Patent Grant
9279291
1. Field of the Invention
Embodiments disclosed herein relate generally to diamond enhanced inserts.
2. Background Art
An earth-boring drill bit is typically mounted on the lower end of a drill string and is rotated by rotating the drill string at the surface or by actuation of downhole motors or turbines, or by both methods. When weight is applied to the drill string, the rotating drill bit engages the earth formation and proceeds to form a borehole along a predetermined path toward a target zone.
There are several types of drill bits, including roller cone bits, hammer bits, and drag bits. The term “drag bits” (also referred to as “fixed cutter drill bits”) refers to those rotary drill bits with no moving elements. Fixed cutter bits include those having cutting elements attached to the bit body, which predominantly cut the formation by a shearing action. Cutting elements used on fixed cutter bits may include polycrystalline diamond compacts (PDCs), diamond grit impregnated inserts (“grit hot-pressed inserts” (GHIs), or natural diamond. Roller cone rock bits include a bit body adapted to be coupled to a rotatable drill string and include at least one “cone” that is rotatably mounted to a cantilevered shaft or journal as frequently referred to in the art. Each roller cone in turn supports a plurality of cutting elements that cut and/or crush the wall or floor of the borehole and thus advance the bit. The cutting elements, either inserts or milled teeth, contact with the formation during drilling to crush, gouge, and scrape rock at the bottom of a hole being drilled. Hammer bits are typically include a one piece body with having crown. The crown includes inserts pressed therein for being cyclically “hammered” and rotated against the earth formation being drilled.
Depending on the type and location of the cutting elements on a drill bit, the cutting elements perform different cutting functions, and as a result, also experience different loading conditions during use. Two kinds of wear-resistant inserts have been developed for use as cutting elements on drill bits: tungsten carbide inserts (TCIs) and polycrystalline diamond enhanced inserts (DEIs). Tungsten carbide inserts are typically formed of cemented tungsten carbide (also known as sintered tungsten carbide): tungsten carbide particles dispersed in a cobalt binder matrix. A polycrystalline diamond enhanced insert typically includes a cemented tungsten carbide body as a substrate and a layer of polycrystalline diamond (“PCD”) directly bonded to the tungsten carbide substrate on the top portion of the insert. A working layer formed of a PCD material can provide improved wear resistance, as compared to the softer, tougher tungsten carbide inserts.
The layer(s) of PCD conventionally include diamond and a metal in an amount of up to about 30 percent by weight of the layer to facilitate diamond intercrystalline bonding and bonding of the layers to each other and to the underlying substrate. Metals employed in PCD are often selected from cobalt, iron, or nickel and/or mixtures or alloys thereof and can include metals such as manganese, tantalum, chromium and/or mixtures or alloys thereof. However, while higher metal content typically increases the toughness of the resulting PCD material, higher metal content also decreases the PCD material hardness, thus limiting the flexibility of being able to provide PCD coatings having desired levels of both hardness and toughness. Additionally, when variables are selected to increase the hardness of the PCD material, typically brittleness also increases, thereby reducing the toughness of the PCD material.
Although the polycrystalline diamond layer is extremely hard and wear resistant, a polycrystalline diamond enhanced insert may still fail during normal operation. Failure typically takes one of three common forms, namely wear, fatigue, and impact cracking. The wear mechanism occurs due to the relative sliding of the PCD relative to the earth formation, and its prominence as a failure mode is related to the abrasiveness of the formation, as well as other factors such as formation hardness or strength, and the amount of relative sliding involved during contact with the formation. Excessively high contact stresses and high temperatures, along with a very hostile downhole environment, also tend to cause severe wear to the diamond layer. The fatigue mechanism involves the progressive propagation of a surface crack, initiated on the PCD layer, into the material below the PCD layer until the crack length is sufficient for spalling or chipping. Lastly, the impact mechanism involves the sudden propagation of a surface crack or internal flaw initiated on the PCD layer, into the material below the PCD layer until the crack length is sufficient for spalling, chipping, or catastrophic failure of the enhanced insert.
External loads due to contact tend to cause failures such as fracture, spalling, and chipping of the diamond layer. Internal stresses, for example thermal residual stresses resulting from the manufacturing process, tend to cause delamination between the diamond layer and the substrate or the transition layer, either by cracks initiating along the interface and propagating outward, or by cracks initiating in the diamond layer surface and propagating catastrophically along the interface.
The primary approach used to address the delamination problem in convex cutting elements is the addition of transition layers made of materials with thermal and elastic properties located between the ultrahard material layer and the substrate, applied over the entire substrate protrusion surface. These transition layers have the effect of reducing the residual stresses at the interface and thus improving the resistance of the inserts to delamination.
Transition layers have significantly reduced the magnitude of detrimental residual stresses and correspondingly increased durability of inserts in application. Nevertheless, basic failure modes still remain. These failure modes involve complex combinations of three mechanisms, including wear of the PCD, surface initiated fatigue crack growth, and impact-initiated failure.
It is, therefore, desirable that an insert structure be constructed that provides desired PCD properties of hardness and wear resistance with improved properties of fracture toughness and chipping resistance, as compared to conventional PCD materials and insert structures, for use in aggressive cutting and/or drilling applications.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
In one aspect, embodiments disclosed herein relate to an insert for a drill bit that includes a substrate; a working layer of polycrystalline diamond material on the uppermost end of the insert, wherein the polycrystalline diamond material includes a plurality of interconnected diamond grains; and a binder material; and an inner transition layer between the working layer and the substrate, wherein the inner transition layer is adjacent to the substrate; wherein the inner transition layer has a hardness that is at least 500 HV greater than the hardness of the substrate.
In another aspect, embodiments disclosed herein relate to a-n insert for a drill bit that includes a substrate; a working layer of polycrystalline diamond material on the uppermost end of the insert, wherein the polycrystalline diamond material includes: a plurality of interconnected diamond grains; and a binder material; and an outer transition layer between the working layer and the substrate, wherein the outer transition layer is adjacent to the working layer; wherein the working layer has a hardness greater than or equal to 4000 HV; and wherein the outer transition layer has a hardness that is less than the working layer hardness by less than 1500 HV.
In yet another aspect, embodiments disclosed herein relate to an insert for a drill bit that includes a substrate; a working layer of polycrystalline diamond material on the uppermost end of the insert, wherein the polycrystalline diamond material includes: a plurality of interconnected diamond grains; and a binder material; and an outer transition layer between the working layer and the substrate, wherein the outer transition layer is adjacent to the working layer; wherein the outer transition layer has a hardness that is less than the working layer hardness by less than 35%.
In another aspect, embodiments disclosed herein relate to a drill bit that includes a bit body and at least one insert that includes a substrate; a working layer of polycrystalline diamond material on the uppermost end of the insert, wherein the polycrystalline diamond material includes a plurality of interconnected diamond grains; and a binder material; and an inner transition layer between the working layer and the substrate, wherein the inner transition layer is adjacent to the substrate; wherein the inner transition layer has a hardness that is at least 500 HV greater than the hardness of the substrate.
In another aspect, embodiments disclosed herein relate to a drill bit that includes a bit body and at least one insert that includes a substrate; a working layer of polycrystalline diamond material on the uppermost end of the insert, wherein the polycrystalline diamond material includes: a plurality of interconnected diamond grains; and a binder material; and an outer transition layer between the working layer and the substrate, wherein the outer transition layer is adjacent to the working layer; wherein the working layer has a hardness greater than or equal to 4000 HV; and wherein the outer transition layer has a hardness that is less than the working layer hardness by less than 1500 HV.
In yet another aspect, embodiments disclosed herein relate to a drill bit that includes a bit body and at least one insert that includes a substrate; a working layer of polycrystalline diamond material on the uppermost end of the insert, wherein the polycrystalline diamond material includes: a plurality of interconnected diamond grains; and a binder material; and an outer transition layer between the working layer and the substrate, wherein the outer transition layer is adjacent to the working layer; wherein the outer transition layer has a hardness that is less than the working layer hardness by less than 35%.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
Embodiments of the present disclosure are described with reference to the following figures.
Embodiments disclosed herein relate generally to diamond enhanced inserts having increased impact resistance. In particular, inserts of the present disclosure may have a substrate, a working layer of polycrystalline diamond (“PCD”) material forming the working surface of the insert, and at least one transition layer there between. The mechanical properties of the at least one transition layer are optimized to improve both impact resistance as well as improved static load carrying capability. According to embodiments disclosed herein, the hardness of the at least one transition layer may be engineered according to the hardness properties of the working layer and/or the substrate.
For example, referring to
PCD Working Layer
As used herein, “polycrystalline diamond” or “PCD” refers to a plurality of interconnected diamond crystals having interstitial spaces there between in which a metal component (such as a metal catalyst) may reside. The interconnected diamond crystal structure of PCD includes direct diamond-to-diamond bonding, and may often be referred to as forming a lattice or matrix structure. Particularly, a metal catalyst material, such as cobalt, may be used to promote re-crystallization of the diamond crystals, wherein the diamond grains are regrown together to form the lattice structure, thus leaving particles of the remaining metal catalyst within the interstitial spaces of the diamond lattice.
Diamond grains useful for forming PCD material of the present disclosure may include synthetic and/or natural diamond grains having an average grain size ranging from submicrometer to 100 microns according to some embodiments, and ranging from about 1 to 80 microns in other embodiments. In other embodiments, the average diamond grain size used to form the polycrystalline diamond working layer may broadly range from about 2 to 30 microns in one embodiment, less than about 20 microns in another embodiment, and less than about 15 microns in yet another embodiment. It is also contemplated that other particular narrow ranges may be selected within the broad range, depending on the particular application and desired properties of the layer. The diamond grains may have a mono- or multi-modal size distribution.
PCD material may be formed using a high pressure/high temperature (“HPHT”) process, wherein the diamond grains are sintered together in the presence of a metal catalyst material, such as one or more elements from Group VIII of the Periodic table. HPHT processing is known in the art, and may use pressures of greater than 5,000 MPa and temperatures ranging from 1,300° C. to 1,500° C., for example. Examples of HPHT processes can be found, for example, in U.S. Pat. Nos. 4,694,918; 5,370,195; and 4,525,178. Briefly to form the PCD material, an unsintered mass of diamond crystalline particles and a metal catalyst is placed within a metal enclosure of the reaction cell of a HPHT apparatus. The reaction cell is then placed under processing conditions sufficient to cause intercrystalline bonding between the diamond particles. Alternatively, a catalyst may be provided by infiltration during HPHT processing from the insert substrate or an adjacent transition layer, for example.
In particular, diamond to diamond bonding is catalyzed by the metal catalyst material, whereby the metal remains in the interstitial regions between the bonded together diamond particles. Thus, the metal particles added to the diamond grains may function as a catalyst and/or binder, depending on the exposure to diamond particles that can be catalyzed as well as the temperature and pressure conditions. For the purposes of this application, when the metallic component is referred to as a metal binder, it does not necessarily mean that no catalyzing function is also being performed, and when the metallic component is referred to as a metal catalyst, it does not necessarily mean that no binding function is also being performed.
PCD material of the present disclosure may be designed to have a desired hardness by, for example, by changing the relative amounts of diamond grains and binder material and/or by changing the diamond grain sizes, the ratio of the binder metal and carbide particles content, and the relative dispersion between secondary phases (including both binder metal and carbide particles) and diamond particles. For example, PCD material may have at least about 80 percent by volume diamond, with the remaining balance of the interstitial regions between the diamond grains occupied by the binder material. In other embodiments, such diamond content may comprise at least 85 percent by volume of the formed PCD material, and at least 90 percent by volume in yet another embodiment. Further, PCD material may have higher diamond densities, such as 95 percent by volume or greater, which is frequently referred to in the art as “high density” PCD. Generally, PCD may have a hardness in the range of about 3,000 HV to 4,000 HV, or greater. PCD having a composition of relatively higher amounts of binder material may have a hardness within the lower part of the range, while PCD having a composition of relatively higher diamond densities may have a hardness within the upper part of the range. Additionally, the hardness of the PCD material may be varied by changing the average diamond grain size. For example, PCD material having an average diamond grain size of greater than 10 microns (often referred to as a “coarse” grain size) may have a relatively higher hardness than a PCD material having a smaller average grain size. However, various combinations of diamond content and grain size may be used to design PCD material having various hardness values.
Insert Transition Layer(s)
As discussed above, the inserts of the present disclosure may have at least one transition layer. The at least one transition layer may include composites of diamond grains, a metal binder, and metal carbide or carbonitride particles, such as carbide or carbonitride particles of tungsten, tantalum, titanium, chromium, molybdenum, vanadium, niobium, hafnium, zirconium, or mixtures thereof. The relative amounts of diamond and metal carbide or carbonitride particles may indicate the extent of diamond-to-diamond bonding within the layer. Further, each of the relative amounts of diamond, metal carbide or carbonitride particles, and binder material, the grain sizes of the diamond and metal carbide or carbonitride material, and the type of metal carbide or carbonitride particles may indicate the hardness of the transition layer. For example, the at least one transition layer may have a lesser amount of diamond content than the working layer of an insert to form a decreasing, non-continuous gradient of diamond between the working layer and the substrate, and may have an increasing amount of carbide/carbonitride content from the working layer to the substrate to form an increasing, non-continuous gradient of carbide/carbonitride between the working layer and the substrate. Transition layers having a relatively higher diamond and/or carbide content and relatively lower binder content may have a higher hardness than transition layers having relatively lower diamond and/or carbide content and relatively higher binder content.
In addition to or alternative to the use of altering diamond and/or carbide content in the at least one transition layer to engineer the transition layer hardness, diamond grain size and/or carbide grain size may be altered to design a transition layer with a desired hardness. For example, as mentioned above, larger sized diamond grains may be used to form a transition layer with improved hardness. For example, a diamond mix containing 37 wt % 17 micron diamond grains would have similar hardness (˜3200 HV) as a diamond mix containing 42 wt % 6 micron diamond grains. However, one skilled in the art may appreciate that many material design criteria must be considered when forming a composite material having a desired hardness. Thus, while some general trends relating material content to the material hardness have been mentioned, various combinations of material design may be used to design a composite material (such as used to form the at least one transition layer) having a desired hardness.
Insert Substrate
The substrate of inserts according to the present disclosure may be made of a metallic carbide material, such as a cemented or sintered carbide of one of the Group IVB, VB, and VIB metals, e.g., tungsten carbide, tantalum carbide, or titanium carbide, which are generally pressed or sintered in the presence of a binder, such as cobalt, nickel, iron, alloys thereof, or mixtures thereof. Particularly, the metal carbide grains are supported within the metallic binder matrix. Such metal carbide composites are often referred to as cermets. A typical insert substrate may be made of a tungsten carbide cobalt composite. However, it is well known that various metal carbide compositions and binders may be used, in addition to tungsten carbide and cobalt. Thus, references to the use of tungsten carbide and cobalt are for illustrative purposes only, and no limitation on the type of substrate or binder used is intended.
Optimized Hardness Properties
Transition layers between a diamond working layer and a carbide substrate have often been used to form diamond enhanced inserts for drill bits. Typically, such transition layers are made of diamond and carbide mixtures to create a compositional gradient between the working layer and the carbide substrate. However, manufacturing inserts having multiple composite transition layers to form compositional gradients is often difficult. Further, while the use of transition layers may improve the fracture resistance and survivability of such inserts during drilling, the mere concept of transition layers does not necessarily guarantee a performance improvement in the inserts. Rather, the use of composite transition layers may reduce insert life if the transition layer composition is not properly engineered. However, inventors of the present disclosure have found a way to improve the performance of multi-layer diamond enhanced inserts through consideration of the load carrying capability of a system of successive layers and by controlling the hardness properties of each layer. By optimizing the mechanical properties of such multi-layered diamond enhanced inserts, particularly the relative hardness of the transition layers with respect to the diamond working layer and/or to the substrate, the transition layer(s) may provide significant support to the working layer and improve the survivability rate of the insert during drilling. Additionally, by forming inserts according to the optimization principles of the present disclosure, the implementation of transition layer(s) may be achieved without over-engineering. For example, some prior art diamond enhanced inserts may have multiple transition layers such that a substantially continuously changing transition is formed between the working surface and the substrate of the insert. However, such inserts may be difficult to manufacture correctly, as well as more expensive to produce.
According to embodiments of the present disclosure, an insert for a drill bit may be formed having a substrate, a working layer of polycrystalline diamond material on the uppermost end of the insert, and at least one transition layer between the substrate and the working layer, wherein the hardness of the at least one transition layer is optimized based on the hardness of the substrate and/or the working layer. For example, referring to
According to embodiments of the present disclosure, an inner transition layer may be engineered to have a hardness value based on the hardness of an adjacent substrate. For example, an inner transition layer may be designed to have a hardness that is at least 500 HV greater than the hardness of an adjacent substrate and that does not exceed the hardness of the adjacent substrate by more than 1500 HV. According to some preferred embodiments, an inner transition layer may have a hardness that is at least 750 HV greater than the hardness of an adjacent substrate and that does not exceed the hardness of the adjacent substrate by more than 1500 HV.
Further, transition layers of the present disclosure may be designed to have a hardness value in the range of 1,900 HV to 3,400 HV. According to some embodiments, a transition layer may be designed to have a hardness value in the range of 2,000 HV to 2,500 HV, while other transition layers may be designed to have a greater hardness value. For example, according to some embodiments, a transition layer adjacent to a substrate may be designed to have a hardness value in the range of 2,000 HV to 2,500 HV, and a transition layer adjacent to an insert working surface may be designed to have a hardness value in the range of 2,500 HV to 3,000 HV.
Referring now to
As discussed above, an insert working layer may be formed of a PCD material, including a plurality of interconnected diamond grains and a binder material. Such working layers may be designed to have a hardness that is equal to or greater than 4,000 HV. However, according to alternative embodiments (described below), a working layer may be designed to have a hardness less than 4,000 HV. A transition layer may be formed of a composite material including a plurality of transition layer diamond grains, a plurality of metal carbide or carbonitride particles, and a transition layer binder material. As mentioned above, such transition layers may be designed to have a hardness ranging from about 1,900 HV to 3,200 HV, depending on the location of the transition layer and the hardness of the insert working layer and/or substrate. Further, a substrate may be made of a metal carbide composite. According to embodiments of the present disclosure, a carbide substrate may have a hardness less than or equal to about 1,600 HV
According to embodiments of the present disclosure, an outer transition layer may be engineered to have a hardness value based on the hardness of an adjacent PCD working layer. For example, referring to
Although the insert shown in
Furthermore, hardness optimization of transition layers in inserts of the present disclosure may be designed in terms of percentage of a working layer and/or substrate hardness. For example, an insert according to the present disclosure may have at least one transition layer that is designed to have a hardness based on the hardness of the working layer, wherein an outer transition layer has a hardness that is less than the working layer hardness by less than 35%, and preferably less than 30%. According to some embodiments, an insert may have a second transition layer between the outer transition layer and substrate, wherein the second transition layer is adjacent to the substrate. In such embodiments, the second transition layer may be designed to have a hardness that is between 30% and 80% greater than the hardness of the substrate. According to other embodiments, an insert may further include a third transition layer disposed between the outer transition layer and the second transition layer, wherein the third transition layer may be designed to have a hardness that is between 30% and 80% greater than the hardness of the substrate.
According to yet other embodiments, a diamond enhanced insert may have a working layer formed of PCD material having a hardness of less than 4,000 HV (and at least 3200 HV). In such embodiments, an adjacent outer transition layer may be designed to have a hardness that is less than the working layer, wherein the hardness difference between the working layer and the outer transition layer is less than 1,200 HV. According to some preferred embodiments, an insert having a working layer with a hardness of less than 4,000 HV may have an adjacent outer transition layer with a hardness less than the working layer, wherein the hardness difference between the working layer and the outer transition layer is less than 1,000 HV (and at least 300 HV in some embodiments).
As discussed above, the inventors of the present disclosure have found that by optimizing the hardness difference between adjacent layers of a diamond enhanced insert, the insert may have improved impact resistance when compared to prior art inserts. For example, referring to
Inserts of the present disclosure may be used with downhole drill bits, such as roller cone drill bits or percussion or hammer drill bits. For example, referring to
The inventors of the present disclosure have advantageously found that when the hardness difference between the working layer and an adjacent transition layer of an insert is within an optimized range disclosed herein, the insert survived higher loading conditions compared to inserts having hardness differences outside the disclosed optimized ranges. For example, prior art inserts having a difference in hardness between the working layer and an adjacent transition layer that exceeded 1,500 HV failed due to chipping and interfacial cracking after certain fatigue loading conditions, whereas inserts engineered according to embodiments of the present disclosure did not fail under the same fatigue loading conditions. Other optimized hardness ranges disclosed herein have also been found to offer the working layer of an insert improved support while at the same time avoiding over-engineering or complex manufacturing processes.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 61/581,757, filed on Dec. 30, 2011, which is incorporated by reference herein in its entirety.
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