WO2017095714A1

WO2017095714A1 - Scoop shaped diamond table on non-planar cutting elements

Info

Publication number: WO2017095714A1
Application number: PCT/US2016/063707
Authority: WO
Inventors: Huimin SONG; Xiaoge Gan; Zhijun Lin; Ke Chen
Original assignee: Smith International, Inc.
Priority date: 2015-11-30
Filing date: 2016-11-24
Publication date: 2017-06-08
Also published as: CN108291428A; CN118292768A

Abstract

A cutting element may include a substrate; and an ultrahard layer on the substrate, the substrate and the ultrahard layer defining a non-planar working surface of the cutting element such that the ultrahard layer forms a cutting portion and the substrate is at least laterally adjacent to the ultrahard layer.

Description

SCOOP SHAPED DIAMOND TABLE ON NON-PLANAR CUTTING ELEMENTS

BACKGROUND

There are several types of downhole cutting tools, such as drill bits, including roller cone bits, hammer bits, and drag bits, reamers and milling tools. 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. 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. Hammer bits generally include a one piece body having a crown. The crown includes inserts pressed therein for being cyclically "hammered" and rotated against the earth formation being drilled.

Drag bits, often referred to as "fixed cutter drill bits," include bits that have cutting elements attached to the bit body, which may be a steel bit body or a matrix bit body formed from a matrix material such as tungsten carbide surrounded by a binder material. Drag bits may generally be defined as bits that have no moving parts. However, there are different types and methods of forming drag bits that are known in the art. For example, drag bits having abrasive material, such as diamond, impregnated into the surface of the material which forms the bit body are commonly referred to as "impreg" bits. Drag bits having cutting elements made of an ultra hard cutting surface layer or "table" (generally made of poly crystalline diamond material or polycrystalline boron nitride material) deposited onto or otherwise bonded to a substrate are known in the art as polycrystalline diamond compact ("PDC") bits.

SUMMARY

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 a cutting element that includes a substrate and an ultrahard layer on the substrate, where the substrate and the ultrahard layer defining a non-planar working surface of the cutting element such that the ultrahard layer forms a cutting portion and the substrate is at least laterally adjacent to the ultrahard layer.

In another aspect, embodiments disclosed herein relate to a cutting tool that includes a tool body; a plurality of blades extending from the tool body; and at least one cutting element attached to one of the plurality of blades. The cutting element includes a substrate; and an ultrahard layer on the substrate, the substrate and the ultrahard layer defining a non-planar working surface of the cutting element such that the ultrahard layer forms a cutting portion and the substrate is at least laterally adjacent to the ultrahard layer.

In yet another aspect, embodiments disclosed herein relate to a cutting tool that includes a tool body; a plurality of blades extending from the tool body; and at least one cutting element attached to one of the plurality of blades, the at least one cutting element having a non-planar working surface and including a substrate and an ultrahard layer, the non-planar working surface being defined by both the substrate and the ultrahard layer.

Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a fixed cutter drill bit.

FIG. 2 is a conventional cutter for fixed cutter drill bit.

FIG. 3 shows an embodiment of a cutting element having a non-planar working surface.

FIG. 4 shows the substrate of the cutting element of FIG. 3, according to an embodiment of the invention.

FIG. 5 shows a cross-sectional view of the cutting element of FIG. 3, according to an embodiment of the invention.

FIG. 6 shows a side view of the cutting element of FIG. 3, according to an embodiment of the invention.

FIG. 7 shows a top view of an embodiment of a cutting element having a non-planar working surface.

FIG. 8 shows a cross-sectional view of the cutting element of FIG. 7, according to an embodiment of the invention.

FIG. 9 the substrate of the cutting element of FIG. 7, according to an embodiment of the invention.

FIG. 10 shows an embodiment of a cutting element having a non-planar working surface.

FIG. 11 shows the substrate of the cutting element of FIG. 10, according to an embodiment of the invention. FIG. 12 shows a side view of the cutting element of FIG. 10, according to an embodiment of the invention.

FIG. 13 shows a side view of the cutting element of FIG. 10, according to an embodiment of the invention. FIG. 14 shows an embodiment of a cutting element having a non-planar working surface.

FIG. 15 shows the substrate of the cutting element of FIG. 14, according to an embodiment of the invention.

FIG. 16 shows a side view of the cutting element of FIG. 14, according to an embodiment of the invention. FIG. 17 shows a side view of the cutting element of FIG. 14, according to an embodiment of the invention.

FIG. 18 an embodiment of a cutting element having a non-planar working surface.

FIG. 19 shows the substrate of the cutting element of FIG. 18, according to an embodiment of the invention. FIG. 20 shows the substrate of the cutting element of FIG. 18, according to an embodiment of the invention.

FIG. 21 shows an embodiment of a cutting element having a non-planar working surface.

FIG. 22 shows the substrate of the cutting element of FIG. 21, according to an embodiment of the invention. FIG. 23 shows a side view of the cutting element of FIG. 21, according to an embodiment of the invention.

FIG. 24 shows a cross-sectional view of the cutting element of FIG. 21, according to an embodiment of the invention.

FIG. 25 shows an embodiment of a cutting element having a non-planar working surface. FIGS. 26-28 show views of the substrate of the cutting element of FIG. 25, according to an embodiment of the invention.

FIG. 29 shows an embodiment of a cutting element having a non-planar working surface.

FIG. 30 shows the substrate of the cutting element of FIG. 29, according to an embodiment of the invention. FIG. 31 shows a side view of the cutting element of FIG. 29, according to an embodiment of the invention.

FIG. 32 shows a cross-sectional view of the cutting element of FIG. 29, according to an embodiment of the invention. FIG. 33 shows a hole opener, according to an embodiment of the invention.

DETAILED DESCRIPTION

In one aspect, embodiments disclosed herein relate to cutting elements having non-planar working surfaces and to cutting tools having such cutting elements attached thereto. In particular, embodiments disclosed herein relate to a cutting element having a non-planar working surface formed of both substrate and diamond.

An example of a drag bit having a plurality of cutting elements with ultra hard working surfaces is shown in FIG. 1. The drill bit 100 includes a bit body 110 having a threaded upper pin end 111 and a cutting end 115. The cutting end 115 generally includes a plurality of ribs or blades 120 arranged about the rotational axis (also referred to as the longitudinal or central axis) of the drill bit and extending radially outward from the bit body 110. Cutting elements, or cutters, 150 are embedded in the blades 120 at predetermined angular orientations and radial locations relative to a working surface and with a desired back rake angle and side rake angle against a formation to be drilled.

FIG. 2 shows an example of a cutting element 150, wherein the cutting element 150 has a cylindrical cemented carbide substrate 152 having an end face or upper surface referred to herein as a substrate interface surface 154. An ultrahard material layer 156, also referred to as a cutting layer, has a top surface 157, also referred to as a working surface, a cutting edge 158 formed around the top surface, and a bottom surface, referred to herein as an ultrahard material layer interface surface 159. The ultrahard material layer 156 may be a polycrystalline diamond or polycrystalline cubic boron nitride layer. The ultrahard material layer interface surface 159 is bonded to the substrate interface surface 154 to form a planar interface between the substrate 152 and ultrahard material layer 156.

Referring to FIG. 3, FIG. 3 shows an embodiment of a cutting element. Cutting element 300 includes a substrate 302 and an ultrahard layer 304 on the substrate 302. Whereas a conventional PDC cutting element includes a ultrahard layer that covers the entirety of the upper surface of the substrate (such that the working surface of the cutting element is entirely ultrahard material), a cutting element of the present disclosure includes an ultrahard layer 304 that has a smaller cross- sectional area than the substrate 302 such that both substrate 302 and ultrahard layer 304 form the working surface 306 of the cutting element 300. Working surface 306 is non-planar. There is no limitation on the shape of the non-planar working surface 306. In the illustrated embodiment, non- planar working surface 306 is generally a parabolic cylinder having planar sides with a peak apex 308 extending from one side of the cutting element to the other and the working surface 306 decreasing in height extending laterally away from the apex 308 (such decreasing lateral portions of the working surface optionally being planar rather than being curved). However, the ultrahard layer 304 does not form the entire surface, but does form at least the cutting edge (at the intersection of the apex 308 and the peripheral edge 310 of the cutting element) and extends radially inward towards a central axis 301 of the cutting element 300. As shown in FIGS. 21-24 and discussed in further detail below, the ultrahard layer 304 does not have to extend the entire diameter of cutting element 300 or even extend as far as the central axis 301. Further, in the embodiment illustrated in FIG. 3, the ultrahard layer 304 is an elongated (longer than it is wide) segment that forms the apex 308 and defines the cutting edge, extending from the cutting edge on a first side of the cutting element to a second side. The substrate 302 extends along both lateral sides of the elongated segment. As a result, the peripheral edge 310 of the non-planar working surface 306 (formed at the intersection between the non-planar working surface 306 and the cylindrical side surface 312 of the cutting element) has at least one substrate portion and at least one ultrahard layer portion. The substrate portion extends away from the cutting edge formed of the ultrahard layer 304. In the illustrated embodiment, the peripheral edge 310 includes two substrate portions and two ultrahard layer portions.

To increase the surface area of the interface between ultrahard layer 304 and substrate 302, the elongated segment of ultrahard layer 304 may have varying dimensions along its length. For example, as shown in FIG. 3 (and FIG. 4, showing the substrate 302 without the ultrahard layer 304, in particular showing the interface surface 303 on which the ultrahard layer 304 is deposited), the ultrahard layer 304 as an elongated segment may be wider at its ends (adjacent cutting edge) than at a radially interior portion (such as, proximate the central axis 301) of the elongated segment. For example, as shown in FIG. 6 (a side view of the cutting element 300 of FIG. 3), the width w of the elongated segment, at its end, may range from about 60 to about 80 percent of the diameter of the cutting element. However, other ranges may be desired depending on the depth of cut for a particular drilling application to ensure diamond surface coverage. For a 16 mm cutter, such width may range from 0.400 to about 0.500 inches.

Additionally, as shown in FIG. 5 (showing a cross-sectional view of the cutting element 300 of FIG. 3), the ultrahard layer 304 as an elongated segment may also be thicker at its ends (adjacent cutting edge) than a radially interior portion (such as, proximate the central axis 301). In an embodiment, at its thinnest, ultrahard layer 304 may have a thickness tl ranging from about 0.030 to about 0.150 inches. However, depending on the cutting element size, this thickness may vary. Thus, for example, in one or more embodiments, the ultrahard layer 304 may have, at its thinnest, a thickness tl that ranges from about 4 to 40 percent of the cutting element outer diameter. Further, one skilled in the art would appreciate that this thickness may be for embodiments extending through the central axis 301, whereas the embodiment illustrated in FIGS. 21-24 with a discontinuous ultrahard layer has a minimum thickness of zero at the central axis. Further, the ultrahard layer 304 may have a thickness t2 measured from the cutting edge to the substrate 302 (measured at the cross-section along the line bisecting the angle formed between the working surface 306 and the side surface 312 of the cutting element 300) that ranges from about 0.120 to about 0.180 inches. In one or more embodiments, the thickness t2 may range from about 10 to 40% of the outer diameter of the cutting element.

In addition to having a non-planar working surface, the interface surface 303 between substrate 302 and ultrahard layer 304, shown in FIGS. 4 and 5, is also non-planar. Specifically, non-planar interface surface 303 may be formed from at least one groove 305 formed in upper surface of substrate 302. In one or more embodiments, the groove 305 may have an elongated (longer than it is wide) shape to receive an elongated segment of ultrahard layer 304. Further, along the length of the elongated groove 305 (shown in the cross-sectional view of FIG. 5), the substrate 302 may have a generally convex curvature, which may be generally parabolic (in the cross-section corresponding to the length of the groove) so that the ends of the elongated segment of ultrahard layer 302 are thicker than a radially inward portion. In one or more embodiments, the groove 305 may have a varying radius of curvature along its length, which may result in the varying width of the elongated segment of ultrahard layer 304. For example, as apparent in FIG. 5, groove 305 may have its smallest radius of curvature proximate the central axis 301 or mid-line (the cross-sectional plane bisecting the elongated curve and on which the central axis lies) and its largest radius of curvature at the intersection with (or proximate) the side surface 312. The ratio between the largest radius of curvature and the smallest radius of curvature may between 200:0.01 and 1:0.99 or between 200: 1 and 1:0.9 or may be less than 100: 1, 50: 1, 25: 1, 10: 1, 5: 1, or 3.5: 1 and/or at least 1.5: 1, 2: 1, or 2.5: 1.

Referring now to FIGS. 7-9, another embodiment of a cutting element is shown. As shown, cutting element 700 includes a substrate 702 and an ultrahard layer 704 on the substrate 702. The cutting element has a non-planar working surface 706 formed by both substrate 702 and ultrahard layer 704 such that the ultrahard layer 704 is an elongated segment, similar to that in FIG. 3. Like the above embodiment, the elongated segment of ultrahard layer 704 has a groove 705 with a varying radius of curvature along the length of the elongated segment to form a non-planar interface 703 between the substrate 702 and ultrahard layer 704. However, unlike the above embodiment where the smallest radius of curvature is proximate the central axis 701, the smallest radius of curvature along the elongated segment between the end(s) of the elongated segment and the central axis 701. Similarly, the thickness and width of the elongated segment of ultrahard layer 704 may vary in the same manner, i.e., having its maximum value(s) at the end(s) of the elongated segment, an intermediate value at the central axis, and its minimum value(s) between the central axis and the end(s) of the elongated segment. Additionally, in such embodiments, along the length of the elongated groove 705 (shown in the cross- sectional view of FIG. 8), the substrate 702 may have a generally convex curvature, with an optional convex portion at or adjacent the central axis 701. In one or more different embodiments, the smallest radius of curvature along the elongated segment may still lie between the end(s) of the elongated segment and the central axis 701; however, the thickness of the elongated segment of the ultrahard layer 704 may be at its minimum value at or proximate the central axis 701 rather than a point between the end and the central axis 701.

Referring now to FIGS. 10-13, another embodiment of a cutting element is shown. As shown, cutting element 1000 includes a substrate 1002 and an ultrahard layer 1004 on the substrate 1002. The cutting element has a non-planar working surface 1006 formed by both substrate 1002 and ultrahard layer 1004 such that the ultrahard layer 1004 is an elongated segment, similar to that in FIG. 3-9. While the above embodiments included a single groove to form a non-planar interface, the embodiment illustrated in FIGS. 10-13 include a plurality of grooves 1005 (two, in this embodiment) extending along the length of the elongated segment of ultrahard material 1004 to form a non-planar interface 1003. Grooves 1005 have a varying radius of curvature (varying from a maximum value adjacent the side surface 1012 to a minimum value at the mid-line proximate the central axis 1001). Further, grooves 1005 are substantially parallel to one another. An elongated peak or protrusion of substrate 1002 extends between the plurality of grooves 1005, also forming a portion of the interface surface 1003. Further, along the length of the elongated grooves 1005, the substrate 1002 may have a generally convex curvature so that the ends of the elongated segment of ultrahard layer 1002 are thicker than a radially inward portion.

Referring now to FIGS . 14-17, another embodiment of a cutting element is shown. As shown cutting element 1400 includes a substrate 1402 and an ultrahard layer 1404 on the substrate 1402. The cutting element has a non-planar working surface 1406 formed by both substrate 1402 and ultrahard layer 1404 such that the ultrahard layer 1404 is an elongated segment, similar to that in FIGS. 3-13. While the above embodiments show grooves that are aligned with the length of the elongated segment to form a non-planar interface, the embodiment illustrate in FIGS. 14-17 includes a first set of grooves 1411 aligned with the length of elongated segment and a second set of grooves 1413 not aligned with the length of elongated segment to form a non-planar interface 1403. In one or more embodiments, the first set of grooves 1411 and the second set of grooves may be substantially perpendicular to each other. Further, as illustrated, each set of grooves 1411, 1413 includes a plurality of parallel grooves (specifically two parallel grooves 1411 and three parallel grooves 1413). However, it is also intended that grooves 1411, 1413 in either direction may include one groove, rather than a plurality or set of grooves. Each of grooves 1411, 1413 has a varying radius of curvature along the length thereof. For grooves 1411, which extend along the length corresponding to the length of elongated segment, the radius of curvature is at its maximum value adjacent the side surface 1412, and decreases moving towards the mid-line (of the elongated segment) proximate the central axis 1401, but increases upon intersecting with groove 1413-1 that extends along the length of the mid-line. Grooves 1413 extend substantially perpendicular to grooves 1411. In the illustrated embodiment, groove 1413-1 extends within an interior portion of substrate 1402 (i.e., not intersecting side surface 1412) along the mid-line 1407 that bisects the length of grooves 1411 and extends through the central axis 1401. Additionally there are two grooves 1413-2 that extend substantially parallel to groove 1413-1 intersecting side surface 1412, at each end corresponding to elongated segment. As mentioned, each of grooves 1413 has a varying radius of curvature that has a maximum value at the ends thereof, and a minimum value between grooves 1411.

While the above described ultrahard layers extend the entire diameter of the cutting element, as mentioned above, the present disclosure is not so limited. Rather, as shown in FIGS. 21-24, cutting element 2100 includes a substrate 2102 and an ultrahard layer 2104 on substrate 2102. The cutting element has a non-planar working surface 2106 formed by both substrate 2102 and ultrahard layer 2104; however, ultrahard layer 2104 does not form an elongated segment extending across the entire length of the cutting element diameter, but rather is a discontinuous layer or layer with two discrete segments with a portion of substrate 2102 therebetween. Thus, an interior portion of the crest 2110 (which extends from the cutting edge to the other side of the cutting element) is formed of substrate 2102, including at the central axis. However, the ultrahard layer 2104 may form at least 50% of the length of crest 2110. Similar to as described for FIG. 3, each segment of ultrahard layer 2104 may have varying dimensions along its length. Specifically, each segment of ultrahard layer 2104 may be wider at its ends (adjacent cutting edge) than a radially interior portion of the segment, and as shown in the side view of FIG. 23, may have a width ranging from about 60 to about 80 percent of the diameter of the cutting element. However, other ranges may be desired depending on the depth of cut for a particular drilling application to ensure diamond surface coverage. Additionally, as shown in FIG. 24, each segment of ultrahard layer 2104 may have a varying thickness. Specifically, each segment of ultrahard layer 2104 may have a thickness t3 at the periphery ranging from about 0.030 to about 0.150 inches (or from about 4 to 40% of the cutting element outer diameter) and a peak thickness t4 which can be anywhere between the outer diameter (OD) of the cutter and the center axis of the cutter and range from about 0.050 to about 0.180 inches (or from about 8 to 45 % of the cutting element outer diameter). In addition to having a non-planar working surface, the interface surface 2103 between substrate 2102 and ultrahard layer 2104 is also non-planar. Specifically, non-planar interface surface 2103 may be formed from two concavities 2105 on either side of the cutting element. Each concavity 2105 may include two substantially parallel grooves 2107 which, with the rest of concavity 2105, define the non-planar interface 2103.

Referring now to FIGS. 18-20, another embodiment of a cutting element is shown. As shown cutting element 1800 includes a substrate 1802 and an ultrahard layer 1804 on the substrate 1802. The cutting element 1800 has an axisymmetric non-planar working surface 1806 formed by both substrate 1802 and ultrahard layer 1804. However, unlike the above described embodiments which have a non-planar working surface that is generally shaped to be a parabolic cylinder, the embodiment illustrated in FIGS. 18-20 includes a substantially conical non-planar working surface 1806 terminating in a rounded apex. The substantially conical non-planar working surface 1806 includes a cutting tip formed of the ultrahard layer 1804 surrounded by substrate 1802. Whereas a conventional substantially conical cutting element has the entire conical surface formed of ultrahard material (and in fact, an ultrahard material may form a portion of a cylindrical side surface), according to the present illustrated embodiment, the substrate 1802 forms a portion of the substantially conical surface. Unlike the embodiments illustrated above, ultrahard layer 1804 is not an elongated segment; however, it still has lateral support by substrate 1802 by virtue of the non-planar interface 1803 therebetween. As illustrated, this lateral support results in a wavy pattern of the interface 1803 at the working surface 1806. The peaks of the substrate may be designed to avoid being engaged with the formation at a particular depth of cut, for a given cutting element backrake (angle between cutting element relative to a line perpendicular to the formation to be engaged), and as illustrated in FIG. 20, having the plane 1820 for a 17 degree backrake and a depth of cut of 0.025 inch. Though, the present disclosure is not limited to a 17 degree backrake and a depth of cut of 0.025 inches, and thus, the thickness may vary depending on the depth of cut and backrake to avoid or minimize the substrate being engaged with the formation. Non-planar interface 1803 is formed by two sets of grooves 1811, 1813, each set having two grooves and the two sets being substantially perpendicular to each other. Each of grooves 1811, 1813 are substantially the same length, giving rotational as well as bit lateral symmetry to the ultrahard layer 1804. Further, each of grooves 1811, 1813 has a varying radius of curvature, with maximum values at the ends and minimum values at the mid-length of grooves 1811, 1813. While two sets of grooves 1811, 1813 are illustrated, it is also intended that a single set of grooves could instead be used in some embodiments.

Referring now to FIGS. 25-28, another embodiment of a cutting element is shown. As shown cutting element 2500 includes a substrate 2502 and an ultrahard layer 2504 on the substrate 2502. The cutting element 2500 has an axisymmetric non-planar working surface 2506 formed by both substrate 2502 and ultrahard layer 2504. Similar to the embodiment illustrated in FIGS. 18-20, the cutting element in FIGS. 25-28 includes a substantially conical non-planar working surface 2506 terminating in a rounded apex. The substantially conical non-planar working surface 2506 includes a cutting tip formed of the ultrahard layer 2504 surrounded by substrate 2502. Whereas a conventional substantially conical cutting element has the entire conical surface formed of ultrahard material (and in fact, an ultrahard material may form a portion of a cylindrical side surface), according to the present illustrated embodiment, the substrate 2502 forms a portion of the substantially conical surface. Unlike the embodiments illustrated above in FIGS. 18-20, ultrahard layer 2504 is an elongated segment and has lateral support by substrate 2502. Because ultrahard layer 2504 is an elongated segment, it extends, in one direction, to the cylindrical portion of the cutting element, but not in the perpendicular direction, thus forming a segment that is longer than it is wide. Further, it is also intended that the ultrahard layer 2504 may be elongated without reaching the cylindrical portion (i.e. outer diameter of the cutting element) but still be longer than it is wide. The elongated segment of ultrahard layer 2504 may have varying dimensions along its length. The ultrahard layer 2504 as an elongated segment may be wider at its ends (adjacent cylindrical portion) than a radially interior portion, but as illustrated, the width proximate the central axis 2501 may also be greater than the smallest width. In one or more embodiments, the groove 2505 may have a varying radius of curvature along its length, which may result in the varying width of the elongated segment of ultrahard layer 2504.

A non-planar interface surface 2503 may be formed from at least one groove 2505 formed in upper surface of substrate 2502. In one or more embodiments, the groove 2505 may have an elongated (longer than it is wide) shape to receive an elongated segment of ultrahard layer 2504. Further, along the length of the elongated groove 2505 (shown in the perspective view of FIG. 26), the substrate 2502 may have a generally convex curvature, which may be generally parabolic (in the cross-section corresponding to the length of the groove).

Referring now to FIGS. 29-32, another embodiment of a cutting element is shown. As shown cutting element 2900 includes a substrate 2902 and an ultrahard layer 2904 on the substrate 2902. The cutting element 2900 has an axisymmetric non-planar working surface 2906 formed by both substrate 2902 and ultrahard layer 2904. Similar to the embodiment illustrated in FIGS. 18-28, the cutting element in FIGS. 29-32 includes a substantially conical non-planar working surface 2906 terminating in a rounded apex. The substantially conical non-planar working surface 2906 includes a cutting tip formed of the ultrahard layer 2904 surrounded by substrate 2902. Whereas a conventional substantially conical cutting element has the entire conical surface formed of ultrahard material (and in fact, an ultrahard material may form a portion of a cylindrical side surface), according to the present illustrated embodiment, the substrate 2902 forms a portion of the substantially conical surface. Unlike the embodiments illustrated above in FIGS. 18-20, and similar to the embodiment illustrated in FIGS. 25-28 ultrahard layer 2904 is an elongated segment and has lateral support by substrate 2902. Because ultrahard layer 2904 is an elongated segment, it extends, in one direction, to the cylindrical portion of the cutting element, but not in the perpendicular direction, thus forming a segment that is longer than it is wide. Further, it is also intended that the ultrahard layer 2904 may be elongated without reaching the cylindrical portion (i.e. outer diameter of the cutting element) but still be longer than it is wide. As illustrated, ultrahard layer 2904 reaches the cylindrical portion (i.e., the other diameter of the cutting element) at one end of the elongated segment, but does not extend to the cylindrical portion at the other end.

The elongated segment of ultrahard layer 2904 may have varying dimensions along its length. The ultrahard layer 2904 as an elongated segment may be wider at its ends (adjacent or proximate cylindrical portion) than a radially interior portion, but the width proximate the central axis 2901 may also be greater than the smallest width or the width proximate the central axis 2901 may be the smallest width. In one or more embodiments, the groove 2905 may have a varying radius of curvature along its length, which may result in the varying width of the elongated segment of ultrahard layer 2904. A non-planar interface surface 2903 may be formed from at least one groove 2905 formed in upper surface of substrate 2902. In one or more embodiments, the groove 2905 may have an elongated (longer than it is wide) shape to receive an elongated segment of ultrahard layer 2904. Further, along the length of the elongated groove 2905 (shown in the perspective view of FIG. 30), the substrate 2902 may have a generally convex curvature, which may be generally parabolic (in the cross-section corresponding to the length of the groove).

In addition to the geometries shown in FIGS 3-17, other shaped non-planar working surfaces may be used, including other axisymmetric non-planar working surfaces that do not have a conical surface, but instead may have a generally convex or concave surface that terminates in a rounded apex. Further, other non-planar working surface may include other types of symmetry, such as bilateral symmetry (an example of which is shown in the embodiment in FIGS. 3-17) or rotational symmetry, as well as asymmetric working surfaces. In any of such non-planar working surfaces, the substrate may define a portion of the non-planar working surface so that the ultrahard layer provides desired thickness in the portion of the cutting element that engages with the formation during drilling and the substrate provides lateral support to the ultrahard layer in a region that is designed to not engage with the formation during drilling.

In the case of a conical or other axisymmetric non-planar working surface cutting element, the backrake angle may be the angle between the cutting element axis and the line perpendicular to the formation to be engaged, whereas in the case of a cutting element as shown in FIGS. 3-17, the backrake may be calculated between a line extending from the cutting tip across the diameter of the cutting element and the line perpendicular to the formation to be engaged. In one or more embodiments, the cutting element of FIG. 18 may have a backrake angle ranging from about -30 to 30 degrees; however, it is also envisioned that a greater backrake, up to 80 degrees may also be used. In one or more embodiments, the cutting elements of FIGS. 3-17 may have a backrake ranging from about 0 to -20 degrees.

Each of the embodiments described herein have at least one ultrahard layer (made of an ultrahard material) included therein. Such ultrahard materials may include a conventional polycrystalline diamond table (a table of interconnected diamond particles having interstitial spaces therebetween in which a metal component (such as a metal catalyst) may reside, a thermally stable diamond layer (i.e., having a thermal stability greater than that of conventional polycrystalline diamond, 750°C) formed, for example, by removing substantially all metal from the interstitial spaces between interconnected diamond particles or from a diamond / silicon carbide composite, or other ultrahard material such as a cubic boron nitride. As known in the art, thermally stable diamond may be formed in various manners. A conventional polycrystalline diamond layer includes individual diamond "crystals" that are interconnected. The individual diamond crystals thus form a lattice structure. A metal catalyst, such as cobalt, may be used to promote recrystallization of the diamond particles and formation of the lattice structure. Thus, cobalt particles are typically found within the interstitial spaces in the diamond lattice structure. Cobalt has a significantly different coefficient of thermal expansion as compared to diamond. Therefore, upon heating of a diamond table, the cobalt and the diamond lattice will expand at different rates, causing cracks to form in the lattice structure and resulting in deterioration of the diamond table.

To obviate this problem, strong acids may be used to "leach" the cobalt from a polycrystalline diamond lattice structure (either a thin volume or entire tablet) to at least reduce the damage experienced from heating diamond-cobalt composite at different rates upon heating. Briefly, a strong acid, typically hydrofluoric acid or combinations of several strong acids may be used to treat the diamond table, removing at least a portion of the co-catalyst from the PDC composite. Suitable acids include nitric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid, phosphoric acid, or perchloric acid, or combinations of these acids. In addition, caustics, such as sodium hydroxide and potassium hydroxide, have been used to the carbide industry to digest metallic elements from carbide composites. In addition, other acidic and basic leaching agents may be used as desired. Those having ordinary skill in the art will appreciate that the molarity of the leaching agent may be adjusted depending on the time desired to leach, concerns about hazards, etc.

By leaching out the cobalt, thermally stable polycrystalline (TSP) diamond may be formed. In certain embodiments, a select portion of a diamond composite is leached, in order to gain thermal stability without losing impact resistance. As used herein, the term TSP includes both of the above (i.e., partially and completely leached) compounds. Interstitial volumes remaining after leaching may be reduced by either furthering consolidation or by filling the volume with a secondary material.

Alternatively, TSP may be formed by forming the diamond layer in a press using a binder other than cobalt, one such as silicon, which has a coefficient of thermal expansion more similar to that of diamond than cobalt has. During the manufacturing process, a large portion, 80 to 100 volume percent, of the silicon reacts with the diamond lattice to form silicon carbide which also has a thermal expansion similar to diamond. Upon heating, any remaining silicon, silicon carbide, and the diamond lattice will expand at more similar rates as compared to rates of expansion for cobalt and diamond, resulting in a more thermally stable layer. PDC cutters having a TSP cutting layer have relatively low wear rates, even as cutter temperatures reach 1200°C. However, one of ordinary skill in the art would recognize that a thermally stable diamond layer may be formed by other methods known in the art, including, for example, by altering processing conditions in the formation of the diamond layer.

The substrate on which the ultrahard layer is disposed may be formed of a variety of hard particles. In one embodiment, the substrate may be formed from a suitable material such as tungsten carbide, tantalum carbide, or titanium carbide. Additionally, various binding metals may be included in the substrate, such as cobalt, nickel, iron, metal alloys, or mixtures thereof. In the substrate, the metal carbide grains are supported within the metallic binder, such as cobalt. Additionally, the substrate may be formed of a sintered tungsten carbide composite structure. 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 substrate or binder used is intended.

While the cutting elements of the present disclosure may be used on a drill bit, such as the type shown in FIG. 1, it is also intended that the cutting elements may be used on other types of downhole tools, including for example, a hole opener. FIG. 33 shows a general configuration of a hole opener 830 that includes one or more cutting elements of the present disclosure. The hole opener 830 comprises a tool body 832 and a plurality of blades 838 disposed at selected azimuthal locations about a circumference thereof. The hole opener 830 generally comprises connections 834, 836 (e.g., threaded connections) so that the hole opener 830 may be coupled to adjacent drilling tools that comprise, for example, a drillstring and/or bottom hole assembly (BHA) (not shown). The tool body 832 generally includes a bore therethrough so that drilling fluid may flow through the hole opener 830 as it is pumped from the surface (e.g., from surface mud pumps (not shown)) to a bottom of the wellbore (not shown).

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words 'means for' together with an associated function.

Claims

CLAIMS What is claimed:

1. A cutting element, comprising:

a substrate; and

an ultrahard layer on the substrate, the substrate and the ultrahard layer defining a non- planar working surface of the cutting element such that the ultrahard layer forms a cutting portion and the substrate is at least laterally adjacent to the ultrahard layer.

2. The cutting element of claim 1, wherein the ultrahard layer forms a cutting edge and extends radially inward toward a central axis of the cutting element.

3. The cutting element of claim 2, wherein the ultrahard layer is an elongated segment extending from the cutting edge on a first side of the cutting element to a second side, and wherein the substrate extends along both sides of the elongated segment.

4. The cutting element of claim 3, wherein the elongated segment is wider at its ends than a radially interior portion of the elongated segment.

5. The cutting element of claim 4, wherein the elongated segment is wider at its ends than proximate the central axis.

6. The cutting element of claim 2, wherein a width of the elongated segment along at one least of its ends ranges from about 60 to about 80 percent of the diameter of the cutting element.

7. The cutting element of claim 3, wherein a thickness of the elongated segment at its thinnest point ranges from about 4 to 40 percent of an outer diameter of the cutting element.

8. The cutting element of claim 3, wherein the elongated segment is thicker at its ends than proximate the central axis.

9. The cutting element of claim 1, wherein the cutting element has an axisymmetric non- planar working surface with a cutting tip formed of the ultrahard layer surrounded by the substrate.

10. The cutting element of claim 1, wherein a peripheral edge of the non-planar working surface has at least one substrate portion and at least one ultrahard layer portion, the at least one substrate portion extending away from the cutting edge formed of the ultrahard layer.

11. The cutting element of claim 1, wherein an interface between the ultrahard layer and the substrate, opposite the non-planar working surface, includes at least one groove formed in the substrate having a varying radius of curvature.

12. The cutting element of claim 11, wherein the interface includes a plurality of parallel grooves.

13. The cutting element of claim 11, wherein the interface includes two sets of parallel grooves, the sets being substantially perpendicular to each other.

14. The cutting element of claim 2, wherein at the central axis, the substrate forms the non- planar working surface.

15. A cutting tool, comprising:

a tool body

a plurality of blades extending from the tool body; and

at least one cutting element of claim 1 attached to one of the plurality of blades.

16. A cutting tool, comprising:

a tool body;

a plurality of blades extending from the tool body; and

at least one cutting element attached to one of the plurality of blades, the at least one cutting element having a non-planar working surface and comprising a substrate and an ultrahard layer, the non-planar working surface being defined by both the substrate and the ultrahard layer.

17. The cutting tool of claim 16, wherein the ultrahard layer is an elongated segment extending from the cutting edge on a first side of the cutting element to a second side, and wherein the substrate extends along both sides of the elongated segment.

18. The cutting tool of claim 16, wherein the cutting element has an axisymmetric non-planar working surface with a cutting tip formed of the ultrahard layer surrounded by the substrate.

19. The cutting tool of claim 16, wherein a peripheral edge of the non-planar working surface has at least one substrate portion and at least one ultrahard layer portion, the at least one substrate portion extending away from the cutting edge formed of the ultrahard layer.

20. The cutting tool of claim 16, wherein an interface between the ultrahard layer and the substrate, opposite the non-planar working surface, includes at least one groove formed in the substrate having a varying radius of curvature.