This invention relates generally to polycrystalline diamond compact (“PDC”) cutters. More particularly, this invention relates to methods to repair worn or eroded PDC cutters, the repaired cutters, and use of the repaired cutters in drill bits and/or other tools.
The bit body 110 includes a plurality of blades 130 extending from the drill bit face 111 of the bit body 110 towards the threaded connection 116. The drill bit face 111 is positioned at one end of the bit body 110 furthest away from the shank 115. The plurality of blades 130 form the cutting surface of the drill bit 100, which may be an infiltrated matrix drill bit. One or more of these plurality of blades 130 are either coupled to the bit body 110 or are integrally formed with the bit body 110. A junk slot 122 is formed between each consecutive blade 130, which allows for cuttings and drilling fluid to return to the surface of the wellbore (not shown) once the drilling fluid is discharged from the nozzles 114. A plurality of cutters 140 are coupled to each of the blades 130 within the sockets 180 formed therein, and extend outwardly from the surface of the blades 130 to cut through earth formations when the drill bit 100 is rotated during drilling. One type of cutter 140 used within the drill bit 100 is a PDC cutter; however other types of cutters are contemplated as being used within the drill bit 100. The cutters 140 and portions of the bit body 110 deform the earth formation by scraping and/or shearing. The cutters 140 and portions of the bit body 110 are subjected to extreme forces and stresses during drilling which causes the surface of the cutters 140 and the bit body 110 to wear. Eventually, the surfaces of the cutters 140 and the bit body 110 wear to an extent that the drill bit 100 is no longer useful for drilling and is either repaired or discarded depending upon the type of damage and/or the extent of the damage. Although one embodiment of the drill bit has been described, other drill bit embodiments or other downhole tools that use PDC cutters, which are known to people having ordinary skill in the art, are applicable to exemplary embodiments of the present invention.
Upon coupling the PCD cutting table 210 to the substrate 220, the cutting surface 212 of the PCD cutting table 210 is substantially parallel to the substrate's bottom surface 224. Additionally, the PDC cutter 140 has been illustrated as having a right circular cylindrical shape; however, the PDC cutter 140 is shaped into other geometric or non-geometric shapes in other examples. In certain examples, the opposing surface 214 and the top surface 222 are substantially planar; however, the opposing surface 214 and/or the top surface 222 is non-planar and complementary in shape in other examples.
The PDC cutters 140 are expensive to manufacture and constitute a significant portion of the cost of PDC mounted bits 100 (
The decision as to whether or not a worn or eroded cutter is reused, rotated, or discarded has been based in part on the condition of the remaining tungsten carbide substrate. The criterion depends on the amount of full cylinder substrate remaining If an insufficient amount of full cylinder substrate remains to allow for a strong braze joint when oriented with a fresh diamond edge towards the formation, then the cutter is typically scrapped or reprocessed as described above.
The foregoing and other features and aspects of the invention will be best understood with reference to the following description of certain exemplary embodiments of the invention, 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.
This invention relates generally to PDC cutters. More particularly, this invention relates to methods to repair worn or eroded PDC cutters, the repaired cutters, and use of the repaired cutters in drill bits and/or other tools. Although the description provided below is related to a PDC cutter, exemplary embodiments of the invention relate to any cutter having a substrate and a superhard material layer, such as a diamond table, attached thereto.
According to some exemplary embodiments, the cutter repair fixture 500 includes a base 510 and at least one sidewall 520 extending substantially orthogonally away from the base 510, thereby forming a first cavity 508 therein. According to certain exemplary embodiments, the base 510 and the at least one sidewall 520 are formed as a single component; however, in other exemplary embodiments, the base 510 and the sidewalls 520 are formed separately and thereafter coupled together, such as by being threadedly coupled together. The first cavity 508 forms a substantially cylindrical shape; however, in some alternative exemplary embodiments, the first cavity 508 forms a different geometric or non-geometric shape, such as a tubular shape having a square, rectangular, triangular, or other non-geometric cross-sectional shape. The height of the first cavity 508 is similar to, or greater than, the height of the substrate 530, which is similar to substrate 220 (
According to some exemplary embodiments, the base 510 includes an interior surface 512 that is non-planar and defines a portion of the first cavity 508. The interior surface 512 includes a second cavity 514 formed therein extending inwardly from a portion of the interior surface 512 of the base 510. The second cavity 514 is fluidly coupled to the first cavity 508. According to certain exemplary embodiments, the second cavity 514 is cylindrically shaped and is dimensioned to receive the diamond table 210 of the damaged PDC cutter 300, 310, 320, 330. Thus, the height of the second cavity 514 is similar to the thickness of the diamond table 210 and the circumference of the second cavity 514 is similar to, but slightly larger than, the circumference of the diamond table 210. In certain exemplary embodiments, the diameter of the first cavity 508 is slightly larger than the diameter of the second cavity 514.
The cutter repair fixture 500 is fabricated using a suitable material capable of withstanding temperatures used in the repair method 400. The temperatures used in the repair method 400 are dependent upon the type of build-up compound 550 that is used and the melting temperatures of these build-up compounds 550. For example, the cutter repair fixture 500 is exposed to temperatures reaching up to about 700 degrees Celsius in some exemplary embodiments, while in other exemplary embodiments, the cutter repair fixture 500 is exposed to temperatures reaching greater than 700 degrees Celsius. In exemplary embodiments where the diamond table 210 is exposed to temperatures of about 700 degrees Celsius or greater, at least the base 510 of the cutter repair fixture 500, and the sidewalls 520 in some exemplary embodiments, is fabricated using a heat sink material, such as aluminum or some other metal or metal alloy, that has a high heat transfer coefficient to keep the diamond table 210 at a temperature below 750 degrees Celsius. Further, the base 510, and optionally the sidewalls 520, are fabricated to include fins (not shown) pursuant to some exemplary embodiments. According to certain alternative exemplary embodiments, a heat sink (not shown), which optionally includes fins, is thermally coupled to at least the base 510 of the cutter repair fixture 500 to keep the diamond table 210 at a temperature below 750 degrees Celsius. The heat sink is optionally used even if the diamond table 210 is exposed to only temperatures less than 700 degrees Celsius. Although one example of a cutter repair fixture has been described herein, alternative types of cutter repair fixtures that are obvious variants to the cutter repair fixture 500 can be used in alternative exemplary embodiments.
After step 420, a damaged PDC cutter 300, 310, 320, 330 having a diamond table 210 coupled to a damaged substrate 530 is placed within the cutter repair fixture 500 at step 430. The damaged PDC cutter 300, 310, 320, 330 is typically worn or eroded in at least the substrate 530. The diamond table 210 is oriented to be positioned and set within the second cavity 514, while the damaged substrate 530 is positioned within the first cavity 508. According to some exemplary embodiments, the damaged PDC cutter 300, 310, 320, 330 is cleaned prior to being placed within the cutter repair fixture 500.
After step 430, the buildup compound 550 is filled into the cutter repair fixture 500 at step 440. The build-up compound 550 is a material capable of being bonded to the substrate 530, which for example is fabricated from tungsten carbide or tungsten carbide matrix. The build-up compound 550 is any element or combination of elements with a melting point higher than the liquidus temperature of the braze filler material that is used to braze the repaired PDC cutter 600 (
After step 440, the build-up compound 550 is bonded to the substrate 530 at step 450. According to some exemplary embodiments, the cutter repair fixture 500 with the damaged PDC cutter 300, 310, 320, 330 and the build-up compound undergoes a microwave sintering process to bond the build-up compound 550 to the substrate 530 and fill the void in the worn or eroded PDC cutter 300, 310, 320, 330. Thus, a fresh thickness of metallic material, or buildup compound 550, is applied, or coupled, all around the outer circumference of the substrate 530 of the previously used and damaged PDC cutter 300, 310, 320, 330. Alternatively, according to other exemplary embodiments, other types of coupling processes, such as a spark sintering process or other known sintering processes having the benefit of the present disclosure, are used to bond the build-up compound 550 to the substrate 530 and form the processed PDC cutter within the cutter repair fixture 500. According to certain exemplary embodiments, the processed PDC cutter has a substrate with a diameter larger than the diameter of the associated diamond table 210. For example, the diameter of the substrate of the processed PDC cutter is substantially the same as the diameter of the first cavity 508.
After step 450 where the build-up compound 550 has coupled around the used PDC cutter 300, 310, 320, 330, the processed PDC cutter is removed from the cutter repair fixture 500 at step 460. According to some exemplary embodiments, the cutter repair fixture 500 is undamaged and reusable after the processed PDC cutter is removed from the cutter repair fixture 500. In other exemplary embodiments, cutter repair fixture 500 is damaged and not reusable once the processed PDC cutter is removed from the cutter repair fixture 500.
After step 460, the processed PDC cutter is grounded to form the repaired PDC cutter 600 (
After step 470, the repair method 400 stops at step 480. Although method 400 has been depicted herein with respect to certain steps, these steps are not limited to the order in which they are presented, but instead, may be performed in a different order in other exemplary embodiments. Further, some steps may be separated into additional steps. Alternatively, some steps may be combined into fewer steps. Furthermore, some steps may be performed in an entirely different manner than the example provided herein and are understood to be included within the exemplary embodiments.
In an alternative exemplary embodiment, the buildup compound 550 is bonded to the damaged PDC cutter 300, 310, 320, 330 via welding to fill in the voided area 535 in the damaged substrate 530. The welding method includes, but is not limited to, laser, plasma transfer arc, thermal plasma spray, or any other appropriate method known to people having ordinary skill in the art having the benefit of the present disclosure. According to the thermal plasma spray method, the buildup compound 550 is welded to the damaged PDC cutter 300, 310, 320, 330 to fill in the voided area 535 in the damaged substrate 530. A copper paste (not shown) is applied over the area that was sprayed with the buildup compound 550 according to certain exemplary embodiments. A flash heating is then performed with an induction unit (not shown), for example, which melts the copper and allows it to infiltrate into the buildup compound 550 that has filled the voided area 535, thereby forming the processed PDC cutter. This infiltration strengthens the bonding between the buildup compound 550 and the damaged substrate 530 of the damaged PDC cutter. Subsequently, a grinder or some other equipment, as previously mentioned, is used to grind the processed PDC cutter to the predetermined diameter, thereby forming the repaired PDC cutter 600. This predetermined diameter has been described above and is not described again for the sake of brevity. During the welding process, a heat sink is optionally placed in thermal contact with the diamond table 210, thereby maintaining the temperature of the diamond table to less than 700° C. The heat sink is a plate or a plate with fins according to some exemplary embodiments. Alternatively, the heat sink is a different shape. The heat sink is fabricated from copper, aluminum, or some other metal or metal alloy having a sufficient thermal coefficient capable of maintaining the temperature of the diamond table to less than 700° C.
According to either of the exemplary embodiments described above and/or any other alternative exemplary embodiments known to people having ordinary skill in the art having the benefit of the present disclosure, one or more additional processes described below is included therein. One process includes using a 3-D scanner (not shown) to scan the damage PDC cutter 300, 310, 320, 330 to determine the minimum amount, or volume, of build-up compound 550 needed and where the build-up compound 550 is needed so that excess build-up compound 550 is not used. Determining the minimum amount, or volume, of build-up compound 550 needed reduces costs by not wasting the build-up compound 550. Hence, less build-up compound 550 is removed during the grinding step. Another process includes dipping at least the damaged portion, or voided area 535, of the damaged PDC cutter 300, 310, 320, 330 into melted cobalt, thereby having the cobalt provide a coating along the damaged, or voided area 535. The coated PDC cutter is placed in the cutter repair fixture 500, or a crucible, fabricated from either ceramic, graphite, or some other suitable material. The build-up compound 550 is packed into the cutter repair fixture 500, or the crucible, and into the damaged portion, or voided area 535, to reform the damaged PDC cutter 300, 310, 320, 330 into the dimensions of the repaired PDC cutter 600. Induction heating is applied onto the processed PDC cutter, thereby forming the repaired PDC cutter 600. The cobalt intermediate coating facilitates the coupling of the build-up compound 550 to the damaged substrate 530 of the damaged PDC cutter 300, 310, 320, 330. In another process, the temperature of the diamond layer 210 is maintained to be less than 700° C. according to some exemplary embodiments. If the temperature of the diamond layer 210 reached 700° C. or higher, the diamond layer 210 has chances to be damaged. For example, graphitization can occur at these elevated temperatures. Thus, in some exemplary embodiments, the build-up compound 550 used has a melting temperature that is less than 700° C., or is at a temperature that prevents the diamond layer 210 from reaching above 700° C. during the repair method 400, or during any of the other alternative exemplary embodiments. The welding process is controlled to ensure that the temperature of the diamond layer 210 remains below 700° C.
However, in certain exemplary embodiments, the cutter repair fixture 500, as previously mentioned, includes a heat sink (not shown) adjacent to the diamond table 210 to keep the polycrystalline diamond layer 210 from overheating and suffering thermal damage during the repair operation. This heat sink is included when the melting temperature of the build-up compound 550 is equal to or higher than 700° C. and is optionally included when the melting temperature of the build-up compound 550 is less than 700° C.
According to certain exemplary embodiments, the paste compound 910 is a copper based braze filler material, which is composed of copper powder, about 75% by weight, in a paste flux. The paste flux promotes reduction of oxides and enhances the flow of the braze filler material. The material of the paste flux is known to people having ordinary skill in the art and therefore is not described in detail herein. Although the copper powder has been mentioned as being about 75% by weight, this weight percent is only an example and may range from about 40% to about 90% in other exemplary embodiments. One example of this paste compound 910 is an off the shelf product from Fusion, Inc., whose part number is LHK-1310-650. In yet other exemplary embodiments, a nickel powder may be used in lieu of the copper powder in the braze filler material and in accordance with the same percentages mentioned above. Further, a combination of copper powder and nickel powder may be used in the braze filler material, where the above mentioned percentage ranges apply to the combination. Essentially, the metal used in the braze filler material can be any non-ferrous metal or alloy having a melting temperature higher than the melting temperature of a braze material that is used to braze the repaired cutter onto a drill bit or other downhole tool. Further, the temperature at which the non-ferrous metal commences melting is lower than the temperature at which the diamond table 210 is damaged, either through graphitization and/or through issues due to the different coefficient of thermal expansions of the diamond and the catalyst used in forming the diamond table 210, which is about 750 ° C. to about 800 ° C. Thus, the melting temperature of the non-ferrous metal may be somewhat higher than the temperature at which the diamond table 210 is damaged. This is due to the fact that the entire paste compound 910 does not reach the actual melting temperature of the non-ferrous metal used therein because it is only the commencement of melting that is used.
In addition to the examples provided above, tungsten carbide spheres may be added on top of the paste compound 910 to enhance wear resistance. These tungsten carbide spheres may be added to the paste compound 910 after the paste compound 910 has been applied onto the damaged substrate 830 and/or into the mix of the paste compound 910 prior to the paste compound 910 being applied onto the damaged substrate 830. Alternatively, according to some exemplary embodiments, the paste compound 910 includes encapsulated diamond particles in copper, nickel, or any non-ferrous metal or alloy as described above. Yet in other exemplary embodiments, encapsulated silicon carbide, encapsulated tungsten carbide, and/or encapsulated cubic boron nitride may be used in lieu of, or in addition to, the encapsulated diamond particles.
According to some exemplary embodiments, the induction heating unit 1000 is used to melt the paste compound 910 within the at least one void 835 (
According to some exemplary embodiments, the induction heating unit 1000 also includes at least one refractory material 1050 positioned below the loops 1036 of the coil 1030, thereby raising the coil 1030 so that it does not contact a surface that the coil 1030 would be resting on and/or the damaged cutter 800 would be resting on. According to some exemplary embodiments, the at least one refractory material 1050 includes one or more tubular components that provide an area for the damaged cutter 800 to be placed on.
In operating the induction heating unit 1000, the amperage is set at 260 amps. However, the amperage may be set to a different value such as 270 amps. Further, in other exemplary embodiments, the amperage is set between 180 amps and 330 amps. The precision control of time and temperature allows the paste compound 910 to be raised to a temperature just above the solidus of the non-ferrous material used therein, which is just high enough to induce flow of the paste compound 910 without excessive melting. The amperage is controllable to a tenth of an amp, while time is controllable to 0.01 seconds. Temperatures, which can be measured using an ICI infrared camera, indicate that the cutter temperature does not exceed 1200° F. during the brazing operation and thus damage to the diamond table 210 is minimized or non-existent. However, this temperature may be able to be over 1200° F., as mentioned above, in other exemplary embodiments.
The damaged cutter 800 that is to be repaired is placed inside the coil 1030 within the channel 1038 such that a portion of the coil 1030 surrounds the cutter 800. According to certain exemplary embodiments, the cutter 800 is resting, or being supported, on the refractory materials 1050. The power supply of the induction heating unit 1000 is turned on allowing alternating current to be passed through the coil 1030, thereby creating an alternating, or oscillating, magnetic field around the coil 1030 and hence inducing eddy currents into the cutter 800 causing the cutter 800 to heat up. According to some exemplary embodiments, the induction heating unit 1000 is on for about half a minute (30 seconds) at about 270 amps; however, the time is dependent upon the set amperage and the temperature that is desired. The eddy currents are induced in both the tungsten carbide substrate 830 and the diamond table 210, heating them both at once, at the “skin”. Induction heating avoids the sudden application of heat, to one or the other, which gives rise to the coefficient of thermal expansion mismatch and hence induces stress within a part and causes it to crack. Induction heating allows for more uniform heating of the entire cutter 800. Although the induction heating unit 1000 is described as the equipment for performing the induction heating, any other heating equipment that provides induction heating and uniform heating of the entire cutter 800 can be used in alternative exemplary embodiments. Further, although induction heating has been described as the choice of heating process, other heating processes can be used in other alternative exemplary embodiments, so long as there is uniform heating of the entire cutter 800.
As the cutter 800 heats up, the paste compound 910 begins to form an outgas 1110 and activate. The outgas 1110 is a vapor formed mostly of water and flux. The flux used in the paste compound 910 reduces oxide formation and promotes the flow of the copper based braze filler metal, or other type of paste compound used as described above, which will flow into the void portion, or eroded/damaged portion, of the cutter 800 and effect the repair. Once the flow of the paste compound 910 initiates, the power supply is immediately turned off to prevent overheating and over melting. It is imperative to supply only enough power and heat to barely raise the temperature above the solidus of the braze filler material, or paste compound 910.
Upon turning the power off to the induction heating unit 1000, the cutter 800 is allowed to cool in certain exemplary embodiments. In other exemplary embodiments, the cutter 800 is removed from the induction heating unit 1000, and allowed to cool elsewhere. The cooling may be controlled in some exemplary embodiments, while in other exemplary embodiments, the cooling is allowed to occur naturally to room temperature. Once the cutter 800 has been cooled, the processed PDC cutter 1200 is formed and the paste compound 910 is properly bonded to the substrate 830. The paste compound 910 has solidified and may extend outwardly from the natural circumference of the substrate 830. The bond between the paste compound 910 and the substrate 830 forms a bondline 1310 and there are no cracks present at or adjacent to the bondline due to the uniform heating of the diamond table 210, the substrate 830, and the paste compound 910.
After step 760, the repair method 700 stops at step 770. Although method 700 has been depicted herein with respect to certain steps, these steps are not limited to the order in which they are presented, but instead, may be performed in a different order in other exemplary embodiments. Further, some steps may be separated into additional steps. Alternatively, some steps may be combined into fewer steps. Furthermore, some steps may be performed in an entirely different manner than the example provided herein and are understood to be included within the exemplary embodiments.
The methods for repairing cutters, as described above, are performed on PDC cutters, whether they have been pre-processed, post-processed, or not processed at all. Some processing examples, which are not meant to be limiting, include leaching, annealing, cryogenic treatment, chemical vapor deposition, or creating a new or larger sized chamfer on the diamond table 210, which are known to people having ordinary skill in the art. Leaching includes face leaching, side leaching, bevel leaching, and/or double bevel leaching, which are terms known to people having ordinary skill in the art. Masking may also be used during the processing. Thus, for example, a PDC cutter that has previously been leached and damaged during use is subjected to any of the repair methods described above. This is an example of repairing a PDC cutter that has been pre-processed. In another example, a PDC cutter that has not been pre-processed and damaged during use is subjected to any of the repair methods described above and then subsequently leached. This is an example of post-processing a repaired PDC cutter.
Exemplary embodiments allow for a more complete use of expensive PDC components, which includes the re-use of damaged PDC components, in drill bits and tools. These exemplary embodiments facilitate in reducing costs and enhancing the retention of cutters that are reused after wear or erosion. These exemplary embodiments offer a more far superior solution than scrapping or wire EDM cutting cutters. Cutters are now salvageable by using the exemplary embodiments, as described above.
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.
The present application is a continuation-in-part of U.S. patent application Ser. No. 13/924,418, entitled “Methods to Repair Worn or Eroded PDC Cutters, Cutters So Repaired, and Use of Repaired PDC Cutters In Drill Bits or Other Tools,” and filed on Jun. 21, 2013, which claims priority to U.S. Provisional Patent Application No. 61/663,205, entitled “Methods to Repair Worn or Eroded PDC Cutters, Cutters So Repaired, and Use of Repaired PDC Cutters In Drill Bits or Other Tools,” filed June 22, 2012, the disclosures of which are incorporated by reference herein.
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Number | Date | Country | |
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Parent | 13924418 | Jun 2013 | US |
Child | 14139302 | US |