Patent Grant
RE48524
This invention relates to cutting elements such as those used in earth boring bits for drilling earth formations. More specifically, this invention relates to cutting elements incorporating a cutting surface having a cutting edge having a continuous varying radius.
A cutting element 1 (
Generally speaking, the process for making a cutting element employs a substrate of cemented tungsten carbide where the tungsten carbide particles are cemented together with cobalt. The carbide body is placed adjacent to a layer of ultra hard material particles such as diamond or cubic boron nitride (CBN) particles along with a binder, such as cobalt, within a refractory metal enclosure (commonly referred to as a “can”), as for example a niobium can, and the combination is subjected to a high temperature at a high pressure where diamond or CBN is thermodynamically stable. This is known as a sintering process. The sintering process results in the re-crystallization and formation of a PCD or PCBN ultra hard material layer on the cemented tungsten carbide substrate, i.e., it results in the formation of a cutting element having a cemented tungsten carbide substrate and an ultra hard material cutting layer. The ultra hard material layer may include tungsten carbide particles and/or small amounts of cobalt. Cobalt promotes the formation of PCD or PCBN. Cobalt may also infiltrate the diamond or CBN from the cemented tungsten carbide substrate.
A TSP is typically formed by “leaching” the cobalt from the diamond lattice structure of PCD. When formed, PCD comprises individual diamond crystals that are interconnected defining a lattice structure. Cobalt particles are often found within the interstitial spaces in the diamond lattice structure. Cobalt has a significantly different coefficient of thermal expansion as compared to diamond, and as such upon heating of the PCD, the cobalt expands, causing cracking to form in the lattice structure, resulting in the deterioration of the PCD layer. By removing, i.e., by leaching, the cobalt from the diamond lattice structure, the PCD layer becomes more heat resistant, i.e., more thermally stable. However, the polycrystalline diamond layer becomes more brittle. Accordingly, in certain cases, only a select portion, measured either in depth or width, of the PCD layer is leached in order to gain thermal stability without losing impact resistance. A TSP material may also be formed by forming PCD with a thermally compatible silicon carbide binder instead of cobalt.
The cemented tungsten carbide substrate is typically formed by placing tungsten carbide powder and a binder in a mold and then heating the binder to melting temperature causing the binder to melt and infiltrate the tungsten carbide particles fusing them together and cementing the substrate. Alternatively, the tungsten carbide powder may be cemented by the binder during the high temperature, high pressure sintering process used to re-crystallize the ultra hard material layer. In such case, the substrate material powder along with the binder are placed in the refractory metal enclosure. Ultra hard material particles are provided over the substrate material to form the ultra hard material polycrystalline layer. The entire assembly is then subjected to a high temperature, high pressure process forming the cutting element having a substrate and a polycrystalline ultra hard material layer over it.
In many instances the cutting edge of the cutting layer, which contacts the earth formation during drilling, such as edge 9, has sharp edges. These sharp edges may be defined by the intersection of the upper and circumferential surfaces defining the cutting layer or by chamfers formed on the cutting edge. These sharp edges create stress concentrations which may cause cracking and chipping of the cutting layer.
In an exemplary embodiment, a cutting element is provided having a substrate and an ultra hard material cutting layer over the substrate. The cutting layer includes a surface portion for making contact with a material to be cut by the cutting element. The surface portion in cross-section has a curvature that has a varying radius of curvature. In other words, the surface portion in cross-section has a continuous curvature that is formed by a plurality of sections, each section having a different radius of curvature than its adjacent section. In another exemplary embodiment, a cutting element is provided having a substrate and an ultra hard material cutting layer over the substrate. The cutting layer includes a surface portion for making contact with a material to be cut by the cutting element. The surface portion in cross-section has a varying curvature that is formed by a plurality of adjacent non-flat sections, each section having a different radius of curvature than its adjacent section. In a further exemplary embodiment, the surface portion in cross-section includes at least two sections. In another exemplary embodiment, all sections curve in the same direction in cross-section. In yet another exemplary embodiment, one section curves in a first direction and another section curves in a second direction opposite the first direction. In yet a further exemplary embodiment, the surface portion in cross-section defines a chamfer. The chamfer may be formed from a plurality of the surface sections. In another exemplary embodiment, the surface portion in cross-section defines a two chamfers. Each of the two chamfers may be formed from a plurality of the surface sections. In one exemplary embodiment, the surface portion extends from a peripheral surface of the cutting layer. In another exemplary embodiment, the surface portion in cross-section includes at least three sections.
In a further exemplary embodiment, the surface portion includes in cross-section a first section adjacent to a second section which is adjacent a third section. With this exemplary embodiment, the first section has a first radius of curvature, the second section has a second radius of curvature, the third section has a third radius of curvature, such that the second radius of curvature is greater than the first radius of curvature, and the third radius of curvature is greater than the first radius of curvature. In another exemplary embodiment, the surface portion includes in cross-section a first section, a first transitional section extending from and adjacent to the first section, a second section extending from and adjacent to the first transitional section, a second transitional section extending from and adjacent to the second section, and a third section extending from and adjacent to the second transitional section. With this exemplary embodiment, the first section has a first radius of curvature, the second section has a second radius of curvature, the third section has a third radius of curvature, such that the second radius of curvature is greater than the first radius of curvature, and the third radius of curvature is greater than the first radius of curvature. In yet another exemplary embodiment, the cutting layer includes a first surface interfacing with the substrate and a second surface opposite the first surface. With this exemplary embodiment, the first section extends from the second surface. In yet a further exemplary embodiment, the cutting layer includes a first surface interfacing with the substrate, a second surface opposite the first surface, and a peripheral surface between the first and second surfaces. With this exemplary embodiment, the third section extends from the peripheral surface.
In yet another exemplary embodiment, the surface portion in cross-section includes at least 35 sections. In yet a further exemplary embodiment, the cutting layer includes a plurality of spaced apart surface portions, each surface portion in cross-section having a continuous curvature that is formed by a plurality of non-flat sections, and each section of each surface portion has a different radius of curvature than its adjacent section.
In another exemplary embodiment, a cutting element is provided having a substrate and an ultra hard material cutting layer over the substrate. The cutting layer has a surface portion for making contact with a material to be cut by the cutting element. The surface portion in cross-section has a first chamfer formed by a plurality of first sections where each first section has a different radius of curvature than its adjacent first section. In another exemplary embodiment, the surface portion for making contact further includes in cross-section a second chamfer extending relative to the first chamfer. In an exemplary embodiment, the second chamfer in cross-section is formed by a plurality of second sections, each second section having a different radius of curvature that its adjacent second section. In yet another exemplary embodiment, the surface portion for making contact further includes in cross-section a curved section adjacent to and between the two chamfers. In a further exemplary embodiment, the surface portion for making contact further includes in cross-section a third chamfer extending relative to the second chamfer. The third chamfer is formed by a plurality of third sections and each third section has a different radius of curvature that its adjacent third section. In yet a further exemplary embodiment, all of the first sections are not flat. In another exemplary embodiment, the cutting layer includes a plurality of spaced apart surface portions, each surface portion in cross-section having a first chamfer formed by a plurality of first sections, each first section having a different radius of curvature than its adjacent first section.
In yet a further exemplary embodiment a bit is provided having a body and any of the aforementioned exemplary embodiment cutting element mounted on such body.
FIGS. 14A, 14B, and 14C are perspective and cross-sectional views of an ultra hard top layer having a varied geometry chamfer circumferentially around the cutting edge of the working surface of the ultra hard layer wherein the size of the chamfer is varied circumferentially around the cutting edge according to one embodiment;
FIG. 15 is a graph showing the average chamfer size as varied with different cutting depths for a cutter having varied chamfer as compared to a cutter having fixed geometry chamfer,
FIG. 16 shows an ultra hard layer according to one or more embodiments.
FIG. 17 shows a cutter according to one or more embodiments.
Applicants have discovered that they can do away with the problems of existing cutting surfaces in a cutting element cutting layer by forming the cutting surface portion of the cutting layer to have a continuously varying radius as viewed in cross-section. The term “cutting surface” as used herein in relation to a cutting layer, refers to the surface portion of the cutting layer that makes contact with the material to be cut, as for example the earth formation, during cutting or drilling. “Cross-section” as used herein refers to the cross-section defined by a plane along the central longitudinal axis of the cutting element. Moreover. the inventive cutting surface geometries as described herein are formed as part of the manufacturing process of the cutting elements.
In one exemplary embodiment, as for example shown in
In another exemplary embodiment, as shown in
In another exemplary embodiment as shown in
In other exemplary embodiments, each chamfer, as for example chamfer 26, chamfer 32 or chamfer 34 may be formed in cross-section from one or more curved sections abutting each other. In further exemplary embodiments, the cutting surface may have three or more chamfers where each chamfer is formed in cross-section from one or more abutting curving sections.
By forming the cutting surface to have a single chamfer, a double chamfer or other multiple chamfers and by forming the cutting surface from multiple sections each having a different radius of curvature as viewed in cross-section, the cutting layer has all the advantages of a cutting layer incorporating a chamfered edge as for example described in Provisional Application No. 60/566,751 on Apr. 30, 2004 and being assigned to Smith International, Inc., as well as in the ordinary application having Ser. No. 11/117,648 and filed on Apr. 28, 2005, which claims priority on Provisional Application No. 60/566,751. The advantages of chamfered edges are also disclosed in U.S. Pat. No. 5,437,343 issued on Aug. 1, 1995. The contents of these provisional applications, ordinary applications and patent are fully incorporated herein by reference. Thus, embodiments may also include cutters having shaped working surfaces with a varied geometry chamfer. Referring now to FIG. 14A, FIG. 14A shows an ultra hard top layer for a cutter that has a shaped working surface 112 including a varied geometry chamfer 114 circumferentially around the cutting edge 116. The bevel 114 is varied in size circumferentially around the cutting edge 116 according to one embodiment. The change in the size or the width of the bevel is demonstrated in the elevation section views of FIGS. 14B and 14C taken along section lines B-B and C-C of FIG. 14A, respectively. In this embodiment, the width 118 in FIG. 10B is smaller than the width 120 in FIG. 14C. The angle 122 of the bevel at section B-B, FIG, 14B, is the same as angle 124 at section line C-C, FIG. 14C; however, in other embodiments, the angle of the bevel is varied circumferentially around the cutting edge. It will be understood that a varied geometry of a bevel could also be provided as a combination of varied size and varied angle. Additionally, in one or more embodiments, the bevel is formed so that its size increases away from the area of the cutter surface engaged with the geological formation. For example, referring to FIG. 15, the amount of the variable size bevel in contact with the formation increases with the depth of cut. Thus, when the cutter digs into the formation, a greater portion of the cutting edge has a larger bevel to give more protection against chipping and spalling.
FIG. 16 shows another embodiment of an ultra hard top layer 140 for a cutter with a shaped working surface 142 and having a varied geometry chamfer 144 circumferentially around a cutting edge 146 at the intersection of the shaped working surface 142 and a side surface 148. The shaped working surface 142 includes one or more depressions 150a 150b, and 150c extending radially outwardly to the cutting edge 146. While three depressions 150a-c are depicted uniformly spaced around the shaped working surface 142, fewer or a greater number with uniform or non-uniform spacing may be formed without departing from certain aspects of the disclosure. For example, one or more depressions 150a-c can be formed as one or more planar surfaces or facets in a face 154.
Depending upon the embodiment, the face 154 may be a planar shaped surface, a dome shaped surface or a surface having another shape. The depressions 150a-c in this embodiment comprise planar surfaces or facets each at an obtuse angle relative to a central axis 152 of the cylindrical ultra hard top layer. The obtuse angle is different from the angle of other portions of the working surface, such that a relative depressed area defining the depressions 150a-c is formed the face 154. Where the surrounding portions of the face 154 are planar and at a 90-degree angle with respect to the axis of the cutter, the obtuse angle is generally greater than 90 degrees with respect to the axis 152 of the cutter. However, according to alternative embodiments of the invention, the obtuse angle may be less than 90 degrees. It will also be understood that in other alternative embodiments, each of the depressions 150a-c can be multi-faceted or comprised of multiple planar surfaces. Alternatively, the depressions 150a-c can also be formed with simple curved surfaces that may be concave or convex or can be formed with a plurality of curved surfaces or with a smooth complex curve.
The depressions 150a-c may be formed and shaped during the initial compaction of the ultra hard layer 140 or can be shaped after the ultra hard layer is formed, for example by Electro Discharge Machining (EDM) or by Electro Discharge Grinding (EDG). The ultra hard layer 140 may, for example, be formed as a polycrystalline diamond compact or a polycrystalline cubic boron nitride compact. Also, in selected embodiments, the ultra-hard layer may comprise a “thermally stable” layer. One type of thermally stable layer that may be used in embodiments may be a TSP element or partially or fully leached polycrystalline diamond. The depressions 150a-c extend generally at an angle relative to the face 154 outward to the edge of the cutter. It has been found that a varied chamfer 144 can be conveniently made with a fixed angle and fixed depth EDM or EDG device. For example, an EDM device will typically cut deepest into the edge 146 where the raise areas of face 154 extend to the edge 146 and will cut less deep where the depressions 150a-c extend to the edge 146. The chamfer 144 is cut the least at the lowest edge point in each depression 150a-c and progressively deeper on either side of the lowest edge point. A varied width or size chamfer is conveniently formed circumferentially around the edge 146 of the ultra hard cutter layer 140. Alternatively, variable or programmable angle and depth EDM or EGM can be used to form the variable geometry chamfer. FIG. 17 shows a three-dimensional model of a cutter 160 having an ultra hard layer 162 with a shaped working surface 164. The ultra hard layer 162 is bonded to a substrate 166 at a non-planar interface 168 according to one embodiment of the invention.
The exemplary continuously curving cutting surface may be formed on a cutting layer beginning at the substrate interface surface 12 and extending to an upper surface 42 of the cutting layer 18. In the embodiment shown in
In an exemplary embodiment, the cutting surface may be defined in cross-section by at least two curvature sections. In another exemplary embodiment, the cutting surface may be defined by thirty-five curvature sections 22 (
In another exemplary embodiment, the cutting surface may be defined in cross-section by sections, each section having a length in cross-section as measured along the surface that is in the range of about 0.003 to 0.005 inch in length. In a further exemplary embodiment, the cutting surface is defined by four sections. In yet a further exemplary embodiments the cutting layers on which the exemplary embodiment cutting surfaces are formed have a diameter in the range of 13 mm to 19 mm.
Some of the advantages provided by the exemplary embodiment cutting elements of the present invention become more evident by comparing the inventive cutting elements to the prior art cutting elements. For example, compared to a 45° straight or flat chamfered surface 50 formed on a cutting layer 51 of the prior art, a chamfered surface 52 formed on cutting layer 54 with varying radius curvature according to an exemplary embodiment of the present invention has increased toughness at location 56 making contact with the earth formation, in comparison with the sharp edge 58 of cutting surface 50 that would make contact with the earth formation (
A varying radius cutting surface is also more efficient in cutting than a single radius cutting surface. As shown in
A varying radius chamfer cutting surface can be configured to have a more efficient back rake angle in the chamfer area than a straight chamfer cutting surface. This is even so in cases where the straight chamfer surface interfaces with another surface of the cutting layer via a constant radius surface. This is evident from
An exemplary embodiment cutting surface of the present invention is shown in
In another exemplary embodiment, the cutting layer may have one or more chamfers in cross-section and at least a variable radius curvature section in cross-section. With this exemplary embodiment, an edge that would otherwise be formed on the cutting surface in cross-section between two chamfers or between a chamfer and a surface of the cutting layer is replaced by a variable radius section in cross-section. For example in the exemplary embodiment disclosed in
The exemplary embodiment cutting surfaces may span the entire span of the cutting surface. In another exemplary embodiment, the exemplary embodiment cutting surface 20 may span around only a portion 102 of the cutting layer 18 as for example shown in
In other exemplary embodiments, the cutting layer is formed having two sections 104, 106 of the cutting layer including an exemplary embodiment cutting surface. These sections may be opposite each other, for example shown in
The exemplary embodiment cutting surfaces may be formed using known methods such as electrode discharge machining (EDM) after forming the cutting element using sintering. In other words, EDM is used to cut the cutting surface so as to leave the appropriate varying radius curvature. In other exemplary embodiments, the can in which the cutting element is sintered is defined such that after sintering, the cutting layer has the desired cutting surface shape in cross-section having the desired varying radius curvature. In some instances, minor machining of the cutting surface may be required.
With the exemplary embodiments cutting elements, the cutting surface may be optimized for the type of cutting or drilling at hand by varying the variable radius curvature in cross-section of the various sections. In other exemplary embodiments, a section defining the varying radius curvature in cross-section may have a curvature opposite its adjacent section. For example, a section may be concave in cross-section while its adjacent section may be convex in cross-section. In other exemplary embodiments, the entire outer surface of the cutting layer may have a varying radius curvature and no sharp edges. By forming cutting layer cutting surfaces to have continuous varying radius of curvature, such cutting layers are susceptible to less edge chipping and wear and have increased wear toughness.
Although the present invention has been described and illustrated to respect to multiple exemplary embodiments thereof, it is to be understood that it is not to be so limited, since changes and modifications may be made therein which are within the full intended scope of this invention as hereinafter claimed.
This application is a continuation of U.S. application Ser. No. 11/638,934, filed Dec. 13, 2006, which is based upon and claims priority to U.S. Provisional Application No. 60/750,457 filed on Dec. 14, 2005, the contents of which are fully incorporated herein by reference.
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| Child | 13958445 | US |
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