Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Reexamination Certificate
1998-09-18
2001-09-11
Jenkins, Daniel J. (Department: 3625)
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
C419S015000, C419S018000, C175S374000
Reexamination Certificate
active
06287360
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a composition for the matrix body of rock bits and other cutting or drilling tools.
BACKGROUND OF THE INVENTION
Polycrystalline diamond compact (“PDC”) cutters have been utilized in earth-boring drill bits. Typically, PDC bits include an integral bit body which may be made of steel or fabricated of a hard matrix material such as tungsten carbide (WC). A plurality of diamond cutter devices, e.g., PDC cutters, are mounted along the exterior face of the bit body. Each diamond cutter has a stud portion which typically is brazed in a recess or pocket in the exterior face of the bit body.
The PDC cutters are positioned along the leading edges of the bit body so that, as the bit body is rotated in its intended direction of use, the PDC cutters engage and drill the earth formation. In use, high forces may be exerted on the PDC cutters, particularly in the forward-to-rear direction. Additionally, the bit and the PDC cutters may be subjected to substantial abrasive forces. In some instances, impact, vibration, and erosive forces have caused drill bit failure and loss of one or more of the PDC cutters.
While steel body bits have toughness and ductility properties which render them resistant to cracking and failure due to impact forces generated during drilling, steel is more susceptible to erosive wear caused by high-velocity drilling fluids and formation fluids which carry abrasive particles, such as sand, rock cuttings, etc. Generally, steel body PDC bits are coated with a more erosion-resistant material, such as tungsten carbide, to improve their erosion resistance. However, tungsten carbide and other erosion-resistant materials are relatively brittle. During use, a thin coating of the erosion-resistant material may crack, peel off or wear, revealing the softer steel body which is then rapidly eroded. This can lead to loss of PDC cutters as the area around the cutter is eroded away, causing the bit to fail.
Tungsten carbide or other hard metal matrix body bits have the advantage of higher wear and erosion resistance. The matrix bit generally is formed by packing a graphite mold with tungsten carbide powder and then infiltrating the powder with a molten copper-based alloy binder. For example, macro-crystalline tungsten carbide and cast tungsten carbide have been used to fabricate the bit body. Macro-crystalline tungsten carbide is essentially stoichiometric WC which is, for the most part, in the form of single crystals. Some large crystals of macro-crystalline WC are bi-crystals. Cast tungsten carbide, on the other hand, is a eutectic two-phase carbide composed of WC and W
2
C. There can be a continuous range of compositions therebetween. Cast tungsten carbide typically is frozen from the molten state and comminuted to a desired particle size.
However, a bit body formed of the aforementioned tungsten carbide or other hard metal matrix materials may be brittle and may crack upon being subjected to impact and fatigue forces encountered during drilling. Additionally, the braze joints between the matrix material and the PDC cutters may crack due to these forces. The formation and propagation of cracks in the matrix body and at the braze joints may result in the loss of one or more PDC cutters. A lost cutter may abrade against the bit, causing further accelerated bit damage.
For the foregoing reasons, there is a need for a new matrix-body composition for drill bits which offers improved ability to retain cutters while maintaining other desired properties, such as toughness, impact strength and wear resistance.
SUMMARY OF THE INVENTION
In one aspect, the invention relates to a new composition for forming a matrix body which includes large-grain carburized tungsten carbide and an infiltration binder including one or more metals or alloys. In some embodiments, the new composition may include a Group VIIIB metal selected from one of Ni, Co, Fe, and alloys thereof. Moreover, it may further include cast tungsten carbide.
In another aspect, the invention relates to a high-strength matrix body manufactured by the method which includes: 1) providing a composition including large-grain carburized tungsten carbide; and 2) infiltrating the composition by an infiltration binder including one or more metals or alloys. In some embodiments, the composition may include a Group VIIIB metal selected from one of Ni, Co, Fe and alloys thereof. Moreover, the composition may further includes cast tungsten carbide. In some embodiments, the composition may include, before infiltration, the large-grain carburized tungsten carbide in an amount of about 62% by weight, the cast tungsten carbide in an amount of about 30% by weight, and Ni in an amount of about 8% by weight. In other embodiments, the large-grain carburized tungsten carbide has an average particle size exceeding approximately 10 &mgr;m before infiltration.
In one aspect, the invention relates to an earth-boring bit which includes 1) a body formed from a composition including large-grain carburized tungsten carbide and a Group VIIIB metal selected from one of Ni, Co, Fe, and alloys thereof, and 2) a cutter which is fixedly attached to the body. The body is formed by infiltrating the composition by an infiltration binder that includes one or more transition metals or alloys thereof. In some embodiments, the composition may further include cast tungsten carbide. In other embodiments, the composition includes, before infiltration, the large-grain carburized tungsten carbide in an amount of about 62% by weight, the cast tungsten carbide in an amount of about 30% by weight, and Ni in an amount of about 8% by weight. In some embodiments, the cutter may be formed of carbide or cemented tungsten carbide. In other embodiments, the cutter may include a polycrystalline diamond compact or a polycrystalline cubic boron nitride compact.
In another aspect, the invention relates to a polycrystalline diamond compact bit which includes 1) a body with a lower end having a face; 2) a plurality of pockets in the face of the body; and 3) a plurality of polycrystalline diamond cutters in the pockets. The body is formed from a composition by infiltrating the composition by an infiltration binder including one or more transition metals or alloys thereof The composition includes large-grain carburized tungsten carbide and a Group VIIIB metal selected from one of Ni, Co, Fe, and alloys thereof In some embodiments, the composition may further include cast tungsten carbide. In other embodiments, the composition includes, before infiltration, the large-grain carburized tungsten carbide in an amount of about 62% by weight, the cast tungsten carbide in an amount of about 30% by weight, and Ni in an amount of about 8% by weight.
In one aspect, the invention relates to an impregnated bit which includes 1) a bit body support; 2) a matrix body attached to the bit body support; and 3) a particle of superhard material bonded in the matrix body. The matrix body is formed from a composition by infiltrating the composition by an infiltration binder including one or more transition metals or alloys thereof. The composition includes large-grain carburized tungsten carbide and a Group VIIIB metal selected from one of Ni, Co, Fe, and alloys thereof.
In another aspect, the invention relates to a method of making a high-strength matrix body. The method includes 1) providing a composition including large-grain carburized tungsten carbide; and 2) infiltrating the composition by an infiltration binder including one or more metals or alloys thereof In some embodiments, the composition may include a Group VIIIB metal selected from one of Ni, Co, Fe, and alloys thereof. The composition may further include cast tungsten carbide. In other embodiments, the composition includes, before infiltration, the large-grain carburized tungsten carbide in an amount of about 62% by weight, the cast tungsten carbide in an amount of about 30% by weight, and Ni in an amount of about 8% by weight.
In one aspect, the invention relates to a method of making an earth-bor
Kembaiyan Kuttaripalayam T.
Oldham Thomas W.
Jenkins Daniel J.
Rosenthal & Osha L.L.P.
Smith International Inc.
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