Patent Application
20130001100
The present invention is directed generally to components having a polycrystalline structure with a catalyst material deposited therein; and more particularly, to an apparatus and method for removing at least a portion of the catalyst material from these components.
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-eight percent being typical. An unbacked PDC can be mechanically bonded to a tool (not shown), according to one example. Alternatively, the PDC is 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.
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 exemplary embodiments. In certain exemplary embodiments, the opposing surface 114 and the top surface 152 are substantially planar; however, the opposing surface 114 and the top surface 152 is non-planar in other exemplary embodiments. Additionally, according to some exemplary embodiments, a bevel (not shown) is formed around at least the circumference of the cutting surface 112.
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 subsequently 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 diamond bonds 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 sintering 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, and other suitable materials, can be used as a catalyst for diamond synthesis. When using these alternative materials 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.
Once the PCD cutting table 110 is formed and placed into operation, 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 conventional acid leaching processes of the PCD cutting table 110 which removes some of the cobalt 214 from the interstitial spaces 212. Conventional leaching processes involve the presence of an acid solution (not shown) which reacts with the cobalt 214, or other binder/catalyst material, that is deposited within the interstitial spaces 212 of the PCD cutting table 110. These acid solutions typically consist of highly concentrated solutions of hydrofluoric acid (HF), nitric acid (HNO3), and/or sulfuric acid (H2SO4). These highly concentrated acid solutions are hazardous to individuals handling these solutions. According to one example of a conventional 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, or other binder/catalyst material, 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 within these conventional leaching processes. For this reason, a tradeoff occurs between conventional leaching process duration and the desired leaching depth, wherein costs increase as the conventional leaching process duration increases. Thus, the leaching depth is typically about 0.2 millimeters, which takes about days to achieve this depth. However, the leached depth 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 conventional leaching processes are costly due to the length of time required.
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:
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.
The present invention is directed generally to components having a polycrystalline structure with a catalyst material deposited therein; and more particularly, to an apparatus and method for removing at least a portion of the catalyst material from these components. Although the description of exemplary embodiments is provided below in conjunction with a polycrystalline diamond compact (“PDC”) cutter, alternate embodiments of the invention may be applicable to other types of cutters or components 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.
The PDC cutter 100 has been previously described with respect to
The substrate 150 includes the top surface 152, the bottom surface 154, and the 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 the cutting surface 112, the opposing surface 114, and the 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 according to methods known to people having ordinary skill in the art, some of which have been previously described above. The shape and geometry of the PDC cutter 100 can be varied according to the descriptions previously provided or according to the knowledge known to people having ordinary skill in the art.
Upon formation of the PDC cutter 100 and in accordance with some exemplary embodiments, the substrate 150 includes tungsten carbide and cobalt, or some other binding compound such as nickel chrome or iron. Also, upon formation of the PDC cutter 100 and in accordance with some exemplary embodiments, the PCD cutting table 110 includes diamond particles 210 bonded to one another and cobalt 214, or some other catalyst material such as iron, nickel, chromium, manganese, and tantalum, deposited within the interstitial spaces 212 formed between the diamond-diamond bonds during the sintering process. Although some materials, such as tungsten carbide and cobalt, have been provided as an example, other materials known to people having ordinary skill in the art can be used to form the substrate 150. Also, although some materials, such as diamond particles and cobalt, have been provided as an example, other materials known to people having ordinary skill in the art can be used to form the PCD cutting table 110.
Referring to
The immersion tank 320 includes a base 322 and a surrounding wall 324 extending substantially perpendicular around the perimeter of the base 322, thereby forming a cavity 326 therein. According to certain exemplary embodiments, the base 322 is substantially planar; however, the base 322 is non-planar in other exemplary embodiments. Also in alternative exemplary embodiments, the surrounding wall 324 is non-perpendicular to the base 322. Also, the immersion tank 320 is formed having a rectangular shape. Alternatively, the immersion tank 320 is formed having any other geometric shape or non-geometric shape. In some exemplary embodiments, the immersion tank 320 is fabricated using a plastic material; however, other suitable materials, such as metal, metal alloys, or glass, are used in other exemplary embodiments. The material used to fabricate the immersion tank 320 is typically non-corrosive and does not react with the electrolyte fluid 330.
The electrolyte fluid 330 is placed within the cavity 326 of the immersion tank 320 and filled to a depth of at least the thickness of the PCD cutting table 110. The electrolyte fluid 330 is a solution that is able to react with the catalyst material 214 (
In certain exemplary embodiments, the diluted HCl solution is about five percent by weight HCl and about ninety-five percent by weight water; however, the diluted HCl solution is in other concentrations of HCl and/or is mixed with other fluids to form the electrolyte fluid 330 in other exemplary embodiments. For example, the diluted HCl solution includes hydrochloric acid ranging from about two weight percent to about fifteen weight percent. The electrolyte fluid 330 is able to react with the catalyst material within the PCD cutting table 110 and form a product, or salt, that is soluble within the electrolyte fluid 330. For instance, when the catalyst material 214 (
In certain exemplary embodiments, the electrolyte fluid 330 is formed from a more complex system where mineral and/or carboxylic and/or sulfonic acids are mixed in different ratios in an aqueous solution to increase the speed of the electrolytic process. In certain alternative exemplary embodiments, acid salts, such as sodium bicarbonate, sodium hydrosulfide, sodium bisulfate, and monosodium phosphate are mixed and dissolved in an aqueous solution to form the electrolyte fluid 330. In a further alternative exemplary embodiment, the electrolyte fluid 330 is a basic aqueous solution, such as a strong basic solution or a basic salt. Examples of a strong basic solution includes, but is not limited to, potassium hydroxide, barium hydroxide, caesium hydroxide, sodium hydroxide, strontium hydroxide, calcium hydroxide, magnesium hydroxide, lithium hydroxide, and rubidium hydroxide. Examples of basic salts include, but are not limited to, calcium carbonate and sodium carbonate. In yet other exemplary embodiments, the electrolyte fluid 330 is a molten salt bath, in lieu of an aqueous solution. Any ionic compound that would melt at a temperature of less than about 800° C., such as potassium chloride which has a melting point of about 772° C., is used within this process. In the molten state, the ions are free to move and the catalyst dissolution process occurs.
The cathode 340 includes a base 341 having a first surface 342 and a second surface 343 facing an opposite direction than the first surface 342. The base 341 is substantially circular in shape; however, the base 341 is shaped differently in other exemplary embodiments. The base 341 also includes an aperture 344 extending from the first surface 342 to the second surface 343 according to certain exemplary embodiments; however, the aperture 344 is not present in other exemplary embodiments. The aperture 344 is centrally positioned within the base 341, but can be positioned elsewhere in the base 341. According to certain exemplary embodiments, the base 341 is substantially planar; however, the base 341 is non-planar in other exemplary embodiments. According to some exemplary embodiments, the cathode 340 also includes a sidewall 345 extending substantially perpendicular around the perimeter of the base 341 and extending from the first surface 342. In alternative exemplary embodiments, the sidewall 345 extends non-perpendicular to the base 341. The cathode 340 is fabricated using platinum; however, other suitable materials, such as gold, palladium, precious metals, and other noble metals, are used in other exemplary embodiments. The material used to fabricate the cathode 340 is relatively corrosion resistant. The cathode 340 is immersed within the electrolyte fluid 330 and positioned on or adjacent to the base 322 of the immersion tank 320. Although a few exemplary geometries of the cathode 340 have been described, the geometry of the cathode 340 can be varied to increase or decrease the electric field near the PDC cutter 100 once coupled to a circuit 390, which is formed using the cathode 340, the PDC cutter 100, the electrolyte fluid 330, and the first power source 360.
Once the cathode 340 has been positioned within the immersion tank 320 and immersed within the electrolyte fluid 330, at least a portion of the PDC cutter 100 along with a portion of the covering 310 also are immersed into the electrolyte fluid 330. Specifically, the PCD cutting table 110 is immersed into the electrolyte fluid 330 and positioned near the base 341 wherein the profile of the perimeter of the PCD cutting table 110 is surrounded by the profile of the perimeter of the base 341. Also, a gap 349 is formed between the cutting surface 112 and the base 341. The gap 349 allows the electrolyte fluid 330 to be in contact with at least a portion of the PCD cutting table 110. The gap 349 ranges from about 1 millimeter to about 10 millimeters; however the size of the gap 349 is increased or decreased in other exemplary embodiments. In certain exemplary embodiments, the cutting surface 112 is positioned near and substantially parallel to the first surface 342 of the cathode 340. Also, in certain exemplary embodiments, the sidewall 345 of the cathode 340 surrounds at least a portion of the PCD cutting table outer wall 116.
The first power source 360 includes a negative terminal 361 and a positive terminal 364. The negative terminal 361 is electrically coupled to the substrate 150, which behaves as an anode, using a first electrically conducting wire 362, while the positive terminal 364 is electrically coupled to the cathode 340 using a second electrically conducting wire 365. The first power source 360 provides current to electrolyze the electrolyte fluid 330, and thereby facilitate the reaction of the electrolyte fluid 330 with the cobalt, or other catalyst material 214 (
The transducer 350 is coupled to the PDC cutter 100 according to some exemplary embodiments. According to some exemplary embodiments, a portion of the transducer 350 is coupled to the bottom surface 154 of the PDC cutter 100; however the transducer 350 can be coupled to a portion of the substrate outer wall 156 in other exemplary embodiments. Alternatively, the transducer 350 is coupled to a portion of the immersion tank 320 or positioned within the electrolyte fluid 330, thereby producing vibrations which propagate through the electrolyte fluid 330 and into the PDC cutter 100. The transducer 350 also is coupled to a second power source 370 using a third electrical wire 371. The transducer 350 converts electric current supplied from the second power source 370 into vibrations that are propagated through the PDC cutter 100. The transducer 350 is shaped into a cylindrical shape and has a circumference sized approximately similarly to the circumference of the bottom surface 154. However, the shape and size of the transducer 350 varies in other exemplary embodiments. The transducer 350 is a piezoelectric transducer; however, the transducer 350 is a magnetostrictive transducer in other exemplary embodiments. The transducer 350 operates at a frequency of about 40 kilohertz (kHz) in some exemplary embodiments. In other exemplary embodiments, the transducer 350 operates at a frequency ranging from about 20 kHz to about 50 kHz; yet, in still other exemplary embodiments, the operating frequency is higher or lower than the provided range. The transducer 350 supplies ultrasonic vibrations 355 which propagate through the PDC cutter 100 and facilitate the CoCl removal from the interstitial spaces 212 (
Once the catalyst removal apparatus 300 has been set up, the first power source 360 is powered “on” to facilitate the electrolysis of the electrolyte fluid 330. The first power source 360 is adjusted to a desired voltage differential value to facilitate the dissolution of cobalt, or the catalyst material 214 (
In certain exemplary embodiments, the transducer 350 and the second power source 370 are included in the catalyst removal apparatus 300 according to the description provided above. The second power source 370 is turned “on” to facilitate removal of the CoCl2 from the PCD cutting table 110 back into the electrolyte fluid 330. The transducer 350 produces ultrasonic vibrations 355 into the PDC cutter 100 which promotes the removal of the CoCl2 from the PCD cutting table 110 back into the electrolyte fluid 330. The operating frequency of the transducer 350 and the intensity of the elastic waves emitted from the transducers can be adjusted to maximize the amount of vibrations 355 delivered to the PCD cutting table 110. Furthermore, the ultrasonic vibrations 355 mechanically improve the electrolyte fluid 330 circulation rate into and out of the interstitial spaces 212 (
Although a single PDC cutter 100 and corresponding cathode 340 is shown to be immersed in the electrolyte fluid 330, several PDC cutters 100 with corresponding cathodes 340 can be immersed into the electrolyte fluid 330 to remove the catalyst material 212 (
The catalyst removal apparatus 700 includes the first power source 360, the PDC cutter 100 the absorbent material 710, and the metal grid 740. The metal grid 740 is fabricated using a metal that behaves as a cathode material. The absorbent material 710 is filled with electrolyte fluid 330 and placed in contact with the metal grid 740. The PDC cutter 100 includes the substrate 150 and the cutter table 110 coupled to the substrate 150, as previously mentioned. The PCD cutting surface 112 of the cutter table 110 is placed in contact with the absorbent material 710. The first power source 360 includes the negative terminal 361 and the positive terminal 364. The negative terminal 361 is electrically coupled to the substrate 150 using the first electrically conducting wire 362 and the negative terminal 364 is electrically coupled to the metal grid 740 using the second electrically conducting wire 365. Thus, an electrical pathway is formed from the negative terminal 361 to the positive terminal 364 which proceeds at least through the first electrically conducting wire 362, the substrate 150, the PCD cutting table 110, the absorbent material 710 filled with electrolyte fluid 330, the metal grid 740, and the second electrically conducting wire 365 in that order. The shape of the absorbent material 710 is changeably depending upon the design choices. For example, the absorbent material 710 is a towel or cloth material in certain exemplary embodiments, and is configured to contact only PCD cutting surface 112 of the PCD cutter 100. In another example, the absorbent material 710 is a sponge material in certain exemplary embodiments, and is configured to contact the PCD cutting surface 112 and at least a portion of the PCD cutting table outer wall 116. Additional embodiments described with respect to the catalyst removal apparatus 300 (
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.
This application claims priority to U.S. Provisional Patent Application No. 61/502,014, entitled “Ultrasound Assisted Electrochemical Catalyst Removal For Superhard Materials,” filed Jun. 28, 2011, the entirety of which is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 61502014 | Jun 2011 | US |
