Patent Description:
In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention.

Abrasive compacts consist of a mass of diamond or cubic boron nitride particles bonded into a coherent, polycrystalline hard conglomerate. Abrasive compacts, particularly based on polycrystalline diamond (PCD) particles, come in various shapes and sizes, but typically are cylindrical and include a volume of abrasive particles attached or joined coherently to a substrate.

One application of abrasive compacts, particularly of abrasive compacts based on polycrystalline diamond, is in cutting tools, such as for metal machining application or for use in geological formation drilling applications. Compacts attached to a substrate, either integrally formed during manufacture of the coherent, polycrystalline hard conglomerate or mounted together subsequently, form blanks and cutters. Compacts, blanks and cutters can be mounted on tools, for example, by brazing or by forming integrally, such as in casting. Often in cutting, milling, grinding, and drilling applications, large forces act on the point or cutting edge of the working surface of the volume of abrasive particles. As a result, cracks develop in or behind the cutting edge or point of contact and these cracks can propagate into and through the coherent, polycrystalline hard conglomerate. In addition, heat generated by the various abrasive operations can negatively impact the coherent, polycrystalline hard conglomerate, particularly of diamond particles - first, by causing back-conversion of diamond to carbon, which reduces strength of the abrasive compact, and second, by causing thermal expansion, which results in cracking of the abrasive compact due to differences in the coefficient of thermal expansion of the various materials in the abrasive compact, particular between the diamond material and any catalyst material within the coherent, polycrystalline hard conglomerate portion. Additionally, abrasive compacts experience impact damage, resulting in large cracks that propagate through the coherent, polycrystalline hard conglomerate, which can lead to large losses of the material, i.e., by spalling or chipping. <CIT> describes a composite constructed body having a continuous core material formed from a polycrystalline diamond (PCD) bonded with an iron group metal and an outer shell layer formed from a sintered body obtained by bonding hard particles with an iron group metal.

Thus, it would be advantageous to have a coherent, polycrystalline hard conglomerate, particularly a polycrystalline diamond compact, blank or cutter, having a composition and features that had, one or more of, a reduced back-conversion at elevated temperatures, a reduced difference in coefficient of thermal expansion to reduce thermal expansion cracking, and an increased toughness to minimize impact damage.

According to a first aspect of the present invention there is provided a polycrystalline diamond compact according to the appended claims. The present disclosure is directed to polycrystalline diamond compacts, polycrystalline diamond blanks, polycrystalline diamond cutters, and tools incorporating same for cutting, milling, grinding, drilling and other abrasive operations, particularly in metal machining applications or for use in geological formation drilling applications, where the diamond table has a gradient in iron content that increases as distance into the volume of the diamond table increases, which imparts improved mechanical properties to the diamond table. Additional features and advantages will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the disclosure will be realized and attained by the structures, particularly pointed out in the written description and claims thereof, as well as the appended drawings.

The present invention relates to a polycrystalline diamond compact comprising a volume of crystalline diamond grains bonded together by diamond-to-diamond bonds to form a diamond body. The diamond body includes a plurality of inter-grain regions disposed between the bonded crystalline diamond grains, a cobalt-based catalyst material present in at least a portion of the plurality of inter-grain regions, and, e.g., in the case of a polycrystalline diamond blank, an iron concentration gradient extends from an exterior surface of the diamond body into an interior volume of the diamond body towards the interface, i.e., the amount of iron in the diamond body decreases from an exterior surface into the interior volume towards the interface.

The present invention can be used for a polycrystalline diamond blank or cutter comprising a volume of crystalline diamond grains bonded together by diamond-to-diamond bonds to form a diamond body and a hard metal substrate. The diamond body includes a plurality of inter-grain regions disposed between the bonded crystalline diamond grains and a cobalt-based catalyst material present in at least a portion of the plurality of inter-grain regions, and the diamond body is bonded to the hard metal substrate to form an interface. An iron concentration gradient in the diamond body extends from the interface into an interior volume of the diamond body. In such a case, the concentration of iron is lower at the interface and increases towards the exterior surface.

For example the invention can be used in cutting tools, such as a drill bit and a drag bit. In drill bits, a metal alloy body (including a front end, a shaft portion, and a rear end adapted to be mounted in a tool holder) has a polycrystalline diamond compact or blank attached to the front end. In drag bits, a plurality of such polycrystalline diamond compacts and/or a plurality of such polycrystalline diamond cutters are arranged on and affixed to a radially outward periphery of a plurality of fins, which are arranged along an exterior surface of the front end of the drag bit body with each fin separated from a sequentially adjacent fin by a rearwardly extending, helically-shaped flute.

In another preferred embodiment the cutting tool comprises a first substrate and a tip affixed to a seating surface of the first substrate. The tip includes a volume of crystalline diamond grains bonded together by diamond-to-diamond bonds to form a diamond body, the diamond body including a plurality of inter-grain regions disposed between the bonded crystalline diamond grains, a cobalt-based catalyst material present in at least a portion of the plurality of inter-grain regions, a second substrate, wherein the second substrate is formed of a hard metal and wherein the diamond body is bonded to the second substrate to form an interface, and an iron concentration gradient in the diamond body extending from the interface into an interior volume of the diamond body. Here again, the iron concentration at the exterior surface is greater than that towards the interior volume and lowest proximate the interface. In exemplary embodiments, the tip is affixed to the first substrate by brazing the tip to the seating surface of the first substrate.

In another aspect, there is provided an embodiment of a method of manufacturing a polycrystalline diamond compact comprising an assembly, wherein the assembly comprises a diamond catalyst source, a layer of diamond feed in contact with the diamond catalyst source, and a refractory container. The refractory container contains the diamond catalyst source and the layer of diamond feed and the method processes the assembly at elevated temperature and elevated pressure sufficient to sinter the diamond feed into a diamond body. The diamond feed includes <NUM> to <NUM> wt. % diamond particles and <NUM> to <NUM> wt. % of a cobalt-iron alloy resulting in a diamond body that includes a volume of crystalline diamond grains bond together by diamond-to-diamond bonds, a plurality of inter-grain regions disposed between the bonded crystalline diamond grains, a cobalt-based catalyst material present in at least a portion of the plurality of inter-grain regions, and an iron concentration gradient extending from an exterior surface of the diamond body into an interior volume of the diamond body.

In another aspect, there is provided an embodiment of a method of manufacturing a polycrystalline diamond blank or cutter comprising forming an assembly, wherein the assembly comprises a hard metal substrate having a composition including cemented carbide or cobalt sintered tungsten carbide (WC-Co), a layer of diamond feed in contact with the diamond catalyst source, and a refractory container. The refractory container contains the diamond catalyst source and the layer of diamond feed and the method processes the assembly at elevated temperature and elevated pressure sufficient to sinter the diamond feed into a diamond body. The hard metal substrate is iron-free and has a composition including cemented carbide or cobalt sintered tungsten carbide (WC-Co). The diamond feed includes <NUM> to <NUM> wt. % diamond particles, where an average diameter of the diamond particles is equal to or greater than <NUM> micron and equal to or less than <NUM> microns. The diamond feed also includes <NUM> to <NUM> wt. % of a cobalt-iron alloy, where the cobalt-iron alloy is CoxFey, where <NUM> ≤ x ≤ <NUM>, <NUM> ≤ y ≤ <NUM>, and x+y=<NUM>. HPHT processing the diamond feed results in a diamond body that includes a volume of crystalline diamond grains bond together by diamond-to-diamond bonds, a plurality of inter-grain regions disposed between the bonded crystalline diamond grains, a cobalt-based catalyst material present in at least a portion of the plurality of inter-grain regions, and an iron concentration gradient extending from an exterior surface of the diamond body into an interior volume of the diamond body.

In exemplary embodiments, the diamond feed consists of <NUM> to <NUM> wt. % diamond particles and a balance to <NUM> wt. % of cobalt-iron alloy.

Other systems, methods, features and advantages will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the present disclosure, and be protected by the following claims. Nothing in this section should be taken as a limitation on those claims. Further aspects and advantages are discussed below in conjunction with the embodiments of the disclosure. It is to be understood that both the foregoing general description and the following detailed description of the present disclosure are examples and explanatory, and are intended to provide further explanation of the invention as claimed.

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate implementations of the invention and together with the description serve to explain the principles of the disclosure.

Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals should be understood to refer to the same elements, features, and structures. Also, for ease of viewing, in some instances only some of the named features in the figures are labeled with reference numerals.

<FIG> shows a schematic perspective view of a cylindrically-shaped abrasive blank <NUM> based on polycrystalline diamond (PCD) particles. The abrasive blank is also referred to as a polycrystalline diamond blank (PDC). The blank <NUM> has a substrate <NUM>, which is made of hard metal, alloy, or composite, and most typically of cemented carbide or cobalt sintered tungsten carbide (WC-Co); and a polycrystalline diamond composite volume <NUM> (also called a diamond table or a diamond body) attached or joined coherently to the substrate along an interface <NUM>. In the polycrystalline diamond composite volume <NUM>, the diamond particle content is high and there is an extensive amount of diamond-to-diamond bonding, i.e., direct particle-to-particle bonding among the diamond particles. Often, a catalyst, such as cobalt metal or its alloys, is present as a diamond bond-forming aid in high pressure and high temperature (HPHT) manufacturing of the polycrystalline diamond cutter <NUM>. The polycrystalline diamond blank <NUM> may be later machined to a desired shape, including machining to specified outer diameter, height and (optionally) the addition of any surface features such as chamfers or beveled surfaces. Chamfers or beveled surfaces are more typically found on polycrystalline diamond cutters as opposed to polycrystalline diamond blanks. All or portions of the top surface <NUM> and side surface <NUM> can be the working surface of the polycrystalline diamond blank <NUM>, i.e. a surface of the polycrystalline diamond blank <NUM> that contacts a workpiece during cutting, milling, grinding or drilling.

The polycrystalline diamond composite volume <NUM> is frequently supported by being bonded to a substrate or support, for example, a substrate of hard metal such as cemented carbide, in which case the integrally formed structure of polycrystalline diamond composite volume <NUM> and substrate is referred to herein as a polycrystalline diamond blank or a blank (for metal machining applications) or as a polycrystalline diamond cutter or a cutter (for geological formation drilling applications). However, it should be noted that in some instances, the polycrystalline diamond composite volume <NUM> can be unsupported, i.e., is without a substrate, in which case the polycrystalline diamond composite volume <NUM> is referred to herein as a polycrystalline diamond compact or a compact.

Both in embodiments as a polycrystalline diamond blank or polycrystalline diamond cutter and in embodiments as a polycrystalline diamond compact, the diamond body is formed from a volume of crystalline diamond grains bonded together by diamond-to-diamond bonds. <FIG> is a schematic representation of a magnified portion of a diamond body <NUM>. In the diamond body, crystalline diamond grains <NUM> are bonded together by diamond-to-diamond bonds <NUM>. The diamond body <NUM> includes a plurality of inter-grain regions <NUM> disposed between the bonded crystalline diamond grains <NUM>. A cobalt-based catalyst material <NUM> is present in at least a portion of the plurality of inter-grain regions <NUM> and/or in a portion of an individual inter-grain region <NUM>. As disclosed herein, optional processing can remove metal catalyst from inter-grain regions, and such inter-grain regions without metal catalyst are also shown in <FIG>.

In addition, the diamond body of the compact, blank or cutter has an iron concentration gradient extending from an exterior surface of the diamond body into an interior volume of the diamond body. When mounted on a substrate, such iron concentration gradient extends from an interface between the diamond body and the substrate. In general, the iron concentration gradient varies from <NUM>-<NUM> wt. % Fe at an exterior surface of a compact or, in the case of a blank, at the interface, and <NUM>-<NUM> wt. % Fe at a location in the diamond body at a distance of approximately <NUM>-<NUM> microns from the exterior surface /interface. According to the present concept, the iron concentration gradient varies from <NUM> to <NUM> wt. % Fe at the exterior surface/interface of the diamond body (for a polycrystalline diamond compact) or from the interface (for polycrystalline diamond blank or cutter) to <NUM> to <NUM> wt. % Fe at a distance of <NUM> to <NUM> microns from the exterior surface/interface.

<FIG> schematically depicts a cross-section of a blank <NUM> with a magnified portion P1 and <FIG> schematically depicts the iron gradient across the diamond table in portion P1. As seen in <FIG>, the overall iron concentration <NUM> increases with distance from the interface <NUM> between the diamond table <NUM> and the substrate <NUM> (such as a cemented WC substrate) to the top surface <NUM> of the diamond table <NUM>. In the schematic in <FIG>, the iron concentration ([Fe]) is in arbitrary unit (a.

<FIG> is a scanning electron microscope (SEM) photomicrograph <NUM> of a cross-section of a portion of a blank consistent with those disclosed herein. The photomicrograph <NUM> shows a portion of the substrate <NUM> and a portion of the diamond table <NUM>. The substrate is tungsten carbide. The photomicrograph <NUM> is at 150X magnification and the scale bar in the lower margin is <NUM> microns.

Superimposed on the photomicrograph <NUM> in <FIG> are results from energy-dispersive X-ray spectroscopy (EDS). The results are from an EDS line scan across the diamond table <NUM> starting from the substrate/diamond table interface <NUM> and extending toward the surface of the diamond table <NUM>, typically toward a portion of the working surface, alternatively toward the top surface <NUM>. The EDS results graphically present elemental content in the diamond table <NUM> as weight percent (wt. %) as a function of distance from the interface (microns). The weight percent (wt. %) is on a logarithmic scale and ranges from <NUM> wt. % to <NUM> wt. % and the distance from the interface <NUM> ranges from <NUM> to greater than <NUM> microns. The far right side of the image is at a distance of <NUM> microns. The elemental content shown in the EDS results are carbon (C) <NUM>, cobalt (Co) <NUM>, tungsten (W) <NUM>, and iron (Fe) <NUM>. Also shown is a curve fit <NUM> for the iron content <NUM>. Because weight percent (wt. %) is on a logarithmic scale the curve fit <NUM> for the iron content <NUM> represents a gradient in iron content (Fe wt. %) that linearly increases as a function of distance from the interface <NUM>. The experimentally determined linear gradient in iron content shown in <FIG> is consistent with the schematically represented iron concentration ([Fe]) <NUM> in <FIG>.

In the photomicrograph <NUM> in <FIG>, the carbon <NUM> content is from the diamond in the diamond table <NUM> and is substantially constant at distances greater than <NUM> microns at an amount greater than <NUM> wt. % after increasing from approximately <NUM> wt. % at or near the interface <NUM>. The cobalt <NUM> and tungsten <NUM> content in the diamond table <NUM> is swept into the diamond table <NUM> from the substrate <NUM> during the HPHT processing and each is at its maximum at the interface <NUM> before becoming substantially constant at distances greater than <NUM> microns at an amount of approximately <NUM> wt. % for cobalt <NUM> and an amount of approximately <NUM> wt. % for tungsten <NUM>. The substrate in this sample was iron-free and the iron <NUM> content is from iron present in the diamond feed used in the HPHT processing. The iron content is also influenced by the sweep of cobalt into the diamond table in that the iron is at least partially swept with the sweep of the cobalt. Therefore, the iron content is lower at the interface <NUM> than in an interior portion of the diamond table <NUM>. In <FIG>, the iron <NUM> content varies from approximately <NUM> wt. %, alternatively <NUM> to <NUM> wt. % Fe, at the interface to approximately <NUM> wt. % at a distance from the interface of <NUM> microns.

<FIG> is a second (SEM) photomicrograph <NUM> of a cross-section of a portion of a blank consistent with those disclosed herein. The photomicrograph <NUM> is at 150X magnification and the scale bar in the lower margin is <NUM> microns. Eight regions are indicated on the photomicrograph <NUM> and correspond to regions that were sampled by area mapping for compositional analysis by EDS area scan. <FIG> is a table showing the results from compositional analysis on the eight regions. The numbering of the "spectrum" in the table in <FIG> corresponds to the numbering of the regions in <FIG> and some details on the location of each region (whether in the substrate <NUM> or diamond table <NUM> and distance relative to the interface <NUM> (which has been annotated with a dashed line) in <FIG>) is shown in the following Table <NUM>.

From the results in <FIG>, one observes that the substrate <NUM> has a composition of, cobalt, tungsten and carbon, which is consistent with a substrate of cobalt tungsten carbide (Co-WC). Furthermore, as seen from Spectrums <NUM> and <NUM>, which are both in the interior of the substrate <NUM>, the composition of the substrate <NUM> is iron-free. Also from the results in <FIG>, one observes that the amount of iron in the diamond table <NUM> varies from <NUM> wt. % (see Spectrum <NUM> corresponding to Region <NUM>) to <NUM> wt. % (see Spectrum <NUM> corresponding to Region <NUM>). This change in amount of iron in the diamond table occurred over approximately <NUM> microns, for an average rate of change of iron as a function of distance from the interface of approximately <NUM> wt. % per micron.

As noted herein, the iron concentration gradient, i.e., the profile or change in amount of iron in the diamond table, varies linearly from the exterior surface of the diamond body (for a polycrystalline diamond compact) or from the interface (for polycrystalline diamond blank or a polycrystalline diamond cutter) into the interior volume of the diamond body. It has further been determined that the slope of the iron concentration gradient varies as the average grain size of the crystalline diamond grains in the diamond feed varies. <FIG> are graphs of elemental Fe content in the diamond table (in weight percent (wt. %)) as a function of distance from the interface (in microns) for three samples (Sample <NUM>, Sample <NUM>, and Sample <NUM>) of a polycrystalline diamond blank.

In <FIG>, Sample <NUM> (squares; indicated at <NUM> with linear curve fit <NUM>) and Sample <NUM> (circles; indicated at <NUM> with linear curve fit <NUM>) both used a diamond feed with crystalline diamond grains having an average grain size of <NUM>-<NUM> microns. In <FIG>, Sample <NUM> (circles; indicated at <NUM> with linear curve fit <NUM>) from <FIG> is represented and new Sample <NUM> (triangles; indicated at <NUM> with linear curve fit <NUM>) is presented. Sample <NUM> used a diamond feed with crystalline diamond grains having an average grain size of <NUM> microns. Thus, the average grain size for Sample <NUM> differed by a factor of 10x as compared to Sample <NUM> and Sample <NUM>.

Based on the curve fit <NUM>, the elemental Fe content in the diamond table for Sample <NUM> varied from about <NUM> wt. % (at the interface) to about <NUM> wt. % at a distance from the interface of <NUM> microns. Based on the curve fit <NUM>, the elemental Fe content in the diamond table for Sample <NUM> varied from <NUM> wt. % (at the interface) to <NUM> wt. % at a distance from the interface of <NUM> microns. Based on the curve fit <NUM>, the elemental Fe content in the diamond table for Sample <NUM> varied from about <NUM> wt. % (at the interface) to about <NUM> wt. % at a distance from the interface of <NUM> microns,.

For each of Sample <NUM>, Sample <NUM>, and Sample <NUM>, the iron composition monotonously increased from the interface (at approximately zero wt. %) into the volume of the diamond table. Furthermore, when all parameters including grain size are the same, the iron concentration gradient are the same (compare Sample <NUM> to Sample <NUM>), indicating that the iron concentration gradient is reproducible. However, when all parameters are the same and only the average grain size differs between samples, the iron concentration gradient differs (compare Sample <NUM> to Sample <NUM> and Sample <NUM>). In the samples shown in <FIG>, increasing the average grain size by ten-times resulted in reducing the slope of the iron concentration gradient to less than half (as compared to the slope for samples with the smaller grain size).

Although <FIG> report results from samples manufactured using a diamond feed with crystalline diamond grains having an average grain size of <NUM> microns or <NUM> microns, other embodiments of polycrystalline diamond compacts, polycrystalline diamond blanks and polycrystalline diamond cutters can be manufactured using a diamond feed with crystalline diamond grains having other average grain sizes. For example, crystalline diamond grains can have an average grain size of <NUM> to <NUM> microns, alternatively <NUM> to <NUM> microns, alternatively <NUM> to <NUM> microns, alternatively <NUM> to <NUM> microns, alternatively <NUM> to <NUM> microns, alternatively <NUM> to <NUM> microns. As demonstrated by <FIG>, selection of the average grain size can affect the iron concentration gradient in the as-manufactured product, and the average grain size can be selected to achieve a desired iron concentration gradient.

It is contemplated that varying other parameters would also vary the iron concentration gradient. Examples of other parameters that can be varied to effect the iron concentration gradient and direction include HPHT (high pressure and high temperature) settings, particle size distribution (PSD), total metal content in carbide substrate, total metal content in the diamond table and sweep direction, i.e., metal sweeping vertically from carbide interface in to PCD, horizontally from refractory cup walls that is holding PCD or vertically from the from cup ends via an external metal sweep source.

Polycrystalline diamond compacts and blanks are used extensively in cutting, milling, grinding, drilling and other abrasive operations and metal cutting applications, and polycrystalline diamond compacts and cutters are used extensively in geological formation drilling applications.

For example, tools used in the metal machining industry, such as drill bits, can incorporate polycrystalline diamond compacts or polycrystalline diamond blanks. Shown in <FIG> are three example drill bits - a perspective view of a solid shaft, round tool 600a, a side view of a helically fluted drill bit 600b, and a perspective view of a helically fluted drill bit 600c. Each of the drill bits include a metal alloy body <NUM> made from, for example, tungsten carbide. The metal alloy body <NUM> includes a front end <NUM>, a shaft portion <NUM>, and a rear end <NUM> adapted to be mounted in a tool holder. The front end <NUM>, the shaft portion <NUM>, and the rear end <NUM> are arranged sequentially along a longitudinal axis <NUM> of the body. The drill bits include a polycrystalline diamond compact <NUM> attached to the front end <NUM>. The polycrystalline diamond compact <NUM> can be attached by brazing or some other attachment technique, or can be integrally formed with the metal alloy body <NUM>. Helical flutes <NUM> can optionally be present, as seen by the example round tools 600b and 600c. These example round tools are used, for example, in the aerospace industry for the machining of workpieces of aluminum, titanium, and alloys thereof and of workpieces of composite materials.

Also, for example, tools used in the drilling industry, such as drag bits <NUM> (see <FIG>), often incorporate multiple polycrystalline diamond cutters or polycrystalline diamond compacts. In exemplary embodiments, the drag bit <NUM> has a metal alloy body <NUM> including a front end <NUM>, a shoulder region <NUM> and a threaded rear end <NUM> arranged sequentially along a longitudinal axis <NUM> of the body <NUM>. The drag bit <NUM> has a plurality of fins <NUM> (also sometimes called blades) arranged along an exterior surface of the front end <NUM>. Each of the fins <NUM> is separated from a sequentially adjacent fin <NUM> by a rearwardly extending, helically-shaped flute <NUM>. Additionally, arranged along a periphery region of the fins <NUM> are a plurality of polycrystalline diamond cutters <NUM>. Although not shown in <FIG>, the polycrystalline diamond cutters <NUM> can be replaced by polycrystalline diamond compacts. In each instance, whether polycrystalline diamond cutters or polycrystalline diamond compacts, the diamond table has the features and characteristics described herein including, for polycrystalline diamond cutters, an iron concentration gradient in the diamond body extending from the interface into an interior volume of the diamond body and, for polycrystalline diamond compacts, an iron concentration gradient extending from an exterior surface of the diamond body into an interior volume of the diamond body.

An interrupted milling test was conducted using a face milling machine and a workpiece of Al - <NUM> at. % Si alloy. Samples of polycrystalline diamond blanks having features and characteristics described herein including an iron concentration gradient in the diamond body extending from the interface into an interior volume of the diamond body were tested in the interrupted milling test. Samples of polycrystalline diamond blanks without an iron concentration gradient in the diamond body extending from the interface into an interior volume of the diamond body were used as a control in the interrupted milling test. Details on the tool testing conditions for the interrupted milling test are in Table <NUM>.

The interrupted milling test was conducted for <NUM> passes, after which samples were removed from the milling test and the flank wear measured using an optical microscope. <FIG> is a graph <NUM> showing results from the interrupted milling tests. In <FIG>, the Y-axis shows tool wear for (a) two inventive polycrystalline diamond tools <NUM>, <NUM> with an iron concentration gradient in the diamond body extending from the interface into an interior volume of the diamond body and (b) a comparative example polycrystalline diamond blank tool insert <NUM> without an iron concentration gradient in the diamond body. Inventive polycrystalline diamond blank tool inserts <NUM>, <NUM>, as well as non-Fe gradient tools, were manufactured using the same grade diamond feed with crystalline diamond grains having an average grain size of <NUM> to <NUM> microns. The results in <FIG> for inventive polycrystalline diamond tools <NUM> and <NUM> was <NUM>-<NUM> microns, the results in <FIG> for comparative example polycrystalline diamond tool <NUM> was <NUM> microns.

<FIG> schematically show additional examples of cutting tools that can be created incorporating the disclosed blanks. The example cutting tools are illustrated in the form of a polycrystalline diamond blank <NUM> (also sometimes referred to as a tip) and a cutting tool <NUM> having at least potions formed from a polycrystalline diamond blank <NUM>. For example, the illustrated polycrystalline diamond blank <NUM> includes a substrate <NUM> formed of a material such as tungsten carbide and a diamond body <NUM>, which includes an outer working layer <NUM> and an intermediate layer <NUM> that is disposed therebetween. The diamond body <NUM>, typically the intermediate layer <NUM>, is bonded to the substrate <NUM>. Preferably, the outer working layer <NUM> will have a thickness between <NUM> and <NUM>. In the illustrated example, the interface <NUM> of the polycrystalline diamond blank <NUM> between the diamond body <NUM> and the substrate <NUM> is non-planar, but other interface geometries and surfaces can be used, including planar. In the illustrated example, the interface <NUM> includes arches, which form the corrugated surface of the substrate <NUM> and which are preferably between <NUM> and <NUM> in height. To maintain a sufficient separation between the arches <NUM> and the outer working layer <NUM>, the intermediate layer <NUM> should be at least <NUM> to <NUM> at its thinnest point (above the peaks of the corrugated surface), and will typically be between <NUM> and <NUM> at its thickest point. <FIG> schematically illustrates an example cutting tool <NUM>, i.e., a tip, affixed to a substrate <NUM> to form a cutting tool insert <NUM>. The tip can be affixed by, for example, brazing the tip to a seating surface of the substrate <NUM>. An optional mounting feature, such as a hole <NUM> extending from a first side of the cutting tool to a second side of the cutting tool insert <NUM>, can be configured to receive a fastener, such as a screw, for mounting the cutting tool insert <NUM>, to a machining tool such as a milling tool (not shown). In <FIG>, the polycrystalline diamond blank <NUM>, i.e., a tip, is in the shape of a triangle, but other geometries can be used including circular, oval, and polygonal.

It should be noted that the properties, images and results, particularly in relation to <FIG>, <FIG>, are for a polycrystalline diamond blanks. However, similar results for the composition and compositional analysis of the diamond table would be expected to be obtained for a polycrystalline diamond compact. In each case, the iron-content is determined from the surface of the diamond body into an interior volume of the diamond body. For the case of the polycrystalline diamond blank, the surface is coincident with the interface between the diamond table and the substrate; for the case of the polycrystalline diamond compact, the surface is an exterior surface from which the HPHT sweep originated to consolidate the diamond table during HPHT processing. Additionally, the discussion and results related to the polycrystalline diamond blank is also translatable and applicable to polycrystalline diamond cutters.

In general, the diamond table of polycrystalline diamond compacts, polycrystalline diamond blanks, and polycrystalline diamond cutters disclosed herein can be formed by sintering diamond particles under high pressure, high temperature (HPHT) conditions in the presence of a metal catalyst (such as cobalt, Co). The metal catalyst can originate from an independent source, such as a metal catalyst powder blended into the diamond particles or in a layer adjacent the diamond particles or from a substrate material as described below. Typical HPHT conditions include pressures at or above about <NUM> GPa and temperatures at or above about <NUM>. Typically, under the HPHT processing conditions, binder material present in an independent source or in a substrate (typically a cemented carbide substrate) positioned adjacent to diamond powders melts and sweeps into the mass of diamond. When a substrate is present, the binder material of the substrate can act as a metal catalyst in the diamond powders. In the presence of the metal catalyst, diamond crystals bond to each other in diamond-to-diamond bonds by a dissolution-precipitation process to form a sintered compact in which a polycrystalline diamond mass, i.e., a diamond table, is formed which is attached to the substrate (if present). The presence of the metal catalyst facilitates formation of diamond-to-diamond bonds and, where applicable, the attachment of the diamond table to the substrate.

In particular embodiments, the diamond particles are contained within a diamond feed. The diamond feed includes <NUM> to <NUM> wt. % diamond particles and <NUM> to <NUM> wt. % of a cobalt-iron alloy. The cobalt-iron alloy is homogenously distributed in the diamond feed, for example by ball milling the diamond feed with both the diamond particles and the cobalt-iron alloy. In some embodiments, the diamond particles in the diamond feed have an average diameter of <NUM> microns or <NUM> microns. In other embodiments, the diamond particles in the diamond feed have other average diameters. For example, diamond particles can have an average diameter of <NUM> to <NUM> microns, alternatively <NUM> to <NUM> microns, alternatively, <NUM> to <NUM> microns, alternatively <NUM> to <NUM> microns, alternatively <NUM> to <NUM> microns, alternatively <NUM> to <NUM> microns. In alternative embodiments, the average diameter can be unimodal or multimodal.

In some embodiments, the cobalt-iron alloy is CoxFey, where <NUM> ≤ x ≤ <NUM>, <NUM> ≤ y ≤ <NUM>, and x+y=<NUM>. Alternatively, the cobalt-iron alloy is CoxFey, where <NUM> ≤ x ≤ <NUM>, <NUM> ≤ y ≤ <NUM>, and x+y=<NUM>. In still other alternative embodiments, the cobalt-iron alloy is CoxFey, where x = <NUM> and y = <NUM>.

The diamond feed is used to form an assembly, which will subsequently undergo HPHT processing at elevated temperature and elevated pressure sufficient to sinter the diamond feed into a diamond body. The assembly comprises a diamond catalyst source and a layer of diamond feed in contact with the diamond catalyst source contained in a refractory container. Forming the assembly continues by positioning a cap over the contents of the refractory container and sealing, such as by crimping.

When forming a polycrystalline diamond compact, the diamond catalyst source can be a metal catalyst powder blended into the diamond particles or a layer of metal catalyst powder adjacent the diamond particles. Example metal catalyst powders have a Co-based composition and are iron-free. A particular iron-free, Co-based composition suitable for use as a metal catalyst powder to form the disclosed polycrystalline diamond compact is cemented carbide or cobalt sintered tungsten carbide (WC-Co) with an addition of metallic cobalt to the feed of approximately <NUM>-<NUM> wt%.

When forming a polycrystalline diamond blank or a polycrystalline diamond cutter, the diamond catalyst source can be a substrate material positioned adjacent the diamond particles. Example substrate materials have a Co-based composition and are iron-free. A particular iron-free, Co-based composition suitable for use as a substrate to form the disclosed polycrystalline diamond blank or cutter is a substrate of cemented carbide or cobalt sintered tungsten carbide (WC-Co) with cobalt content ranging from <NUM>-<NUM> wt% in the substrate.

Metal catalyst remaining in the diamond table after the HPHT sintering process can be detrimental to polycrystalline diamond performance when used in cutting or machining applications or when drilling subterranean geologic formations. Therefore, metal catalyst remaining in the diamond table after the HPHT sintering process can optionally be removed in a subsequent leaching process. In the leaching process, at least a portion of the diamond body is exposed to an acid suitable for the dissolution of metal catalyst, such as aqua regia (a mixture of nitric acid and hydrochloric acid, optimally in a molar ratio of <NUM>:<NUM>). Catalyst material in the portion of the diamond body exposed to the acid will be removed by the leaching process, leaving inter-grain regions in the acid-leached portion of the diamond body that are substantially free of catalyst material. As known in the art, at least partial catalyst material removal may provide a polycrystalline diamond material with increased thermal stability, which may also beneficially affect the wear resistance of the polycrystalline diamond material. When present, the acid-leached portion of the diamond body extends from a working surface into an interior volume of the diamond body.

Although the present invention has been described in connection with embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departure from the spirit and scope of the invention as defined in the appended claims. For example, although described in relation to fissionable fuel materials, nuclear reactors, and associated components, the principles, compositions, structures, features, arrangements and processes described herein can also apply to other materials, other compositions, other structures, other features, other arrangements and other processes as well as to their manufacture and to other reactor types.

The various singular/plural permutations are not expressly set forth herein for sake of clarity.

The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures may be implemented which achieve the same functionality. Likewise, any two components so associated can also be viewed as being "operably connected", or "operably coupled," to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "operably couplable," to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components, and/or wirelessly interactable, and/or wirelessly interacting components, and/or logically interacting, and/or logically interactable components.

Claim 1:
A polycrystalline diamond compact, comprising:
a diamond table (<NUM>) having a top surface (<NUM>) and/or a side surface (<NUM>) as working surfaces, and an exterior surface or interface as a non-working surface, the interface being defined when the diamond table (<NUM>) is mounted on a substrate and extending between the diamond table (<NUM>) and the substrate, and an interior volume, the diamond table comprising
a volume of crystalline diamond grains bonded together by diamond-to-diamond bonds to form the diamond table (<NUM>), the diamond table (<NUM>) including a plurality of inter-grain regions disposed between the bonded crystalline diamond grains;
a cobalt-based catalyst material present in at least a portion of the plurality of inter-grain regions; and
an iron concentration gradient extending from the exterior surface or interface into the interior volume of the diamond table (<NUM>),
wherein an iron concentration increases along the iron concentration gradient from <NUM> wt.% to <NUM> wt.% Fe at the exterior surface or interface to <NUM> wt.% to <NUM> wt.% at a distance of <NUM> microns to <NUM> microns from the exterior surface or interface into the interior volume of the diamond table (<NUM>).