Method for manufacturing forming tool parts

Abstract

The present disclosure relates to a method of manufacturing a polycrystalline diamond (PCD) body including a PCD table having a height of at least 10 mm.

Description

[Technical Field]

[0001] The present disclosure relates to shaped cemented carbide tool parts for cutting wear-resistant products, and in particular to methods of making said shaped tool parts, more particularly those comprising polycrystalline diamond. [Background technology]

[0002] Hard or abrasive workpieces, such as metal alloys, ceramics, cermets, certain composites, and stone, may need to be machined using tools with hard or superhard cutting tips. Tungsten carbide is the most widely used tool material for machining hard workpieces, combining hardness and toughness. Polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) are superhard materials that are sometimes used to machine certain metal alloys, such as those widely used in the automotive industry. Superhard materials are very hard, with a Vickers hardness of at least approximately 25 GPa. However, superhard materials generally have lower strength and toughness than hardmetal materials and, as a result, may be more susceptible to fracture and chipping than hardmetals. Carbide tool inserts are sometimes constructed by bonding a carbide structure to a support substrate ("backing"), which is most typically formed from tungsten carbide. Tool tips with complex geometries are uncommon due to the costs associated with manufacturing and subsequently shaping PCD.

[0003] There is a need to develop more economical methods for producing mold tool inserts from PCD. Summary of the Invention

[0004] According to the present invention, there is provided a method for producing a polycrystalline diamond (PCD) body having a height of at least 10 mm, the method comprising the steps of: a. adding diamond feedstock to a refractory cup; b. compressing a sufficient amount of diamond feedstock to form a compact having a compressed height of at least 10 mm, wherein the compression is carried out at a temperature in the range of 1300°C to 1500°C, at a pressure in the range of 5 to 8 GPa, and for a time in the range of 15 to 25 minutes; c. sintering the compact at a temperature between 1400°C and 2100°C and a pressure of at least 7 GPa for at least 30 seconds to form a sintered PCD body; Includes:

[0005] Optional and / or preferred features of the invention are set out in the dependent claims.

[0006] The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic perspective view showing a part of a circular saw for cutting wood. [Figure 2] FIG. 2 is a schematic side view of a tool insert for use with the circular saw of FIG. [Figure 3] FIG. 3 is a schematic flow diagram illustrating a method of manufacturing a tool insert. [Figure 4] FIG. 4 is a schematic flow diagram illustrating an alternative method for manufacturing a tool insert. [Figure 5] FIG. 5 is a schematic flow diagram illustrating yet another method of manufacturing a tool insert. [Figure 6] FIG. 6 is a schematic perspective view of a first PCD sintered precursor. [Figure 7] FIG. 7 is a side view of the PCD sintered precursor of FIG. 6, particularly showing the PCD table sinter bonded to the cemented carbide substrate at the interface. [Figure 8] FIG. 8 is a front view of the PCD sintered precursor of FIG. [Figure 9] FIG. 9 is a plan view of the PCD sintered precursor of FIG. [Figure 10]FIG. 10 is a schematic side view of a tool blank sliced ​​from the PCD sintered precursor of FIG. 6, with a tool profile superimposed showing the excess material of the PCD table specifically intended for removal. [Figure 11] FIG. 11 is a schematic side view of the forming tool part of FIG. 10 after excess material has been removed. [Figure 12] FIG. 12 is a schematic perspective view of a second PCD sintered precursor. [Figure 13] FIG. 13 is a side view of the PCD sintered precursor of FIG. [Figure 14] FIG. 14 is a front view of the PCD sintered precursor of FIG. [Figure 15] FIG. 15 is a plan view of the PCD sintered precursor of FIG. [Figure 16] FIG. 16 is a schematic side view of a tool blank sliced ​​from the PCD sintered precursor of FIG. 12, with different tool profiles superimposed, particularly showing the excess material of the PCD table intended for removal. [Figure 17] FIG. 17 is a schematic side view of the forming tool part of FIG. 16 after excess material has been removed. [Figure 18] 18a-18c are a set of three schematic diagrams illustrating the forming of an L-shaped partial backing piece from a tool blank. [Figure 19] Figures 19a to 19c are a set of three schematic diagrams illustrating the forming of a triangular shaped backing piece from a tool blank. [Figure 20] Figure 20a shows Sample A, a 10 mm compact specimen, after removal from the HPHT press, with the PCD table delaminated from the substrate, and Figure 20b shows the delaminated PCD table separated from the substrate. [Figure 21] FIG. 21 shows sample B from a 20 mm compact sample after removal from the HPHT press. [Figure 22] Figure 22a shows Sample 1 after sintering with the standard sintering profile, and Figure 22b shows Sample 2 with the extended sintering profile. [Figure 23]Figure 23a shows Sample 3 after sintering with a long sintering profile, and Figure 23b shows Sample 4 after sintering with a long sintering profile. [Figure 24] Figure 24a shows Sample 3, where the PCD table was sinter-bonded to the substrate and subsequently processed; Figure 24b shows Sample 4, where the PCD table was delaminated and subsequently processed; and Figure 24c shows a standard oil and gas cutter for comparison. [Figure 25] Figure 25 shows two PCD bodies obtained using intentional exfoliation and then machined into an oil and gas cutter configuration. [Figure 26] FIG. 26 shows one of the cutters of FIG. 25 after chemical leaching.

[0008] The same references refer to the same respective features in all drawings. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1 and 2, a circular saw 10 for cutting hard-wearing wood products, such as laminate flooring, is comprised of a plurality of tool inserts 12 brazed to the periphery of a blade base 14. Each tool insert 12 is derived from a molded tool part, as described in more detail below. Each tool insert 12 includes a PCD table 16 sinter-bonded to a cemented carbide substrate 18 at an interface 20. The tool insert 12 is positioned so that a rake face 22 of the PCD table 16 faces the direction of rotation of the saw 10 during use, and a cutter edge 24 is positioned at the radially outermost position capable of cutting a workpiece (not shown) when the saw 10 rotates during use.

[0010] In longitudinal cross section, interface 20 comprises a series of interconnected arcuate and linear interface segments. The ratio of PCD table 16 to cemented carbide substrate 18 within tool insert 12 varies from first end 26 to second end 28, which is spaced apart from first end 26. The first end is located at cutter edge 24. The ratio of PCD table 16 to cemented carbide substrate 18 is highest near cutter edge 24 and gradually decreases toward second end 28. This arrangement allows PCD 16 to be placed only in areas actually needed during use, i.e., near the cutting edge, reducing manufacturing costs for the tool insert.

[0011] Turning now to Figures 3, 4 and 5, the manufacture of the tool insert will be described, with the following numbering corresponding to the numbers used in the previous figures.

[0012] S1. The diamond raw material is added to a cup made of a refractory material such as niobium, tantalum, or molybdenum. The cup is usually cylindrical.

[0013] S1a. Optionally, a cemented carbide body is also added to the cup adjacent to the diamond feedstock.

[0014] S1b. Optionally, the cemented carbide body is shaped before being added to the cup.

[0015] S2. The diamond feedstock and cemented carbide body, if present, are compressed to form a compact. If desired, an initial pre-compression of the diamond feedstock may be performed before the diamond feedstock and cemented carbide body are added to the cup. Final compression is then performed within the cup.

[0016] The compacts are outgassed to minimize distortion of the final shape, sometimes before they are placed in a can.

[0017] After outgassing, the compact and cup are assembled into a "pre-composite" along with additional cupping material.

[0018] S3. The precomposite is then sintered in a high pressure, high temperature (HPHT) capsule in a HPHT belt press or HPHT cubic press at a temperature of 1400-1800°C for at least 30 seconds. This produces a PCD sintered precursor having a height of at least 10 mm in a single sintering operation.

[0019] S4. The PCD sintered precursor is removed from the HPHT capsule as soon as reasonably possible and allowed to cool to room temperature.

[0020] S5. The PCD sintered precursor is then sliced ​​longitudinally to produce one or more sliced ​​sections called "tool blanks."

[0021] Depending on the end use, the thickness of each tool blank may vary. For example, the tool blank may be relatively thick and rectangular cube-shaped for ultimate use in a circular saw tool insert. Alternatively, the tool blank may be relatively thin and plate-like for ultimate use in, for example, a turning or milling tool element.

[0022] S6. The tool blank is removed from the remainder of the PCD sintered precursor.

[0023] S7. Using electrical discharge machining (EDM) or laser cutting, the tool blank is formed into the final formed tool part. [Example]

[0024] Example Referring to Figures 6 to 11, a second forming tool part was fabricated generally according to the methodology described above, including optional steps 1a) and 1b).

[0025] The cemented carbide body 18 was made of cemented tungsten and had an initial diameter of about 21 mm and a maximum height of 12 mm.

[0026] As shown in Figure 7, prior to insertion into the refractory cup, the cemented carbide body 18 was formed by electrical discharge machining to include a generally horizontal, planar first portion 30 extending to a downwardly sloping, planar second portion 32. The planar first portion 30 extends horizontally between points P and Q located on the periphery, with point Q being radially inward of point P. The planar second portion 32 slopes axially downward between points Q and R, with point R located circumferentially spaced from point P on the periphery.

[0027] In this example, the maximum height of the cemented carbide body measured at point P was a starting height of 12 mm measured from the bottom surface of the cemented carbide body 18. The minimum height of the cemented carbide body measured at point R was 4 mm, also measured from the bottom surface.

[0028] The diamond raw material used had an average grain size of 22 μm and contained a very small amount of cobalt.

[0029] After HPHT sintering, the PCD sinter precursor, generally designated 34, was removed from the HPHT capsule and cooled to room temperature. The outer cupping material was polished to expose the inner PCD sinter precursor 34.

[0030] The PCD sintered precursor 34 was sliced ​​longitudinally using EDM to separate one portion from the other, and the sliced ​​portion was then removed to provide a tool blank 36. The tool blank 36 had a generally rectangular planar shape and a thickness of 8 mm or less.

[0031] Again, EDM was used to machine a tool profile 38 into the PCD table 16 of the tool blank 36 and remove the unwanted PCD 40 to produce a forming tool part 42. Figures 10 and 11 show an example of a forming tool part 42 with an overly simplified tool profile 36, which is not intended for practical use. The tool profile 38 can be any shape, size, or orientation. What is important is that the tool profile 38 follows the overall contour of the cemented carbide substrate 18. As the height of the substrate 18 changes, so does the height of the PCD table 16 above it, measured from the bottom surface of the cemented carbide substrate 18. Given the configuration of the cemented carbide substrate 18, it is possible to make the PCD table 16 deeper, but there is no need to force it to be deeper where unnecessary.

[0032] Example 12 to 17, a third forming tool part was produced generally according to the methodology described above, including optional steps 1a) and 1b). The PCD sintered precursor from which the forming tool part was obtained is generally designated 44. The third forming tool part is similar to the second variation, except for the contouring of the cemented carbide body 18 before insertion into the refractory cup.

[0033] 16 and 17, the underlying cemented carbide substrate 18 includes a generally horizontal, planar first portion 30 and a downwardly sloping, arcuate second portion 46 instead of an inclined, planar second portion 32. Again, the contour of the PCD table 16 generally follows the contour of the underlying forming substrate 18.

[0034] This method of manufacturing forming tool parts only requires providing the required thickness of the PCD table, and nothing more. Conventional methods require a thicker PCD table to achieve the required depth of the forming tool part, resulting in more unusable PCD table.

[0035] Any tool profile can be provided on the PCD table. For example, in profile, the tool profile can consist of arc-shaped, linear, rectangular, sawtooth, or sinusoidal segments. Multiple segment shapes such as these can also be used, or any combination thereof.

[0036] In this third variation, a second tool profile 48, different from the first-mentioned tool profile 38, was machined into the PCD table 16 of the resulting tool blank 50. Unwanted PCD 40 material from the PCD table 16 was removed to produce a further shaped tool part 52.

[0037] The profile of the PCD table 16 does not have to be the same as the profile of the underlying cemented carbide substrate 18, as shown in the second and third modified examples, but may be the same as the profile of the underlying cemented carbide substrate 18, as shown in the first modified example.

[0038] 18a-18c and 19a-19c illustrate how backed (i.e., having a carbide substrate) and partially backed tool parts can be partially formed from tool blanks. Using the method of slicing two-dimensional tool blanks from three-dimensional PCD sintered precursors, irregularly shaped tool parts can be produced with minimal waste.

[0039] In all variations, forming need not be limited to creating a profile on a PCD table. Forming can also extend to creating a profile on a substrate. Most importantly, forming can also extend to machining the contours of a formed tool part that are entirely contained within the footprint of the tool blank. For example, an entire letter "A" can be formed from a tool blank. Tool parts of any desired shape can be formed from tool blanks, regardless of whether the parent PCD sintered precursor is comprised of a cemented carbide substrate.

[0040] Although some embodiments have been described that include a cemented carbide body / substrate, the cemented carbide body may be omitted from the method of manufacturing the formed tool part. Indeed, forming may be limited to forming a tool blank made of sintered PCD sliced ​​from a PCD sintered precursor. In this case, the formed tool part may have any shape.

[0041] In this regard, the inventors investigated increasingly deeper PCD tables during their development work. Two samples were produced, each with a planar cemented carbide substrate. In sample A, the compact was milled to a depth of 10 mm. In sample B, the compact was milled to a depth of 20 mm. Both compacts were then sintered.

[0042] Sample A was successfully sintered, but the PCD layer delaminated from the substrate. Figure 20a shows Sample A after pressing, while Figure 20b shows the same PCD table separated from the substrate. This delamination could be due to the high stresses associated with the volume collapse of the PCD, or simply due to the synthesis conditions being slightly too hot.

[0043] A closer look at Sample B reveals that the cobalt infiltration may have occurred in two waves: one that swept uniformly up from the substrate, and one that swept up and encompassed the top surface (see Figure 21). This resulted in the bottom half of the PCD layer sintering and the top half cracking, leaving a soft, unsintered core.

[0044] To address the soft green core issue resulting from attempting to achieve very thick (greater than 10 mm) PCD tables, many variables were investigated, including synthesis conditions (pressure, temperature, time), use of outgassing, pre-compression load and temperature, different substrate depths, different HPHT press capsule placements, and the use of a cobalt interlayer in the compact between the diamond feedstock and the cemented carbide substrate.

[0045] At a later stage, four more samples were prepared (see Table 1).

[0046] [Table 1]

[0047] Sample 1, produced with sintering profile No. 1, showed no improvement over the previous work and had a soft core. For Sample 2, a different sintering profile was used, with an extended sintering time. Sample 2 was almost entirely sintered. Figure 22a shows Sample 1 after sintering, and Figure 22b shows Sample 2 after sintering.

[0048] After outgassing, Samples 3 and 4 were sintered using the second, longer sintering profile. Sample 3 was a fully sintered, extra-thick PCD substrate with no visible defects. Sample 4 was also fully sintered, but the PCD layer had delaminated from the substrate due to the presence of excess Co foil at the interface. Figure 23a shows Sample 3 after sintering, and Figure 23b shows Sample 4 after sintering.

[0049] Samples 3 and 4 were cleaned from the cup material for subsequent characterization testing. Figure 24a shows Sample 3. Figure 24b shows Sample 4 after peeling and subsequent machining to match the overall shape and size of a standard oil and gas cutter (Figure 24c). The cutter in Figure 24c has a diameter of 16 mm and a PCD table height of 3.5 mm. In contrast, Sample 4 in Figure 24b has a diameter of 16 mm and a PCD table height of 12 mm.

[0050] Hot pre-compression has proven essential for successful sintering of samples with extremely thick PCD bodies. These particular samples were sintered at approximately 1400°C for 20 minutes at 5.5 GPa. However, a wider operating window is feasible. Pre-compression is performed at temperatures ranging from 1300°C to 1500°C, pressures ranging from 5 to 8 GPa, and times ranging from 15 to 25 minutes. The compaction stage is characterized by the absence or very small amount of catalyst / binder material, such as cobalt, in amounts insufficient for complete sintering. This is primarily added later and may involve one or more of the following methods: the use of cobalt foil, a layer of cobalt powder, for example, at the interface between the diamond feedstock and the substrate, or a cobalt-containing cemented carbide substrate. Furthermore, the pre-compression step is performed in a first HPHT press, while sintering is performed in a second HPHT press, which requires a separate capsule assembly.

[0051] The inventors have discovered a surprising new method for obtaining extremely thick PCD bodies, which can be either backed (i.e., with a substrate) based on the results of Sample 3, or unbacked (i.e., freestanding) based on the results of Sample 4. In comparison, oil and gas cutters with PCD tables up to 5-6 mm deep have been obtained to date. The impact on cutters used in oil and gas drilling is significant, as PCD tables that have been detached from the substrate, as in Sample 4, can potentially be machined into freestanding cutters.

[0052] To investigate further, diamond feedstock containing particles with an average diameter of 17 μm was used. A sample was further prepared and machined into a cutter without a substrate (see Figure 25). This sample was then sent for chemical leaching, a process that removes cobalt from the interstitial regions of the PCD body. Removing cobalt from the diamond lattice structure improves the heat resistance of PCD, making it suitable for oil and gas drilling operations.

[0053] Removal of the tungsten carbide substrate facilitated a new, rapid leaching method for the cutters. This method did not require complex fixtures to protect the substrate, and the cutters could be placed in a sealed container of hydrochloric acid (HCl) and heated to much higher temperatures than standard cutters. As can be seen in Figure 26, the 16 mm diameter cutter was leached from all sides, leaving only a small amount of cobalt in the center, an impressive result.

[0054] The leached cutter was subjected to property testing and the cutter performed extremely well in subsequent performance tests.

[0055] Although the present invention has been shown and described with particular reference to illustrative embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.

[0056] definition Standard terms and concepts used herein are briefly explained below.

[0057] PCD consists of an agglomerate of intergrown diamond abrasive grains, forming a skeletal mass that defines the interstices between the diamond abrasive grains. PCD materials typically consist of at least 80% by volume of diamond, are obtained by HPHT sintering in the presence of sintering aids, and are also called diamond catalyst materials. Diamond catalyst materials are understood to be materials that can promote the direct intergrowth of diamond abrasive grains under pressure and temperature conditions where diamond is more thermodynamically stable than graphite.

[0058] Diamond catalyst materials often contain Group VIII elements, with common examples including cobalt, iron, nickel, and certain alloys of these elements. PCDs can be formed on cobalt-carbide substrates, which provide the source of cobalt catalyst material for PCDs. During sintering of the PCD body, components of the cemented carbide substrate, such as cobalt in the case of a cobalt-carbide substrate, liquefy and are swept from the area adjacent to the diamond grain volume into the interstitial areas between the diamond grains. The cobalt acts as a catalyst to promote the formation of bonded diamond abrasive grains. Optionally, a metal solvent catalyst may be mixed with the diamond grains before subjecting the diamond grains and substrate to the HPHT process. The interstitial spaces within the PCD material are at least partially filled with the catalyst material. The intergrown diamond structure thus consists of the original diamond abrasive grains and newly precipitated or regrown diamond phases bridging the original abrasive grains. The final sintered structure typically contains residual catalyst / solvent material within at least some of the interstitial spaces between the sintered diamond abrasive grains.

[0059] A known problem with such conventional PCD compacts is their susceptibility to thermal degradation when exposed to high temperatures during cutting and / or abrasion applications. This is believed to be due, at least in part, to the presence of residual solvent / catalyst material in the microstructural interstices, which is believed to adversely affect the performance of the PCD compact at high temperatures due to the difference in thermal expansion properties between the interstices' solvent-metal catalyst material and the intercrystalline bonded diamond. This thermal expansion difference is known to occur at temperatures of approximately 400°C and is believed to cause rupture of the interdiamond bonds, which can ultimately lead to the formation of cracks or chips in the PCD structure. Chipping or cracking of the PCD table can reduce the mechanical properties of the cutting elements that make up the PCD table or lead to the breakage of the cutting elements during drilling or cutting operations, thereby rendering the PCD structure unsuitable for further use.

[0060] As used herein, the "rake side" of a tool insert is the side that constitutes the "rake face," the surface of the tool through which chips flow during use. As used herein, "chips" refer to workpieces removed from the work surface by the machine tool during use. As used herein, the "cutting edge" refers to the end of the rake face that performs the cutting operation.

[0061] As used herein, "machining" refers to the selective removal of material from an object, called a workpiece. Sawing and cutting are examples of machining.

Claims

1. 1. A method for producing a polycrystalline diamond (PCD) body having a height of at least 10 mm, comprising the steps of: a. adding diamond feedstock to a refractory cup; b. compressing a sufficient amount of diamond feedstock to form a compact having a compressed height of at least 10 mm, wherein the compression is carried out at a temperature in the range of 1300°C to 1500°C, at a pressure in the range of 5 to 8 GPa, and for a time in the range of 15 to 25 minutes; c) adding a cemented carbide body to the refractory cup prior to sintering and / or disposing an intermediate layer of non-carbide material between the cemented carbide body and the diamond feedstock; d. sintering the compact at a temperature between 1400°C and 2100°C and a pressure of at least 7 GPa for at least 30 seconds to form a sintered PCD body; Including, A method comprising steps a, b, c and d in this order.

2. The method of claim 1 , further comprising slicing the PCD body longitudinally to produce one or more sliced ​​portions of the PCD body, each sliced ​​portion being a tool blank.

3. 3. The method of claim 1 or 2, further comprising processing the sintered PCD body into a compact.

4. The method of claim 3 , comprising using a laser to shape the PCD body.

5. 10. The method of claim 1, further comprising adding a cemented carbide body to the refractory cup prior to sintering, such that the PCD sintered body then comprises a PCD table sinter-bonded to a cemented carbide substrate at an interface.

6. 6. The method of claim 5, further comprising shaping the cemented carbide body prior to adding it to the refractory cup.

7. The method of claim 1 , wherein the intermediate layer is a foil.

8. The method of claim 1 or 7, wherein the intermediate layer comprises a non-carbide powder layer.

9. The method of claim 1, wherein the PCD body has a thickness of 10 to 20 mm.

10. The method of claim 1 , wherein the PCD body is cylindrical.

11. The method of claim 10, wherein the PCD body has a diameter of 8 to 25 mm.

12. 12. The method of claim 11, wherein the PCD body has a diameter of 16 mm.

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