Abstract:
Apparatuses for forming chamfers on superabrasive tables of cutting elements for earth-boring tools include a chuck for temporarily holding and positioning a cutting element, and at least one emitter for emitting a beam of energy toward an edge of a superabrasive table of a cutting element held and positioned by the chuck. Methods of forming cutting elements for earth-boring tools and methods for forming earth-boring tools are also disclosed.

Description:
CROSS CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional patent application, Ser. No. 60/985,339, filed Nov. 5, 2007, which is incorporated herein in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments of the present invention relate generally to forming bore holes in subterranean earth formations and, more particularly, to apparatuses and methods for forming cutting elements for earth-boring tools used in drilling such bore holes. 
     BACKGROUND 
     Various earth-boring tools such as rotary drill bits (including roller cone bits and fixed-cutter or drag bits), core bits, eccentric bits, bicenter bits, reamers, and mills are commonly used in forming bore holes or wells in earth formations. Such tools often may include one or more cutting elements on a formation-engaging surface thereof for removing formation material as the earth-boring tool is rotated or otherwise moved within the bore hole. 
     For example, fixed-cutter bits (often referred to as “drag” bits) have a plurality of cutting elements affixed or otherwise secured to a face (i.e., a formation-engaging surface) of a bit body. Such cutting elements generally have either a disk shape, or in some instances, a more elongated, substantially cylindrical shape.  FIG. 1  illustrates an example of a conventional cutting element  100 . The cutting element  100  includes a layer of superabrasive material  105  (which is often referred to as a “table”), such as mutually bound particles of polycrystalline diamond, formed on and bonded to a supporting substrate  110  of a hard material such as cemented tungsten carbide. The table of superabrasive material  105  includes a front cutting face  115 , a rear face (not shown) abutting the supporting substrate  110 , and a peripheral surface  120 . During a drilling operation, a portion of a cutting edge, which is at least partially defined by the peripheral portion of the cutting face  115 , is pressed into the formation. As the earth-boring tool moves relative to the formation, the cutting element  100  is drug across the surface of the formation and the cutting edge of the cutting face  115  shears away formation material. Such cutting elements  100  are often referred to as “polycrystalline diamond compact” (PDC) cutting elements, or cutters. 
     During drilling, cutting elements  100  are subjected to high temperatures, high loads, and high impact forces. These conditions can result in damage to the layer of superabrasive material  105  (e.g., chipping, spalling). Such damage often occurs at or near the cutting edge of the cutting face  115  and is caused, at least in part, by the high impact forces that occur during drilling. Damage to the cutting element  100  results in decreased cutting efficiency of the cutting element  100 . In severe cases, the entire layer of superabrasive material  105  may separate (i.e., delaminate) from the supporting substrate  110 . Furthermore, damage to the cutting element  100  can eventually result in separation of the cutting element  100  from the surface of the earth-boring tool to which it is secured. 
     As shown in  FIG. 1 , it has been found that the incidence of damage to the cutting element  100  may be reduced by beveling the cutting edge of the cutting face  115  to provide an angled, arcuate surface or “chamfer”  125  along at least a portion of the periphery of the layer of superabrasive material  105 . In other words, a chamfered edge  125  may be formed for durability and long-term cutting efficiency. Conventionally, the chamfered edge  125  is formed by mechanical processes, such as lapping and grinding processes. Such conventional mechanical processes are historically prone to generating residual and subsurface microscopic damage. The damage is a result of the mechanical means by which a surface is abrasively manufactured and can only be minimized, not eliminated, through successively finer polishing steps. Such residual microfractures can remain at, and even beneath, the polished surface. These residual defects can propagate under the severe cutting stresses and loads into longer or larger defects, leading ultimately to the aforementioned spalling and delamination of the superabrasive material layer  105 . 
     Additionally, in order to provide an improved finish (i.e., a more polished surface), an increasing number of polishing steps are required, which proportionally increases the amount of time required, and the attainable increments of finish improvement using conventional techniques are limited. Further, the high number of required steps for achieving a fine, polished finish cannot be reduced by applying a fine polish directly to a very rough surface. Indeed, attempting to achieve a fine polished surface directly from a very rough surface of a hard material will actually take longer than first achieving an intermediate finish prior to a fine finish. 
     BRIEF SUMMARY 
     Various embodiments of the present invention comprise apparatuses for forming chamfers on a cutting element for an earth-boring tool. In one or more embodiments, the apparatus may comprise a device configured to temporarily hold and position a cutting element for an earth-boring tool. At least one emitter is configured and oriented to emit a beam of energy toward an edge of a superabrasive table of a cutting element held and positioned by the device. 
     Other embodiments comprise methods of forming a cutting element. One or more embodiments of such methods may comprise forming a layer of superabrasive material on a substrate. A chamfer may be formed at least partially along a peripheral edge of the layer of superabrasive material using an energy beam. 
     Still other embodiments of the present invention comprise methods for forming an earth-boring tool. One or more embodiments of such methods may comprise temporarily securing a cutting element for an earth-boring tool in a chuck. At least one energy beam may be directed onto an edge of a superabrasive table of the cutting element. A point of contact between the at least one energy beam and the superabrasive table may be moved along the edge of the superabrasive table of the cutting element to form a chamfer along at least a portion of the edge. The cutting element may be secured to a body of an earth-boring tool. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a conventional cutting element; 
         FIG. 2  is a schematic figure illustrating a configuration that may be employed in embodiments of apparatuses and methods of the present invention that may be used for forming a chamfer on a cutting element for an earth-boring tool; 
         FIGS. 3A and 3B  are schematic figures illustrating non-limiting examples of gas jet configurations that may be used in apparatuses and methods according to the configuration shown in  FIG. 2 ; 
         FIG. 4  is a schematic figure illustrating another configuration that may be employed in embodiments of apparatuses and methods of the present invention that may be used for forming a chamfer on a cutting element for an earth-boring tool; 
         FIGS. 5A and 5B  illustrate embodiments of nozzles that may be employed to provide gas jets in the apparatuses and methods illustrated schematically in  FIGS. 2 ,  3 A,  3 B, and  4 ; and 
         FIG. 6  illustrates an example of an embodiment of an earth-boring tool having at least one cutting element comprising a chamfer at least partially formed and/or polished using embodiments of apparatuses and methods of the present invention, such as those shown in  FIGS. 2 ,  3 A,  3 B, and  4 . 
     
    
    
     DETAILED DESCRIPTION 
     The illustrations presented herein are, in at least some instances, are not actual views of any particular cutting element insert, cutting element, drill bit, system or method, but are merely idealized representations which are employed to describe the present invention. Additionally, elements common between figures may retain the same numerical designation. 
     As used herein, the term “chamfer” refers to any surface formed along at least a portion of a peripheral edge of a cutting element, such as the peripheral edge of the cutting face on a diamond or other superabrasive table of a PDC cutting element. By way of example and not limitation, the term “chamfer,” as used herein, may refer to a single-surface chamfer, a dual-surface chamfer, a triple-surface chamfer, a rounded edge, or any other protective structural configuration for a cutting edge. 
     In some embodiments, the present invention provides apparatuses and methods for forming and/or polishing a chamfer on a cutting element.  FIG. 2  is a schematic figure illustrating a configuration that may be employed in such embodiments of apparatuses and methods. As shown in  FIG. 2 , such apparatuses and methods may be used to form and/or polish a chamfer along a peripheral edge of a layer, or “table” of superabrasive material  105  on a cutting element  100 . A chuck  205  may be used to hold and position the cutting element  100 , and at least one emitter  210  may be positioned and oriented to emit a focused beam of energy toward the peripheral edge of the layer of superabrasive material  105 . As used herein, the term “chuck” means any tool or device configured to temporarily hold and position a cutting element  100 . As shown in  FIG. 2 , in some embodiments, two emitters  210  may be employed, although one emitter  210  or more than two emitters  210  may be employed in other embodiments of the present invention. 
     As further shown in  FIG. 2 , one or more optional gas jets  215  may be positioned and oriented to direct a stream of gas toward the peripheral edge of the layer of superabrasive material  105 . For example, the gas jets  215  may be positioned and oriented to direct a stream of gas toward a contact area  310  ( FIGS. 3A and 3B ) on the layer of superabrasive material  105  at which an energy beam emitted by an emitter  210  contacts the layer of superabrasive material  105 . 
     The chuck  205  may be configured to rotate the cutting element  100  about an axis  220 , which may comprise a symmetrical axis of the cutting element  100  (a longitudinal axis about which the cutting element  100  is symmetric). The chuck  205  may be configured to rotate the cutting element  100  in either a clockwise or counter-clockwise direction. In additional embodiments, the chuck  205  may hold the cutting element  100  in a fixed position while the one or more emitters  210  used to form and/or polish the chamfer rotate around the cutting element  100 . In yet other embodiments, the chuck  205  may remain in a fixed position and the one or more emitters  210  may remain fixed with relation to its position to the cutting element  100  while the beam of energy may be manipulated in some way such as, but not limited to, employing mobile mirrors, beam splitters, and/or rotating, tilting, or otherwise adjusting the direction of the beam of energy. In still other embodiments, both the cutting element  100  and the one or more emitters  210  may be rotated relative to one another. By way of example and not limitation, the chuck  205  may comprise a rotatable chuck or similar device. Other embodiments comprising additional configurations are also possible for directing the beam of energy around the peripheral edge of the layer of superabrasive material  105 . 
     The at least one emitter  210  may comprise a device configured to emit a beam of energy that may be used to form and/or polish a chamfer on the cutting element  100  without subjecting the cutting element  100  to the forces and other conditions typically encountered when forming a chamfer using conventional mechanical grinding and polishing techniques. In some embodiments, the at least one emitter  210  may be positioned above the cutting element  100  and oriented to direct a beam of energy toward the peripheral edge of the layer of superabrasive material  105  in a direction generally parallel to the longitudinal axis  220 . In other embodiments, the at least one emitter  210  may be positioned above the cutting element  100  and oriented to direct a beam of energy toward the peripheral edge of the layer of superabrasive material  105  in a direction generally perpendicular to the longitudinal axis  220 . In yet additional embodiments, the at least one emitter  210  may be positioned generally above and to the side of the cutting element  100  and oriented to direct a beam of energy toward the peripheral edge of the layer of superabrasive material  105  in a direction oriented at an acute angle to the longitudinal axis  220  (e.g., an angle between about 15 degrees and about 75 degrees, such as, for example, about 30 degrees, about 45 degrees, or about 60 degrees to the longitudinal axis  220 ), as shown in  FIG. 2 . 
     In some embodiments, the at least one emitter  210  may comprise a laser device configured to emit a beam of electromagnetic radiation. In other embodiments, the at least one emitter  210  may comprise a device configured to emit a beam of particles, such as an ion beam or a molecular beam. 
     In embodiments employing one or more lasers as the at least one emitter  210 , the one or more lasers may be positioned and controlled in a manner analogous to standardized computer numerical control (CNC) machining processes employed in various other applications. The one or more lasers may be configured to emit a beam of electromagnetic radiation at any wavelength that will be at least partially absorbed by the material of the layer of superabrasive material  105 . When two or more lasers are employed, the two or more lasers may be configured to emit electromagnetic radiation at the same wavelength as well as different wavelengths. By way of example and not limitation, a first laser (e.g., a Nd-YAG laser) may be employed that is configured to emit radiation having a wavelength of 532 nm. A second laser (e.g., an ArF excimer laser) may be employed that is configured to emit radiation having a wavelength of 193 nm. In this non-limiting example, the first laser may be used to roughly form the chamfer, and the second laser may be used to refine and smooth the finish of the chamfer roughly formed by the first laser. Although non-limiting examples are given of suitable lasers and wavelengths, it should be noted that a variety of suitable lasers, as well as suitable wavelengths are available and may be employed according to the particular application. 
     In other embodiments, the at least one laser may be configured to emit electromagnetic radiation at a wavelength that is not entirely absorbed by the layer of superabrasive material  105 . In such embodiments, a thin layer of material (not shown) selected to absorb the radiation emitted by the at least one laser may be disposed over the layer of superabrasive material  105  in such a manner that energy absorbed by the thin layer of material may be transferred into the layer of superabrasive material  105 . 
     In some embodiments, one or more gas jets  215  may be provided to enhance the formation and/or polishing of the chamfer by the at least one emitter  210 . For example, at least one gas jet  215  may be configured to direct a stream of gas at the point where the beam emitted by an emitter  210  is impinging on the cutting element  100 , also referred to herein as the contact area  310  and illustrated in  FIGS. 3A and 3B . The stream of gas may comprise a steady stream, or alternatively, a pulsed stream. Furthermore, the composition of the gas may be selected or adjusted to increase the efficiency by which the emitter  210  is capable of removing (e.g., ablating) material from the layer of superabrasive material  105 . In embodiments in which the layer of superabrasive material  105  comprises a layer of diamond material (e.g., polycrystalline diamond material), the gas jet  215  may be configured to provide a steady stream of pure oxygen (O 2 ) gas, or a gaseous mixture comprising oxygen (O 2 ) gas. The use of oxygen (O 2 ) gas may facilitate the conversion of diamond and/or graphite byproducts to carbon dioxide (CO 2 ) by supplying an amount of oxygen (O 2 ) in excess of that required for the corresponding reactions. The stream of gas may also entrain gaseous or other ablative byproducts therein and carry these byproducts away from the contact area  310  to further enhance the efficiency at which material is removed from the layer of superabrasive material  105 . 
     In some embodiments, if the cutting element  100  comprises a PDC cutting element  100  in which the layer of superabrasive material  105  comprises a layer of polycrystalline diamond material with a cobalt binder, at least a portion of the layer of polycrystalline diamond material may be leached by conventional techniques to at least partially remove the cobalt binder from the layer of polycrystalline diamond material before the chamfer is formed using the at least one emitter  210 . By removing at least a portion of the cobalt binder from the layer of polycrystalline diamond material in the regions at which the chamfer is to be formed using the one or more emitters  210 , the efficiency by which the polycrystalline diamond material is removed during formation of the chamfer may be increased. 
     The gas jet  215  may be positioned and oriented so as to direct a gas stream toward the area on the cutting element  100  at which the chamfer is to be formed (e.g., the peripheral edge of the layer of superabrasive material  105 ). Referring to  FIGS. 2 ,  3 A, and  3 B, the gas jet  215  may be positioned and oriented so that the stream of gas emitted thereby is generally tangential to the lateral surface of the cutting element  100  and contacts the peripheral edge of the layer of superabrasive material  105  at which the chamfer is to be formed. Furthermore, the gas jet  215  may be positioned and oriented so that the predominant velocity vector of the stream of gas emitted thereby is generally parallel to the velocity vector (due to rotation of the cutting element  100 ) of the chamfer edge at the point of laser contact on the cutting element  100  over which the stream of gas impinges on the cutting element  100 . Such a configuration may reduce or minimize turbulent flow of the gas emitted by the gas jet  215  over the contact area  310 . Any heating of the gas emitted by the gas jet  215  by the energy emitted by the at least one emitter  210  may ultimately result in reduced power being transmitted to the cutting element  100 . Furthermore, turbulent flow of the gas emitted by the gas jet  215  may result in distortion of the energy beam emitted by the at least one emitter  210  thus reducing the efficiency of the process. By reducing or minimizing turbulence in the flow of gas emitted by the gas jet  215  over the contact area  310 , distortion of the energy beam emitted by the at least one emitter  210  may be reduced, minimizing the loss of power ultimately transferred to the cutting element  100 . Furthermore, the cross-sectional area and shape of the stream of gas emitted by the gas jet  215 , as well as the velocity of the stream of gas emitted by the gas jet  215 , may be tailored to maximize the efficiency of material removal from the cutting element  100 . 
     In the non-limiting examples illustrated in  FIGS. 3A and 3B , two gas jets  215  are employed, one for each of two emitters  210 . In other words, a plurality of gas jets  215  may be used to direct a stream of gas toward each contact area  310  on the cutting element  100  at which an energy beam emitted by an emitter  210  impinges on the cutting element  100 . 
     In embodiments employing a particle beam etching process (e.g., an ion beam etching process or a molecular beam etching process), the gas jet  215  may be omitted as unnecessary, as the use of such may hinder the particle beam etching process. 
       FIG. 4  is a schematic figure illustrating another configuration that may be employed in embodiments of apparatuses and methods of the present invention that may be used for forming a chamfer on a cutting element for an earth-boring tool. The configuration shown in  FIG. 4  is generally similar to that shown in  FIG. 2  and includes two emitters  210  each configured to direct an energy beam toward an edge of a cutting element  100  on which it is desired to form a chamfer. In contrast to the configuration shown in  FIG. 2 , however, the configuration of  FIG. 4  includes gas jets  215  positioned and oriented at an acute angle relative to the longitudinal axis  220 . The gas jets  215  may be positioned and oriented such that the gas streams emitted thereby flow across the edge of the cutting element  100 . 
     The gas jets  215  described herein may include a nozzle having an aperture configured to define the cross-sectional profile (i.e., the cross-sectional area and cross-sectional shape) of the gas stream emitted thereby. Many suitable nozzle aperture designs comprising symmetric and asymmetric cross-sections may be employed. By way of example and not limitation, a nozzle aperture  505  may have a substantially round or circular geometry, as shown in  FIG. 5A . As another non-limiting example, a nozzle aperture  515  may have a substantially flat or oblong geometry, as shown in  FIG. 5B . A nozzle like that shown in  FIG. 5B  may be oriented relative to the cutting element  100  such that the substantially flat aperture is oriented to coincide with a profile of the chamfer being formed. In other words, the longer flat sides of the aperture of the nozzle may be oriented so as to be oriented parallel to a plane tangent to the chamfer being formed, which may further optimize the gas flow over the cutting element  100 . 
     In still other embodiments, a thin film of material (not shown) may be disposed over at least the portion of the layer of superabrasive material  105  to be chamfered. The thin film of material may comprise a material that is reactive with the superabrasive material, whereby a reaction between the film material and the superabrasive material is initiated and/or sustained by the emitter. The thin film may be applied in a separate processing step or in situ ahead of the emitter interaction spot thereby creating either a static or continuous process. By way of example and not limitation, if the layer of superabrasive material  105  comprises a diamond material, the thin film of material may comprise iron, since iron reacts with diamond at temperatures at or above approximately 700° C. The thin film of material may be disposed so as to only be positioned over the areas of the layer of superabrasive material  105  in which it is desired to form the chamfer or it may cover the entire surface of the table, being affected only by the laser along the desired chamfer location. As the energy beam emitted by the at least one emitter  210  impinges on the cutting element  100 , the layer of superabrasive material  105  and the thin film of material thereon may be heated to a temperature that causes a reaction between the iron in the thin film of material and the diamond material in the layer of superabrasive material  105  in such a way that the diamond carburizes at that location. In some embodiments, the use of a gas stream may be employed to remove or aid in the removal of reacted species and/or to further enable the conversion process. 
     In operation of a chamfering device of an embodiment of the invention, a cutting element  100  may be secured in a chuck  205 . As described above, the cutting element  100  may have a thin film of material positioned over the superabrasive material  105 , covering at least the portion to be chamfered. A steady flow of gas may be streamed across the contact area  310  and the emitter or emitters  210  may be energized such that an energy beam is directed to the peripheral edge of the table of superabrasive material  105 . The chamfer may be formed by rotating the cutting element  100 , the emitter  210  emitter  210 , or both or both, about the cutting element&#39;s longitudinal axis  220  in either a clockwise or counter-clockwise rotation while removing the material from the peripheral edge of the table of superabrasive material  105 . Additionally, the chamfer may be polished by the same chamfering device or by a separate chamfering device. 
     Forming and polishing the chamfer using at least one chamfering device in accordance with an embodiment of the invention may reduce damage to the cutting element  100  (e.g., damage to the regions of the layer of superabrasive material  105  proximate the chamfer). By reducing such damage, cutting elements  100  having one or more chamfers formed according to embodiments of methods of the present invention may exhibit improved performance relative to cutting elements  100  having chamfers formed using conventional mechanical polishing and lapping processes. Additionally, the speed at which chamfers may be formed using embodiments of methods of the present invention may be increased relative to chamfering speeds achievable using conventional techniques. 
       FIG. 6  illustrates an embodiment of an earth-boring tool. The earth-boring tool illustrated in  FIG. 6  comprises a fixed-cutter drill bit  600  (often referred to as a “drag” bit) including cutting elements  616  having a chamfer around at least a portion of a peripheral edge of a layer of superabrasive material  105  ( FIG. 1 ). The drill bit  600  may include a bit body  602  having a face  604  and generally radially extending blades  606 , forming fluid courses  608  therebetween extending to junk slots  610  between circumferentially adjacent blades  606 . Bit body  602  may comprise a metal or metal alloy, such as steel, or a particle-matrix composite material, as are known in the art. 
     Blades  606  may include a gage region  612  which is configured to define the outermost radius of the drill bit  600  and, thus, the radius of the wall surface of a bore hole drilled thereby. Gage regions  612  comprise longitudinally upward (as the drill bit  600  is oriented during use) extensions of blades  606  and may have wear-resistant inserts or coatings, such as hardfacing, cutting elements, or wear resistant pads, bricks, or studs, on radially outer surfaces thereof as known in the art to inhibit excessive wear thereto. 
     Drill bit  600  may also be provided with pockets  614  in blades  606  which may be configured to receive cutting elements  616 . Cutting elements  616  may be affixed within the pockets  614  on the blades  606  of drill bit  600  by way of brazing, welding, or as otherwise known in the art. Cutting elements  616  include at least one chamfer at least partially extending along an edge thereof formed and/or polished using embodiments of methods of the present invention, such as those previously described herein. 
     While certain embodiments have been described and shown in the accompanying drawings, such embodiments are merely illustrative and not restrictive of the scope of the invention, and this invention is not limited to the specific constructions and arrangements shown and described, since various other additions and modifications to, and deletions from, the described embodiments will be apparent to one of ordinary skill in the art. For example, although the embodiments describe the cutting elements as having a diamond table, at least some of the techniques described herein may be applied to other cutter materials as well. Thus, the scope of the invention is only limited by the literal language, and legal equivalents, of the claims which follow.