The embodiments herein generally relate to earth-boring drill bits and other tools that may be used to drill subterranean formations having abrasive, wear-resistant hardfacing materials that may be used on surfaces of the cutting elements of such earth-boring drill bits. The embodiments herein also relate to methods for applying abrasive wear-resistant hardfacing materials to surfaces of earth-boring drill bits.
A typical fixed-cutter, or “drag,” rotary drill bit for drilling subterranean formations includes a bit body having a face region thereon carrying cutting elements for cutting into an earth formation. The bit body may be secured to a hardened steel shank having a threaded pin connection for attaching the drill bit to a drill string that includes tubular pipe segments coupled end-to-end between the drill bit and other drilling equipment. Equipment such as a rotary table or top drive may be used for rotating the tubular pipe and drill bit. Alternatively, the shank may be coupled directly to the drive shaft of a down-hole motor to rotate the drill bit.
Typically, the bit body of a drill bit is formed from steel or a combination of a steel blank embedded in a matrix material that includes hard particulate material, such as tungsten carbide, infiltrated with a binder material such as a copper alloy. A steel shank may be secured to the bit body after the bit body has been formed. Structural features may be provided at selected locations on and in the bit body to facilitate the drilling process. Such structural features may include, for example, radially and longitudinally extending blades, cutting element pockets, ridges, lands, nozzle displacements, and drilling fluid courses and passages. The cutting elements generally are secured within pockets that are machined into blades located on the face region of the bit body.
Generally, the cutting elements of a fixed-cutter type drill bit each include a cutting surface comprising a hard, super-abrasive material such as mutually bound particles of polycrystalline diamond. Such “polycrystalline diamond compact” (PDC) cutters have been employed on fixed-cutter rotary drill bits in the oil and gas well drilling industries for several decades.
The embodiments herein include an abrasive wear-resistant material that includes a matrix material and either cast tungsten carbide, sintered tungsten carbide, or macrocrystalline tungsten carbide or a mixture thereof applied to the cutting elements of a fixed-cutter type drill bit.
The features, advantages, and alternative aspects of the embodiments herein will be apparent to those skilled in the art from a consideration of the following detailed description considered in combination with the accompanying drawings.
While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the embodiments herein, the advantages of these embodiments may be more readily ascertained from the following description of the embodiments when read in conjunction with the accompanying drawings in which:
The present embodiments herein include a rotary drill bit for drilling subterranean formations that includes a bit body and at least one cutting element secured to the bit body along an interface. As used herein, the term “drill bit” includes and encompasses drilling tools of any configuration, including core bits, eccentric bits, bicenter bits, reamers, mills, drag bits, roller cone bits, and other such structures known in the art. A brazing alloy is disposed between the bit body and the at least one cutting element at the interface and secures the at least one cutting element to the bit body. An abrasive wear-resistant material that includes a matrix having either cast tungsten carbide, sintered tungsten carbide, or macrocrystalline tungsten carbide, or a mixture of thereof is applied to portions of cutters thereon.
In another aspect, the present embodiments herein include a method for securing a cutting element to a bit body of a rotary drill bit. The method includes providing a rotary drill bit including a bit body having an outer surface including a pocket therein that is configured to receive a cutting element, and positioning a cutting element within the pocket. A brazing alloy is provided, melted, and applied to adjacent surfaces of the cutting element and the outer surface of the bit body within the pocket defining an interface therebetween and solidified. An abrasive wear-resistant material is applied to a surface of the drill bit. At least a continuous portion of the abrasive wear-resistant material is bonded to a surface of the cutting element and may be bonded to a portion of the outer surface of the bit body. The continuous portion extends over at least the interface between the cutting element and the outer surface of the bit body and covers the brazing alloy.
A rotary drill bit 10 may be used numerous times to perform successive drilling operations during which the surfaces of the bit body 12 and cutting elements 22 may be subjected to extreme forces and stresses as the cutting elements 22 of the rotary drill bit 10 shear away the underlying earth formation. These extreme forces and stresses cause the cutting elements 22 and the surfaces of the bit body 12 to wear. Eventually, the cutting elements 22 and the surfaces of the bit body 12 may wear to an extent at which the rotary drill bit 10 is no longer suitable for use.
The bonding material 24 typically is much less resistant to wear than are other portions and surfaces of the rotary drill bit 10 and of cutting elements 22. During use, small vugs, voids and other defects may be formed in exposed surfaces of the bonding material 24 due to wear. Solids-laden drilling fluids and formation debris generated during the drilling process may further erode, abrade and enlarge the small vugs and voids in the bonding material 24. The entire cutting element 22 may separate from the drill bit body 12 during a drilling operation if enough bonding material 24 is removed. Loss of a cutting element 22 during a drilling operation can lead to rapid wear of other cutting elements and catastrophic failure of the entire rotary drill bit 10. Therefore, there is a need in the art for an effective method for preventing the loss of cutting elements during drilling operations.
The materials of an ideal drill bit must be extremely hard to efficiently shear away the underlying earth formations without excessive wear. Due to the extreme forces and stresses to which drill bits are subjected during drilling operations, the materials of an ideal drill bit must simultaneously exhibit high fracture toughness. In practicality, however, materials that exhibit extremely high hardness tend to be relatively brittle and do not exhibit high fracture toughness, while materials exhibiting high fracture toughness tend to be relatively soft and do not exhibit high hardness. As a result, a compromise must be made between hardness and fracture toughness when selecting materials for use in drill bits.
In an effort to simultaneously improve both the hardness and fracture toughness of earth-boring drill bits, composite materials have been applied to the surfaces of drill bits that are subjected to extreme wear. These composite materials are often referred to as “hardfacing” materials and typically include at least one phase that exhibits relatively high hardness and another phase that exhibits relatively high fracture toughness.
Typically, hardfacing material includes tungsten carbide particles substantially randomly dispersed throughout an iron-based matrix material or other suitable material. The tungsten carbide particles exhibit relatively high hardness, while the matrix material exhibits relatively high fracture toughness.
Tungsten carbide particles used in hardfacing materials may comprise one or more of cast tungsten carbide particles, sintered tungsten carbide particles, and macrocrystalline tungsten carbide particles. The tungsten carbide system includes two stoichiometric compounds, WC and W2C, with a continuous range of compositions therebetween. Cast tungsten carbide generally includes a eutectic mixture of the WC and W2C compounds. Sintered tungsten carbide particles include relatively smaller particles of WC bonded together by a matrix material. Cobalt and cobalt alloys are often used as matrix materials in sintered tungsten carbide particles. Sintered tungsten carbide particles can be formed by mixing together a first powder that includes the relatively smaller tungsten carbide particles and a second powder that includes cobalt particles. The powder mixture is formed in a “green” state. The green powder mixture then is sintered at a temperature near the melting temperature of the cobalt particles to form a matrix of cobalt material surrounding the tungsten carbide particles to form particles of sintered tungsten carbide. Finally, macrocrystalline tungsten carbide particles generally consist of single crystals of WC.
Various techniques known in the art may be used to apply a hardfacing material to a surface of a drill bit. In the current instance, a rod may be configured as a hollow, cylindrical tube formed from the matrix material of the hardfacing material that is filled with tungsten carbide particles. At least one end of the hollow, cylindrical tube may be sealed. The sealed end of the tube then may be melted onto the desired surface on the drill bit. As the tube melts, the tungsten carbide particles within the hollow, cylindrical tube mix with the molten matrix material as it is deposited onto the drill bit. An alternative technique involves forming a cast rod of the hardfacing material and using a torch to apply or weld hardfacing material disposed at an end of the rod to the desired surface on the drill bit.
When a hardfacing material is applied to a surface of a drill bit, relatively high temperatures are used to melt at least the matrix material. At these relatively high temperatures, atomic diffusion may occur between the tungsten carbide particles and the matrix material. In other words, after applying the hardfacing material, at least some atoms originally contained in a tungsten carbide particle (tungsten and carbon, for example) may be found in the matrix material surrounding the tungsten carbide particle. In addition, at least some atoms originally contained in the matrix material (iron, for example) may be found in the tungsten carbide particles. At least some atoms originally contained in the tungsten carbide particle (tungsten and carbon, for example) may be found in a region of the matrix material immediately surrounding the tungsten carbide particle. In addition, at least some atoms originally contained in the matrix material (iron, for example) may be found in a peripheral or outer region of the tungsten carbide particle.
Atomic diffusion between the tungsten carbide particle and the matrix material may embrittle the matrix material in the region surrounding the tungsten carbide particle and reduce the hardness of the tungsten carbide particle in the outer region thereof, reducing the overall effectiveness of the hardfacing material. There is a need in the art for methods of applying such abrasive wear-resistant hardfacing materials, and for drill bits and drilling tools that include such materials wear using a minimum of time and heat for the application of hardfacing material.
The illustrations presented herein are not meant to be actual views of any particular material, apparatus, 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.
Corners, sharp edges, and angular projections may produce residual stresses, which may cause tungsten carbide material in the regions of the particles proximate the residual stresses to melt at lower temperatures during application of the abrasive wear-resistant material 54 to a surface of a drill bit. Melting or partial melting of the tungsten carbide material during application may facilitate atomic diffusion between the tungsten carbide particles and the surrounding matrix material.
Abrasive wear-resistant materials that embody teachings of the present invention, such as the abrasive wear-resistant material 54 illustrated in
Certain locations on a surface of a drill bit may require relatively higher hardness, while other locations on the surface of the drill bit may require relatively higher fracture toughness. In addition to being applied to selected areas on surfaces of drill bits and drilling tools that are subjected to wear, the abrasive wear-resistant materials that embody teachings of the present invention may be used to protect structural features or materials of drill bits and drilling tools that are relatively more prone to wear.
A portion of a representative rotary drill bit 50 that embodies teachings of an embodiment is shown in
The rotary drill bit 50 further includes an abrasive wear-resistant material 54 disposed on a surface of the drill bit 50. Moreover, regions of the abrasive wear-resistant material 54 may be configured to protect exposed surfaces of the bonding material 24.
In this configuration, the continuous portions of the abrasive wear-resistant material 54 may cover and protect at least a portion of the bonding material 24 disposed between the cutting element 22 and the bit body 12 from wear during drilling operations. By protecting the bonding material 24 from wear during drilling operations, the abrasive wear-resistant material 54 helps to prevent separation of the cutting element 22 from the bit body 12 during drilling operations, damage to the bit body 12, and catastrophic failure of the rotary drill bit 50.
The continuous portions of the abrasive wear-resistant material 54 that cover and protect exposed surfaces of the bonding material 24 may be configured as a bead or beads of abrasive wear-resistant material 54 provided along and over the edges of the interfacing surfaces of the bit body 12 and the cutting element 22.
A lateral cross-sectional view of a cutting element 22 of another representative rotary drill bit 50′ that embodies teachings of the present invention is shown in
As illustrated in
The abrasive wear-resistant material 54 may be used to cover and protect interfaces between any two structures or features of a drill bit or other drilling tool. For example, abrasive wear-resistant material 54 may cover and protect the interface between a bit body and a periphery of wear knots or any type of insert in the bit body. In addition, the abrasive wear-resistant material 54 is not limited to use at interfaces between structures or features and may be used at any location on any surface of a drill bit or drilling tool that is subjected to wear.
Abrasive wear-resistant materials, such as the abrasive wear-resistant material 54, may be applied to the selected surfaces of a drill bit or drilling tool using variations of techniques known in the art. For example, a pre-application abrasive wear-resistant material that embodies teachings of the present invention may be provided in the form of a rod, such as a KUTRITE® rod, sold by M&M metals, Houston, Tex. The rod may comprise a solid cast or extruded rod consisting of the abrasive wear-resistant material 54. Alternatively, the rod may comprise a hollow cylindrical tube formed from a matrix material and filled with a plurality of sintered tungsten carbide pellets and a plurality of cast tungsten carbide granules. An oxyacetylene torch or any other type of welding torch may be used to heat at least a portion of the welding rod to a temperature above the melting point of the matrix material 60 and less than about 1200° C. to melt the matrix material. This may minimize the extent of atomic diffusion occurring between the matrix material and either the sintered tungsten carbide, cast tungsten carbide or macrocrystalline tungsten carbide.
The rate of atomic diffusion occurring between the matrix material and either the sintered tungsten carbide, cast tungsten carbide, or macrocrystalline tungsten carbide is at least partially a function of the temperature at which atomic diffusion occurs. The extent of atomic diffusion, therefore, is at least partially a function of both the temperature at which atomic diffusion occurs and the time for which atomic diffusion is allowed to occur. Therefore, the extent of atomic diffusion occurring between the matrix material and either the sintered tungsten carbide, cast tungsten carbide, or macrocrystalline tungsten carbide may be controlled by controlling the distance between the torch and the rod (or pre-application abrasive wear-resistant material), and the time for which the rod is subjected to heat produced by the torch.
Oxyacetylene and atomic hydrogen torches may be capable of heating materials to temperatures in excess of 1200° C. It may be beneficial to slightly melt the surface of the drill bit or drilling tool to which the abrasive wear-resistant material 54 is to be applied just prior to applying the abrasive wear-resistant material 54 to the surface. For example, an oxyacetylene and atomic hydrogen torch may be brought in close proximity to a surface of a drill bit or drilling tool and used to heat to the surface to a sufficiently high temperature to slightly melt or “sweat” the surface. The rod comprising pre-application wear-resistant material then may be brought in close proximity to the surface and the distance between the torch and the welding rod may be adjusted to heat at least a portion of the welding rod to a temperature above the melting point of the matrix material and less than about 1200° C. to melt the matrix material. The molten matrix material, at least some of either the sintered tungsten carbide, cast tungsten carbide, or macrocrystalline tungsten carbide may be applied to the surface of the drill bit, and the molten matrix material may be solidified by controlled cooling. The rate of cooling may be controlled to control the microstructure and physical properties of the abrasive wear-resistant material 54.
Alternatively, the abrasive wear-resistant material 54 may be applied to a surface of a drill bit or drilling tool using oxyacetylene and an atomic hydrogen torches, arc to maintain the bonding material 24 in a molten liquidus state or plastic molten state with the application of either the sintered tungsten carbide, cast tungsten carbide, or macrocrystalline tungsten carbide in a powder state being applied thereto through the use of gas under pressure, such as by blowing the powder into the bonding material 24. For example, the matrix material may be provided in the form of a powder having either the sintered tungsten carbide, cast tungsten carbide, or macrocrystalline tungsten carbide as a powder mixed with the powdered matrix material to provide a pre-application wear-resistant material in the form of a powder mixture.
As the powdered pre-application wear-resistant material passes through the torch it is heated to a temperature at which at least some of the wear-resistant material will melt and mix with or be embedded in the bonding material 24. Once the at least partially molten wear-resistant material has been deposited on the surface of the substrate, the wear-resistant material is allowed to solidify.
The temperature to which the pre-application wear-resistant material is heated as the material passes through the torch may be at least partially controlled by suitable manners known in the art to 1200° C. or less to heat at least a portion of the pre-application wear-resistant material to a temperature above the melting point of the matrix material 60 and less than about 1200° C. to melt the matrix material. This may minimize the extent of atomic diffusion occurring between the matrix material and either the sintered tungsten carbide, cast tungsten carbide, or macrocrystalline tungsten carbide.
Arc welding, metal inert gas (MIG) arc welding techniques, tungsten inert gas (TIG) arc welding techniques, and flame spray welding techniques are known in the art and may be used to apply the abrasive wear-resistant material 54 to a surface of a drill bit or drilling tool.
The present embodiments herein have been described herein with respect to certain preferred embodiments, those of ordinary skill in the art will recognize and appreciate that it is not so limited. Rather, many additions, deletions and modifications to the preferred embodiments may be made without departing from the scope of the invention as hereinafter claimed. In addition, features from one embodiment may be combined with features of another embodiment while still being encompassed within the scope of the embodiments as contemplated by the inventors. Further, the embodiments herein have utility in drill bits and core bits having different and various bit profiles as well as cutter types.
This application claims the benefit of U.S. provisional patent application Ser. No. 61/077,752, filed Jul. 2, 2008, which is incorporated herein in its entirety. This application is also related to application Ser. No. 11/223,215, which was filed Sep. 9, 2005, and is currently pending, the contents of which are incorporated herein in their entirety.
Number | Date | Country | |
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61077752 | Jul 2008 | US |