prior to sintering. The metallic catalyst in the small layer may diffuse from the substrate during sintering. The second region may comprise a sintered natural diamond, a single crystal natural diamond, a single crystal synthetic diamond, or combinations thereof. The second region may comprise a coarse saw grade diamond. The second region may comprise cubic boron nitride. The second region may comprise an asymmetrical shape. The second region may comprise a nonmetallic catalyst. The second region may be pre-sintered prior to being sintered with the first region. The second region may comprise fully dense diamond, which was processed in high enough pressure to not need a catalyst.

The pre-sintered second region may be leached prior to being re-sintered with the first region. The diamond body may be thicker than the substrate. The diamond body may comprise a conical side wall that forms a 40 to 50 degree angle with a central axis of the insert. The first region may separate the second region from the substrate. The second region may be substantially free of the metallic catalyst. The different portions of the polycrystalline diamond body may comprise different volumes of the metallic catalyst. The first and the second regions may be joined at a non-planar interface.

In another aspect of the invention, a method of forming an insert may comprise the steps of placing diamond powder in a conical metallic carbide can, compressing the carbide can under a high pressure/high temperature such that the powder forms a pointed sintered compact, removing the metallic catalyst from the sintered compact, and re-sintering the pointed sintered compact to another sintered diamond body such that the pointed sintered compact forms a tip.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagram of an embodiment of an insert.

FIG. 2 is a diagram of an embodiment of a diamond region.

FIG. 3 is a cross-sectional diagram of another embodiment of an insert.

FIG. 4 is a cross-sectional diagram of another embodiment of an insert.

FIG. 5 is a cross-sectional diagram of another embodiment of an insert.

FIG. 6 is a cross-sectional diagram of another embodiment of an insert.

FIG. 7 is a cross-sectional diagram of another embodiment of an insert.

FIG. 8 is a cross-sectional diagram of another embodiment of an insert.

FIG. 9 is a cross-sectional diagram of another embodiment of an insert.

FIG. 10 is a cross-sectional diagram of another embodiment of an insert.

FIG. 11 is a cross-sectional diagram of another embodiment of an insert.

FIG. 12 is a cross-sectional diagram of another embodiment of an insert.

FIG. 13 is a cross-sectional diagram of another embodiment of an insert.

FIG. 14 is a cross-sectional diagram of another embodiment of an insert.

FIG. 15 is a cross-sectional diagram of another embodiment of an insert.

FIG. 16 is a cross-sectional diagram of another embodiment of an insert.

FIG. 17 is a cross-sectional diagram of another embodiment of an d insert.

FIG. 18 is a cross-sectional diagram of another embodiment of an insert.

FIG. 19 is a cross-sectional diagram of another embodiment of an insert.

FIG. 20 is a cross-sectional diagram of another embodiment of an insert.

FIG. 21 a is a top orthogonal diagram of a carbide disk comprising a number of tip molds.

FIG. 21 b is a cross-sectional diagram of an embodiment of a carbide disk.

FIG. 21 c is a cross-sectional diagram of an embodiment of a cube for HPHT processing comprising a plurality of carbide disks.

FIG. 21 d is an orthogonal diagram of an embodiment of a leaching process.

FIG. 21 e is an perspective diagram of an embodiment of a plurality of thermally stable diamond tips.

FIG. 21 f is a cross-sectional diagram of another embodiment of an insert.

FIG. 22 a is a cross-sectional diagram of another embodiment of a carbide disk.

FIG. 22 b is a perspective diagram of another embodiment of a plurality of thermally stable diamond tips.

FIG. 22 c is a perspective diamond of another embodiment of an insert.

FIG. 23 is a perspective diagram of an embodiment of a rotary drag bit.

FIG. 24 is a perspective diagram of an embodiment of a roller cone bit.

FIG. 25 is a cross-sectional diagram of an embodiment of a pick.

FIG. 26 is a cross-sectional diagram of another embodiment of a pick.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT

FIG. 1 is a cross-sectional diagram of an embodiment of an insert 101 comprising a diamond bonded body 102 and a cemented metal carbide substrate 103. The diamond body 102 may comprise a substantially conical shape with conical side wall terminating at an apex 150. The diamond body 102 may comprise a first region 105 with a metallic catalyst dispersed through interstices between the diamond grains and a second region 104 proximate the apex and having the characteristic of higher thermal stability than the first region 105. The conical side wall may form a 40 to 50 degree angle with a central axis 151 of the insert 101. In the preferred embodiment, the first region 105 separates the second region 104 from the cemented metal carbide substrate 103. In some embodiments, the substrate comprises an interface adapted to for brazing to another object such as a bit, pick, shank, face, or combinations thereof. In some embodiments the substrate will comprise a diameter with a long enough length for press fitting into a pocket of another object.

In the preferred embodiment, the diamond regions are thicker than the cemented metal carbide substrate. The diamond regions also preferably comprise a greater volume than the substrate. The apex of the overall diamond structure may be rounded, with a 0.050 to 0.150 inch radius. Such a radius is sharp enough to penetrate the hard formations such as granite, while, with the combination of the angle of the side wall, buttress the apex under high loads. In many applications, the apex will be subjects to the most abuse, thus, experiencing the highest wear and greatest temperatures.

Most attempts of the prior art to make diamond thermally stable have resulted in weakened impact strength. Some prior art references teach that their structure simply does not compromise the impact strength of their part (see Griffin cited in the background). The present invention, not only improves the thermal stability of the entire tool, but its shape actually increases its impact strength as well.

To achieve both the increased impact strength and thermal stability, the diamond of the first region must be at least 0.100 inches, but no more than 0.275 inches, preferably about 0.150 inches from the apex to the non-planar interface. This range is much thicker than what is typically commercial available at the time of this application's filing. It is believed that this critical range allows for the compressive forces to propagate through the diamond, and the radial expansion caused by that compression to be mostly accommodated in the carbide substrate below the first region of diamond. This range solves a long standing problem in the art because generally parts enhanced with diamond have thin thicknesses, typically under 0.070 inches. In such cases with thin diamond, the point of impact on the diamond is supported by the carbide and will flex under high loads. The thick diamond on the other hand will not flex because its point of impact is supported by more diamond. However, under impacts not only does a section of a tool compress, but a section will also tend to expand radially as well. The critical range allows the radial expansion to occur in the carbide substrate which is much more flexible than the diamond. If the diamond were too thick, the diamond may be prone to cracking from the radial expansion forces because the diamond may be weaker in tension than the carbide.

Thus, the thermal stability near the apex combined with the collective shapes of the first and second regions overcome a long standing need in the art by increasing both the thermal stability of the tool and increasing the impact strength.

Several molecular structures may be used to create the thermally stable characteristic of the second region. The second region 104 may comprise a natural diamond 106. The natural diamond 106 may form the apex as in FIG. 1, or the natural diamond may be situated below the surface of the diamond of the first region as shown in FIG. 3. Because natural diamond 106 lacks a metallic binder, in high temperature conditions the natural diamond is not subjected to differing thermal expansions, which leads to diamond failure in the field.

Another molecular structure that may achieve the high thermally stable characteristic is sintered polycrystalline diamond void of metallic binder in its interstices. The tips of the first region may be leached to remove the binder and, thus, form the thermally stable second region. In other embodiments, the second region may be sintered separately, leached and then attached to the first region. The attachment may be achieved through sintering the regions together, brazing, or other bonding methods.

Other molecular structures that may achieve the higher thermal stability include single crystal natural diamond, a single crystal synthetic diamond, coarse saw grade diamond, or combinations thereof. The average size of natural diamond crystal is 2.5 mm or more. The second region 104 may comprise a cubic boron nitride, which generally exhibits a greater thermal stability than polycrystalline diamond comprising the metallic binder. The second region may also comprise fully dense PCD grains sintered at extremely high temperature and pressure where catalysts are not used to promote diamond to diamond bonding. In other embodiments a nonmetallic catalyst may be used in the second region to achieve higher thermal stability. Such non-metallic catalysts may include silicon, silicon carbide, boron, carbonates, hydroxide, hydride, hydrate, phosphorus-oxide, phosphoric acid, carbonate, lanthanide, actinide, phosphate hydrate, hydrogen phosphate, phosphorus carbonate, or combinations thereof. In some cases, a chemical may be doped into the second region to react with metallic catalyst such that the catalyst no longer exhibits such drastic difference in thermal expansion as the diamond.

FIG. 2 is a diagram of an embodiment of the first region 105 of the insert 101 having a material microstructure comprising diamond crystal grains 202 and metallic binder. The diamond grains are intergrown and bonded to one another as a result of the sintering process. The metallic binders 204 disposed in the interstices or voids among the diamond grains. During sintering these metal binders promoted the diamond to diamond bonding. The metallic binder 204 may be selected from the group consisting of palladium, rhodium, tin, iron, manganese, nickel, selenium, cobalt, chromium, molybdenum, tungsten, titanium, zirconium, vanadium, niobium, tantalum, platinum, copper, silver, or combinations thereof. Under hot conditions, the metallic binder will expand more than the diamond grain and generate internal stress in the diamond. The stress is believed to be a significant factor to most diamond failure in downhole drilling applications.

FIG. 3 is discloses a sintered natural diamond 106 as the second region. The sintered natural diamond 106 may be covered with a small layer of polycrystalline diamond of the first region. The surrounding diamond of the first region may be bonded to the diamond of the second region resulting in a strong attachment. The embodiment of FIG. 3 also discloses a substantially conical side wall that comprises a slight concavity 303.

FIG. 4 discloses a plurality of second regions 104 mixed in the first region. In this embodiment, the second regions are composed of natural diamonds. The average natural diamond size may be about 0.03 mm or more. The insert 101 may also comprise a slightly convex side wall.

FIG. 5 is discloses additional second regions that dispersed through the upper portion of the first region. As disclosed in the embodiment of FIG. 5, the second regions may be dispersed through any area of the diamond that may come into contact with a formation during a cutting operation.

The second region may also comprise boron doped into the interstices to react with metallic binders. The melting temperature of boron is very high The second region may also comprise boron doped into interstices where the metallic binder has already been removed.

FIG. 6 discloses an insert with an off center apex 155. In this embodiment, a second region of more thermally stable diamond forms the apex.

FIGS. 7-14 disclose different embodiments of non-planar interfaces that may be used between the first and second regions. In some embodiments, a planar interface (not shown) may be used. The non-planar interfaces may help interlock the regions together.

FIGS. 15-20 disclose several regions layered over each other with non-planar interfaces. Third and fourth region 1500, 1520 may comprise diamond grains of different sizes and/or different binder concentrations than each other or the first or second regions. The second region 104 may comprise diamond grains of size 0-10 micron. The third region 1500 may comprise diamond grains of size 10-20 micron. The fourth region 1520 may comprise diamond grain of size 20-30 micron. The first region 105 may comprise diamond grain size of 10-40 micron.

A method for manufacturing an embodiment of the invention is referred to in FIGS. 21a-f. Thermally stable diamond tips 2200 may be made in a first sintering process. A carbide disc 2210 with a plurality of shaped cavities 2201 may form the molds for the tips. The cavities 2201 are filled with diamond powder and multiple discs 2210 are stacked together inside a cube 2240. The cube 2240 is loaded into a high pressure, high temperature press and compressed by a plurality of opposing anvils while in a high temperature environment. The metal, usually cobalt, from the carbide discs diffuse into the diamond powder acting as a catalyst to promote the diamond to diamond bonding. The diffused metal remains in the interstices of the diamond tips after the sintering cycle is finished. The metal may be removed from the sintered tips by putting the discs in a container 2250 filled with a leaching agent. The leaching agent 2230 may be selected from the group consisting of toluene, xylene, acetone, an acid or alkali aqueous solution, and chlorinated hydrocarbons. Once the tips have been separated from the discs and are leached, the leached tips may be attached to the first region. In the preferred method, the leached tips are loaded into a can first and then the can is back filled with more diamond powder. The can is again assembled in a cube for high temperature and high pressure processing. In some embodiments, the carbide discs are removed through sand blasting.

FIGS. 22 a-c disclose steps in another embodiment of a method for forming the second region. The cavities 2300 of the discs are filled with a large single crystal of diamond and back filled with diamond powder. A single crystal the single crystal may be synthetic or natural During sintering the single crystal diamond and diamond powder may bond to one another forming a pointed sintered compact as shown in FIG. 22b. The compact may require grinding or sand blasting before re-sintering with the rest of the diamond body.

FIG. 23 is a perspective diagram of an embodiment of a rotary drag bit 2410 that may comprise the inserts. The rotary drag bit 2410 may comprise a plurality of blades 2400 formed in the working face 2420 of the drag bit 2410. The rotary drag bit 2410 may comprise at least one degradation assembly comprising the diamond bonded inserts 101.

FIG. 24 is a perspective diagram of an embodiment of a roller cone bit that may also incorporate the insert 101 as well, which may be bonded to the cones 2500FIGS. 25 and 26 are cross-sectional diagrams of embodiments of picks that may incorporate the insert. The picks may be milling pick, mining pick, pick, excavation pick, trenching pick or combinations thereof.

Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.

Claims

1. An insert, comprising: a sintered polycrystalline diamond body bonded to a cemented metal carbide substrate;the diamond body comprising a substantially conical shape with conical side wall terminating at an apex;the diamond body comprising a first region intermediate the substrate and the apex;the first region comprising a characteristic thermal stability, and a second region proximate the apex comprising a characteristic thermal stability higher than the first region.

2. The insert of claim 1, wherein the second region comprises a natural diamond.

3. The insert of claim 2, wherein the natural diamond forms the apex.

4. The insert of claim 2, wherein the natural diamond is covered by a small layer of first region.

5. The insert of claim 4, wherein prior to sintering, a metallic catalyst in the small layer is mixed with the diamond grains.

6. The insert of claim 5, wherein during sintering, the metallic catalyst in the small layer diffuses from the substrate.

7. The insert of claim 1, wherein the second region comprises a sintered natural diamond, a single crystal natural diamond, a single crystal synthetic diamond or combinations thereof.

8. The insert of claim 1, wherein the second region comprises coarse saw grade diamond.

9. The insert of claim 1, wherein the second region comprises cubic boron nitride.

10. The insert of claim 1, wherein the second region comprises an asymmetrical shape.

11. The insert of claim 1, wherein the second region comprises a non metallic catalyst.

12. The insert of claim 1, wherein the second region is pre-sintered prior to being sintered with the first region.

13. The insert of claim 12, wherein the pre-sintered second region is leached prior to being re-sintered with the first region.

14. The insert of claim 1, wherein the diamond body is thicker than the substrate.

15. The insert of claim 1, wherein the first region separates the second region from the substrate.

16. The insert of claim 1, wherein the second region is substantially free of the metallic catalyst.

17. The insert of claim 1, wherein first and second regions are joined at a non-planar interface.

18. A method for forming an insert, comprising the steps of: placing diamond powder in a conical metallic carbide can;compressing the carbide can under a high pressure/high temperature such that the powder forms a pointed sintered compact;removing the metallic catalyst from the sintered compact; andre-sintering the pointed sintered compact to another sintered diamond body such that the pointed sintered compact forms a tip.

19. A bit, comprising: an insert with a sintered polycrystalline diamond body bonded to a cemented metal carbide substrate;the diamond body comprising a substantially conical shape with conical side wall terminating at an apex;the diamond body comprising a first region with a metallic catalyst dispersed through interstices between the diamond grains and a second region proximate the apex with the characteristic of higher thermal stability than the first region.

20. The bit of claim 19, wherein the bit is a drill bit, a drag bit, a roller cone bit, a percussion bit or combinations thereof.

21. The bit of claim 19, wherein the bit is a milling pick, mining pick, pick, excavation pick, trenching pick or combinations thereof.