Alloys With Low Coefficient Of Thermal Expansion As PDC Catalysts And Binders

A cutting table includes a lattice structure and a catalyst material deposited within voids formed within the lattice. The catalyst material is deposited in the voids during a sintering process that forms the lattice. The catalyst material has a coefficient of thermal expansion that is less than that of cobalt. The catalyst material is any one of chromium, tantalum, ruthenium, an alloy of cobalt, an alloy of a Group VIII metal and at least one non-catalyst metal, an alloy of two or more Group VIII metals, or a eutectic alloy. In certain embodiments, the catalyst material has a thermal conductivity that is greater than that of cobalt. In certain embodiments, the cutting table is bonded to a substrate, which is formed from a substrate material and a binder material. In some embodiments, the binder material and the catalyst material are the same; while in others, they are different.

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Description
RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patent Application No. 61/364,122, entitled “Alloys With Low Coefficient Of Thermal Expansion As PDC Catalysts And Binders” and filed on Jul. 14, 2010, which is incorporated by reference herein.

TECHNICAL FIELD

The present invention relates generally to polycrystalline diamond compact (“PDC”) cutters; and more particularly, to PDC cutters having improved thermal stability.

BACKGROUND

Polycrystalline diamond compacts (“PDC”) have been used in industrial applications, including rock drilling applications and metal machining applications. Such compacts have demonstrated advantages over some other types of cutting elements, such as better wear resistance and impact resistance. The PDC can be formed by sintering individual diamond particles together under the high pressure and high temperature (“HPHT”) conditions referred to as the “diamond stable region,” which is typically above forty kilobars and between 1,200 degrees Celsius and 2,000 degrees Celsius, in the presence of a catalyst/solvent which promotes diamond-diamond bonding. Some examples of catalyst/solvents for sintered diamond compacts are cobalt, nickel, iron, and other Group VIII metals. PDCs usually have a diamond content greater than seventy percent by volume, with about eighty percent to about ninety-five percent being typical. An unbacked PDC can be mechanically bonded to a tool (not shown), according to one example. Alternatively, the PDC can be bonded to a substrate, thereby forming a PDC cutter, which is typically insertable within a downhole tool (not shown), such as a drill bit or a reamer.

FIG. 1 shows a side view of a PDC cutter 100 having a polycrystalline diamond (“PCD”) cutting table 110, or compact, in accordance with the prior art. Although a PCD cutting table 110 is described in the exemplary embodiment, other types of cutting tables, including cubic boron nitride (“CBN”) compacts, are used in alternative types of cutters. Referring to FIG. 1, the PDC cutter 100 typically includes the PCD cutting table 110 and a substrate 150 that is coupled to the PCD cutting table 110. The PCD cutting table 110 is about one hundred thousandths of an inch (2.5 millimeters) thick; however, the thickness is variable depending upon the application in which the PCD cutting table 110 is to be used.

The substrate 150 includes a top surface 152, a bottom surface 154, and a substrate outer wall 156 that extends from the circumference of the top surface 152 to the circumference of the bottom surface 154. The PCD cutting table 110 includes a cutting surface 112, an opposing surface 114, and a PCD cutting table outer wall 116 that extends from the circumference of the cutting surface 112 to the circumference of the opposing surface 114. The opposing surface 114 of the PCD cutting table 110 is coupled to the top surface 152 of the substrate 150. Typically, the PCD cutting table 110 is coupled to the substrate 150 using a high pressure and high temperature (“HPHT”) press. However, other methods known to people having ordinary skill in the art can be used to couple the PCD cutting table 110 to the substrate 150. In one embodiment, upon coupling the PCD cutting table 110 to the substrate 150, the cutting surface 112 of the PCD cutting table 110 is substantially parallel to the substrate's bottom surface 154. Additionally, the PDC cutter 100 has been illustrated as having a right circular cylindrical shape; however, the PDC cutter 100 is shaped into other geometric or non-geometric shapes in other embodiments. In certain embodiments, the opposing surface 114 and the top surface 152 are substantially planar; however, the opposing surface 114 and the top surface 152 can be non-planar in other embodiments. Additionally, according to some exemplary embodiments, a bevel (not shown) is formed around at least the circumference of the PCD cutting table 110.

According to one example, the PDC cutter 100 is formed by independently forming the PCD cutting table 110 and the substrate 150, and thereafter bonding the PCD cutting table 110 to the substrate 150. Alternatively, the substrate 150 is initially formed and the PCD cutting table 110 is then formed on the top surface 152 of the substrate 150 by placing polycrystalline diamond powder onto the top surface 152 and subjecting the polycrystalline diamond powder and the substrate 150 to a high temperature and high pressure process. Alternatively, the substrate 150 and the PCD cutting table 110 are formed and bonded together at about the same time. Although a few methods of forming the PDC cutter 100 have been briefly mentioned, other methods known to people having ordinary skill in the art can be used.

According to one example for forming the PDC cutter 100, the PCD cutting table 110 is formed and bonded to the substrate 150 by subjecting a layer of diamond powder and a mixture of tungsten carbide and cobalt powders to HPHT conditions. The cobalt is typically mixed with tungsten carbide and positioned where the substrate 150 is to be formed. The diamond powder is placed on top of the cobalt and tungsten carbide mixture and positioned where the PCD cutting table 110 is to be formed. The entire powder mixture is then subjected to HPHT conditions so that the cobalt melts and facilitates the cementing, or binding, of the tungsten carbide to form the substrate 150. The melted cobalt also diffuses, or infiltrates, into the diamond powder and acts as a catalyst for synthesizing diamonds and forming the PCD cutting table 110. Thus, the cobalt acts as both a binder for cementing the tungsten carbide and as a catalyst/solvent for the sintering of the diamond powder to form diamond-diamond bonds. The cobalt also facilitates in forming strong bonds between the PCD cutting table 110 and the cemented tungsten carbide substrate 150.

Cobalt has been a preferred constituent of the PDC manufacturing process. Traditional PDC manufacturing processes use cobalt as the binder material for forming the substrate 150 and also as the catalyst material for diamond synthesis because of the large body of knowledge related to using cobalt in these processes. The synergy between the large bodies of knowledge and the needs of the process have led to using cobalt as both the binder material and the catalyst material. However, as is known in the art, alternative metals, such as iron, nickel, chromium, manganese, and tantalum, can be used as a catalyst for diamond synthesis. When using these alternative metals as a catalyst for diamond synthesis to form the PCD cutting table 110, cobalt, or some other material such as nickel chrome or iron, is typically used as the binder material for cementing the tungsten carbide to form the substrate 150. Although some materials, such as tungsten carbide and cobalt, have been provided as examples, other materials known to people having ordinary skill in the art can be used to form the substrate 150, the PCD cutting table 110, and form bonds between the substrate 150 and the PCD cutting table 110.

FIG. 2 is a schematic microstructural view of the PCD cutting table 110 of FIG. 1 in accordance with the prior art. Referring to FIGS. 1 and 2, the PCD cutting table 110 has diamond particles 210, one or more interstitial spaces 212 formed between the diamond particles 210, and cobalt 214 deposited within the interstitial spaces 212. During the sintering process, the interstitial spaces 212, or voids, are formed between the carbon-carbon bonds and are located between the diamond particles 210. The diffusion of cobalt 214 into the diamond powder results in cobalt 214 being deposited within these interstitial spaces 212 that are formed within the PCD cutting table 110 during the sintering process.

Once the PCD cutting table 110 is formed, the PCD cutting table 110 is known to wear quickly when the temperature reaches a critical temperature. This critical temperature is about 750 degrees Celsius and is reached when the PCD cutting table 110 is cutting rock formations or other known materials. The high rate of wear is believed to be caused by the differences in the thermal expansion rate between the diamond particles 210 and the cobalt 214 and also by the chemical reaction, or graphitization, that occurs between cobalt 214 and the diamond particles 210. The coefficient of thermal expansion for the diamond particles 210 is about 1.0×10−6 millimeters−1×Kelvin−1 (“mm−1K−1”), while the coefficient of thermal expansion for the cobalt 214 is about 13.0×10−6 mm−1K−1. Thus, the cobalt 214 expands much faster than the diamond particles 210 at temperatures above this critical temperature, thereby making the bonds between the diamond particles 210 unstable. The PCD cutting table 110 becomes thermally degraded at temperatures above about 750 degrees Celsius and its cutting efficiency deteriorates significantly.

Efforts have been made to slow the wear of the PCD cutting table 110 at these high temperatures. These efforts include performing an acid leaching process of the PCD cutting table 110 which removes the cobalt 214 from the interstitial spaces 212. Typical leaching processes involve the presence of an acid solution (not shown) which reacts with the cobalt 214 that is deposited within the interstitial spaces 212 of the PCD cutting table 110. According to one example of a typical leaching process, the PDC cutter 100 is placed within an acid solution such that at least a portion of the PCD cutting table 110 is submerged within the acid solution. The acid solution reacts with the cobalt 214 along the outer surfaces of the PCD cutting table 110. The acid solution slowly moves inwardly within the interior of the PCD cutting table 110 and continues to react with the cobalt 214. However, as the acid solution moves further inwards, the reaction byproducts become increasingly more difficult to remove; and hence, the rate of leaching slows down considerably. For this reason, a tradeoff occurs between leaching process duration, wherein costs increase as the leaching process duration increases, and the leaching depth. Thus, the leaching depth is typically about 0.2 millimeter, but can be more or less depending upon the PCD cutting table 110 requirements and/or the cost constraints. The removal of cobalt 214 alleviates the issues created due to the differences in the thermal expansion rate between the diamond particles 210 and the cobalt 214 and due to graphitization. However, the leaching process is costly and also has other deleterious effects on the PCD cutting table 110, such as loss of strength.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and aspects of the invention are best understood with reference to the following description of certain exemplary embodiments, when read in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a side view of a PDC cutter having a PCD cutting table in accordance with the prior art;

FIG. 2 is a schematic microstructural view of the PCD cutting table of FIG. 1 in accordance with the prior art;

FIG. 3A is a side view of a pre-sintered PDC cutter in accordance with an exemplary embodiment of the present invention;

FIG. 3B is a side view of a PDC cutter formed from sintering the pre-sintered PDC cutter of FIG. 3A in accordance with an exemplary embodiment of the present invention;

FIG. 4A is a side view of a pre-sintered PDC cutter in accordance with another exemplary embodiment of the present invention;

FIG. 4B is a side view of a PDC cutter formed from sintering the pre-sintered PDC cutter of FIG. 4A in accordance with another exemplary embodiment of the present invention; and

FIG. 5 is a phase diagram of cobalt and Element X in accordance with an exemplary embodiment of the present invention.

The drawings illustrate only exemplary embodiments of the invention and are therefore not to be considered limiting of its scope, as the invention may admit to other equally effective embodiments.

BRIEF DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention is directed generally to polycrystalline diamond compact (“PDC”) cutters; and more particularly, to PDC cutters having improved thermal stability. Although the description of exemplary embodiments is provided below in conjunction with a PDC cutter, alternate embodiments of the invention may be applicable to other types of cutters or compacts including, but not limited to, polycrystalline boron nitride (“PCBN”) cutters or PCBN compacts. As previously mentioned, the compact is mountable to a substrate to form a cutter or is mountable directly to a tool for performing cutting processes. The invention is better understood by reading the following description of non-limiting, exemplary embodiments with reference to the attached drawings, wherein like parts of each of the figures are identified by like reference characters, and which are briefly described as follows.

FIG. 3A is a side view of a pre-sintered PDC cutter 300 in accordance with an exemplary embodiment of the present invention. FIG. 3B is a side view of a PDC cutter 350 formed from sintering the pre-sintered PDC cutter 300 of FIG. 3A in accordance with an exemplary embodiment of the present invention. FIGS. 3A and 3B provide one example for forming the PDC cutter 350. Referring to FIGS. 3A and 3B, the pre-sintered PDC cutter 300 includes a substrate layer 310 and a PCD cutting table layer 320, while the PDC cutter 350 includes a substrate 360 and a PCD cutting table 370. The substrate layer 310 is positioned at the bottom of the pre-sintered PDC cutter 300 and forms the substrate 360 upon performing the sintering process. The PCD cutting table layer 320 is positioned atop the substrate layer 310 and forms the PCD cutting table 370 upon performing the sintering process. Thus, the PCD cutting table 370 is positioned atop the substrate 360.

The substrate layer 310 is formed from a mixture of substrate powder 332 and a binder/catalyst material 334. The substrate powder 332 is tungsten carbide powder; however, the substrate powder 332 is formed from other suitable material known to people having ordinary skill in the art without departing from the scope and spirit of the exemplary embodiment according to other exemplary embodiments. The binder/catalyst material 334 is any material capable of behaving as a binder material for the substrate powder 310 and as a catalyst material for the diamond powder 336, or any other material, that forms the PCD cutting table layer 320. Additionally, the binder/catalyst material 334 has a coefficient of thermal expansion that is less than the coefficient of thermal expansion of cobalt and/or has a higher thermal conductivity than the thermal conductivity of cobalt. The coefficient of thermal expansion for cobalt is about 13.0×10−6 mm−1 K−1. The thermal conductivity for cobalt is about 100.0 Watts/(meters×Kelvin) (“W/(mK)”). Some examples of the binder/catalyst material 334 includes, but is not limited to, chromium, tantalum, ruthenium, certain alloys of cobalt such as cobalt/molybdenum, cobalt/chromium, or cobalt/nickel/chrome, certain alloys of a Group VIII metal and at least one non-catalyst metal, and certain alloys of two or more Group VIII metals, wherein the alloys furnish a net reduction in the coefficient of thermal expansion and/or a net increase in the thermal conductivity. Other examples of suitable alloys are determinable by people having ordinary skill in the art once having the benefit of the present disclosure. The binder/catalyst material 334 includes any eutectic or near eutectic alloy that is effective as a catalyst material for diamond synthesis while exhibiting either a lower coefficient of thermal expansion than cobalt and/or a higher thermal conductivity than cobalt. A near eutectic alloy is defined to include alloy compositions that are within plus or minus ten atomic weight percent from the eutectic composition as long as the melting point of cobalt is not exceeded.

If the binder/catalyst material 334 has a lower coefficient of thermal expansion than cobalt, the carbon-carbon bonds which form the PCD cutting table 370 are more stable than if cobalt were used because the binder/catalyst material 334 expands at a lesser rate than cobalt. Hence, the carbon-carbon bonds are better able to withstand the expansion of the binder/catalyst material 334 than the expansion of cobalt at the same temperature. If the binder/catalyst material 334 has a higher thermal conductivity than cobalt, the heat generated within the PCD cutting table 370 dissipates better when the binder/catalyst material 334 is used to form the PCD cutting table 370 than when cobalt is used. Thus, the PCD cutting table 370 is able to withstand more heat generation and hence higher temperatures when the binder/catalyst material 334 is used to form the PCD cutting table 370.

Once subjected to high pressure and high temperature conditions, the substrate layer 310 forms the substrate 360. The substrate layer 310 includes a top layer surface 312, a bottom layer surface 314, and a substrate layer outer wall 316 that extends from the circumference of the top layer surface 312 to the circumference of the bottom layer surface 314. The substrate layer 310 is formed into a right circular cylindrical shape according to one exemplary embodiment, but can be formed into other geometric or non-geometric shapes.

The PCD cutting table layer 320 is formed from a diamond powder 336; however, other suitable materials known to people having ordinary skill in the art can be used without departing from the scope and spirit of the exemplary embodiment. Although not depicted, according to some exemplary embodiments, the PCD cutting table layer 320 includes the diamond powder 336 and the binder/catalyst material 334. Once subjected to high pressure and high temperature conditions, the PCD cutting table layer 320 forms the PCD cutting table 370. The PCD cutting table layer 320 includes a cutting layer surface 322, an opposing layer surface 324, and a PCD cutting table layer outer wall 326 that extends from the circumference of the cutting layer surface 322 to the circumference of the opposing layer surface 324.

Once the pre-sintered PDC cutter 300 is formed, the pre-sintered PDC cutter 300 is subjected to high pressure and high temperature conditions to form the PDC cutter 350. During the HPHT conditions, the binder/catalyst material 334 liquefies within the substrate layer 310 and advances, or infiltrates, into the PCD cutting table layer 320. The binder/catalyst material 334 behaves as a binder material for the substrate powder 332, which then is cemented, or binded, to form a cemented substrate powder 382. This cemented substrate powder 382, along with the binder/catalyst material 334 being interspersed therein, forms the substrate 360 upon completion of the sintering process. The liquefied binder/catalyst material 334 diffuses into the PCD cutting table layer 320 from the substrate layer 310 and also behaves as a catalyst material for the diamond powder 336 within the PCD cutting table layer 320. The binder/catalyst material 334 facilitates diamond crystal intergrowth, thereby transforming the diamond powder 336 into a diamond lattice 386. The diamond lattice 386 includes interstitial spaces (not shown), which is similar to the interstitial spaces 212 (FIG. 2), that are formed during the sintering process. The binder/catalyst material 334 is deposited within these interstitial spaces. Thus, the diamond lattice 386, along with the binder/catalyst material 334 deposited within the interstitial spaces, forms the PCD cutting table 370 upon completion of the sintering process. Although the diamond lattice 386 is formed in the PCD cutting table 370, other lattices are formed in the PCD cutting table 370 when other materials, different than diamond powder 336, is used. The binder/catalyst material 334 also facilitates in forming bonds between the PCD cutting table 370 and the substrate 360.

The PDC cutter 350 is formed once the substrate 360 and the PCD cutting layer 370 are completely formed and the substrate 360 is bonded to the PCD cutting layer 370. The substrate 360 includes a top surface 362, a bottom surface 364, and a substrate outer wall 366 that extends from the circumference of the top surface 362 to the circumference of the bottom surface 364. The substrate 360 includes cemented substrate powder 382 and binder/catalyst material 334 interspersed therein. The substrate 360 is formed into a right circular cylindrical shape according to one exemplary embodiment, but can be formed into other geometric or non-geometric shapes depending upon the application for the PDC cutter 350.

The PCD cutting table 370 includes a cutting surface 372, an opposing surface 374, and a PCD cutting table outer wall 376 that extends from the circumference of the cutting surface 372 to the circumference of the opposing surface 374. The PCD cutting table 370 includes the diamond lattice 386 and the binder/catalyst material 334 deposited within the interstitial spaces formed within the diamond lattice 386. The opposing surface 374 is bonded to the top surface 362. According to some exemplary embodiments, a bevel (not shown) is formed around the circumference of the PCD cutting table 370.

The PCD cutting table 370 is bonded to the substrate 360 according to methods known to people having ordinary skill in the art. In one example, the PDC cutter 350 is formed by independently forming the PCD cutting table 370 and the substrate 360, and thereafter bonding the PCD cutting table 370 to the substrate 360. In another example, the substrate 360 is initially formed and the PCD cutting table 370 is then formed on the top surface 362 of the substrate 360 by placing polycrystalline diamond powder 336 onto the top surface 362 and subjecting the polycrystalline diamond powder 336 and the substrate 360 to a high temperature and high pressure process.

In one exemplary embodiment, upon coupling the PCD cutting table 370 to the substrate 360, the cutting surface 372 of the PCD cutting table 370 is substantially parallel to the bottom surface 364 of the substrate 360. Additionally, the PDC cutter 350 has been illustrated as having a right circular cylindrical shape; however, the PDC cutter 350 is shaped into other geometric or non-geometric shapes in other exemplary embodiments. In certain exemplary embodiments, the opposing surface 374 and the top surface 362 are substantially planar; however, the opposing surface 374 and the top surface 362 can be non-planar in other exemplary embodiments.

FIG. 4A is a side view of a pre-sintered PDC cutter 400 in accordance with another exemplary embodiment of the present invention. FIG. 4B is a side view of a PDC cutter 450 formed from sintering the pre-sintered PDC cutter 400 of FIG. 4A in accordance with another exemplary embodiment of the present invention. FIGS. 4A and 4B provide one example for forming the PDC cutter 450. Referring to FIGS. 4A and 4B, the pre-sintered PDC cutter 400 includes a substrate layer 410 and a PCD cutting table layer 420, while the PDC cutter 450 includes a substrate 460 and a PCD cutting table 470. The substrate layer 410 is positioned at the bottom of the pre-sintered PDC cutter 400 and forms the substrate 460 upon performing the sintering process. The PCD cutting table layer 420 is positioned atop the substrate layer 410 and forms the PCD cutting table 470 upon performing the sintering process. Thus, the PCD cutting table 470 is positioned atop the substrate 460.

The substrate layer 410 is formed from a mixture of a substrate powder 432 and a binder material 434. The substrate powder 432 is tungsten carbide powder; however, the substrate powder 432 is formed from other suitable material known to people having ordinary skill in the art without departing from the scope and spirit of the exemplary embodiment according to some other exemplary embodiments. The binder material 434 is any material capable of behaving as a binder for the substrate powder 410. Some examples of the binder material 434 include, but are not limited to, cobalt, nickel chrome, and iron. Once subjected to high pressure and high temperature conditions, the substrate layer 410 forms the substrate 460. The substrate layer 410 includes a top layer surface 412, a bottom layer surface 414, and a substrate layer outer wall 416 that extends from the circumference of the top layer surface 412 to the circumference of the bottom layer surface 414. The substrate layer 410 is formed into a right circular cylindrical shape according to one exemplary embodiment, but can be formed into other geometric or non-geometric shapes.

The PCD cutting table layer 420 is formed from a mixture of a diamond powder 436 and a catalyst material 438. Although diamond powder 436 is used to form the PCD cutting table layer 420, other suitable materials known to people having ordinary skill in the art can be used without departing from the scope and spirit of the exemplary embodiment. The catalyst material 438 is any material capable of behaving as a catalyst for the diamond powder 436 that forms the PCD cutting table layer 420 or for any other material that is used to form the PCD cutting table 470. Additionally, the catalyst material 438 has a coefficient of thermal expansion that is less than the coefficient of thermal expansion of cobalt and/or has a higher thermal conductivity than the thermal conductivity of cobalt. The coefficient of thermal expansion for cobalt is about 13.0×10−6 mm−1 K−1. The thermal conductivity for cobalt is about 100.0 W/(mK). Some examples of the catalyst material 438 include, but are not limited to, chromium, tantalum, ruthenium, certain alloys of cobalt such as cobalt/molybdenum, cobalt/chromium, or cobalt/nickel/chrome, certain alloys of a Group VIII metal and at least one non-catalyst metal, and certain alloys of two or more Group VIII metals, wherein the alloys furnish a net reduction in the coefficient of thermal expansion and/or a net increase in the thermal conductivity. Other examples of suitable alloys are determinable by people having ordinary skill in the art once having the benefit of the present disclosure. The catalyst material 438 includes any eutectic or near eutectic alloy that is effective as a catalyst for diamond synthesis while exhibiting a lower coefficient of thermal expansion than cobalt and/or a higher thermal conductivity than cobalt.

If the catalyst material 438 has a lower coefficient of thermal expansion than cobalt, the carbon-carbon bonds which form the PCD cutting table 470 are more stable than if cobalt were used because the catalyst material 438 expands at a lesser rate than cobalt. Hence, the carbon-carbon bonds are better able to withstand the expansion of the catalyst material 438 than the expansion of cobalt at the same temperature. If the catalyst material 438 has a higher thermal conductivity than cobalt, the heat generated within the PCD cutting table 470 dissipates better when the catalyst material 438 is used to form the PCD cutting table 470 than when cobalt is used. Thus, the PCD cutting table 470 is able to withstand more heat generation and hence higher temperatures when the catalyst material 438 is used to form the PCD cutting table 470.

According to some exemplary embodiments, the melting point of the catalyst material 438 is lower than the melting point of the binder material 434. The melting point of cobalt, which can be used as the binder material 434, is about 1495 degrees Celsius. According to some exemplary embodiments, the binder material 434 and the catalyst material 438 are different materials; however, the binder material 434 and the catalyst material 438 can be the same material according to some exemplary embodiments. Once subjected to high pressure and high temperature conditions, the PCD cutting table layer 420 forms the PCD cutting table 470. The PCD cutting table layer 420 includes a cutting layer surface 422, an opposing layer surface 424, and a PCD cutting table layer outer wall 426 that extends from the circumference of the cutting layer surface 422 to the circumference of the opposing layer surface 424. According to some exemplary embodiments, a bevel (not shown) is formed around the circumference of the PCD cutting table 470.

According to exemplary embodiments where the melting point of the catalyst material 438 is lower than the melting point of the binder material 434, once the pre-sintered PDC cutter 400 is formed, the pre-sintered PDC cutter 400 is subjected to high pressure and high temperature conditions to form the PDC cutter 450. During the HPHT conditions, the temperature is initially brought to a first temperature, which is the melting point of the catalyst material 438 according to some exemplary embodiments. According to some exemplary embodiments, the first temperature is higher than the melting point of the catalyst material 438, but maintained below a second temperature, which is discussed in further detail below. The first temperature can be varied within this range that is between the first temperature and the second temperature. At this first temperature, the catalyst material 438 liquefies within the PCD cutting table layer 470 and facilitates diamond crystal intergrowth, thereby transforming the diamond powder 436 into a diamond lattice 486. The diamond lattice 486 includes interstitial spaces (not shown), which is similar to the interstitial spaces 212 (FIG. 2), that are formed during the sintering process. The catalyst material 438 is deposited within these interstitial spaces. Thus, the diamond lattice 486, along with the catalyst material 438 deposited within the interstitial spaces, forms the PCD cutting table 470 upon completion of the sintering process. Although the diamond lattice 486 is formed in the PCD cutting table 470, other lattices are formed in the PCD cutting table 470 when other materials, different than diamond powder 436, is used.

Once the PCD cutting table 470 is formed, the temperature is then increased from the first temperature to at least a second temperature, which is the melting point of the binder material 434 or some other higher temperature above the melting point of the binder material 434. The binder material 434 liquefies within the substrate layer 410 and facilitates cementing of the substrate powder 432, thereby transforming the substrate powder 432 into a cemented substrate powder 482. This cemented substrate powder 482, along with the binder material 434 being interspersed therein, forms the substrate 460 upon completion of the sintering process. The binder material 434 and/or the catalyst material 438 facilitate forming bonds between the PCD cutting table 470 and the substrate 460.

The PDC cutter 450 is formed once the substrate 460 and the PCD cutting layer 470 are completely formed and the substrate 460 is bonded to the PCD cutting layer 470. The substrate 460 includes a top surface 462, a bottom surface 464, and a substrate outer wall 466 that extends from the circumference of the top surface 462 to the circumference of the bottom surface 464. The substrate 460 includes cemented substrate powder 482 and binder material 434 interspersed therein. The substrate 460 is formed into a right circular cylindrical shape according to one exemplary embodiment, but can be formed into other geometric or non-geometric shapes depending upon the application for the PDC cutter 450.

The PCD cutting table 470 includes a cutting surface 472, an opposing surface 474, and a PCD cutting table outer wall 476 that extends from the circumference of the cutting surface 472 to the circumference of the opposing surface 474. The PCD cutting table 470 includes the diamond lattice 486 and the catalyst material 438 deposited within the interstitial spaces formed within the diamond lattice 486. The opposing surface 474 is bonded to the top surface 462.

The PCD cutting table 470 is bonded to the substrate 460 according to methods known to people having ordinary skill in the art. In one example, the PDC cutter 450 is formed by independently forming the PCD cutting table 470 and the substrate 460, and thereafter bonding the PCD cutting table 470 to the substrate 460. In another example, the substrate 460 is initially formed and the PCD cutting table 470 is then formed on the top surface 462 of the substrate 460 by placing polycrystalline diamond powder 436 onto the top surface 462 and subjecting the polycrystalline diamond powder 436 and the substrate 460 to a high temperature and high pressure process.

In one exemplary embodiment, upon coupling the PCD cutting table 470 to the substrate 460, the cutting surface 472 of the PCD cutting table 470 is substantially parallel to the bottom surface 464 of the substrate 460. Additionally, the PDC cutter 450 has been illustrated as having a right circular cylindrical shape; however, the PDC cutter 450 is shaped into other geometric or non-geometric shapes in other exemplary embodiments. In certain exemplary embodiments, the opposing surface 474 and the top surface 462 are substantially planar; however, the opposing surface 474 and the top surface 462 can be non-planar in other exemplary embodiments.

As previously mentioned, the binder/catalyst material 334 (FIG. 3) and the catalyst material 438 are an alloy of cobalt or some other group VIII metal which exhibit a lower coefficient of thermal expansion than cobalt and/or a higher thermal conductivity than cobalt according to some exemplary embodiments. An alloy is a combination, either in solution or compound, of two or more elements, at least one of which is a metal, and where the resultant material alloy has metallic properties. Unlike pure metals, many alloys do not have a single melting point. Instead, many alloys have a temperature range where the material begins melting at one lower temperature and is completely melted at another higher temperature. Thus, during the melting of the alloy, the material is a mixture of solid and liquid phases when subjected to a temperature between these two temperatures. The temperature at which the alloy starts melting is referred to as the solidus, while the temperature at which the alloy is completely melted is referred to as the liquidus. However, also as previously mentioned and according to some exemplary embodiments, the binder/catalyst material 334 (FIG. 3) and the catalyst material 438 are a eutectic alloy or near eutectic alloy which exhibits a lower coefficient of thermal expansion than cobalt and/or a higher thermal conductivity than cobalt. Eutectic alloys are fabricated to melt at a single melting point temperature and not within a temperature range. The eutectic alloy is an alloy formed from the mixture of two or more elements which has a lower melting point that any of its elements that are used to form the eutectic alloy. In one example, the alloy or eutectic alloy is formed by preparing a homogeneous mixture of the two or more elements that form the alloy or eutectic alloy. The proper ratios of components to obtain a eutectic alloy is identified by the eutectic point on a phase diagram, which is discussed in further detail with respect to FIG. 5.

Provided below in Table I is a list of elements that can be alloyed with cobalt to form a eutectic alloy that has a resulting coefficient of thermal expansion that is lower than the coefficient of thermal expansion for cobalt. The elements of carbon and cobalt are provided as references in Table I since carbon is used to form the PCD cutting table, while cobalt is the typical catalyst material 438 or binder/catalyst material 334 (FIG. 3) that is deposited within the interstitial spaces formed between the carbon bonds in the PCD cutting table 370 and 470. Thus, the eutectic alloy being used as the catalyst material 438 or the binder/catalyst material 334 (FIG. 3) in exemplary embodiments of the present invention should have a lower resulting coefficient of thermal expansion and/or a higher resulting thermal conductivity than cobalt alone. Although cobalt is being chosen as one of the alloying elements, any other group VIII metal can be chosen as the alloying element according to other exemplary embodiments.

TABLE I Thermal Co- Expansion Melting Thermal Eu ×10−6 Point conductivity Element Sym C m · m−1 · K−1 C W/(m · K) Carbon C 1.0 3675 900.00 Silicon Si 1195 2.6 1410 149.00 Tungsten W 1471 4.5 3407 173.00 Molybdenum Mo 1335 4.8 2617 138.00 Chromium Cr 1402 4.9 1857 93.90 Osmium Os 1590 5.1 3027 87.60 Zirconium Zr 1232 5.7 1852 22.60 Hafnium Hf 1270 5.9 2227 23.00 Boron B 6.0 2300 27.40 Germanium Ge 810 6.0 938 60.20 Rhenium Re 1520 6.2 3180 48.00 Cerium Ce 6.3 798 11.30 Tantalum Ta 1276 6.3 2996 57.50 Iridium Ir 6.4 2443 147.00 Ruthenium Ru 1390 6.4 2250 117.00 Praseodymium Pr 541 6.7 931 12.50 Niobium Nb 1237 7.3 2468 53.70 Rhodium Rh 1390 8.2 1966 150.00 Vanadium V 1242 8.4 1902 30.70 Titanium Ti 1020 8.6 1660 21.90 Platinum Pt 1430 8.8 1772 71.60 Gadolinium Gd 650 9.4 1312 10.60 Neodymium Nd 566 9.6 1016 16.50 Dysprosium Dy 714 9.9 1407 10.70 Lutetium Lu 9.9 1663 16.40 Scandium Sc 790 10.2 1539 15.80 Terbium Tb 960 10.3 1357 11.10 Yttrium Y 715 10.6 1526 17.20 Promethium Pm 11.0 931 17.90 Antimony Sb 623 11.0 631 24.40 Thorium Th 975 11.0 1755 54.00 Holmium Ho 770 11.2 1470 16.20 Beryllium Be 11.3 1287 200.00 Iron Fe 1476 11.8 1535 80.40 Palladium Pd 1219 11.8 1552 71.80 Lanthanum La 500 12.1 920 13.40 Erbium Er 800 12.2 1522 14.50 Samarium Sm 575 12.7 1072 13.30 Cobalt Co 13.0 1495 100.00

As shown in the above table, each element is provided with values for a “Co-Eu,” a “thermal expansion,” a “melting point,” and a “thermal conductivity.” The value for the “Co-Eu” is the eutectic melting temperature, or eutectic melting point, when the corresponding element is alloyed with cobalt in accordance with a eutectic composition. The value for the “thermal expansion” is the coefficient of thermal expansion for the corresponding element. These coefficients of thermal expansion are less than the coefficient of thermal expansion for cobalt. Once the element is alloyed with cobalt, the resulting coefficient of thermal expansion for the alloy is less than the coefficient of thermal expansion for cobalt. Hence, the coefficient of thermal expansion for the eutectic alloy also is less than the coefficient of thermal expansion for cobalt. The value for the “melting point” is the melting point for the corresponding element. As seen the eutectic melting temperature for when the corresponding element is alloyed with cobalt is less than the melting point of either the cobalt and the corresponding element. The value for the “thermal conductivity” is the thermal conductivity for the corresponding element. These thermal conductivity values are higher or lower than the thermal conductivity for cobalt. Once the element is alloyed with cobalt, the resulting thermal conductivity value for the alloy is between the thermal conductivity for the corresponding element and the thermal conductivity for cobalt. Hence, depending upon the applications that the PDC cutter 350 and 450 is to be used in, the alloy, or eutectic alloy, that is to be used for the catalyst material 438 and the binder/catalyst material 334 (FIG. 3) can be chosen appropriately to have either a lower coefficient of thermal expansion and/or a higher thermal conductivity.

FIG. 5 is a phase diagram of cobalt and Element X 500 in accordance with an exemplary embodiment of the present invention. Although phase diagram of cobalt and Element X 500 is provided as an example according to one exemplary embodiment, different phase diagrams of cobalt and one or more other elements or a group VIII element with one or more other elements can be used for obtaining a eutectic point, which is described in further detail below, according to other exemplary embodiments. Referring to FIG. 5, the phase diagram of cobalt and Element X 500 includes a composition axis 510, a temperature axis 520, a liquidus line 534, a solidus line 536, and a eutectic point 538.

The composition axis 510 is positioned on the x-axis and represents the composition of the alloy used as the catalyst material and/or the binder/catalyst material. The composition is measured in atomic weight percent of Element X. Proceeding from left to right along the composition axis 510, the composition of Element X increases. Thus, at the extreme left of the composition axis 510, the material is one hundred percent cobalt. Conversely, at the extreme right of the composition axis 510, the material is one hundred percent element X. The composition axis 510 includes a eutectic composition 540, which is discussed in further detail below.

The temperature axis 520 is positioned on the y-axis and represents the various temperatures that can be subjected on the alloy. The temperature is measured in degrees Celsius. Proceeding from top to bottom along the temperature axis 520, the temperature decreases. The temperature axis 520 includes a cobalt melting temperature 532, an Element X melting temperature 530, and a eutectic melting temperature 539, which is discussed in further detail below. The cobalt melting temperature 532 is the temperature at which a material having one hundred percent cobalt melts. The Element X melting temperature 530 is the temperature at which a material having one hundred percent Element X melts.

The phase diagram of cobalt and Element X 500 provides information on different phases of the cobalt and Element X alloy and under what compositions and temperatures these different phases exist. These phases include the total liquid phase 550 (“Liquid”), the total solid phase 552 (“Solid”), a cobalt slurry phase 554 (“L+Cos”), an Element X slurry phase 556 (“L+Xs”), a cobalt solid phase 558 (“Cos”), and a Element X solid phase 560 (“Xs”). The total liquid phase 550 occurs when both cobalt and Element X are both completely in the liquid phase. The total solid phase 552 occurs when both cobalt and Element X are both completely in the solid phase. The cobalt slurry phase 554 occurs when the material has cobalt crystals that is suspended in a slurry which also includes liquid cobalt. The Element X phase 556 occurs when the material has Element X crystals that is suspended in a slurry which also includes liquid Element X. The cobalt solid phase 558 occurs when all the cobalt is in solid phase and at least some portion of the Element X is in liquid phase. The Element X solid phase 560 occurs when all the Element X is in solid phase and at least some portion of the cobalt is in liquid phase.

The liquidus line 534 extends from the cobalt melting temperature 532 to a eutectic point 538 and then to the Element X melting temperature 530. The liquidus line 534 represents the temperature at which the alloy completely melts and forms a liquid. Thus, at temperatures above the liquidus line 534, the alloy is completely liquid. The solidus line 536 also extends from the cobalt melting temperature 532 to a eutectic point 538 and then to the Element X melting temperature 530. The solidus line 536 is positioned below the liquidus line 534, except for at the eutectic point 538. The solidus line 536 represents the temperature at which the alloy begins to melt. Thus, at temperatures below the solidus line 536, the alloy is completely solid. At the eutectic point 538, the liquidus line 534 intersects with the solidus line 536. The eutectic point 538 is defined on the phase diagram 500 as the intersection of the eutectic temperature 539 and the eutectic composition 540. The eutectic composition 540 is the composition where the alloy behaves as a single chemical composition and has a melting point where the total solid phase turns into a total liquid phase at a single temperature. Thus, one benefit for using the eutectic alloy for the catalyst material and/or the binder/catalyst material is that the eutectic alloy behaves as a single composition.

Although each exemplary embodiment has been described in detail, it is to be construed that any features and modifications that are applicable to one embodiment are also applicable to the other embodiments. Furthermore, although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons of ordinary skill in the art upon reference to the description of the exemplary embodiments. It should be appreciated by those of ordinary skill in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures or methods for carrying out the same purposes of the invention. It should also be realized by those of ordinary skill in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. It is therefore, contemplated that the claims will cover any such modifications or embodiments that fall within the scope of the invention.

Claims

1. A cutting table, comprising:

a lattice structure forming interstitial spaces therein; and
a catalyst material deposited within the interstitial spaces during a sintering process that forms the lattice structure, the catalyst material facilitating the growth of the lattice structure, the catalyst material having a coefficient of thermal expansion that is less than the coefficient of thermal expansion of cobalt.

2. The cutting table of claim 1, wherein the catalyst material is selected from a group consisting of chromium, tantalum, and ruthenium.

3. The cutting table of claim 1, wherein the catalyst material is selected from a group consisting of alloys of cobalt, alloys of a Group VIII metal and at least one non-catalyst metal, and alloys of two or more Group VIII metals.

4. The cutting table of claim 1, wherein the catalyst material comprises a eutectic alloy, the eutectic alloy comprising a eutectic composition.

5. The cutting table of claim 1, wherein the catalyst material comprises a near eutectic alloy.

6. The cutting table of claim 1, wherein the catalyst material has a thermal conductivity that is greater than the thermal conductivity of cobalt.

7. The cutting table of claim 1, wherein the lattice structure comprises a polycrystalline diamond.

8. A cutter, comprising:

a substrate comprising a top surface;
a cutting table, comprising: a cutting surface; an opposing surface coupled to the top surface; a cutting table outer wall extending from the circumference of the opposing surface to the circumference of the cutting surface; a lattice structure forming interstitial spaces therein; and a catalyst material deposited within the interstitial spaces during a sintering process that forms the lattice structure, the catalyst material facilitating the growth of the lattice structure, the catalyst material having a coefficient of thermal expansion that is less than the coefficient of thermal expansion of cobalt.

9. The cutter of claim 8, wherein the catalyst material is selected from a group consisting of chromium, tantalum, and ruthenium.

10. The cutter of claim 8, wherein the catalyst material is selected from a group consisting of alloys of cobalt, alloys of a Group VIII metal and at least one non-catalyst metal, and alloys of two or more Group VIII metals.

11. The cutter of claim 8, wherein the catalyst material comprises a eutectic alloy, the eutectic alloy comprising a eutectic composition.

12. The cutter of claim 8, wherein the catalyst material comprises a near eutectic alloy.

13. The cutter of claim 8, wherein the catalyst material has a thermal conductivity that is greater than the thermal conductivity of cobalt.

14. The cutter of claim 8, wherein the lattice structure comprises a polycrystalline diamond.

15. The cutter of claim 8, wherein the substrate is formed from a substrate powder and a binder material, the binder material cementing the substrate powder to form the substrate, the binder material being the same as the catalyst material.

16. The cutter of claim 15, wherein the catalyst material originates in the substrate and infiltrates into the cutting table.

17. The cutter of claim 8, wherein the substrate is formed from a substrate powder and a binder material, the binder material cementing the substrate powder to form the substrate, the binder material being different than the catalyst material.

18. The cutter of claim 17, wherein the melting point of the catalyst material is lower than the melting point of the binder material.

19. A method for fabricating a cutter, comprising:

forming a cutter table, the cutter table comprising: a lattice structure forming interstitial spaces therein; and a catalyst material deposited within the interstitial spaces during a sintering process that forms the lattice structure, the catalyst material facilitating the growth of the lattice structure, the catalyst material having a coefficient of thermal expansion that is less than the coefficient of thermal expansion of cobalt;
forming a substrate; and
bonding the cutter table to a substrate.

20. The method of claim 19, wherein the catalyst material is selected from a group consisting of chromium, tantalum, and ruthenium.

21. The method of claim 19, wherein the catalyst material is selected from a group consisting of alloys of cobalt, alloys of a Group VIII metal and at least one non-catalyst metal, and alloys of two or more Group VIII metals.

22. The method of claim 19, wherein the catalyst material comprises a eutectic alloy, the eutectic alloy comprising a eutectic composition.

23. The method of claim 19, wherein the catalyst material comprises a near eutectic alloy.

24. The method of claim 19, wherein the catalyst material has a thermal conductivity that is greater than the thermal conductivity of cobalt.

25. The method of claim 19, wherein the lattice structure comprises a polycrystalline diamond.

26. The method of claim 19, wherein forming the substrate comprises:

mixing a substrate powder and a binder material together to form a substrate mixture;
raising the pressure and temperature to a first temperature range to liquefy the binder material and allow the binder material to cement the substrate powder.

27. The method of claim 19, wherein forming the cutter table comprises:

placing a diamond powder on top of the substrate;
allowing the liquefied binder material to infiltrate from the substrate into the diamond powder; and
converting the diamond powder into the lattice structure,
wherein the binder material and the catalyst material are the same.

28. The method of claim 19, wherein forming the cutter table comprises:

mixing a diamond powder and a catalyst material together to form a PCD table mixture;
placing the mixture on top of the substrate;
raising the pressure and temperature to a second temperature range to liquefy the catalyst material; and
allowing the catalyst material to sinter the diamond powder to form the lattice structure,
wherein the binder material and the catalyst material are different, and wherein the second temperature range is less than the first temperature range, and wherein the second temperature range is below the melting point of the binder material.
Patent History
Publication number: 20120012402
Type: Application
Filed: Jul 11, 2011
Publication Date: Jan 19, 2012
Applicant: Varel International Ind., L.P. (Carrollton, TX)
Inventors: Gary M. Thigpen (Houston, TX), William W. King (Houston, TX)
Application Number: 13/180,414