Patent Application
20100108399
Embodiments of the present invention generally relate to hard particles, materials including such hard particles, and to earth-boring tools including such hard particles or materials. Embodiments of the present invention also relate to methods of manufacturing such particles, materials, and earth-boring tools.
Bodies of earth-boring tools, such as earth-boring rotary drill bits, may be formed from a particle-matrix composite material. Such particle-matrix composite materials include particles of hard material such as, for example, tungsten carbide dispersed throughout a metal matrix material (often referred to as a “binder” material). Particle-matrix composite materials exhibit relatively higher erosion and wear resistance relative to steel and other metal materials.
There are three primary types of tungsten carbide particles most often used in earth-boring tools, those being cast tungsten carbide particles, sintered tungsten carbide particles, and macrocrystalline tungsten carbide particles. The tungsten carbide system includes the two stoichiometric compounds of monotungsten carbide (WC) and ditungsten carbide (W2C), as well as a continuous range of mixtures there between of these two compounds. Cast tungsten carbide particles generally include a eutectic mixture of the monotungsten carbide and ditungsten carbide stoichiometric compounds. Sintered tungsten carbide particles generally include relatively smaller particles of monotungsten carbide (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 may be formed by mixing together a first powder that includes the tungsten carbide particles and a second powder that includes the relatively smaller 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 comprise single crystals of monotungsten carbide (WC).
Typically, the body of an earth-boring drill bit is formed by providing particulate tungsten carbide material in a mold cavity having a shape corresponding to the body of the drill bit to be formed, melting a metal matrix material, such as a copper-based alloy, and infiltrating the particulate tungsten carbide material with the molten metal matrix material. After infiltration, the molten metal matrix material is allowed to cool and solidify. The resulting bit body may then be removed from the mold. Cast tungsten carbide particles are often used for at least a portion of the particulate tungsten carbide material in such infiltration processes.
During such infiltration processes, the cast tungsten carbide particles may interact chemically with the surrounding metal matrix material at the elevated temperatures at which infiltration is carried out. For example, atomic diffusion may occur between the cast tungsten carbide particles and the metal matrix material during infiltration. As a result, carbon and tungsten may diffuse out from the cast tungsten carbide particles and into the metal matrix material during infiltration, resulting in the formation of relatively small deposits or regions of unintended metal carbide satellite materials (such as, for example, so-called “eta-phase” carbides or carbides having a composition of the form M6C, where M is a metal) within the matrix material proximate the cast tungsten carbide particles. In these metal carbide satellite materials, the metal may be contributed by the matrix and the carbon may be contributed by the tungsten carbide particles. When a body of an earth-boring tool that includes such small metal carbide phases surrounding cast tungsten carbide particles cracks during use, the cracks may exhibit a tendency to propagate through the metal matrix material along a pathway that appears to follow the small metal carbide phases surrounding the cast tungsten carbide particles.
In some embodiments, the present invention includes a powder of particles which may be used in forming a composite material for earth-boring tools. The composite material includes a first discontinuous phase within a continuous matrix phase. The first discontinuous phase includes the powder of the present invention. In some embodiments, the powder of the present invention may comprise partially carburized monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles wherein the particles have two layers: an inner core of montungsten carbide (WC) and ditungsten carbide (W2C) eutectic material and an outer shell of monotungsten carbide (WC). In another embodiment, the powder of the present invention may comprise fully carburized monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles which comprise particles wherein the particles are at least substantially monotungsten carbide. The partially carburized particles and fully carburized particles may be generally spherical or at least substantially spherical.
Further embodiments include earth-boring tools, drill bits, and hardfacing materials comprising a particle-matrix composite material wherein the continuous matrix phase comprises of one or more metals or alloys and the hard particles comprise the partially carburized particles or fully carburized particles of the present invention. The partially carburized particles and fully carburized particles may be less reactive with the continuous matrix phase than monotungsten carbide and ditungsten carbide eutectic particles.
In further embodiments, the present invention includes methods of forming the particles of the current invention. The methods include carburizing a plurality of monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles. One example is to carburize the monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles by exposing the monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles to a gas containing carbon. In still further embodiments, the present invention includes methods of forming earth-boring tools, drill bits, and hardfacing materials. The methods include providing a plurality of partially carburized particles or fully carburized particles in a matrix material forming a particle-matrix material which can then be used in forming the earth-boring tools, drill bits, and hardfacing materials.
While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, the advantages of this invention may be more readily ascertained from the description of embodiments of the invention when read in conjunction with the accompanying drawings, in which:
Some of the illustrations presented herein are not meant to be actual views of any particular material, device, or system, 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 shown in
Metal carbide satellite deposits 110 are a product of chemical reactions between the monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles 106 and the surrounding matrix material 108. In the monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles 108, while the W2C phase is harder then the WC phase, the WC phase is chemically more stable then the W2C phase. Therefore, relatively more of the metal carbide satellite deposits 110 may be formed from reactions between the W2C phase and the metal matrix material 108 than from reactions between the WC phase and the metal matrix material 108.
In some embodiments of the present invention, powders may be formed using partially carburized particles 114, fully carburized particles 120, or both partially carburized particles 114 and fully carburized particles 120, and such powders may be used in forming bodies and components of earth-boring tools. Such powders may also comprise other tungsten carbide particles such as uncarburized monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles, macrocrystalline tungsten carbide, sintered tungsten carbide, as well as other hard particles such as diamond particles, silicon carbide particles, silicon nitride particles, boron nitride particles, etc.
In some embodiments of the present invention, powders may be formed using partially carburized particles 114 and/or fully carburized particles 120 having different average particle sizes. For example, a powder comprising partially carburized particles 114 and/or fully carburized particles 120 may have a multi-modal average particle size distribution (e.g., bi-modal, tri-modal, tetra-modal, penta-modal, etc.). In other embodiments, however, the partially carburized particles 114 and/or fully carburized particles 120 may have a single and substantially unifonm average particle size, and the particles may exhibit a Gaussian or log-normal average particle size distribution. By way of example and not limitation, the partially carburized particles 114 and/or fully carburized particles 120 in a powder or powder mixture may include a plurality of particles having an average particle diameter of less than about 500 microns. In some embodiments, the partially carburized particles 114 and/or fully carburized particles 120 in a powder or powder mixture may include a plurality of particles having an average particle diameter of between about 44 microns and about 250 microns. In other embodiments, the partially carburized particles 114 and/or fully carburized particles 120 in a powder or powder mixture may include a plurality of particles having an average particle diameter of between about 105 microns and about 250 microns. Using conventional ASTM measurements, the partially carburized particles 114 and/or fully carburized particles 120 may comprise −60/+140 ASTM (American Society for Testing and Materials) mesh size particles. As used herein, the phrase “−60/+140 ASTM mesh size particles” means particles that pass through an ASTM No. 60 U.S.A. standard testing sieve, but not through an ASTM No. 140 U.S.A. standard testing sieve as defined in ASTM Specification E11-04, which is entitled Standard Specification for Wire Cloth and Sieves for Testing Purposes.
In some embodiments, partially carburized particles 114 and/or fully carburized particles 120 of the present invention may comprise generally rough, non-rounded (e.g., polyhedron-shaped) particles. In other embodiments, partially carburized particles 114 and/or fully carburized particles 120 of the present invention may comprise generally smooth, rounded particles. Particle-matrix composite materials that include generally smooth, round particles may exhibit higher fracture toughness relative to particle-matrix composite materials that include rough, non-rounded particles, as relatively sharper points and edges on particles may promote the formation of cracks in the resulting particle-matrix composite material. In some embodiments, partially carburized particles 114 and fully carburized particles 120 as described hereinabove may have a generally spherical shape having an average sphericity (Ψ) of 0.6 or higher. Sphericity (Ψ) is defined by the equation:
wherein Vp is the volume of the particle and Ap is the surface area of the particle. In additional embodiments, partially carburized particles 114 and fully carburized particles 120 as described hereinabove may have an at least substantially spherical shape and may have an average sphericity (Ψ) of 0.9 or greater.
According to embodiments of the present invention, fully carburized particles 120 may be generally or at least substantially spherical in shape. The resulting particles may be at least substantially comprised by monotungsten carbide (WC), and may not include the relatively sharp points and edges that are typically present on monotungsten carbide (WC) macrocrystalline particles. The fully carburized particles 120, which may be at least substantially comprised by monotungsten carbide (WC), also may be larger than monotungsten carbide (WC) macrocrystalline particles currently known in the art.
As previously mentioned, partially carburized particles 114 and/or fully carburized particles 120, as described hereinabove, may be dispersed throughout a matrix material 108 to form a particle-matrix composite material 104. In some embodiments, the matrix material 108 may comprise a commercially pure metal such as copper, cobalt, iron, nickel, aluminum, or titanium. In additional embodiments, the metal matrix material 108 may comprise a metal alloy material such as a copper-based alloy, a cobalt-based alloy, an iron-based alloy, a nickel-based alloy, a cobalt- and nickel-based alloy, an iron- and nickel-based alloy, an iron- and cobalt-based alloy, an aluminum-based alloy, a magnesium-based alloy, or a titanium-based alloy. In some embodiments of the invention, the particle matrix composite material 104 may be at least substantially free of metal carbide satellite deposits 110.
The partially carburized particles 114 and/or fully carburized particles 120 may be formed by at least partially carburizing monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles. The monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles may be formed by melting a eutectic mixture of carbon and tungsten (e.g., between about fifty-nine atomic percent (59 at %) and about sixty-three atomic percent (63 at %) carbon, and between about forty-one atomic percent (41 at %) and about thirty-seven atomic percent (37 at %) tungsten). The mixture may be melted by heating the mixture to a temperature above about 2735° C. As the mixture cools from just below a temperature of 2735° C. to room temperature, the monotungsten carbide (WC) phases and ditungsten carbide (W2C) phases will at least substantially simultaneously solidify. The mixture may be allowed to cool in a crucible or the mixture may be cooled quickly by splat cooling, wherein the melted mixture is poured onto a cool surface. The resulting material will comprise a microstructure of alternating regions of monotungsten carbide (WC) phases and ditungsten carbide (W2C) phases. The solidified material may then be crushed to form monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles. In additional embodiments, an atomizer may be used to form the monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles. For example, the molten carbon and tungsten eutectic mixture may be sprayed out from a nozzle into a cold gas, such as, for example, helium or argon within a container to form small particles of the monotungsten carbide and ditungsten carbide eutectic composition.
The monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles may be carburized by, for example, exposing the eutectic particles to a gas containing carbon such as, for example, an alkane (e.g., methane, ethane, propane, etc.) at an elevated temperature (e.g., within the range extending from about 2,000° C. to about 2,600° C.). The carburizing process may be performed in a fluidized bed or a powder bed.
The ditungsten carbide (W2C) phase near the surface of the particle may react with the carbon gas such that carbon atoms from the gas are used to convert the ditungsten carbide (W2C) phase to a monotungsten carbide (WC) phase in an outer shell 118 of the particles. The thickness of the outer shell 118 may be controlled by either limiting the time the monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles are exposed to the gas containing carbon, or by limiting the amount of carbon to which the monotungsten carbide (WC) and ditungsten carbide (W2C) eutectic particles are exposed. It is noted, however, that in some embodiments, the carburization process may be a self-limiting or rate-limiting process in which, after carrying out the carburization reaction for a period of time, the rate at which the ditungsten carbide (W2C) phase in the eutectic particles is being converted to a monotungsten carbide (WC) phase is essentially zero. In other words, the outer shell 118 may be grown or otherwise formed in the particles from the exterior surfaces thereof in an inward direction. After a certain period of time, the rate at which the thickness of the outer shell 118 is increasing (and, hence, the average diameter of the inner core 116 is decreasing) may decrease to essentially zero, at which time no significant further conversion of the ditungsten carbide (W2C) phase to a monotungsten carbide (WC) phase will be performed by continuing the carburization process.
As previously mentioned, embodiments of partially carburized particles 114 and/or fully carburized particles 120 of the present invention may be used to form a body or component of any earth-boring tool. By way of example and not limitation, an earth-boring rotary drill bit may include a body comprising partially carburized particles 114 and/or fully carburized particles 120 as previously described herein. A non-limiting embodiment of an earth-boring rotary drill bit 100 of the present invention is shown in
In some embodiments, nozzle inserts (not shown) may be provided at the face 128 of the bit body 102 within the internal fluid passageways 130. The drill bit 100 may include a plurality of cutting structures on the face 128 thereof. By way of example and not limitation, a plurality of polycrystalline diamond compact (PDC) cutters 132 may provided on each of the blades 134, as shown in
In some embodiments, the bit body 102 may be formed using so-called “infiltration” casting techniques.
After forming the mold assembly 139, a powder comprising a plurality of partially carburized particles 114 (
After forming the powder bed 148, particles 150 of matrix material 108 (
As the particles 150 melt, molten matrix material 108 may be allowed or caused to infiltrate the spaces between the partially carburized particles 114 (
After the powder bed 142 comprising the partially carburized particles 114 and/or fully carburized particles 120 has been infiltrated with the molten matrix material 108 within the mold assembly 139, the molten matrix material 108 may be allowed to cool and solidify around the partially carburized particles 114 and/or fully carburized particles 120, thereby forming the solid matrix material 108 of the particle-matrix composite material 104.
In additional embodiments, the bit body 102 may be formed using so-called particle compaction and sintering techniques such as, for example, those disclosed in pending U.S. patent application Ser. No. 11/271,153, filed Nov. 10, 2005, entitled Earth-Boring Rotary Drill Bits and Methods of Forming Earth-Boring Rotary Drill Bits, and pending U.S. patent application Ser. No. 11/272,439, filed Nov. 10, 2005, entitled Earth-Boring Rotary Drill Bits and Methods of Manufacturing Earth-Boring Rotary Drill Bits Having Particle-Matrix Composite Bit Bodies the entire disclose of each of which application is incorporated herein by this reference. An example of a manner in which the bit body 102 may be formed using powder compaction and sintering techniques is described briefly below.
Referring to
The container 154 may include a fluid-tight deformable member 156 such as, for example, deformable polymeric bag and a substantially rigid sealing plate 158. Inserts or displacement members 160 may be provided within the container 154 for defining features of the bit body 102 such as, for example, the internal fluid passageways 130 (
The container 154 (with the powder mixture 152 and any desired displacement members 160 contained therein) may be pressurized within a pressure chamber 162. A removable cover 164 may be used to provide access to the interior of the pressure chamber 162. A fluid (which may be substantially incompressible) such as, for example, water, oil, or gas (such as, for example, air or nitrogen) is pumped into the pressure chamber 162 through an opening 166 at high pressures using a pump (not shown). The high pressure of the fluid causes the walls of the deform able member 156 to deform, and the fluid pressure may be transmitted substantially uniformly to the powder mixture 152.
Pressing of the powder mixture 152 may form a green (or unsintered) body 168 shown in
The green body 168 shown in
The partially shaped green body 170 shown in
By way of example and not limitation, internal fluid passageways 130, cutting element pockets 136, and buttresses 138 (
In other methods, the green body 168 shown in
The sintering process may include conventional sintering in a vacuum furnace, sintering in a vacuum furnace followed by a conventional hot isostatic pressing process, and sintering immediately followed by isostatic pressing at temperatures near the sintering temperature (often referred to as sinter-HIP). Furthermore, the sintering processes may include subliquidus phase sintering. In other words, the sintering processes may be conducted at temperatures proximate to but below the liquidus line of the phase diagram for the matrix material. For example, the sintering processes may be conducted using a number of different methods known to one of ordinary skill in the art, such as the Rapid Omnidirectional Compaction (ROC) process, the CERACON™ process, hot isostatic pressing (HIP), or adaptations of such processes.
When the bit body 102 is formed by particle compaction and sintering techniques, the bit body 102 may not include a metal blank 124 and may be secured to the metal shank 126 by, for example, one or more of brazing or welding. Furthermore, in such embodiments, an extension comprising a machinable metal or metal alloy (e.g., a steel alloy) may be secured to the bit body 102 and used to secure the bit body 102 to a shank 126.
Additional embodiments of the present invention comprise components of earth-boring tools that include a plurality of partially carburized particles 114 (
Additional embodiments of the present invention comprise hardfacing materials that include a plurality of partially carburized particles 114 (
Briefly, a hardfacing material may be formed by heating a metal matrix material 108 to a temperature above its melting point forming a molten metal matrix material 108. Partially carburized particles 114 and/or fully carburized particles 120, as previously described herein, together with the molten metal matrix material 108 may be applied to one or more surfaces of an earth-boring tool to which the hardfacing material is to be applied. The partially carburized particles 114 may be fully formed prior to application of the hardfacing material. The molten particle-matrix material 108 is then allowed to cool and solidify around the partially carburized particles 114 and/or fully carburized particles 120 on the one or more surfaces of the earth-boring tool, thereby forming a hardfacing material comprising a solid particle-matrix composite material 104 on the surface of the earth-boring tool.
While the present invention is described herein in relation to embodiments of concentric earth-boring rotary drill bits that include fixed cutters and to embodiments of methods for forming such drill bits, the present invention also encompasses other types of earth-boring tools such as, for example, core bits, eccentric bits, bicenter bits, reamers, mills, and roller cone bits, as well as methods for forming such tools. Thus, as employed herein, the term “bit body” includes and encompasses bodies of all of the foregoing structures, as well as components and subcomponents of such structures.
While the present invention has been described herein with respect to certain 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 embodiments described herein 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 invention as contemplated by the inventor.
