Patent Application
20150021100
Embodiments of the present disclosure relate generally to polycrystalline compacts, such as polycrystalline diamond compacts, that have a volume that includes interstitial metal solvent catalyst material and another volume that does not include such interstitial metal solvent catalyst material, as well as to earth-boring tools including such compacts, and to related methods.
Cutting elements used in earth-boring tools often include polycrystalline diamond compact (often referred to as “PDC”) cutting elements, which are cutting elements that include a volume of polycrystalline diamond material. One or more surfaces of the volume of polycrystalline diamond material define one or more cutting surfaces of the PDC cutting element. Polycrystalline diamond material is material that includes inter-bonded grains or crystals of diamond material. In other words, polycrystalline diamond material includes direct, inter-granular diamond-to-diamond atomic bonds between the grains or crystals of diamond material. The terms “grain” and “crystal” are used synonymously and interchangeably herein.
PDC cutting elements are formed by sintering and bonding together relatively small diamond grains under conditions of high temperature and high pressure in the presence of a metal solvent catalyst (for example, cobalt, iron, nickel, or alloys or mixtures thereof) to form a layer or “table” of polycrystalline diamond material on a cutting element substrate. These processes are often referred to as high-temperature/high-pressure (or “HTHP”) processes. The cutting element substrate may comprise a cermet material (i.e., a ceramic-metal composite material) such as cobalt-cemented tungsten carbide. In such instances, the cobalt (or other catalyst material) in the cutting element substrate may diffuse into the spaces between the diamond grains during sintering and serve as the catalyst material for forming the inter-granular diamond-to-diamond bonds, and the resulting diamond table, from the diamond grains. In other methods, powdered catalyst material may be mixed with the diamond grains prior to sintering the grains together in an HTHP process.
Upon formation of a diamond table using an HTHP process, catalyst material may remain in interstitial spaces between the grains of diamond in the resulting polycrystalline diamond table. The presence of the catalyst material in the diamond table may contribute to thermal damage in the diamond table when the cutting element is heated during use due to friction at the contact point between the cutting element and the rock formation being cut.
PDC cutting elements in which the catalyst material remains in the diamond table are generally thermally stable up to a temperature of about 750° C., although internal stress within the cutting element may begin to develop at temperatures exceeding about 400° C. due to a phase change that occurs in cobalt at that temperature (a change from the “beta” phase to the “alpha” phase). Also beginning at about 400° C., there is an internal stress component that arises due to differences in the thermal expansion of the diamond grains and the catalyst material at the grain boundaries. This difference in thermal expansion may result in relatively large tensile stresses at the interface between the diamond grains, and may contribute to thermal degradation of the microstructure when PDC cutting elements are used in service. Differences in the thermal expansion between the diamond table and the cutting element substrate to which it is bonded may further exacerbate the stresses in the polycrystalline diamond compact. This differential in thermal expansion may result in relatively large compressive and/or tensile stresses at the interface between the diamond table and the substrate that eventually leads to the deterioration of the diamond table, causes the diamond table to delaminate from the substrate, or results in the general ineffectiveness of the cutting element.
Furthermore, at temperatures at or above about 750° C., some of the diamond crystals within the diamond table may react with the catalyst material causing the diamond crystals to undergo a chemical breakdown or conversion to another allotrope of carbon. For example, the diamond crystals may graphitize at the diamond crystal boundaries, which may substantially weaken the diamond table. Also, at extremely high temperatures, in addition to graphite, some of the diamond crystals may be converted to carbon monoxide and/or carbon dioxide.
In order to reduce the problems associated with differences in thermal expansion and chemical breakdown of the diamond crystals in PDC cutting elements, so-called “thermally stable” polycrystalline diamond compacts (which are also known as thermally stable products, or “TSPs”) have been developed. Such a TSP may be formed by leaching or otherwise removing the catalyst material (e.g., cobalt) out from interstitial spaces between the inter-bonded diamond crystals in the diamond table using, for example, an acid or combination of acids (e.g., aqua regia). A substantial amount of the catalyst material may be removed from the diamond table, or catalyst material may be removed from only a portion thereof. TSPs in which substantially all catalyst material has been leached out from the diamond table have been reported to be thermally stable up to temperatures of about 1,200° C. It has also been reported, however, that such fully leached diamond tables are relatively more brittle and vulnerable to shear, compressive, and tensile stresses than are non-leached diamond tables. In addition, it may be difficult to secure a completely leached diamond table to a supporting substrate. In an effort to provide cutting elements having diamond tables that are more thermally stable relative to non-leached diamond tables, but that are also relatively less brittle and vulnerable to shear, compressive, and tensile stresses relative to fully leached diamond tables, cutting elements have been provided that include a diamond table in which the catalyst material has been leached from a portion or portions of the diamond table. For example, it is known to leach catalyst material from the cutting face, from the side of the diamond table, or both, to a desired depth within the diamond table, but without leaching all of the catalyst material out from the diamond table.
In some embodiments, the present disclosure includes a generally planar polycrystalline compact comprising a body of inter-bonded grains of hard material. The body of inter-bonded grains of hard material has a first major surface defining a front cutting face of the polycrystalline compact, a second major surface on an opposing back side of the body, at least one lateral side surface extending between the first major surface and the second major surface, and a central axis extending through a center of the body and generally perpendicular to the first major surface and the second major surface. The hard material of the inter-bonded grains of hard material comprises diamond or cubic boron nitride. The polycrystalline compact further includes an interstitial material. A first volume of the polycrystalline compact is at least substantially free of the interstitial material, such that voids exist in interstitial spaces between surfaces of the inter-bonded grains of hard material within the first volume. A second volume of the polycrystalline compact includes the interstitial material in interstitial spaces between surfaces of the inter-bonded grains of hard material within the second volume. An interface between the first volume and the second volume is configured, located and oriented such that at least one crack originating proximate a point of contact between the polycrystalline compact and a subterranean formation near the at least one lateral side surface of the body and propagating along the interface generally toward the central axis will propagate generally toward the second major surface of the body at an acute angle or angles to each of the first major surface and the second major surface.
In another embodiment, an earth-boring tool comprises a tool body and a plurality of cutting elements attached to the tool body, wherein at least one cutting element of the plurality of cutting elements comprises a polycrystalline compact as described in the above paragraph.
In additional embodiments, the present disclosure includes a method of forming a polycrystalline compact comprising a body of inter-bonded grains of hard material. In accordance with the method, a high-temperature/high-pressure (HTHP) sintering process is used to form a body of inter-bonded grains of hard material having a first major surface defining a front cutting face of the polycrystalline compact, a second major surface on an opposing back side of the body, at least one lateral side surface extending between the first major surface and the second major surface, and a central axis extending through a center of the body and generally perpendicular to the first major surface and the second major surface. The hard material is selected to comprise diamond or cubic boron nitride. During the HTHP sintering process, the formation of inter-granular bonds between the inter-bonded grains of hard material is catalyzed using a catalyst, and the catalyst forms an interstitial material in the resulting body of inter-bonded grains of hard material. The interstitial material is removed from interstitial spaces between surfaces of the inter-bonded grains of hard material within the first volume, and the interstitial material is left in interstitial spaces between surfaces of the inter-bonded grains of hard material within the second volume, such that the first volume is at least substantially free of the interstitial material and voids exist in the interstitial spaces between surfaces of the inter-bonded grains of hard material within the first volume. An interface is formed between the first volume and the second volume that is configured, located and oriented such that at least one crack originating proximate a point of contact between the polycrystalline compact and a subterranean formation near the at least one lateral side surface of the body, and propagating along the interface generally toward the central axis, will propagate generally toward the second major surface at an acute angle or angles to each of the first major surface and the second major surface.
While the specification concludes with claims particularly pointing out and distinctly claiming what are regarded as embodiments of the invention, various features and advantages of embodiments of the disclosure may be more readily ascertained from the following description of some embodiments of the disclosure when read in conjunction with the accompanying drawings, in which:
The illustrations presented herein are not actual views of any particular cutting element or earth-boring tool, and are not drawn to scale, but are merely idealized representations that are employed to describe embodiments of the disclosure. Elements common between figures may retain the same numerical designation.
As used herein, relational terms, such as “first,” “second,” “top,” “bottom,” “upper,” “lower,” “over,” “under,” etc., are used for clarity and convenience in understanding the disclosure and accompanying drawings and does not connote or depend on any specific preference, orientation, or order, except where the context clearly indicates otherwise.
As used herein, the term “substantially,” in reference to a given parameter, property, or condition, means to a degree that one skilled in the art would understand that the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances.
As used herein, the term “configured” refers to a shape, material composition, and arrangement of one or more of at least one structure and at least one apparatus facilitating operation, response to an external stimulus, or both, of one or more of the structure and the apparatus in a pre-determined or intended way.
As used herein, the terms “earth-boring tool” means and includes any type of bit or tool used for drilling during the formation or enlargement of a wellbore in a subterranean formation and includes, for example, fixed-cutter bits, roller cone bits, percussion bits, core bits, eccentric bits, bicenter bits, reamers, mills, drag bits, hybrid bits (e.g., rolling components in combination with fixed cutting elements), and other drilling bits and tools known in the art.
As used herein, the term “polycrystalline material” means and includes any material comprising a plurality of grains (i.e., crystals) of the material that are bonded directly together by inter-granular bonds. The crystal structures of the individual grains of the material may be randomly oriented in space within the polycrystalline material.
As used herein, the term “polycrystalline compact” means and includes any structure comprising a polycrystalline material formed by a process that involves application of pressure (e.g., compaction) to the precursor material or materials used to form the polycrystalline material.
As used herein, the term “inter-granular bond” means and includes any direct atomic bond (e.g., covalent, ionic, metallic, etc.) between atoms in adjacent grains of hard material.
As used herein, the ten “hard material” means and includes any material having a Knoop hardness value of greater than or equal to about 3,000 Kgf/mm2 (29,420 MPa). Non-limiting examples of hard materials include diamond (e.g., natural diamond, synthetic diamond, or combinations thereof) and cubic boron nitride.
As used herein, the term “grain size” means and includes a geometric mean diameter measured from a 2D section through a bulk material. The geometric mean diameter for a group of particles may be determined using techniques known in the art, such as those set forth in Ervin E. Underwood, Quantitative Stereology, 103-105 (Addison-Wesley Publishing Company, Inc. 1970), which is incorporated herein in its entirety by this reference.
The supporting substrate 104 may have a first end surface 114, a second end surface 116, and a generally cylindrical lateral side surface 118 extending between the first end surface 114 and the second end surface 116. As depicted in
The supporting substrate 104 may be formed of include a material that is relatively hard and resistant to wear. By way of non-limiting example, the supporting substrate 104 may be formed from and include a ceramic-metal composite material (which are often referred to as “cermet” materials). In some embodiments, the supporting substrate 104 is formed of and includes a cemented carbide material, such as a cemented tungsten carbide material, in which tungsten carbide particles are cemented together in a metallic binder material. As used herein, the teem “tungsten carbide” means any material composition that contains chemical compounds of tungsten and carbon, such as, for example, WC, W2C, and combinations of WC and W2C. Tungsten carbide includes, for example, cast tungsten carbide, sintered tungsten carbide, and macrocrystalline tungsten carbide. The metallic binder material may include, for example, a catalyst material such as cobalt, nickel, iron, or alloys and mixtures thereof. In at least some embodiments, the supporting substrate 104 is formed of and includes a cobalt-cemented tungsten carbide material.
The polycrystalline compact 102 may be disposed on or over the second end surface 116 of the supporting substrate 104. The polycrystalline compact 102 includes a body of inter-bonded grains of hard material, and has a first major surface 108 defining the front cutting face of the polycrystalline compact 102, a second major surface 109 on an opposing back side of the body, and at least one lateral side surface 110 extending between the first major surface 108 and the second major surface 109. As shown in
The polycrystalline compact 102 may also include a chamfered edge 112 at a periphery of the cutting face 108. The chamfered edge 112 shown in
As illustrated in
The inter-bonded grains of hard material (i.e., the polycrystalline material of the polycrystalline compact 102) may comprise, for example, diamond or cubic boron nitride. The polycrystalline material may comprise more than about seventy percent (70%) by volume of the polycrystalline compact 102, more than about eighty percent (80%) by volume of the polycrystalline compact 102, or even more than about ninety percent (90%) by volume of the polycrystalline compact 102. The grains or crystals of the hard polycrystalline material are bonded together to form the polycrystalline compact 102.
Interstitial spaces or regions between the grains of hard material may be filled with an interstitial material (e.g., a metal solvent catalyst) in one or more regions of the polycrystalline compact 102, while voids may be present in the interstitial spaces or regions between the grains of hard material in one or more other regions of the polycrystalline compact 102.
The polycrystalline compact 102 may be formed using an HTHP sintering process to bond together relatively small diamond (synthetic, natural or a combination) or cubic boron nitride grains, termed “grit,” under conditions of high temperature and high pressure in the presence of a catalyst (e.g., cobalt, iron, nickel, or alloys and mixtures thereof). The metal solvent catalyst material used to catalyze the formation of the inter-granular bonds between the grains of hard material may remain in interstitial spaces between the inter-bonded grains of hard material. The metal solvent catalyst material may be leached out of the interstitial spaces using, for example, an acid or combination of acids (e.g., aqua regia) to form and define first and second regions within the polycrystalline compact 102, including a first leached region and a second unleached region, as discussed in further detail below.
For example, with reference to
As shown in
The interstitial material 128 may comprise a metal-solvent catalyst, such as iron, cobalt, nickel, or an alloy or mixture based on one or more such elements. In other embodiments, the interstitial material 128 may comprise another metal, a ceramic material, or any other material.
Referring again to
As shown in
Stated another way, in some embodiments, the interface 130 between the first volume 120 and the second volume 122 may have a dish shape. Further, the interface 130 between the first volume 120 and the second volume 122 may have a smooth profile or a stepped profile in a plane containing the central axis A, such as the plane of the cross-sectional view of
In this configuration, an annular portion of the interface 130 between the first volume 120 and the second volume 122 is located a distance 134 from the second major surface 109 of the body of inter-bonded grains of hard material, and regions of the interface 130 circumscribed by the annular portion are located at one or more distances 136 from the second major surface 109 of the body of inter-bonded grains of hard material. Each of the one or more distances 136 may be shorter than the first distance 134, as shown in
In such embodiments, a first portion of the interface 130 between the first volume 120 and the second volume 122 is located at a first distance 134 from the second major surface 109 of the body of inter-bonded grains of hard material and at a second distance 140 from the central axis A of the body of inter-bonded grains of hard material, and a second portion of the interface 130 between the first volume 120 and the second volume 122 is located at a third distance 136 from the second major surface 109 of the body of inter-bonded grains of hard material and at a fourth distance 142 from the central axis A of the body of inter-bonded grains of hard material. As shown in
As shown in
Additional embodiments of the present disclosure include methods of making polycrystalline compacts for cutting elements as described herein. In some embodiments, controlled leaching of interstitial material 128 (
As shown in
As shown in
This masking and leaching process may be repeated as shown in
In the method described with reference to
In additional embodiments of the present disclosure, the front cutting face of a polycrystalline compact may not be planar, and the front cutting face or a central portion thereof may have a generally concave shape. In such embodiments, a single leaching process may be used to form a first leached volume and a second unleached volume within the polycrystalline compact, and the interface between the first and second volumes may have a concave shape similar to that of the interfaces previously described herein. For example,
Due to the varying thickness of the mask layer 460 over the polycrystalline compact 452, the effective residence time during which any particular region of the polycrystalline compact 452 will be subjected to the leaching agent will be at least partially a function of the thickness of the mask layer 460 overlying that particular region of the polycrystalline compact 452. Regions of the polycrystalline compact 452 underlying thinner regions of the mask layer 460 will be subjected to the leaching agent for relatively longer residence times resulting in relatively deeper leaching depths therein, while regions of the polycrystalline compact 452 underlying thicker regions of the mask layer 460 will be subjected to the leaching agent for relatively shorter residence times resulting in shallower leaching depths therein. Thus, subjecting the PDC cutting element 450 of
Embodiments of cutting elements according to the present description, such as the PDC cutting elements 100, 200, 300, 400, may be secured to an earth-boring tool and used to remove subterranean formation material in a drilling operation or other operation used to form a wellbore in a subterranean formation. The earth-boring tool may comprise, for example, an earth-boring rotary drill bit, a percussion bit, a coring bit, an eccentric bit, a reamer tool, a milling tool, etc. As a non-limiting example,
Additional non-limiting example embodiments of the disclosure are described below.
A generally planar polycrystalline compact, comprising: a body of inter-bonded grains of hard material having a first major surface defining a front cutting face of the polycrystalline compact, a second major surface on an opposing back side of the body, at least one lateral side surface extending between the first major surface and the second major surface, and a central axis extending through a center of the body and generally perpendicular to the first major surface and the second major surface, the hard material comprising diamond or cubic boron nitride; and an interstitial material; and wherein a first volume of the polycrystalline compact is at least substantially free of the interstitial material such that voids exist in interstitial spaces between surfaces of the inter-bonded grains of hard material within the first volume, a second volume of the polycrystalline compact includes the interstitial material in interstitial spaces between surfaces of the inter-bonded grains of hard material within the second volume, and an interface between the first volume and the second volume is configured, located and oriented such that at least one crack originating proximate a point of contact between the polycrystalline compact and a subterranean formation near the at least one lateral side surface of the body and propagating along the interface generally toward the central axis will propagate generally toward the second major surface of the body at an acute angle or angles to each of the first major surface and the second major surface.
The polycrystalline compact of Embodiment 1, wherein an annular portion of the interface between the first volume and the second volume is located a first distance from the second major surface of the body of inter-bonded grains of hard material, and regions of the interface circumscribed by the annular portion are located at one or more distances from the second major surface of the body of inter-bonded grains of hard material, each of the one or more distances being shorter than the first distance.
The polycrystalline compact of Embodiment 1 or Embodiment 2, wherein a first portion of the interface between the first volume and the second volume is located at a first distance from the second major surface of the body of inter-bonded grains of hard material and at a second distance from the central axis of the body of inter-bonded grains of hard material, and a second portion of the interface between the first volume and the second volume is located at a third distance from the second major surface of the body of inter-bonded grains of hard material and at a fourth distance from the central axis of the body of inter-bonded grains of hard material, the first distance being greater than the third distance, and the second distance being greater than the fourth distance.
The polycrystalline compact of any one of Embodiments 1 through 3, wherein at least a portion of the interface between the first volume and the second volume has substantially a dish shape.
The polycrystalline compact of any one of Embodiments 1 through 3, wherein at least a portion of the interface between the first volume and the second volume has a stepped profile in a plane containing the central axis.
The polycrystalline compact of any one of Embodiments 1 through 4, wherein at least a portion of the interface between the first volume and the second volume has a smooth profile in a plane containing the central axis.
The polycrystalline compact of any one of Embodiments 1 through 6, wherein the first major surface of the body of inter-bonded grains of hard material comprises a surface of the first volume of the polycrystalline compact.
The polycrystalline compact of any one of Embodiments 1 through 7, wherein the second major surface of the body of inter-bonded grains of hard material comprises a surface of the second volume of the polycrystalline compact.
The polycrystalline compact of any one of Embodiments 1 through 8, wherein at least a portion of the at least one lateral side surface of the body of inter-bonded grains of hard material comprises another surface of the first volume of the polycrystalline compact.
The polycrystalline compact of any one of Embodiments 1 through 9, wherein the first volume extends along the first major surface and along at least a portion of the at least one lateral side surface of the body of inter-bonded grains of hard material, and the second volume extends along the second major surface of the body of inter-bonded grains of hard material.
An earth-boring tool, comprising: a tool body; and a plurality of cutting elements attached to the tool body, wherein at least one cutting element of the plurality of cutting elements comprises a polycrystalline compact as recited in any one of Embodiments 1 through 10.
The earth-boring tool of Embodiment 11, wherein the earth-boring tool comprises at least one of a rotary drill bit for drilling a wellbore and a reamer for enlarging a wellbore.
A method of forming a generally planar polycrystalline compact, comprising: using a high-temperature/high-pressure (HTHP) sintering process to form a body of inter-bonded grains of hard material having a first major surface defining a front cutting face of the polycrystalline compact, a second major surface on an opposing back side of the body, at least one lateral side surface extending between the first major surface and the second major surface, and a central axis extending through a center of the body and generally perpendicular to the first major surface and the second major surface, the hard material comprising diamond or cubic boron nitride, using the high-temperature/high-pressure (HTHP) sintering process including catalyzing the formation of inter-granular bonds between the inter-bonded grains of hard material using a catalyst, the catalyst forming an interstitial material in the body of inter-bonded grains of hard material; and removing the interstitial material from interstitial spaces between surfaces of the inter-bonded grains of hard material within the first volume and leaving the interstitial material in interstitial spaces between surfaces of the inter-bonded grains of hard material within the second volume such that the first volume is at least substantially free of the interstitial material and voids exist in the interstitial spaces between surfaces of the inter-bonded grains of hard material within the first volume, and forming an interface between the first volume and the second volume configured, located and oriented such that at least one crack originating proximate a point of contact between the polycrystalline compact and a subterranean formation near the at least one lateral side surface of the body and propagating along the interface generally toward the central axis will propagate generally toward the second major surface at an acute angle or angles to each of the first major surface and the second major surface.
The method of Embodiment 13, wherein removing the interstitial material from interstitial spaces between surfaces of the inter-bonded grains of hard material within the first volume and leaving the interstitial material in interstitial spaces between surfaces of the inter-bonded grains of hard material within the second volume comprises: covering a portion of the first major surface of the body of inter-bonded grains of hard material with a first patterned mask layer; leaching a first portion of the body of inter-bonded grains of hard material through at least one aperture in the first patterned mask layer and removing the interstitial material from interstitial spaces between surfaces of the inter-bonded grains of hard material within the first portion of the body; removing the first patterned mask layer from the body; covering a portion of the first major surface of the body of inter-bonded grains of hard material with a second patterned mask layer different from the first patterned mask layer; and leaching a second portion of the body of inter-bonded grains of hard material through at least one aperture in the second patterned mask layer and removing the interstitial material from interstitial spaces between surfaces of the inter-bonded grains of hard material within the second portion of the body.
The method of Embodiment 13 or Embodiment 14, further comprising forming the interface such that an annular portion of the interface between the first volume and the second volume is located a first distance from the second major surface of the body of inter-bonded grains of hard material, and regions of the interface circumscribed by the annular portion are located at one or more distances from the second major surface of the body of inter-bonded grains of hard material, each of the one or more distances being shorter than the first distance.
The method of any one of Embodiments 13 through 15, further comprising forming the interface such that a first portion of the interface between the first volume and the second volume is located at a first distance from the second major surface of the body of inter-bonded grains of hard material and at a second distance from the central axis of the body of inter-bonded grains of hard material, and such that a second portion of the interface between the first volume and the second volume is located at a third distance from the second major surface of the body of inter-bonded grains of hard material and at a fourth distance from the central axis of the body of inter-bonded grains of hard material, the first distance being greater than the third distance, and the second distance being greater than the fourth distance.
The method of any one of Embodiments 13 through 16, further comprising forming at least a portion of the interface between the first volume and the second volume to have substantially a dish shape.
The method of any one of Embodiments 13 through 16, further comprising foaming at least a portion of the interface between the first volume and the second volume to have a stepped profile in a plane containing the central axis.
The method of any one of Embodiments 13 through 17, further comprising forming at least a portion of the interface between the first volume and the second volume to have a smooth profile in a plane containing the central axis.
The method of any one of Embodiments 13 through 19, further comprising forming the first volume to extend along the first major surface and along at least a portion of the at least one lateral side surface of the body of inter-bonded grains of hard material, and forming the second volume to extend along the second major surface of the body of inter-bonded grains of hard material.
The foregoing description is directed to particular embodiments for the purpose of illustration and explanation. It will be apparent to one skilled in the art that many modifications and changes to the embodiments as set forth above are possible without departing from the scope of the embodiments disclosed herein as hereinafter claimed, including legal equivalents. For example, elements and features of one disclosed embodiment may be combined with the elements and features of other disclosed embodiments to provide further embodiments of the disclosure. It is intended that the following claims be interpreted to embrace all such modifications and changes.
