Double Sintered Thermally Stable Polycrystalline Diamond Cutting Elements

Abstract

Embodiments of the invention include a polycrystalline diamond compact comprising a plurality of double-sintered polycrystalline diamond segments. The polycrystalline diamond segments are configured to remain thermally stable at a first temperature. The polycrystalline diamond segments are positioned upon and bonded to a transition layer of single-sintered polycrystalline diamond that is configured to remain thermally stable at a second temperature lower than the first temperature. The transition layer is positioned upon and bonded to a substrate. Embodiments of the invention have improved thermally stability, resulting in fewer defects during manufacturing and improved longevity in use.

Description

PRIORITY CLAIM

This application claims the benefit of and priority from U.S. Provisional Patent Application No. 61/164,770 filed on Mar. 30, 2009, which is incorporated herein in its entirety for all purposes by this reference.

FIELD

Embodiments of the present invention relate generally to the field of earth boring tools and in particular relates to polycrystalline diamond cutting elements used on drill bits for earth boring.

BACKGROUND

Specialized drill bits are used to drill well-bores, boreholes, or wells in the earth for a variety of purposes, including water wells; oil and gas wells; injection wells; geothermal wells; monitoring wells, mining; and, other similar operations. These drill bits come in two common types, roller cone drill bits and fixed cutter drill bits.

Wells and other holes in the earth are drilled by attaching or connecting a drill bit to some means of turning the drill bit. In some instances, such as in some mining applications, the drill bit is attached directly to a shaft that is turned by a motor, engine, drive, or other means of providing torque to rotate the drill bit.

In other applications, such as oil and gas drilling, the well may be several thousand feet or more in total depth. In these circumstances, the drill bit is connected to the surface of the earth by what is referred to as a drill string and a motor or drive that rotates the drill bit. The drill string typically comprises several elements that may include a special down-hole motor configured to provide additional or, if a surfaces motor or drive is not provided, the only means of turning the drill bit. Special logging and directional tools to measure various physical characteristics of the geological formation being drilled and to measure the location of the drill bit and drill string may be employed. Additional drill collars, heavy, thick-walled pipe, typically provide weight that is used to push the drill bit into the formation. Finally, drill pipe connects these elements, the drill bit, down-hole motor, logging tools, and drill collars, to the surface where a motor or drive mechanism turns the entire drill string and, consequently, the drill bit, to engage the drill bit with the geological formation to drill the well-bore deeper.

As a well is drilled, fluid, typically a water or oil based fluid referred to as drilling mud is pumped down the drill string through the drill pipe and any other elements present and through the drill bit. Other types of drilling fluids are sometimes used, including air, nitrogen, foams, mists, and other combinations of gases, but for purposes of this application drilling fluid and/or drilling mud refers to any type of drilling fluid, including gases. In other words, drill bits typically have a fluid channel within the drill bit to allow the drilling mud to pass through the bit and out one or more jets, ports, or nozzles. The purpose of the drilling fluid is to cool and lubricate the drill bit, stabilize the well-bore from collapsing or allowing fluids present in the geological formation from entering the well-bore, and to carry fragments or cuttings removed by the drill bit up the annulus and out of the well-bore. While the drilling fluid typically is pumped through the inner annulus of the drill string and out of the drill bit, drilling fluid can be reverse-circulated. That is, the drilling fluid can be pumped down the annulus (the space between the exterior of the drill pipe and the wall of the well-bore) of the well-bore, across the face of the drill bit, and into the inner fluid channels of the drill bit through the jets or nozzles and up into the drill string.

Roller cone drill bits were the most common type of bit used historically and featured two or more rotating cones with cutting elements, or teeth, on each cone. Roller cone drill bits typically have a relatively short period of use as the cutting elements and support bearings for the roller cones typically wear out and fail after only 50 hours of drilling use.

Because of the relatively short life of roller cone bits, fixed cutter drill bits that employ very durable polycrystalline diamond (PCD) compact cutters, tungsten carbide cutters, natural or synthetic diamond, other hard materials, or combinations thereof, have been developed. These bits are referred to as fixed cutter bits because they employ cutting elements positioned on one or more fixed blades in selected locations or randomly distributed. Unlike roller cone bits that have cutting elements on a cone that rotates, in addition to the rotation imparted by a motor or drive, fixed cutter bits do not rotate independently of the rotation imparted by the motor or drive mechanism. Through varying improvements, the durability of fixed cutter bits has improved sufficiently to make them cost effective in terms of time saved during the drilling process when compared to the higher, up-front cost to manufacture the fixed cutter bits.

Typically, a diamond cutter for use in a drill bit having a geometric size and shape normally characterized by unleached diamond cutting elements fabricated by assembling a plurality of polycrystalline diamond compact cutting elements in an array in a cutting slug that supports the cutting element. A challenge occurs, however, in bonding the PCD cutting elements to the cutting slug because the cutting slug—typically a cemented carbide substrate—has a different material than the PCD cutting elements and, therefore, has different material properties, such as a different rate of thermal expansion than the PCD cutting element. The differences in material properties can cause thermal stresses that lead the PCD cutting element to crack, delaminate, or otherwise become weakened and/or damaged at the interface between the cutting slug and the PCD cutting element.

Thus, there exists a need for a PCD cutting element that is, at least in part, has improved thermal compatibility with the underlying cutting slug.

Further, there is a need for a PCD cutting element that has improved bonding to a cutting slug as compared to the prior art.

In addition, there is a need for a PCD manufacturing process that improves the yield of usable PCD cutting elements coupled to cutting slugs that reduces the probability that the PCD cutting elements break and/or crack during a double sintering process.

SUMMARY

Various features and embodiments of the invention disclosed herein provide robust and durable PCD cutting elements coupled to a cutting slug. In addition, methods of coupling a PCD cutting elements to a cutting slug are also disclosed.

Embodiments of the invention include a first layer comprising at least one polycrystalline diamond segment positioned upon a second layer or transition layer. In those embodiments that include a plurality of PCD segments, a first PCD segment is positioned proximate a second PCD segment and separated therefrom by an interfacial boundary. The interfacial boundary optionally is non-planar relative to the first and/or the second PCD segment. Optionally, the interfacial boundary includes an abrasive material. Optionally, the interfacial boundary is contiguous with and formed of the same material as the second layer. In some embodiments, the first layer remains thermally stable at a higher temperature than the temperature below which the second table remains thermally stable. In some embodiments, the second layer is coupled to a substrate or cutting slug.

Embodiments of the PCD segments include those that have been processed to provide a granular structure comprising interstices with a reduced number of metallic catalysts. Other embodiments of the PCD segments include those that have been processed to provide a granular structure that include interstices infiltrated with a material that remains thermally stable at a higher temperature than the temperature below which the metallic catalysts remain thermally stable. Other embodiments of the granular structure of the PCD segments comprise interstices that include one or more non-metallic catalysts. Yet other embodiments of the granular structure of the PCD segments comprise substantially fully dense diamond, i.e., a granular structure being substantially free of voids and/or interstices with or without other materials within any remaining interstices.

Other embodiments of the invention include a body of abrasive material coupled to a substrate. The body includes a substantially pointed or conical shaped cutting surface. The body optionally includes one or more PCD segments coupled to and exposed in the conical cutting surface.

A method of forming a PCD cutting elements coupled to a cutting slug includes providing a canister or other container configured to receive a plurality of thermally stable pre-sintered polycrystalline diamond segments. The canister is filled with grains of polycrystalline diamond and, optionally, a catalytic material. The polycrystalline diamond segments are positioned upon the grains of polycrystalline diamond such that an interfacial boundary is formed from the grains of polycrystalline diamond to separate each of the plurality of polycrystalline diamond segments. A press than applies a temperature and a pressure to the container to sinter the grains of polycrystalline diamond and bond the polycrystalline diamond segments to the sintered grains of polycrystalline diamond.

As used herein, “at least one,” “one or more,” and “and/or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C,” “at least one of A, B, or C,” “one or more of A, B, and C,” “one or more of A, B, or C” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.

Various embodiments of the present inventions are set forth in the attached figures and in the Detailed Description as provided herein and as embodied by the claims. It should be understood, however, that this Summary does not contain all of the aspects and embodiments of the one or more present inventions, is not meant to be limiting or restrictive in any manner, and that the invention(s) as disclosed herein is/are and will be understood by those of ordinary skill in the art to encompass obvious improvements and modifications thereto.

Additional advantages of the present invention will become readily apparent from the following discussion, particularly when taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of the one or more present inventions, reference to specific embodiments thereof are illustrated in the appended drawings. The drawings depict only exemplary embodiments and are therefore not to be considered limiting. One or more embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1 is an isometric view of an embodiment of a PCD compact cutting element;

FIG. 2 is a microscopic level view of an embodiment of a granular structure of a PCD segment;

FIG. 3 is a microscopic level view of another embodiment of a granular structure of a PCD segment;

FIG. 4 is an isometric view of an embodiment of a metallic carbide disc for use in embodiments of methods of making a PCD segment;

FIG. 5 is an isometric view of another embodiment of a metallic carbide disc for use in embodiments of methods of making a PCD segment;

FIG. 6A is a cross-sectional view of an embodiment of a canister for use in embodiments of methods of making a PCD segment;

FIG. 6B is a cross-sectional view of an embodiment of a canister for use in embodiments of methods of making a PCD compact;

FIG. 7 is an orthogonal view of an embodiment of a PCD cutting element;

FIG. 8 is an orthogonal diagram of another embodiment of a PCD cutting element;

FIG. 9 is an orthogonal diagram of another embodiment of a PCD cutting element;

FIG. 10 is an orthogonal diagram of another embodiment of a PCD cutting element;

FIG. 11 is an orthogonal diagram of another embodiment of a PCD cutting element;

FIG. 12 is an orthogonal diagram of another embodiment of a PCD cutting element;

FIG. 13 is an orthogonal diagram of another embodiment of a PCD cutting element;

FIG. 14 is an orthogonal diagram of another embodiment of a PCD cutting element;

FIG. 15 is a cross-sectional view of an embodiment of a PCD cutting element;

FIG. 16 is a cross-sectional view of another embodiment of a PCD cutting element;

FIG. 17 is a cross-sectional view of another embodiment of a PCD cutting element;

FIG. 18 is a cross-sectional view of another embodiment of a PCD cutting element;

FIG. 19 is a cross-sectional view of another embodiment of a PCD cutting element;

FIG. 20 is a cross-sectional view of another embodiment of a PCD cutting element;

FIG. 21 is an isometric view of an embodiment of a rotary drag bit that includes an embodiment of a PCD compact cutting element in a close-up view;

FIG. 22 is an isometric view of an embodiment of a PCD compact cutting element that includes a transition layer with a conical surface;

FIG. 23 is an isometric view of another embodiment of a rotary drag bit that includes an embodiment of a PCD compact cutting element that includes a conical surface in a close-up view;

FIG. 24 is an orthogonal view of another embodiment of a PCD cutting element;

FIG. 25 is an orthogonal view of another embodiment of a PCD cutting element; and,

FIG. 26 is an orthogonal view of another embodiment of a PCD cutting element;

The drawings are not necessarily to scale.

DETAILED DESCRIPTION

FIG. 1 shows an isometric view of an embodiment of a polycrystalline diamond (PCD) compact 101. The PCD compact 101 includes a first table or layer 105 formed of a plurality of PCD segments 110 that, optionally, are sintered and/or preformed, as will be described in further detail below. The PCD segments 110 optionally are leached diamond, natural diamond, synthetic diamond, highly pressurized diamond, calcium carbonate sintered diamond, combinations thereof, and similar materials and for purposes of the claims a PCD segment and/or polycrystalline diamond encompasses all these materials and those that fall within the scope of this disclosure. In addition, the PCD segments 110 optionally are thermally stable as will be described in further detail below. In the embodiment of the PCD compact 101 illustrated in FIG. 1, the first layer 105 has a diameter of 130. Of course, one of skill in the art will appreciate that the first layer 105 can optionally have different dimensions and different shapes, including ovoid, half-circle, square, and other such shapes, and that all of these embodiments fall within the scope of the disclosure.

The plurality of PCD segments 110 are separated by an interfacial boundary 150 between each of the plurality of PCD segments 110. Optionally, the interfacial boundaries 150 comprises an abrasive material selected from a group that includes, but is not limited to, tungsten carbide, cubic boron nitride, thermally stable polycrystalline diamond, polycrystalline diamond, and the like. The interfacial boundaries 150 optionally are non-linear and/or non-planar relative to adjacent PCD segments 110. Optionally, the non-linear and/or non-planar quality of the interfacial boundary 150 creates an interlocking feature—best seen as interlocking feature 760 in FIG. 7 and interlocking feature 960 in FIG. 9—between the diamond segments 110, thereby reducing the likelihood that adjacent PCD segments 110 will move relative to each other and, therefore, reducing the likelihood of a PCD segment 110 being torn and/or damaged and/or removed undesirably from the PCD compact 101 during use.

The PCD compact 101 also includes a second table or layer 115, also referred to as a transition layer 115. The PCD segments 110 are positioned upon and bonded to the second layer 115. The second layer 115 optionally comprises an abrasive material selected from a group that includes, but is not limited to, tungsten carbide, cubic boron nitride, thermally stable polycrystalline diamond, polycrystalline diamond, and the like. The embodiment of the PCD compact 101 illustrates a second layer 115 that includes sintered PCD grains 120 that is optionally interspersed with a metallic catalyst. Optionally, the second layer 115 is contiguous with and comprises the same material as the interfacial boundary 150. In the embodiment of the PCD compact 101 illustrated in FIG. 1, the second layer 115 has a diameter of 135 that is the same, within manufacturing tolerances, as the diameter 130 of the first layer 105. Of course, one of skill in the art will appreciate that the second layer 115 can optionally have different dimensions and different shapes, including ovoid, half-circle, square, and other such shapes, including dimensions and shapes different from the first layer 105, and that all of these embodiments fall within the scope of the disclosure.

The second table 115 is bonded to a substrate 125 made from, for example, a metallic material. For example, the substrate 125 can be made from a metallic material selected from the group that includes, but is not limited to, tungsten carbide, titanium carbide, tungsten molybdenum carbide, tantalum carbide, combinations thereof, and other similar materials. In the embodiment of the PCD compact 101 illustrated in FIG. 1, the substrate 125 has a diameter of 140 that is the same, within manufacturing tolerances, as the diameter 130 of the first layer 105 and the diameter 135 of the second layer 115. Of course, one of skill in the art will appreciate that the substrate 125 can optionally have different dimensions and different shapes, including ovoid, half-circle, square, and other such shapes, including dimensions and shapes different from the first layer 105 and/or the second layer 115, and that all of these embodiments fall within the scope of the disclosure.

As noted, the PCD segments 110 typically are formed by sintering powdered diamond, and, optionally, various catalysts, typically metallic powders mixed with the diamond powder. The catalysts, typically metallic materials, such as cobalt and other similar metallic materials, act as a catalyst to reduce the temperature and/or the pressure at which the sintering process occurs and/or speeds the reaction by which the diamond grains and any other materials crystallize and form a granular structure. The diamond powder and any catalysts and/or other materials are placed in a canister or form that is compressed under a pressure and a temperature sufficient to sinter and crystallize the diamond powder and any other materials into a solid PCD segment.

Referring to FIG. 3, a sintered PCD granular structure 300 comprises polycrystalline diamond grains or crystals 301 and a catalyzing material 310 dispersed between the polycrystalline diamond grains or crystals 301. Optionally, the catalyzing material 310 is selected from a group of metallic materials, including, but not limited to, cobalt, nickel, iron, ruthenium, rhodium, palladium, platinum, chromium, manganese, tantalum, osmium, iridium, and combinations thereof.

Cobalt and other catalysts, however, typically result in a PCD granular structure that typically suffers from thermal degradation at temperatures (typically around from about 650 degrees Celsius to about 700 degrees Celsius) that the PCD granular structure can be exposed to during normal use. That is, the PCD granular structure exhibits increased tendencies to fail, crack, chip, delaminate, or otherwise wear more quickly during use at normal operating temperatures, leading to premature wear and reduced life.

To address the side-effect the catalysts 310 have on the thermal stability of the PCD granular structure 300, the PCD segments (such as segments 110 in FIG. 1) are processed after they have been sintered to reduce the amount of catalyst 310 present in the PCD granular structure 300 or remove the catalyst 310, either from the entire PCD segment or at least to a depth at which the PCD segment is heated through the transfer of heat generated during use less than the temperature at which the PCD granular structure begins to exhibit decreased thermal stability. Typically, the catalysts are removed via leaching and/or acid etching with acids that react with the catalysts and/or other known methods, leaving a PCD segment that is said to be thermally stable, typically referred to as thermally stable polycrystalline (TSP).

Illustrated in FIG. 2 is an idealized microscopic level view of a sintered PCD granular structure 200 that has been processed to remove the catalyst (e.g., catalyst 220 in FIG. 3), thereby leaving voids 220 and PCD grains 201, as discussed above. That is, the thermally stable PCD segments 110 of FIG. 1 optionally have been processed in such a way to improve the thermal stability of the PCD segments 110 relative to PCD segments that have not undergone such processing. Improved thermal stability means that the diamond segments remain stable, e.g., do not exhibit increased tendencies to fail, crack, chip, delaminate, or otherwise wear more quickly during use at higher temperatures than these failure modes would otherwise manifest themselves.

The PCD grains 201 typically are submicron in size, providing dimensional context for the FIGS. 2 and 3, typically from about 1 micron to about 50 microns and, more preferably, from about 5 microns to about 35 microns and, more preferably still, from about 7 microns to about 25 microns. In some embodiments, the PCD granular structure is processed to provide PCD grains 201 large enough such that the PCD grains 201 do not easily oxidize and burn up when subjected to the heat caused by friction during use.

Optionally, the PCD granular structure 200 is then subjected to additional processing, such as another sintering process (i.e., double sintering) to cause the PCD grains 201 to grow and expand into the interstices or voids 220, leaving PCD granular structure that is substantially diamond dense. That is, the PCD granular structure 200 comprises at least 90% PCD grains 201.

In other embodiments, the PCD granular structure 200 is sintered while in contact with non-catalytic materials, i.e., those materials that typically do not catalyze or cause the PCD granular structure to change crystal structure (e.g., from diamond to graphite) and/or lower the temperature at which the PCD granular structure 200 and PCD grains 201 begin to become thermally unstable. For example, a non-metallic catalyst 210 that is thermally stable, e.g., one having a coefficient of thermal expansion similar to that of the PCD grains 201 can be placed in contact with the PCD granular structure 201 during the sintering process, thereby causing the non-metallic catalyst 210 to infiltrate and/or grow within one or more of the interstices or voids 220. The non-metallic catalyst 210 can be selected from a group that includes, but is not limited to, silicon, silicon carbide, boron, carbonates, hydroxide, hydride, hydrate, phosphorus-oxide, phosphoric acid, carbonate, lanthanide, actinide, phosphate hydrate, hydrogen phosphate, phosphorus carbonate, combinations thereof, and other similar materials.

In yet other embodiments, the PCD granular structure 200 is sintered with one or more thermally stable materials 215, including, but not limited to, cobalt silicide, titanium, niobium, molybdenum, tungsten, tantalum, combinations thereof, and other similar materials. A benefit of these thermally stable materials 215 is that they tend to act to make the PCD granular structure 200 less brittle under impact loads.

Prior art PCD compacts typically had a PCD segment bonded directly to a substrate. This arrangement caused difficulties during manufacturing and use because, among other problems, the coefficient of thermal expansion differed, sometimes greatly, between the substrate and the PCD segment. During manufacturing, in which the PCD segment was to be bonded to the substrate, the different rates of thermal expansion often resulted in PCD segments that cracked due to the thermal stresses created at the interface of the substrate and the PCD segment as the substrate and PCD segment expanded and contracted at different rates while heating and cooling. Similar results occurred during use in which the PCD segment would be subjected to direct heating caused by friction, whereas the substrate is heated primarily through heat transferred by conduction through the PCD segment and to the substrate.

A benefit of the second layer or transition layer 115 is that it solves the previously unresolved problem of bonding a PCD segment to a substrate that has a different coefficient of thermal expansion. That is, embodiments of PCD compacts of the invention have improved thermal stability, improved bonding of the PCD segments to a substrate, improved reliability, and other benefits as described herein and one having skill in the art will understand by reading the disclosure.

Embodiments of methods of making first the PCD segments 110 are first discussed. As noted above, PCD segments 110 are formed by sintering diamond powder or other similar material and, optionally, a catalyst. Illustrated in FIGS. 4 and 5 are discs 405, 410, that are provided. The discs 405, 410 optionally formed of a metallic carbide, such as those materials discussed above. The discs 405 and 410 are used to shape the PCD segments 110. The discs 405, 410 include one or more areas 415 in which the PCD segments 110 are formed, the areas 415 being separated by one or more ribs 420 on a front surface 409 of the discs 405, 410. The ribs 420 may be straight, non-liner, curvilinear, non-planar, combinations thereof, and the like. (It should be noted that shape and location of the ribs 420 is a mirror of the shape and location of the interfacial boundary 150 of the PCD compact 101 discussed above. Thus, the ribs 420 can optionally be of any shape and any dimension contemplated for the interfacial boundaries.) In addition, the ribs 420 separate the PCD segments 110 from coming into contact with each other during the manufacturing process.

Embodiments of the method making PCD include providing a canister or can 601 as seen in FIG. 6A. At least one disc or a first disc 405 is placed within the canister 601 and each area 415 of the disc 405 is filled with, for example, diamond powder 650 (and any catalysts and other materials, which are considered present in the discussion of the diamond powder 650), as discussed above, that will be sintered to form the PCD segment 110, as discussed above. In those instances in which a plurality of discs 405 are placed into the canister 601 so as to form a plurality of PCD segments 110, optionally another disc 630 separates each disc 405 from the diamond powder 650 proximate to a back surface 407 of each disc 405. The disc 630 optionally is made of niobium and/or similar such materials, which prevents, at least to some degree, the flow of diamond powder 650 and the growth of crystallized diamond grains into the back surface 407 of the disc 405 during sintering. The number of discs 405 positioned in the canister 601 and, consequently, the number of PCD segments 110 produced, is a function, in part, of the thickness 655 of the layer of diamond powder 650 and the thickness 408 of the discs 405. Of course, the thickness 655 of the diamond powder 650 and the thickness 408 of the disc 405 optionally can be varied in the same canister 601, thus producing PCD segments of different dimensions in one manufacturing batch. Further, as one having skill in the art will appreciate, the quantity of PCD segments 110 produced is a function, in part, on the configuration and number of ribs 420 on each disc 405. Further, different discs 405 with different configurations of ribs 420 can be used in a given canister 601, thus further affecting the yield of PCD segments 110.

Prior to placing the lid 660 on the canister 601 and sealing the canister 601, the diamond powder 650 may be tamped down or compacted with an applied pressure low enough to avoid breakage of any of the discs 405 and 630. Optionally, the canister 650 is heated to reduce or eliminate some or all of any impurities present in the diamond powder 650 and elsewhere in the canister 601 before sealing the canister 601. Typically, the lid 660 is sealed to the canister 601 through welding, such as laser welding and other known methods. In some embodiments of the present invention, the canister is sealed using a process described in U.S. Pat. No. 7,575,425 to Hall et al., which is herein incorporated by reference for all that it contains.

After the canister 601 is sealed, it is placed within a salt form (not shown). One or more salt forms are then stacked and placed on an anvil of a high-temperature, high-pressure press (not shown). The press applies a pressure and a temperature sufficiently high to cause the diamond powder 650 (and any catalysts and other materials) to sinter. During the sintering process, the diamond powder 650 typically reduces in volume as it becomes solid.

Once the sintering process is complete and the canister 601 is removed from both the press and the salt form, the diamond powder 650 will have become the sintered PCD segments 110. An advantage of the ribs 420 of the discs 405 is that the separate PCD segments 110 are easily separable from the discs 420, thus eliminating a step of cutting the PCD segments 110 out a solid cylinder of polycrystalline diamond with an electron discharge machining (EDM), a process that typically is time consuming and expensive. The separated PCD segments 110 are now ready for any post-sintering treatment such as leaching and/or acid baths, and other such treatments to improve the thermal stability of the PCD segments 110 as discussed above.

Embodiments of the method further include forming PCD compacts, such as those illustrated in FIG. 1, to combine PCD segments 110 with an unsintered abrasive powder or material that will form the second or transition layer 115 and a substrate 125. One or more PCD segments 2610 are placed in a canister 2601, similar to the canister 601, as illustrated in FIG. 6B. Unsintered abrasive material 2620, such as diamond powder, by way of example, is placed in the canister in between—at the interfacial boundary 2650—and on top of the PCD segments 2610 that typically have been processed to improve the thermal stability of the PCD segments 2610, as discussed above. As noted above, the unsintered abrasive material optionally includes metallic catalysts and/or non-metallic catalysts and/or other thermally stable materials as discussed above.

The substrate 2625 is placed on top of the unsintered abrasive material 2620. Prior to placing the lid 2660 on the canister 2601 and sealing the canister 2601, the unsintered abrasive material 2620 may be tamped down or compacted with an applied pressure low enough to avoid breakage of any of the PCD segments 2610. Optionally, the canister 2601 is heated to reduce or eliminate some or all of any impurities present in the unsintered abrasive material 2620 and elsewhere in the canister 2601 before sealing the canister 2601. Typically, the lid 2660 is sealed to the canister 2601 through welding, such as laser welding and other known methods. In some embodiments of the present invention, the canister is sealed using a process described in U.S. Pat. No. 7,575,425 to Hall et al. After the canister 2601 is sealed, it is placed within a salt form (not shown). One or more salt forms are then stacked and placed on an anvil of a high-temperature, high-pressure press (not shown). The press applies a pressure and a temperature sufficiently high to cause the unsintered abrasive material 2620 (and any catalysts and other materials) to sinter. During the sintering process, the abrasive material 2620 typically reduces in volume as it becomes solid. In addition, the PCD segments 2610 undergo a second, or double, sintering process, by which the PCD grains grow and/or other non-metallic catalysts and/or other thermally stable materials are incorporated and sintered into the PCD segments as discussed above.

During the sintering process, the abrasive material 2620 forms both a mechanical and a chemical bond or attachment with the PCD segments 2610 at the interfacial boundary 2650 and at a lower surface 2611. For example, the PCD segments 2610 would exhibit, in part, growth of PCD grains 201 (FIG. 2) into the interstices and voids 220 (FIG. 2) across and into a transition zone 2621 of the now sintered abrasive material 2620. In so doing, a solid, rigid diamond layer at the transition zone 2621 forms a mechanical bond between the sintered layer of abrasive material 2620 and the PCD segments 2610, reducing any residual stress concentrations that may otherwise occur. Further, the abrasive material 2620 may reduce in volume as it sinters, provided further space into which PCD grains may grow during the sintering process, further improving the mechanical bond. It should be noted that while the grain size of the PCD grains and the sintered abrasive material can vary substantially, a grain size that is similar between the PCD grains and the sintered abrasive material can improve and provide a more uniform bond between the two materials as compared to the bond that occurs when the grain sizes are dissimilar.

Another benefit is that whereas the PCD segments 2610—typically processed to be thermally stable—and the substrate 2625 typically have coefficients of thermal expansion that are quite different, as discussed above, the layer of sintered abrasive material 2620 acts as a transition layer, and is typically selected and prepared to have a coefficient of thermal expansion somewhere between that of the PCD segments 2610 and the substrate 2625. In so doing, the gradient of thermal stresses is changed gradually throughout the PCD compact rather than having a sharp transition at each interface. That is, a first layer of PCD segments 2610 is configured to remain thermally stable at a first temperature and a second layer or transition layer 2620 is configured to remain thermally stable at a second temperature lower than the first temperature.

Disclosed in FIGS. 7-14 are various, non-limiting embodiments of PCD compacts comprising PCD segments of various shapes and the interfacial boundaries between each PCD segment.

For example, the PCD compact 710 includes two PCD segments 710 and a single interfacial boundary 750 that is non-linear and non-planar and includes interlocking features 760, such as the illustrated dimples.

As illustrated in FIGS. 7-14, the PCD segments 710, 810, 910, 1010, 1110, 1210, 1310, and 1410 can be a variety of shapes, including, but not limited to, circular, square, hexagonal or a polygonal working surface. The PCD segments 710, 810, 910, 1010, 1110, 1210, 1310, and 1410 can be arranged symmetrically or asymmetrically around the PCD compacts 701, 801, 901, 1001, 1101, 1201, 1301, and 1401. Further, the PCD segments can be oriented relative to the direction of work so that the PCD segments perform the majority of the work as compared to the abrasive material.

As noted, the interfacial boundaries 750, 950, and others can include comprise interlocking features. The interfacial boundaries 950 includes a series of steps 960. The interlocking features 750, 850, 950, 1050, 1150, 1250, 1350, and 1450 optionally include also comprise complementary projections and recesses. For example, PCD compact 1201 in FIG. 12 includes a PCD segment 1210 that has a interfacial boundary 1250 that is a plurality of oval openings.

Disclosed in FIGS. 15-20 are cross-sections of various, non-limiting embodiments of PCD compacts 1501, 1601, 1701, 1801, 1901, and 2001. Each of the PCD compacts 1501, 1601, 1701, 1801, 1901, and 2001 include a plurality of PCD segments 1510, 1610, 1710, 1810, 1910, and 2010, respectively, with an interfacial boundary 1550, 1650, 1750, 1850, 1950, and 2050 separating them, respectively. The transition layers 1515, 1615, 1715, 1815, 1925, and 2015 are bonded at lower surface 1511, 1611, 1711, 1811, 1911, and 2011 to the PCD segments 1510, 1610, 1710, 1810, 1910, and 2010. Likewise, the transition layers 1515, 1615, 1715, 1815, 1925, and 2015 are bonded at upper surfaces 1524, 1624, 1724, 1824, 1924 and 2024 to the substrates 1525, 1625, 1725, 1825, 1925, and 2025, respectively. The lower surfaces 1511, 1611, 1711, 1811, 1911, and 2011 and the upper surfaces 1524, 1624, 1724, 1824, 1924 and 2024 optionally are non-linear and/or non-planar and/or include interlocking features, such as protrusions and steps.

FIG. 21 shows an embodiment of a drag bit 2800 that includes a plurality of PCD compacts or shear cutters 2801 as described above. The shear cutters 2801 are attached to blades 2880 that each extend from a head 2890 of the drag bit 2800 for cutting against the subterranean formation being drilled.

FIG. 22 discloses an embodiment of a PCD compact or pointed cutting element 3101 that includes PCD segments 3110 arranged about the PCD compact or cutting element 3101. The PCD segments 3110 can be arranged symmetrically or asymmetrically about the PCD compact 3101 as required for a particular application. A sintered abrasive material 3120 having a conical surface 3123 supports the PCD segments 3110 that, in turn, is supported by a substrate 3125.

FIG. 23 shows an embodiment of another drag bit 3100 that includes a plurality of pointed PCD compacts or cutting elements 3101. The PCD compacts 3101 may be pressed or machined into the desired shape or configuration. In other embodiments, the PCD compact 3101 may be used in road milling, pavement resurfacing, mining, and trenching applications.

Disclosed in FIGS. 24-26 are various, non-limiting embodiments of arrangements of the PCD segments 2410, 2510, and 2710 around conical or pointed PCD compacts 2401, 2501, and 2701, that are analogous to the PCD segments 3110 and the conical PCD compacts 3101 in FIGS. 22 and 23. The PCD segments 2410, 2510, and 2710 can be of various shapes and sizes, non-limiting examples of which include, but are not limited to, rectangular, trapezoidal, square, hexagonal or triangular shape and disposed within or exposed in the conical surface, such as conical surface 3123 in FIG. 22, as noted. The interfacial boundaries 2450, 2550, and 2750 can be formed of a sintered abrasive material.

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.

The present invention, in various embodiments, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments hereof, including in the absence of such items as may have been used in previous devices or processes, e.g., for improving performance, achieving ease and/or reducing cost of implementation.

The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. In the foregoing Detailed Description for example, various features of the invention are grouped together in one or more embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate preferred embodiment of the invention.

Moreover, though the description of the invention has included description of one or more embodiments and certain variations and modifications, other variations and modifications are within the scope of the invention, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.

Claims

1. A polycrystalline diamond compact comprising:

a first layer, said first layer including a plurality of polycrystalline diamond segments positioned thereupon; said plurality of polycrystalline diamond segments being separated by an interfacial boundary formed of an abrasive material;

a second layer, said first layer being bonded to a second layer, said second layer being formed in part from said abrasive material; and,

a substrate, said second layer being positioned upon and bonded to said substrate.

2. The compact of claim 1, wherein said polycrystalline diamond segments have a granular structure comprised of polycrystalline diamond grains and interstices, said interstices being substantially free of a catalytic material.

3. The compact of claim 2, wherein said interstices include a non-catalytic material.

4. The compact of claim 3, wherein said non-catalytic material is a non-metallic material.

5. The compact of claim 1, wherein said polycrystalline diamond segments have a granular structure comprised substantially of polycrystalline diamond grains and substantially free of interstices.

6. The compact of claim 1, wherein said abrasive material comprises a granular structure comprised of polycrystalline diamond grains and a catalyst.

7. The compact of claim 1, wherein the second layer further comprises a substantially conical surface.

8. The compact of claim 1, wherein said first layer is configured to remain thermally stable at a first temperature and said second layer is configured to remain thermally stable at a second temperature lower than said first temperature.

9. A polycrystalline diamond compact comprising:

a plurality of double-sintered polycrystalline diamond segments, said diamond segments configured to remain thermally stable at a first temperature;

a transition layer of single-sintered polycrystalline diamond configured to remain thermally stable at a second temperature lower than said first temperature, said polycrystalline diamond segments positioned upon and bonded to said transition layer; and,

a substrate, said transition layer positioned upon and bonded to said substrate.

10. The compact of claim 9, wherein said polycrystalline diamond segments have a granular structure comprised of polycrystalline diamond grains and interstices, said interstices being substantially free of a catalytic material.

11. The compact of claim 10, wherein said interstices include a non-catalytic material.

12. The compact of claim 11, wherein said non-catalytic material is a non-metallic material.

13. The compact of claim 9, wherein said polycrystalline diamond segments have a granular structure comprised substantially of polycrystalline diamond grains and substantially free of interstices.

14. The compact of claim 9, wherein said transition layer comprises a granular structure comprised of polycrystalline diamond grains and a catalyst.

15. The compact of claim 9, wherein the transition layer further comprises a substantially conical surface.

16. A method of forming a polycrystalline diamond compact comprising:

providing a canister configured to receive a plurality of sintered polycrystalline diamond segments and an unsintered abrasive powder;

filling said canister with said unsintered abrasive powder;

positioning said plurality of polycrystalline diamond segments upon said unsintered abrasive powder, an interfacial boundary formed of said unsintered abrasive powder separating each of said plurality of polycrystalline diamond segments; and

applying a temperature and a pressure to said canister to sinter said unsintered abrasive powder and bond said polycrystalline diamond segments to said sintered abrasive powder.

17. The method of claim 16, further comprising positioning a substrate in said canister, said unsintered abrasive powder being positioned between said substrate and said sintered polycrystalline diamond segments.

18. The method of claim 16, further comprising:

providing another canister configured to receive at least a first disc, said first disc including at least one rib on a front surface of said first disc;

filling said canister with at least diamond powder;

placing said first disc in said canister such that said front surface of said first disc is in contact with said diamond powder; and,

applying a temperature and a pressure to said canister to sinter said diamond powder to form said sintered polycrystalline diamond segments.

19. The method of claim 18, further comprising:

removing said sintered polycrystalline diamond segments from said another canister;

processing said polycrystalline diamond segments to make said polycrystalline diamond segments more thermally stable than unprocessed polycrystalline diamond segments.