System for processing body of polycrystalline diamond material

Abstract

A system for leaching a polycrystalline diamond (PCD) cutting element having a body of PCD material, the system comprising: a leaching vessel for receiving a volume of a liquid acid leaching mixture; a clamp adapted to maintain the PCD cutting element to be leached spaced apart from the volume of leach mixture in the leach vessel; and a sealing member positionable in the recess of the jig for positioning around the PCD cutting element to be leached. The leaching vessel and the clamp are adapted to interconnect to form a closed system.

Description

[0001] The present disclosure relates to a system for machining a body of polycrystalline diamond (PCD) material. Background Art

[0002] Cutting inserts for machine tools and other tools may typically include a layer of polycrystalline diamond (PCD) material bonded to a cemented carbide substrate. PCD is an example of a superhard material (also known as a superabrasive material) with hardness values ​​much higher than that of cemented tungsten carbide.

[0003] Components containing PCD are used in a wide variety of tools for cutting, machining, drilling, or degrading hard or abrasive materials such as rock, metal, ceramics, composites, and wood-containing materials. PCD comprises a mass of substantially inter-grown (interbonded) diamond grains that form a framework material that defines interstices between the diamond grains. PCD material typically comprises at least about 80% diamond by volume and can be produced by subjecting an aggregate mass of diamond grains to ultra-high pressures exceeding about 5 GPa, typically about 5.5 GPa or greater, and temperatures of at least about 1200°C, typically about 1440°C, in the presence of a sintering aid, also known as a solvent catalyst material for diamond. A solvent catalyst material for diamond is understood to be a material capable of promoting the direct intergrowth of diamond grains under pressure and temperature conditions at which diamond is thermodynamically more stable than graphite.

[0004] Examples of solvent catalyst materials for diamond include cobalt, iron, nickel, and certain alloys (including alloys of any of these elements). PCD can be formed, for example, on a cobalt-bonded tungsten carbide substrate, which can provide a source of cobalt catalyst material for the PCD. During sintering of the PCD material body, components of the bonded carbide substrate (e.g., cobalt from the cobalt-bonded tungsten carbide substrate) liquefy and are swept from regions adjacent to the bulk of the diamond grains into the interstitial regions between the diamond grains. In this example, cobalt acts as a solvent catalyst to promote the formation of bonded diamond grains. Alternatively, a metal-solvent catalyst can be mixed with the diamond grains before subjecting the diamond grains and substrate to the HPHT process. Interstices within the PCD material can be at least partially filled with the solvent catalyst material. Consequently, the intergrown (interbonded) diamond structure includes the original diamond grains and newly precipitated or regrown diamond phases bridging the original grains. In the final sintered structure, the solvent catalyst material typically remains within at least some of the interstices existing between the sintered diamond grains.

[0005] Sintered PCD typically possesses sufficient wear resistance and hardness for use in aggressive wear, cutting, and drilling applications. However, a well-known problem encountered with this type of PCD compact or cutting element is that the presence of residual solvent catalyst material in the microstructural interstices can adversely affect the performance of the PCD compact at elevated temperatures, as the presence of the solvent catalyst in the diamond slice is believed to reduce the thermal stability of the diamond slice at these elevated temperatures. For example, the difference in thermal expansion coefficient between the diamond grains and the residual solvent / catalyst is believed to lead to chipping or cracking of the PCD slice of the cutting element during drilling or cutting operations, where operating temperatures can reach 700°C or higher. Chipping or cracking in the PCD material can degrade the mechanical properties of the cutting element or lead to its failure. Additionally, at elevated temperatures, the diamond grains may undergo chemical decomposition or reverse conversion with the solvent catalyst. At extremely high temperatures, portions of the diamond grains may be converted to carbon monoxide, carbon dioxide, graphite, or a combination thereof, thereby degrading the mechanical properties of the PCD material.

[0006] A potential solution to these problems is to remove the residual solvent catalyst (also known as the binder phase) from the PCD material.

[0007] Chemical leaching is often used to remove metal-solvent catalysts, such as cobalt, from interstitial regions within a body of PCD material, such as from areas adjacent to the working surface of the PCD. Effectively removing the bulk of the metal-solvent catalyst from a PCD slice, particularly from the thicker PCD slices required for current applications, is often very difficult and time-consuming. In general, current technology focuses on achieving high diamond density PCD and corresponding PCD with a very fine distribution of metal-solvent catalyst pools. This fine network is typically resistant to penetration by the leaching agent, so that residual solvent catalyst often remains in the leached compact. Furthermore, achieving appreciable leaching depths may require so long a time as to be commercially unfeasible, or require undesirable interventions, such as extreme acid treatment or physical drilling of the PCD slice.

[0008] A common method of removing catalyst from PCD material is to leach the PCD material to remove some or substantially all of the interstitial catalyst from the PCD lattice structure, thereby converting the PCD material into a more thermally stable polycrystalline diamond material. Leaching typically involves placing the cutting element in a strong acid bath at an elevated temperature to expose the PCD slice to the acid. Typical suitable acids for leaching include nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, and combinations thereof. While such leaching acids can help remove catalyst from the PCD material, they can also damage the underlying substrate to which the PCD slice is fixed, and appropriate sealing is required to protect the substrate from such damage. Conventional leaching techniques using acid baths are relatively time-consuming and may require days or weeks to remove a sufficient amount of residual solvent catalyst from the PCD material. This increases the overall time and associated costs of manufacturing the cutting element and the fixed cutting drill bit in which such a cutter is located during use.

[0009] Therefore, there is a need for a system for handling or processing a body of PCD material that overcomes or substantially ameliorates the above-mentioned problems. Summary of the Invention

[0010] Viewed from a first aspect, there is provided a system for leaching a polycrystalline diamond (PCD) cutting element having a body of PCD material including a non-diamond phase comprising a solvent catalyst material, the system comprising:

[0011] a leach container for receiving a volume of liquid acid leach mixture;

[0012] a fixture adapted to hold the PCD cutting element to be leached spaced apart from the volume of leach mixture in the leach vessel;

[0013] The leaching vessel and the fixture are arranged to be interconnected to form a closed system; and

[0014] A sealing member is positionable in the recess of the fixture for positioning around the PCD cutting element to be leached. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Various variants will now be described in more detail, by way of example, with reference to the accompanying drawings, in which:

[0016] Figure 1 is a schematic perspective view of a PCD cutter insert for a cutting drill bit for drilling into the earth;

[0017] Figure 2 yes Figure 1 A schematic cross-sectional view of a portion of a PCD cutter insert showing the Figure 1The microstructure of PCD material in PCD cutter inserts;

[0018] Figure 3 is a schematic partial cross-sectional illustration of an example of a system for vapor leaching PCD cutting elements according to the principles disclosed herein; and

[0019] Figure 4 is a schematic flow chart illustrating an example of a method for leaching a PCD cutting element according to the principles disclosed herein.

[0020] Throughout the drawings, like reference numerals refer to like corresponding features. DETAILED DESCRIPTION

[0021] The present disclosure is directed to methods for machining superabrasive articles such as superabrasive cutting elements, superabrasive bearings, and superabrasive discs. The superabrasive articles disclosed herein can be used in a variety of applications, such as drilling tools (e.g., compacts, cutting elements, gauge dressers, etc.), machine tools, bearing devices, wire drawing machinery, and other devices.

[0022] As used herein, a "superhard material," also referred to as a "superabrasive" material, is a material having a Vickers hardness of at least about 28 GPa. Diamond and cubic boron nitride (cBN) materials are examples of superhard or superabrasive materials.

[0023] As used herein, a "superhard structure" or "superabrasive structure" means a structure or compact comprising a body of polycrystalline superhard or superabrasive material. In such a structure, a substrate may be attached thereto, or alternatively the body of polycrystalline material may be free-standing and unsupported.

[0024] As used herein, polycrystalline diamond (PCD) is a polycrystalline superhard (PCS) material comprising a plurality of diamond grains, wherein a majority of the diamond grains are directly bonded to one another, and wherein the diamond content is at least about 80 volume percent of the material. In one example of PCD material, the interstices between the diamond grains may be at least partially filled with a binder material comprising a solvent catalyst for diamond. As used herein, "interstices" or "interstitial regions" are regions between the diamond grains of PCD material. In examples of PCD material, the interstices or interstitial regions may be substantially or partially filled with a material other than diamond, or they may be substantially empty. PCD material may include at least one region from which catalyst material has been removed from the interstices, thereby leaving interstitial voids between the diamond grains.

[0025] The "catalyst material" used for superhard materials can promote the growth or sintering of the superhard material.

[0026] As used herein, the term "substrate" means any substrate on which a superhard material layer is formed. For example, as used herein, a "substrate" may be a transition layer formed on another substrate.

[0027] As used herein, the term "integrally formed" regions or portions are produced contiguously with each other and are not separated by different types of materials.

[0028] As used herein, the term "molarity" may refer to concentration in mol / L at a temperature of about 25° C. For example, a solution containing solute A at a molarity of 1 M may contain 1 mol of solute A per liter of solution.

[0029] As used herein, the term "depth of leaching" or "leaching depth" refers to the distance from the outer surface of the PCD cutting element into the PCD cutting element that the leaching acid penetrates during the leaching process to remove residual solvent catalyst therefrom.

[0030] In such Figure 1 In the example shown, the cutting element 1 includes a substrate 10 and a body 12 of PCD material in the form of a layer formed on the substrate 10. The substrate 10 may be formed of a hard material such as cemented tungsten carbide. The cutting element 1 may be mounted in a drill bit body such as a drag bit body (not shown) and may be suitable, for example, for use as a cutter insert in a drill bit for drilling into the earth.

[0031] The exposed top surface of the superhard material opposite the substrate forms the cutting face 14, which is the surface that cuts together with its edge 16 in use.

[0032] At one end of the substrate 10 is an interface surface 18 which forms an interface with the body of PCD material 12, the body of PCD material being attached thereto at this interface surface. Figure 1 As shown in the example of FIG, substrate 10 is generally cylindrical and has a peripheral surface 22 and a peripheral top edge 20.

[0033] As used herein, a PCD grade is a PCD material that is characterised by the volume content and size of the diamond grains, the volume content of the interstitial regions between the diamond grains and the composition of the material that may be present in the interstitial regions. A grade of PCD material may be produced by a process comprising providing an aggregate mass of diamond grains having a size distribution suitable for the grade, optionally introducing a catalyst material or additive material into the aggregate mass, and subjecting the aggregate mass, in the presence of a source of catalyst material for diamond, to pressures and temperatures at which diamond is more thermodynamically stable than graphite and the catalyst material is molten. Under these conditions, molten catalyst material may infiltrate the aggregate mass from the source and may promote direct intergrowth between the diamond grains during sintering to form a PCD structure. The aggregate mass may comprise loose diamond grains or diamond grains held together by a binder material, and the diamond grains may be natural or synthetic diamond grains.

[0034] Different PCD grades may have different microstructures and different mechanical properties, such as elastic (or Young's) modulus E, elastic modulus, transverse rupture strength (TRS), toughness (such as the so-called K1C toughness), hardness, density and coefficient of thermal expansion (CTE). Different PCD grades may also behave differently in use. For example, different PCD grades may have different wear rates and fracture resistance.

[0035] All PCD grades may include interstitial regions filled with a material comprising cobalt metal, an example of a solvent catalyst material for diamond.

[0036] The PCD structure 12 may include one or more PCD grades.

[0037] Figure 2 is a cross-section through a body of PCD material that may form part of an exemplary cutting element 1. Figure 1 During the formation of a conventional polycrystalline diamond structure, diamond grains 23 are directly bonded to adjacent grains, and the interstices 24 between the diamond grains 23 may be at least partially filled with a non-superhard phase material. This non-superhard phase material, also referred to as filler material, may include residual solvent catalyst material, such as cobalt, nickel, or iron.

[0038] According to some examples, a sintered PCD material body 12 is produced having diamond-to-diamond bonding and a second phase comprising a solvent catalyst material dispersed throughout at least a portion of its microstructure. The PCD material body 12 and attached substrate 10 forming the cutting element 1 can be formed using HPHT conditions according to standard methods to produce a sintered compact. For example, the PCD layer 12 can be formed by subjecting a plurality of diamond particles (e.g., diamond particles having an average particle size between about 0.5 μm and about 150 μm) to an HPHT sintering process in the presence of a metal solvent catalyst (e.g., cobalt, nickel, iron, and / or any other suitable Group VIII element). During the HPHT sintering process, adjacent diamond grains within the plurality of diamond particles can bond to one another, thereby forming a PCD sheet (PCD material body 12) comprising bonded diamond grains. In one example, the diamond grains in the sheet 12 can have an average grain size of about 20 μm or less. Additionally, during the HPHT sintering process, the diamond grains may bond to the adjacent substrate 10 at the interface 18 .

[0039] In various examples, the substrate 10 is formed from a cemented tungsten carbide material, and after sintering, the resulting PCD material body 12 may contain tungsten and / or tungsten carbide in addition to the diamond grains and residual solvent catalyst material. For example, tungsten and / or tungsten carbide may be swept from the substrate 10 into the PCD layer 12 during HPHT sintering because, during HPHT sintering, the liquefied solvent catalyst from the substrate 10 (e.g., cobalt from a cobalt-cemented tungsten carbide substrate) may dissolve and / or carry tungsten and / or tungsten carbide from the substrate 10 into the mass of diamond grains used to form the PCD thin sheet 12. In other examples, tungsten and / or tungsten carbide grains may be intentionally mixed with the diamond grains prior to forming the PCD material body 12.

[0040] It has been found that in various applications, removal of the non-binder phase from within PCD slices (conventionally referred to as leaching) is desirable. One reason for this is that the presence of residual solvent catalyst material in the microstructural interstices is believed to have a detrimental effect on the performance of the PCD compact at elevated temperatures, as the presence of solvent catalyst in the diamond slice is believed to reduce the thermal stability of the diamond slice at these elevated temperatures.

[0041] To improve the performance and thermal resistance of the surface region of the PCD material body 12, at least a portion of the metal-solvent catalyst (e.g., cobalt) is removed from the interstices 24 of at least a portion of the PCD material body 12. Additionally, in some examples, tungsten and / or tungsten carbide may be removed from at least a portion of the PCD material body 12.

[0042] Chemical leaching is typically used to remove residual solvent catalyst from the body of PCD material 12 to a desired depth from the outer surface of the body of PCD material, or from substantially all of the PCD material 12. Thus, after leaching, the body of PCD material 12 may comprise a first volume that is substantially free of solvent catalyst material. However, small amounts of solvent catalyst material may remain in interstices that are inaccessible to the leaching process. Additionally, after leaching, the body of PCD material 12 may also comprise a volume or region that contains solvent catalyst material. In some examples, this additional volume may be remote from one or more exposed surfaces of the body of PCD material 12.

[0043] Interstitial material, which may include, for example, a metal solvent catalyst and one or more additives in the form of carbide additives, may be leached from the interstices 24 in the body of PCD material 12 by exposing the PCD material to an exemplary leaching mixture (eg, in liquid or vapor form).

[0044] Example of a System to be Used The PCD region 12 of a leached PCD compact 1 may typically, but not exclusively, have a thickness of about 1.5 mm to about 4 mm.

[0045] Figure 3 is a schematic partial cross-sectional view of an example of a system 30 for vapor leaching a PCD cutting element 1 according to the principles disclosed herein. The system 30 includes a leaching vessel 32 in which, in some examples, a liner 34 may be located. The liner may be acid-resistant to protect the interior of the leaching vessel 32 from the leaching acid mixture disposed therein. Generally speaking, the liner 34 may be made of any material suitable for use with the leaching acid mixture for an extended period of time at the relatively high temperatures experienced during the leaching process described in more detail below. Examples of suitable materials for the liner 34 may include, but are not limited to, fluoropolymers such as PTFE.

[0046] A volume of liquid acid leach mixture 36 is inserted into the leach vessel 32. The PCD cutting element 1 is attached to the fixture 38. A sealing member 40 is applied around the peripheral side edge of the cutting element 1, thereby exposing a portion of the surface of the PCD material body 12 of the cutting element. The fixture 38, with the PCD cutting element 1 attached, is positioned in the leach vessel 32 to suspend the PCD cutting element 1 above and spaced apart from the acid leach mixture 36. The leach vessel 32 is sealed to the top fixture 38, thereby providing a closed system. In some examples, a threaded connection or other mechanical locking mechanism may be used to connect the top fixture 38 to the leach vessel 32 to close the system 30. A threaded connection or connection may have the advantage of providing an evenly distributed load during the assembly process and throughout the leach cycle. However, alternative mechanical mechanisms, such as clamping or bolting mechanisms, may be used.

[0047] To treat the PCD cutting element to leach residual solvent catalyst from at least a portion thereof, the system 30 is heated to above ambient conditions, such as to a temperature of about 100° C. to about 300° C., to convert at least some of the liquid acid leach mixture into one or more acid vapors. The exposed surface of the PCD material body 12 of the PCD cutting element 1 is spaced apart from the acid leach mixture and exposed to the one or more acid vapors, which leach non-diamond phase components from the PCD material body 12. In some examples, the temperature may be from about 140° C. to about 200° C., and in other examples, from about 145° C. to about 180° C.

[0048] In some examples, the sealing member 40 around the PCD cutting element is an O-ring seal that extends around the PCD cutting element to protect the substrate from one or more acid vapors. Such a seal can provide mechanical and chemical protection of the unexposed portion of the PCD cutting element from the acid vapors and can also be used to control the form of the leaching profile obtained in the body of PCD material 12. Exemplary materials that may be suitable for forming the sealing member 40 may include fluoroelastomers, such as fluorinated carbon-based rubbers (including, for example, Viton®, grade VI780 FKM). TM o-rings). Other examples include, but are not limited to, those made from perfluoroelastomer compounds (FFKM).

[0049] like Figure 3 As shown, in the closed system configuration, a sealing member 40 is disposed in a cooperating annular groove 42 adjacent the free open end of the clamp 38 to form an annular seal around the peripheral outside surface of the body of PCD material 12. The sealing member 40 also contacts the leach vessel 32 at its junction with the clamp 38 to provide an additional sealing mechanism for the system 30 in the assembled configuration.

[0050] Likewise Figure 3 As shown in the example of FIG. 3 , the fixture 38 suspends the PCD cutting element 1 above the acid leaching mixture 36 , with the PCD material 12 of the cutting element 1 facing the acid leaching mixture 36 but spaced therefrom.

[0051] Suitable acid leaching mixtures 36 for use in system 30 can include, for example, acid leaching mixtures comprising any one or more of hydrochloric acid (HCl), hydrofluoric acid (HF), nitric acid (HNO ), sulfuric acid (H SO ) and / or phosphoric acid (H PO ) having a molar concentration of about 4M to about 9M and water. In some instances, acid leaching mixtures 36 can comprise hydrofluoric acid having a molar concentration of about 4M to about 9M, nitric acid having a molar concentration of about 4M to about 9M, and water. In still other instances, acid leaching mixtures 36 comprising hydrofluoric acid having a molar concentration of about 5M to about 7M, nitric acid having a molar concentration of about 6.7M to about 8M, and water can be used. Water can be deionized water. In some instances, hydrofluoric acid accounts for about 10 vol % to about 30 vol % of the acid mixture, nitric acid or one or more other acids account for about 30 vol % to about 60 vol % of the acid mixture, and water forms about 20 vol % to about 50 vol % of the mixture.

[0052] One or both of the clamp 38 and the leach vessel 32 may be formed, for example, from stainless steel, or may be made from any suitable material capable of withstanding the elevated temperatures within the leach vessel 32 during the leaching process described in more detail below.

[0053] Figure 4 FIG1 is a flow chart of a method 1000 for processing a body of PCD material 12 using an exemplary system. Method 1000 will be described as being performed using the previously described system 30. As illustrated in this figure, and as indicated at 1002, a liquid acid mixture 36 is disposed within a leach vessel 32. The acid leach mixture can be any suitable acid for leaching a body of PCD material, including, but not limited to, any of the previously described leach acid mixtures. Next, at stage 1010, a PCD cutting element 1 is positioned in a fixture 38, and a sealing member 40 is positioned around a portion of the peripheral side surface of the body of PCD material to be leached. Stage 1010 may occur before or after stage 1002. At stage 1020, the acid leach mixture 36 is poured into the leach vessel 32 to a level below its open end 46. The system 30 is then sealed by attaching the fixture 38, which holds the PCD cutting element 1, to the leach vessel 32 via a threaded connection in this example, thereby causing partial compression of the sealing member 40 to further seal the system 30. In a closed configuration, the cutting element 1 is suspended within the leach vessel 32 above and spaced apart from the liquid acid mixture 36 so that the cutting element 1 does not contact the liquid acid mixture. The temperature within the leach vessel 32 is increased in stage 1040 so that at least a portion of the acid mixture 36 begins to evaporate and leach the PCD material body of the cutting element 1. The substrate 10 of the cutting element is protected from the one or more leaching acid vapors by a sealing member 40 or other suitable means.

[0054] At stage 1040 of method 1000, the elevated temperature within the leach vessel 32 is maintained for a period of time to enable leaching of the body of PCD material to a desired leach depth. Figure 3 As shown, the body of PCD material to be leached is at least partially exposed and suspended above the acid leach mixture 36. Thus, the cutting element 1 does not directly contact the liquid acid mixture 36 during the leaching process at stage 1040.

[0055] In stage 1040, the temperature of the system 30 is increased to begin converting the acid leach mixture 36 from a liquid to a vapor in the leach vessel 32. The temperature can be increased using any suitable technique or device known in the art. For example, a heat generating component can be coupled to or placed in contact with an outer surface of the leach chamber 32 so that heat generated by the heat generating component can increase the temperature within the leach vessel 32. The temperature of the leach vessel 32 during the leaching process can be, for example, from about 100° C. to about 300° C.

[0056] During stage 1040, the acid vapor or vapors of the acid leach mixture 36 in the leach vessel 32 come into contact with the exposed body of PCD material 12 of the PCD cutting element 1 held within the fixture 38, but are confined and / or prevented from contacting the substrate 10 via the sealing member 40. It may be advantageous to heat the leach vessel 32 and / or directly heat the acid leach mixture 36 therein, and maintain the acid leach mixture 36 at a selected temperature during the leaching process, as this is believed to help maintain the integrity of the sealing member 40.

[0057] After exposure to the acid leach mixture for the desired period of time, the body of PCD material is rinsed to remove residual acid leach mixture therefrom, such as Figure 4 The rinsing step may include cooling the leach container after the step of exposing the PCD cutting element to one or more acid vapors to leach the PCD cutting element, removing the residual acid leach mixture from the leach container, and then rinsing, for example, with deionized water to remove the residual acid leach mixture from the PCD cutting element 1. The rinsing step may include introducing deionized water into the leach container, sealing the leach container in the same manner as the leaching process, and increasing the temperature of the leach container and / or the water therein for a period of time to evaporate the water and rinse the PCD material. The rinsing step may be repeated as many times as needed or necessary with clean water. The necessity of this may be determined by testing the pH of the waste water to determine its acidity. Multiple rinse cycles may be required to achieve a pH of 5 or higher, which means that the sample is safe for handling (with PPE) before being dried, for example, at about 60°C to about 90°C for several hours.

[0058] The rinse step can be repeated as many times as needed or necessary with clean water. The necessity of this can be determined by testing the pH of the waste water to determine its acidity. Multiple rinse cycles may be required to achieve a pH of 5 or higher, which means the sample is safe for handling (with PPE) before being dried, for example, at about 60°C to about 90°C for several hours.

[0059] Some variations are described in more detail with reference to the following examples, which are not intended to be limiting.The following examples provide further details related to the above examples.

[0060] Example 1

[0061] Cutting elements were formed by HPHT sintering diamond particles in the presence of cobalt. Each cutting element included a PCD body 12 attached to a tungsten carbide substrate 10. The sintered PCD body included cobalt within interstitial regions between the interbonded diamond grains. Each PCD body 12 was leached using a leaching mixture comprising 44 vol% 6.7M nitric acid, 18 vol% 5M hydrofluoric acid, and 38 vol% deionized water. The processing technique used was a vapor leaching technique, in which the cutter was placed in a separate leaching chamber and suspended above a volume of an exemplary acid leach mixture that filled approximately 50% of the chamber volume. The chamber was sealed and heated to a temperature of approximately 180°C to evaporate at least a portion of the acid leach mixture. The PCD body was subjected to acid vapor leaching for 100 hours. At this point, the leaching depth of the PCD body was determined for different portions of the PCD wafer by x-ray analysis. An average leaching depth of approximately 800 to approximately 1541 microns was found to have been achieved after 100 hours. This is in contrast to an equivalent cutting element formed from the same PCD sheet attached to a tungsten carbide substrate leached using a conventional aqueous leaching technique according to a conventional leaching mixture, wherein the body of PCD material to be leached was partially immersed in a conventional acid leaching mixture comprising hydrofluoric acid (HF) and nitric acid (HNO3) diluted in water (HF:HNO3 (1:3)) and heated to about 40°C-70°C for about 100 hours to leach the PCD material, and using this technique the body of PCD material so leached was found to have an average leached depth of about 345 microns after 100 hours.

[0062] Example 2

[0063] Cutting elements were formed by HPHT sintering diamond particles in the presence of cobalt. Each cutting element included a PCD body 12 attached to a tungsten carbide substrate 10. The sintered PCD body included cobalt within interstitial regions between the interbonded diamond grains. Each PCD body 12 was leached using a leaching mixture comprising 44 vol% 6.7M nitric acid, 18 vol% 5M hydrofluoric acid, and 38 vol% deionized water. The processing technique used was a vapor leaching technique, in which the cutter was placed in a separate leaching chamber and suspended above a volume of an exemplary acid leach mixture that filled approximately 50% of the chamber volume. The chamber was sealed and heated to a temperature of approximately 200°C to evaporate at least some of the acid leach mixture. The PCD body was acid vapor leached for 100 hours. At this point, the leaching depth of the PCD body was determined for different portions of the PCD wafer by x-ray analysis. An average leaching depth of approximately 800 to approximately 1133 microns was found to have been achieved after 100 hours.

[0064] Example 3

[0065] Cutting elements were formed by HPHT sintering diamond particles in the presence of cobalt, each comprising a PCD body 12 attached to a tungsten carbide substrate 10. The sintered PCD body included cobalt within interstitial regions between the interbonded diamond grains. Each PCD body 12 was leached using a leaching mixture comprising approximately 44 vol% 6.7M nitric acid, approximately 18 vol% 5M hydrofluoric acid, and approximately 38 vol% deionized water. The processing technique used was a vapor leaching technique, in which the cutter was placed in a separate leaching chamber and suspended above a volume of an exemplary acid leach mixture that filled approximately 50% of the chamber volume. The chamber was sealed and heated to a temperature of approximately 200°C to evaporate at least some of the acid leach mixture. The PCD body was subjected to acid vapor leaching for 100 hours. At this point, the leaching depth of the PCD body was determined for different portions of the PCD wafer by x-ray analysis. An average leaching depth of approximately 1023 microns was found to have been achieved after 100 hours.

[0066] Example 4

[0067] The same technique as described above in Examples 1 to 3 was used to leach PCD cutting tools, each having a body of PCD material 12 to be leached, but in this example, a leaching mixture comprising approximately 30-60 vol% 7.5M nitric acid, approximately 10-30 vol% 6.7M hydrofluoric acid, and the remaining vol% deionized water was used. The PCD body was leached by acid vapor for 100 hours. At this point, the leaching depth of the PCD body was determined for different portions of the PCD wafer by x-ray analysis. It was found that an average leaching depth of approximately 1029 microns had been achieved after 100 hours.

[0068] Example 5

[0069] The same technique as described above in Examples 1 to 3 was used to leach PCD cutting tools, each having a body of PCD material 12 to be leached, but in this example, a leaching mixture comprising approximately 40-50 vol% 8.5M nitric acid, approximately 10-20 vol% 8M hydrofluoric acid, and the remaining vol% deionized water was used. The PCD body was leached by acid vapor for 100 hours. At this point, the leaching depth of the PCD body was determined for different portions of the PCD wafer by x-ray analysis. It was found that an average leaching depth of approximately 894 microns had been achieved after 100 hours.

[0070] Example 6

[0071] The same technique as described above in Examples 1 to 3 was used to leach PCD cutting tools, each having a body of PCD material 12 to be leached, but in this example, a leaching mixture comprising approximately 30-60 vol% 9.2M nitric acid, approximately 10-30 vol% 9.6M hydrofluoric acid, and the remaining vol% deionized water was used. The PCD body was leached by acid vapor for 100 hours. At this point, the leaching depth of the PCD body was determined for different portions of the PCD wafer by x-ray analysis. It was found that an average leaching depth of approximately 762 microns had been achieved after 100 hours.

[0072] Example 7

[0073] The same technique as described above in Examples 1 to 3 was used to leach PCD cutting tools, each having a body of PCD material 12 to be leached, but in this example, a leach mixture comprising approximately 30-60 vol% 6.9M nitric acid, approximately 10-30 vol% 9.6M hydrofluoric acid, and the remaining vol% (approximately 10-50 vol%) deionized water was used. The PCD body was leached by acid vapor for 100 hours. At this point, the leaching depth of the PCD body was determined for different portions of the PCD wafer by x-ray analysis. It was found that an average leaching depth of approximately 824 microns had been achieved after 100 hours.

[0074] When compared to the leach depths achievable using conventional leach solutions, such as mixtures of HCl and water or hydrofluoric acid (HF) and nitric acid diluted in water (HF:HNO3 (1:3)), it was determined that examples including the above-described leach mixtures can enable greater leaching efficiencies, wherein greater leach depths can be achieved in shorter periods of time, in some cases enabling desired leach depths to be achieved about 4 times to about 6 times faster than using conventional acid leach mixtures and processing techniques.

[0075] The foregoing description has been provided to enable others skilled in the art to best utilize the various aspects described herein by way of example. This description is not intended to be exhaustive or limited to any precise form disclosed. Many modifications and variations are possible. In particular, some of the exemplary methods may be equally applicable to the effective leaching of PCD with other additives or interstitial materials, such as those in the form of other metal carbides, including one or more of tungsten, titanium, niobium, tantalum, zirconium, molybdenum, vanadium, or chromium carbides.

Claims

1. A system for leaching a PCD cutting element having a body of polycrystalline diamond (PCD) material, the body of PCD material including a non-diamond phase comprising a solvent catalyst material, the system comprising: a leach container for receiving a volume of liquid acid leach mixture; a fixture adapted to hold the PCD cutting element to be leached spaced apart from the volume of leach mixture in the leach vessel; a sealing member positionable in a recess of the fixture for positioning around the PCD cutting element to be leached; and The leaching vessel and the clamp are adapted to be interconnected to form a closed system.

2. The system of claim 1 , further comprising a heat source arranged to heat the liquid acid leach mixture to above ambient conditions to convert at least some of the liquid acid leach mixture into one or more acid vapors.

3. A system as claimed in any one of the preceding claims, wherein: The sealing member includes an O-ring seal.

4. A system as claimed in any one of the preceding claims, wherein: The sealing member includes a seal formed from a fluoroelastomer and / or perfluoroelastomer compound.

5. A system as claimed in any one of the preceding claims, wherein: Any one or more of the leaching vessel and the fixture comprises stainless steel.

6. The system of any preceding claim, further comprising a liner located in the leach vessel.

7. The system of claim 6, wherein: The lining is formed of an acid-resistant material.

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