A method of extrusion-based additive manufacturing of a multi-material alternating wrapped pdc substrate and applications

Abstract

This invention relates to a method for preparing high-toughness polycrystalline diamond composite substrates with alternating hard and soft layers based on powder extrusion printing; belonging to the field of PDC design and fabrication technology. This invention is the first to attempt to increase the toughness of PDCs by alternating hard and soft layers. During the technology development process, it was discovered that ceramic materials with alternating hard and soft layers have the characteristics of extending crack propagation paths and significantly improving the fracture toughness and energy absorption capacity of the material, providing a solution for high-toughness PDC substrates. This invention uses powder extrusion printing, and through the synergistic effect of composition and process, obtains high-quality products with high wear ratio and high impact toughness. The process of this invention is controllable, and the resulting product has excellent performance, facilitating large-scale industrial applications.

Description

Technical Field

[0001] This invention relates to a method for preparing a high-toughness polycrystalline diamond composite substrate with alternating multi-material encapsulation based on powder extrusion printing; it belongs to the field of PDC design and fabrication technology. Background Technology

[0002] Polycrystalline diamond composite (PDC) is an ultrahard composite material formed by sintering diamond and a cemented carbide substrate under high temperature and high pressure (HTHP) conditions. Due to its excellent low friction, high hardness, high wear resistance, good corrosion resistance, and brazing performance, it is widely used in coal mining, oil and gas extraction, deep well drilling, and in the production of difficult-to-machine materials such as carbon fiber and titanium alloys. During the HTHP synthesis of PDC, Co in the cemented carbide gradually melts and sweeps across the diamond layer as temperature and pressure increase, promoting the densification of the diamond layer and the formation of the polycrystalline diamond layer. However, Co is the main contributor to the toughness of cemented carbide; due to Co migration, the impact toughness of cemented carbide often decreases significantly. In PDC, wear resistance is provided by polycrystalline diamond, while toughness is provided by the cemented carbide substrate. Therefore, in industrial production, the toughness of the PDC cemented carbide substrate often cannot meet the high impact toughness requirements of PDC in increasingly complex and harsh service environments.

[0003] To overcome the decrease in impact toughness of PDC caused by massive Co migration, traditional methods mainly involve placing a Co diffusion barrier layer, such as a W layer, Ti layer, or Si3N4 layer, between the PDC substrate and the polycrystalline diamond layer. However, this approach often suffers from poor compatibility between the barrier layer material and the cemented carbide or diamond, introducing new challenges along with the transition layer. In addition, there are toughening methods for PDC substrates, i.e., cemented carbide, primarily involving the introduction of additives and the control of WC particle morphology and size distribution. On the one hand, additives inhibit WC grain growth, improving the material's yield strength; on the other hand, adding WC particles with different morphologies and sizes allows them to coordinate and absorb crack propagation energy, enhancing the material's fracture toughness. However, this method often faces challenges such as high material compatibility, operational difficulties, and complex preparation processes, resulting in limited contributions to cemented carbide toughness and hindering industrialization.

[0004] The search revealed that there are few reports on techniques for increasing the toughness of PDC by alternating hard and soft layers. There are also few reports on techniques for preparing encapsulated PDC substrates with alternating hard and soft layers using extrusion additive manufacturing processes. Summary of the Invention

[0005] This invention is the first to attempt to increase the toughness of PDC by using alternating hard and soft layers. During the technology development process, it was discovered that ceramic materials with alternating hard and soft layers have the characteristics of extending the crack propagation path and significantly improving the fracture toughness and energy absorption capacity of the material, providing a solution for high-toughness PDC substrates. Therefore, this invention proposes a PDC substrate with an interlaced encapsulation structure. In this interlaced encapsulation structure PDC substrate, hard alloy layers and soft layers alternate and encapsulate each other from the core to the surface, with soft phase layers sandwiched between the hard alloy layers, forming an approximate concentric sphere or concentric cylinder structure. This structure can improve the axial high toughness of the PDC substrate while possessing excellent radial impact resistance, making it suitable for the complex stress environment during PDC service. Its application in the fabrication of PDC substrates will help improve the impact toughness of polycrystalline diamond composite sheets and ensure operational efficiency.

[0006] Due to its multi-material composition and high complexity, this structure is difficult to fabricate using traditional powder metallurgy methods such as molding. Additive manufacturing, however, offers significant advantages in the low-cost fabrication of customized products with complex shapes and structures. It allows for precise control of composition and structural features in three-dimensional space, with the external shape and internal gradient distribution of the product unrestricted by molds. Among these, MEX-AM (Metal Extrusion Additive Manufacturing), based on organic materials and powder mixtures, achieves densification sintering through highly compatible processing techniques. It features low-temperature, low-stress forming and high powder content filling, making it particularly advantageous for high-density additive manufacturing of high-melting-point materials such as cemented carbides. Furthermore, MEX-AM's dual-nozzle feature enables the customized fabrication of various materials, facilitating the mass production of PDC substrates with interlocking encapsulation structures.

[0007] Therefore, this invention utilizes an extrusion additive manufacturing method to prepare a wrapped, multilayered PDC substrate. By taking advantage of the high defect tolerance and high energy absorption of the layered structure, as well as the multi-material and high structural design flexibility of extrusion additive manufacturing, a complex PDC substrate with both high hardness and toughness and adaptability to the service environment of polycrystalline diamond composite sheets is prepared. The high-toughness substrate improves the impact resistance of polycrystalline diamond composite sheets, thereby improving their efficiency and lifespan in complex service environments.

[0008] During the synthesis of polycrystalline diamond composites (PDCs), some liquid Co in the cemented carbide substrate sweeps across the diamond layer under the drive of capillary force and interfacial energy, densifying the diamond layer and promoting polycrystalline formation. However, the loss of Co from the cemented carbide leads to a decrease in its toughness, affecting the impact toughness of the PDC and making it difficult to use for extended periods in demanding service environments. To address this issue, this invention utilizes the characteristics of an encapsulated layered structure to suppress crack initiation and propagation, and extrudes an additive manufacturing process to produce a high-toughness PDC substrate with a multi-material alternating encapsulation structure, thereby improving the impact resistance and service life of the PDC in complex environments.

[0009] This invention discloses a method for extruding additive manufacturing of a multi-material alternating-coating PDC substrate, wherein the multi-material alternating-coating PDC substrate includes a working portion; the preparation of the working portion of the multi-material alternating-coating PDC substrate includes the following steps:

[0010] Step 1: Preparation of Soft Material Feed

[0011] A soft material is selected, wherein the elastic modulus of the soft material is lower than that of cemented carbide, and the coefficient of thermal expansion is 3~15×10⁻⁶. -6 / ℃, melting point not lower than 1300℃, and amount used accounting for no more than 50 vol.% of the total matrix.

[0012] The soft material feedstock is prepared by mixing and granulation using organic polymer binders, soft material powders, and metal binders as raw materials. The soft material and metal binder are pre-mixed mechanically to a uniform mass ratio of 70-95:5-30, preferably 80-90:10-20. The loading of the soft material powder + metal binder powder is 43-65 vol.%, preferably 48-62 vol.%. The d90 of the soft material powder and metal binder is <50 μm.

[0013] Step 2: Preparation of cemented carbide feedstock

[0014] Prepare cemented carbide powder, wherein the cemented carbide is WC-Co, and the mass fraction of Co is 5-25 wt.%, preferably 8-20 wt.%, and the mass fraction of WC is 75-95 wt.%, preferably 80-92 wt.%. Use an organic polymer binder and cemented carbide powder as raw materials, and prepare cemented carbide feedstock by mixing, kneading, and granulation. The volume percentage of cemented carbide powder in the cemented carbide feedstock is 43-65 vol.%, preferably 48-62 vol.%.

[0015] In steps one and two, the organic polymer adhesive includes filler, skeleton, plasticizer, and surfactant, with a mass ratio of 50-75:15-35:5-20:1-8, respectively.

[0016] The filler includes one or more of solid paraffin (PW), liquid paraffin (LPW), and microcrystalline wax (MW), preferably a mixture of PW and MW, and more preferably, PW and MW are mixed in a mass ratio of 3 to 5:1;

[0017] The skeleton includes one or more of vegetable oil (EO), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), and ethylene-vinyl acetate copolymer (EVA), preferably a mixture of HDPE and EVA, and more preferably, HDPE and EVA are mixed in a mass ratio of 1.0~1.5:1.0~1.5;

[0018] The plasticizer is selected from at least one of dioctyl phthalate (DOP), dibutyl phthalate (DBP), trimethylol phosphate (TCP), and tributyl citrate (TBC), preferably DOP.

[0019] The surfactant is selected from at least one of stearic acid (SA) and oleic acid, preferably SA;

[0020] Step 3: Two-dimensional structure construction

[0021] Based on the target 3D structure model, the 3D structure is converted into a multi-layer 2D structure diagram that can be recognized by the printing equipment using slicing software. The model consists of a cemented carbide layer and a soft layer, with the two materials alternating and wrapping each other from the core to the surface. The soft layer is sandwiched between the cemented carbide layers. The current state of any soft layer is similar to that of its corresponding cemented carbide layer. The number of soft layers is greater than or equal to 2, and the number of cemented carbide layers is greater than or equal to 3. The outermost layer of the model is a cemented carbide layer.

[0022] Step 4: Printing Preparation

[0023] Place the soft material feedstock and hard alloy feedstock obtained in steps one and two into different hoppers of the extrusion 3D printer; select printing strategy parameters according to the target structure accuracy, and import the modeling and slicing file;

[0024] Step 5: Extrusion Printing

[0025] The cemented carbide preform with a multi-material alternating wrapping structure is extruded and printed. During extrusion printing, the nozzle size is generally selected as 0.1-0.8mm. During printing, the single layer thickness is 0.1-0.2mm, the extrusion temperature is set to 140-180℃, the printing platform temperature is set to 70-100℃, and the filling flow rate is set to 50-100%. Other parameters are as follows: filling speed is 10-40mm / s, the line width is consistent with the nozzle size, the upper and lower layer line direction is [0, 90°], and the single layer line method is one of straight line, serrated, or concentric circle.

[0026] In the multi-material alternating-wrap type cemented carbide green blank, the axial thickness of both the hard layer and the soft layer is not less than 0.1 mm, and the radial thickness is greater than or equal to the nozzle diameter. The relationship between the radial thickness and the axial thickness of a single layer is: axial thickness = radial thickness × total height of the model / total diameter; the number of soft phase layers is not less than 2.

[0027] Step 6: Solvent Degreasing

[0028] Degreasing was performed on a PDC substrate green body with alternating multi-material encapsulation structure. Using n-heptane as the degreasing solvent, PW, MW, and SA were removed by degreasing at 45~55℃ for 20-28h to obtain the degreased composite green body.

[0029] Step 7: Hot degreasing and vacuum sintering

[0030] The composite preform after degreasing in step six was placed in a vacuum furnace for thermal degreasing. The temperature was slowly increased to 400-550℃ in an H2 atmosphere at a flow rate of 45-55 L / min and held for 30-90 min to completely remove the polymer binder. Subsequently, the temperature was continuously increased to 1200-1500℃ under vacuum, and Ar high pressure of 3-6 bar was introduced and held for 40-90 min. The sample was then cooled in the furnace to obtain a PDC substrate with a multi-material alternating encapsulation structure.

[0031] As a preferred embodiment, the present invention provides a method for extrusion additive manufacturing of a multi-material alternating encapsulation type PDC substrate; wherein the soft material is ceramic particles and the metal binder is Co; the Co content in the soft material feed is 0.95 to 1.05 times the Co content in the cemented carbide; and the ceramic particles are selected from at least one of alumina, zirconium oxide, and yttrium oxide.

[0032] Preferably, the present invention provides a method for extruding additive manufacturing of a multi-material alternating-encapsulation PDC substrate; the soft particles have a particle size of 0.8-2.5 μm, preferably 1-2 μm. The Co powder mixed with it has a particle size of 0.8 to 1.2 times that of the soft particles.

[0033] As a preferred embodiment, the present invention provides a method for extruding additive manufacturing of a multi-material alternating encapsulation type PDC substrate; in the soft layer, the ratio of ceramic particles and Co is less than or equal to the Co content in the cemented carbide used.

[0034] As a preferred embodiment, the present invention provides a method for extruding additive manufacturing of a multi-material alternating encapsulation type PDC substrate; the powder particle size of the cemented carbide is 0.5-3μm, preferably 1.2-2.5μm.

[0035] As a further preferred option, the adhesive is composed of PW, MW, EO, EVA, HDPE, DOP, and SA in a mass ratio of PW:MW:EO:EVA:HDPE:DOP:SA = 47:11:4:15:16:5:2.

[0036] The multi-material alternating encapsulation type PDC substrate of the present invention can be composed entirely of the working part, or the working part can be connected to a support member made of hard alloy material.

[0037] To address the issues of inconsistent and poor impact toughness in different directions, a multi-material alternating-encapsulation PDC substrate, consisting entirely of the working part, is generally used, which exhibits better performance.

[0038] In practical applications, when using a multi-material alternating-encapsulation PDC substrate composed entirely of working parts, the core is made of hard alloy and the soft material is composed of Co and aluminum oxide. The hard alloy and soft material are arranged alternately from the inside out until the outermost layer is a hard alloy layer.

[0039] In industrial applications, the thickness in both the longitudinal and transverse directions is not less than 0.1 mm, and the number of soft phase layers is not less than 2, preferably 3-12, and more preferably 6-10.

[0040] Preferably, the equivalent diameter of the cemented carbide core is 1-2 times the radial thickness of the cemented carbide layer wrapped in the soft material; the thickness of the single cemented carbide layer wrapped in the soft material is 0.2-0.8 mm, preferably 0.45-0.55 mm, and the thickness of the single soft material layer is 0.05-0.2 mm, preferably 0.08-0.12 mm.

[0041] Preferably, excluding the core material, the ratio of the axial thickness of the single-layer cemented carbide layer to the axial thickness of the single-layer soft material is 3~6:1, more preferably 4~5.5:1, and even more preferably 4.9~5.1:1. By controlling and optimizing this ratio, the present invention achieves a significantly improved wear ratio and average impact toughness of the product.

[0042] This invention relates to an application of a method for extrusion additive manufacturing of multi-material alternating-coating PDC substrates. The method includes assembling the working portion of a sintered multi-material alternating-coating PDC substrate with a polycrystalline diamond layer into a high-temperature, high-pressure synthesis block, which is then placed in a hexahedral press for high-temperature, high-pressure synthesis. The synthesis process involves a pressure of 5-7.5 GPa, preferably 6-7 GPa, and a temperature of 1400-1700℃, preferably 1450-1550℃.

[0043] This invention relates to an application of a method for extrusion additive manufacturing of multi-material alternating-encapsulation PDC substrates. After the resulting substrate is combined with diamond, the PDC wear ratio of the product is greater than or equal to 37.1 × 10⁻⁶. 4 The average impact toughness is greater than or equal to 972J.

[0044] After optimization, the application of the extrusion additive manufacturing method for multi-material alternating-coating PDC substrates of this invention results in a PDC wear ratio greater than or equal to 37.4 × 10⁻⁶ after the substrate is combined with diamond. 4 The average impact toughness is greater than or equal to 1097J.

[0045] Principles and advantages

[0046] This invention is the first attempt to prepare a high-toughness PDC substrate with alternating multi-material encapsulation by extrusion additive manufacturing, which alleviates the problem of reduced toughness of hard alloy substrate caused by Co loss during high temperature and high pressure process, and thus reduced impact resistance of PDC.

[0047] During the high-temperature, high-pressure synthesis of PDC, Co in the cemented carbide gradually melts and sweeps across the diamond layer as temperature and pressure increase, promoting the densification of the diamond layer and the formation of polycrystalline diamond. However, Co is the main contributor to the toughness of cemented carbide, and due to Co migration, the impact toughness of cemented carbide often decreases significantly. In PDC, wear resistance is provided by polycrystalline diamond, while toughness is provided by the cemented carbide substrate. Therefore, in industrial production, the toughness of PDC cemented carbide substrates often cannot meet the high impact toughness requirements of PDCs in increasingly complex and harsh service environments. Therefore, the preparation of cemented carbide substrates with low Co content and high hardness and toughness is of great significance for improving the mechanical properties and working efficiency of polycrystalline diamond.

[0048] This invention applies an interlaced wrapping structure to the preparation of high-hardness and high-toughness cemented carbide substrates. By utilizing the characteristics of the interlaced wrapping structure, such as scattering stress waves and promoting crack deflection, the initiation and propagation of cracks in the cemented carbide substrate during PDC operation are suppressed. This improves the fracture toughness of cemented carbide while enhancing the impact resistance and service life of polycrystalline diamond composite sheets. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the multi-material alternating wrapping structure PDC substrate designed in Example 1;

[0050] Figure 2 This is a schematic diagram of the multi-material alternating wrapping structure designed in Example 3 distributed in the working part of the PDC substrate.

[0051] Figure 3 This is a schematic cross-sectional view of the PDC substrate of the multi-material alternating wrapping structure involved in Example 1. Detailed Implementation

[0052] Example 1 - A globally distributed multi-material alternating wrapping model.

[0053] Step 1

[0054] Commercial YG13 cemented carbide powder, alumina powder, and Co powder were prepared. The WC particle size of the commercial YG13 powder was 1.2~1.6μm, and the density was 14.2g / cm3. The average particle size of the alumina was 1.2μm, and the average particle size of the Co powder was 1.5μm. The alumina and Co were weighed and mixed at a mass ratio of 87:13 to obtain Al2O3-13Co mixed powder.

[0055] Step Two

[0056] Organic polymers were formulated with a mass ratio of PW:MW:EO:EVA:HDPE:DOP:SA = 47:11:4:15:16:5:2 to obtain a binder; by volume ratio, the binder:YG13 powder = 43:57, and the binder:Al2O3-13Co mixed powder = 45:55. The powders and binder were placed in an internal mixer and heated to 145~160℃ for uniform mixing. During this process, the mixture was cooled to allow for thorough shearing and kneading of the powders and organic polymers to ensure uniform mixing. The cooled internally mixed material was then crushed and sieved to obtain the target feed pellets. The cooling temperature-time was 125℃-30min, and the total internal mixing time was 2h. The internally mixed feed was then fed into a granulator for granulation to obtain two types of molding feeds.

[0057] Step 3: Design a globally distributed multi-material alternating wrapping model. This model consists of alternating wrappings of YG13 and Al2O3-13Co, with Al2O3-13Co layers sandwiched between YG13 layers. The model dimensions are φ17.6 × 8.6 mm (diameter × height). The axial thickness of the Al2O3-13Co layer is 0.1 mm, and its radial thickness, obtained by multiplying its axial thickness by the total model diameter / total height, is 0.2 mm. The ratio of the axial thickness of the YG13 layer to that of the Al2O3-13Co layer is set to 1:1 (Group A), 3:1 (Group B), 5:1 (Group C), and 7:1 (Group D). The two materials are arranged alternately from the outside to the inside, with YG13 layers on the outside and Al2O3-13Co layers on the inside, until the core of the model is reached. When the last Al2O3-13Co layer is completed, if the remaining space in the model is enough for one but not two more YG13 layers, the remaining space in the core is filled entirely with YG13.

[0058] The designed globally distributed multi-material alternating wrapping model was imported into the corresponding slicing software and extrusion printer. YG13 and Al2O3-13Co were each assigned to two extrusion heads, and the printing strategy parameters for each head were set in the software: nozzle size 0.1 mm, layer thickness 0.1 mm, extrusion temperature 165℃, infill flow rate 90%, printing platform temperature 80℃, infill speed 30 mm / s, line width 0.1 mm, single-layer line routing as a straight line, and upper layer line routing direction [0, 90°]. The prepared YG13 and Al2O3-13Co materials were then fed into the two hoppers of the extrusion 3D printer, and printing was performed according to the preset parameters.

[0059] Step 4: Degrease the printed preform with solvent at a temperature of 50°C, using n-heptane as the solvent, for 24 hours.

[0060] Step 5: Place the degreased green compact in an H2 atmosphere furnace at a flow rate of 50 L / min and slowly heat it to 550℃, holding it at that temperature for 1 hour. Continue heating under vacuum to 1400℃, then introduce 5.8 bar high-pressure Ar and hold for 25 minutes. Subsequently, the sample is cooled with the furnace to obtain a multi-material alternating encapsulated PDC substrate sintered body.

[0061] Step Six

[0062] Diamond-4wt.%Co powder with an average diamond grain size of 10μm and a pre-prepared multi-material alternating-coating PDC substrate were sequentially placed in a molybdenum cup. NaCl, carbon nanotubes, pyrophyllite, conductive sheets, and graphite sheets were then assembled into a high-temperature, high-pressure composite block, which was then subjected to high-temperature, high-pressure sintering to obtain a polycrystalline diamond composite sheet. The high-temperature, high-pressure process was performed at 1500℃-9.0GPa for 10 minutes to obtain the polycrystalline diamond composite (PDC) product.

[0063] The prepared multi-material alternating-encapsulation PDC substrate green body exhibited regular morphology and dimensional deviation <5%, with no blistering or cracking defects after solvent degreasing. After vacuum sintering (i.e., completing step five), the radial dimension shrank by approximately 16.22%, the axial dimension shrank by approximately 18.31%, and the density was >98%. No significant dimensional change was observed after high temperature and high pressure. The wear ratio of the polycrystalline diamond sample was tested using a SiC grinding wheel, and the impact resistance was tested using a PDC dynamic load resistance tester. The testing method was as follows: starting with an impact energy of 20J, ten tests were conducted; if no damage (cracking, delamination, etc.) was observed, the impact energy was increased to 25J, and ten more tests were conducted; if no damage still occurred, the impact energy was increased again by 5J, and ten more tests were conducted, gradually accumulating until the sample was damaged. The impact energy × the number of impacts was the impact energy, and the average value was taken for each layer after five tests. The obtained wear ratio of group A PDC was 38.9 × 10⁻⁶. 4The average impact toughness was 972 J; the PDC wear ratio of group B was 40.3 × 10⁻⁶. 4 The average impact toughness was 1089 J; the PDC wear ratio of group C was 37.4 × 10⁻⁶. 4 The average impact toughness is 1218J; the PDC wear ratio of group D is 36.8×10. 4 The average impact toughness is 1145J.

[0064] Example 2—The thickness of the Al2O3-13Co layer was increased from 0.1 to 0.2 mm, and the ratio of the axial thickness of the YG13 layer to the axial thickness of the Al2O3-13Co layer was set to 5:1.

[0065] In Example 1, the Al2O3-13Co layer thickness was set to 0.2 mm, and the ratio of the axial thickness of the YG13 layer to the axial thickness of the Al2O3-13Co layer was 5:1. Other printing, degreasing, and sintering steps and parameters remained unchanged. The resulting multi-material alternating-encapsulation PDC substrate green body exhibited a regular morphology, dimensional deviation <5%, and solvent degreasing showed no blistering or cracking defects. After vacuum sintering (i.e., completing step five), the radial dimension shrank by 17.03%, the axial dimension shrank by 18.51%, and the density >98%. No significant change in substrate size was observed after high temperature and high pressure testing. Following the testing method described in Example 1, the obtained PDC wear ratio was 37.5 × 10⁻⁶. 4 The average impact toughness is 1103 J;

[0066] Example 3—Homogeneous substrate control group

[0067] A YG13 cemented carbide green blank with a diameter × height of φ17.6 × 8.6 mm was prepared by additive manufacturing. The forming, debinding, and sintering parameters and steps were consistent with those in Example 1, resulting in a polycrystalline diamond composite sheet with YG13 as the substrate. After vacuum sintering (i.e., completing step five), the radial dimension shrank by 17.01%, the axial dimension shrank by 19.36%, and the density was >98%. After high temperature and high pressure, the wear ratio of the composite sheet was 39.6 × 10⁻⁶. 4 The average impact toughness is 885J.

[0068] Example 4—Changing Global Packages to Work-Specific Packages

[0069] The globally distributed multi-material alternating-encapsulation cemented carbide substrate described in step three is replaced with a multi-material alternating-encapsulation cemented carbide substrate distributed in the upper half of the axis. Using the model core as a reference, the model structure of the core and the portion above it remains unchanged. Except for the core, the Al2O3-13Co layers in the lower half of the model are shortened and brought closer to the bottom of the core. The spacing between the Al2O3-13Co layers in the lower half is such that the thickness of the YG13 layer in the lower half is equal to the thickness of the Al2O3-13Co layer, which is 0.1 mm. The material in the spacing region is YG13. Other steps and parameters remain unchanged. During high temperature and high pressure, the end with the semi-encapsulated structure is brought into contact with diamond powder to synthesize PDC. The prepared multi-material alternating semi-encapsulated PDC substrate has a regular morphology, a dimensional deviation of <5%, and exhibits no bubbling or cracking defects after solvent degreasing. After vacuum sintering (i.e., completing step five), the radial dimension of the upper half shrinks by 16.07%, the radial dimension of the lower half shrinks by 16.93%, and the axial dimension shrinks by 17.92%, with a density >98%. The polycrystalline diamond composite sheet obtained after high temperature and high pressure has a wear ratio of 38.2 × 10⁻⁶. 4 The average impact toughness is 1097 J. This scheme reduces the coverage area of ​​the encapsulated structure to the working area of ​​the PDC substrate, thereby improving sample fabrication efficiency while maintaining the performance of the original global multi-material alternating encapsulation structure.

[0070] Example 5—Adjusting the shape of the soft layer structure to a spherical shape

[0071] The parameters of the globally distributed multi-material alternating-encapsulation cemented carbide substrate described in step three were adjusted. YG13 and Al2O3-13Co were arranged alternately in a spherical encapsulation structure. In this structure, the axial thickness of a single Al2O3-13Co layer was 0.1 mm, and the ratio of the axial thickness of the YG13 layer to the axial thickness of the Al2O3-13Co layer was set to 5:1. The two materials were alternately and cyclically arranged from the outside to the inside of the model core, with YG13 layers on the outside and Al2O3-13Co layers on the inside. When the last Al2O3-13Co layer was arranged, if the remaining space in the model could accommodate one but not two YG13 layers, the remaining space in the core was filled entirely with YG13. Other steps and parameters remained unchanged. The resulting polycrystalline diamond composite sheet had a wear ratio of 35.7 × 10⁻⁶. 4 The average impact toughness is 1172J.

[0072] Example 6—Adjusting the mass ratio of alumina to cobalt

[0073] Al2O3 and Co were mixed at a mass ratio of 90:10 in Example 1 to prepare Al2O3-10Co raw material mixed powder. The axial thickness of the Al2O3-13Co layer was 0.1 mm, and the radial thickness, obtained by multiplying the axial thickness by the total diameter / total height of the model, was 0.2 mm. The ratio of the axial thickness of the YG13 layer to that of the Al2O3-13Co layer was set to 5:1, with other steps and parameters remaining unchanged. The prepared PDC green body had a regular morphology, a dimensional deviation of <5%, a relative density of 98%, and no bubbling or cracking defects after solvent degreasing. After vacuum sintering, the radial shrinkage was 16.13%, the axial shrinkage was 17.86%, and the microstructure was uniform. After high-temperature and high-pressure sintering, the wear ratio of the obtained PDC was 37.1 × 10⁻⁶. 4 The average impact toughness is 1033J.

[0074] Comparative Example 1—Verification of insufficient radial impact resistance of simple laminated structures

[0075] Step 1

[0076] Commercial YG13 cemented carbide powder, alumina powder, and Co powder were prepared. The WC particle size of the commercial YG13 powder was 1.2~1.6μm, and the density was 14.2g / cm3. The average particle size of the alumina was 1.2μm, and the average particle size of the Co powder was 1.5μm. The alumina and Co were weighed and mixed at a mass ratio of 87:13 to obtain Al2O3-13Co mixed powder.

[0077] Step Two

[0078] Organic polymers were formulated with a mass ratio of PW:MW:EO:EVA:HDPE:DOP:SA = 47:11:4:15:16:5:2; and a volume ratio of binder:YG13 powder = 43:57, and binder:Al2O3-13Co mixed powder = 45:55. The powders and binders were placed in an internal mixer and heated to 145-160℃ for uniform mixing. During this process, the mixture was cooled to allow for thorough shearing and kneading of the powders and organic polymers to ensure uniform mixing. The cooled internally mixed material was then crushed and sieved to obtain the target feed pellets. The cooling temperature and time were 125℃-30min, and the total mixing time was 2h. The internally mixed feed was then fed into a granulator for granulation to obtain two types of shaped feed pellets.

[0079] Step 3

[0080] A multi-material unencapsulated structural model was designed with alternating YG13 and Al2O3-13Co layers distributed from bottom to top and from left to right, respectively. The model features alternating YG13 and Al2O3-13Co layers, with dimensions of φ17.6 × 8.6 mm (diameter × height). The axial thickness of a single Al2O3-13Co layer is 0.1 mm, and its radial thickness, calculated as 0.2 mm (axial thickness × total model diameter / total height), is calculated from this radial thickness. The ratio of the axial thickness of the YG13 layer to that of the Al2O3-13Co layer is set to 5:1. The two materials are arranged alternately from bottom to top (Group A) and from left to right (Group B) to the other end, with the YG13 layer on the outside and the Al2O3-13Co layer on the inside. The sample end face is YG13.

[0081] Subsequently, extrusion additive manufacturing and solvent degreasing were performed according to the steps and parameters described in Example 1.

[0082] Step Four

[0083] The degreased green blank was placed in an H2 atmosphere furnace at a flow rate of 50 L / min and slowly heated to 550 °C, and held at that temperature for 1 h. Under vacuum, the temperature was continuously increased to 1400 °C, and Ar at a high pressure of 5.8 bar was introduced and held for 25 min. Subsequently, the sample was cooled with the furnace to obtain two types of non-encapsulated hard alloy sintered bodies, Group A and Group B.

[0084] Step 5

[0085] The two types of non-encased PDC substrates obtained in step four were subjected to drop-weight impact toughness tests. The impact toughness of the cemented carbide in group A (non-encased structures arranged alternately from top to bottom) was 1093 J, and that in group B (non-encased structures arranged alternately from left to right) was 726 J. This indicates that the multi-material non-encased structure has excellent axial impact resistance, but its radial impact resistance is significantly insufficient, making it unsuitable for the complex service environment of PDCs.

[0086] In Comparative Example 1, the impact toughness of the unwrapped structure was tested. The unwrapped structure has strong directionality. The structure distributed in layers from bottom to top showed excellent performance in the drop hammer impact toughness test, while the structure distributed from left to right showed a significant decrease in performance. In this case, the structure from bottom to top represents the axial force, and the structure from left to right represents the radial force.

[0087] Comparative Example 2—Defatting Temperature Adjustment

[0088] In step four of Example 1, the degreasing temperature was adjusted to 70℃. The axial thickness of the Al2O3-13Co layer was 0.1 mm, and the radial thickness, obtained by multiplying the axial thickness by the total diameter / total height of the model, was 0.2 mm. The ratio of the axial thickness of the YG13 layer to that of the Al2O3-13Co layer was set to 5:1, while other steps and parameters remained unchanged. During the solvent degreasing process, the prepared multi-material PDC substrate sintered green body blistered and cracked due to excessively high temperature and a too-fast degreasing rate. After vacuum sintering, the sample showed a radial shrinkage of 17.59% and an axial shrinkage of 19.36%, a slight increase in dimensional shrinkage, but the shape remained well maintained. The PDC wear ratio obtained after high temperature and high pressure was 36.9 × 10⁻⁶. 4 Its impact toughness is 1076J.

[0089] Comparative Example 3—Reduced alumina particle size leads to increased printing difficulty;

[0090] Step 1

[0091] Commercial YG13 cemented carbide powder, alumina powder, and Co powder were prepared. Compared with Example 1, the particle size of alumina powder was reduced to 0.5 μm, and the average particle size of Co powder was 1.5 μm. The WC particle size in the commercial YG13 powder was 1.2~1.6 μm, and the density was 14.2 g / cm3. Alumina and Co were weighed and mixed at a mass ratio of 87:13 to obtain Al2O3-13Co mixed powder.

[0092] Step Two

[0093] Organic polymers were formulated with a mass ratio of PW:MW:EO:EVA:HDPE:DOP:SA = 47:11:4:15:16:5:2; and a volume ratio of binder:YG13 powder = 43:57, and binder:Al2O3-13Co mixed powder = 45:55. The powders and binders were placed in an internal mixer and heated to 145-160℃ for uniform mixing. During this process, the mixture was cooled to allow for thorough shearing and kneading of the powders and organic polymers to ensure uniform mixing. The cooled internally mixed material was then crushed and sieved to obtain the target feed pellets. The cooling temperature and time were 125℃-30min, and the total mixing time was 2h. The internally mixed feed was then fed into a granulator for granulation to obtain two types of shaped feed pellets.

[0094] Step 3: Design a globally distributed multi-material alternating wrapping model, with model parameters consistent with those described in Example 1. Import the designed globally distributed multi-material alternating wrapping model into the corresponding slicing software and extrusion printer. Set two extrusion heads for YG13 and Al2O3-13Co respectively, and set the printing strategy parameters for the two extrusion heads in the software. Select a nozzle size of 0.1mm, a layer thickness of 0.1mm, an extrusion temperature of 165℃, a filling flow rate of 90%, a printing platform temperature of 80℃, a filling speed of 30mm / s, a line width of 0.1mm, a straight line for each layer, and an upper layer line direction of [0, 90°]. Then, feed the prepared YG13 and Al2O3-13Co materials into the two hoppers of the extrusion 3D printer respectively, and print according to the preset parameters.

[0095] YG13 printing is normal, but Al2O3-13Co feed printing results in discontinuous lines and uneven extrusion. Increasing the extrusion temperature to 175℃ and increasing the filler flow rate by 100% did not improve the situation. Adjusting the extrusion temperature to 180℃ caused the feeder to flow out uncontrollably due to the excessive temperature. When printing stops and the machine is empty, the screw rotates for 3-5 seconds before the material is ejected, and the ejected line is riddled with obvious holes. This is because the powder particle size is small, resulting in poor compatibility with the feeder and making it unsuitable for high loading. Adjusting the filler and surfactant amounts or reducing the powder loading may help.

[0096] Comparative Example 4—Increasing the printing speed of YG13 and the extrusion temperature of Al2O3-13Co mixed powder

[0097] Step 1

[0098] Commercial YG13 cemented carbide powder, alumina powder, and Co powder were prepared. The WC particle size of the commercial YG13 powder was 1.2~1.6μm, and the density was 14.2g / cm3. The average particle size of the alumina was 1.2μm, and the average particle size of the Co powder was 1.5μm. The alumina and Co were weighed and mixed at a mass ratio of 87:13 to obtain Al2O3-13Co mixed powder.

[0099] Step Two

[0100] Organic polymers were formulated with a mass ratio of PW:MW:EO:EVA:HDPE:DOP:SA = 47:11:4:15:16:5:2; and a volume ratio of binder:YG13 powder = 43:57, and binder:Al2O3-13Co mixed powder = 45:55. The powders and binders were placed in an internal mixer and heated to 145-160℃ for uniform mixing. During this process, the mixture was cooled to allow for thorough shearing and kneading of the powders and organic polymers to ensure uniform mixing. The cooled internally mixed material was then crushed and sieved to obtain the target feed pellets. The cooling time was 125℃-30min, and the total mixing time was 2h. The internally mixed feed was then fed into a granulator for granulation to obtain two types of molding feeds.

[0101] Step 3: Design a globally distributed multi-material alternating wrapping model. This model consists of alternating wrappings of YG13 and Al2O3-13Co, with Al2O3-13Co layers sandwiched between YG13 layers. The model dimensions are φ17.6 × 8.6 mm (diameter × height). The axial thickness of the Al2O3-13Co layer is 0.1 mm, and its radial thickness, obtained by multiplying its axial thickness by the total model diameter / total height, is 0.2 mm. The ratio of the axial thickness of the YG13 layer to that of the Al2O3-13Co layer is set to 5:1. The two materials are arranged alternately from the outside to the inside, with YG13 layers on the outside and Al2O3-13Co layers on the inside, until the core of the model is filled. When the last Al2O3-13Co layer is completed, if there is enough space for one but not two more YG13 layers, the remaining space in the core is filled entirely with YG13.

[0102] The designed globally distributed multi-material alternating wrapping model was imported into the corresponding slicing software and extrusion printer. YG13 and Al2O3-13Co feedstocks were set to their respective extrusion heads, and the printing strategy parameters for each head were configured in the software: nozzle size 0.1mm, layer thickness 0.1mm, line width 0.1mm, and printing platform temperature 80℃. The extrusion temperature for YG13 feedstock was 165℃, fill flow rate 90%, and fill speed 65mm / s; the extrusion temperature for Al2O3-13Co feedstock was 195℃, fill flow rate 85%, and fill speed 30mm / s. Single-layer line routing was straight, with the uppermost layer line routing direction [0, 90°]. The prepared YG13 and Al2O3-13Co feedstocks were then placed into the two hoppers of the extrusion 3D printer, and printing was performed according to the preset parameters.

[0103] Due to excessively high extrusion temperature, the Al2O3-13Co feedstock became uncontrollably leaked molten filaments from the nozzle, preventing normal printing. When the extrusion temperature was reduced to 185℃, the diameter of the leaking molten filaments decreased significantly but continued to flow out. When the extrusion temperature was further reduced to 170℃, the uncontrolled leakage disappeared, the nozzle could print normally, and subsequent operations could proceed as normal.

[0104] Step Four

[0105] Following the same molding, degreasing, and sintering steps and parameters as in Example 1, a gradient PDC substrate with an outer Co-depleted layer and an inner Co-rich layer, with the sides and top wrapped around the substrate, was prepared. This PDC substrate and diamond-4wt.%Co powder (4% of the total mass of diamond + Co) with an average grain size of 10μm were then placed in a molybdenum cup, with the diamond powder added first, followed by the PDC substrate (ensuring the top of the gradient PDC substrate was in contact with the diamond). NaCl, carbon nanotubes, pyrophyllite, conductive sheets, and graphite sheets were sequentially assembled into a high-temperature, high-pressure composite block, which was then subjected to high-temperature, high-pressure sintering to obtain a polycrystalline diamond composite sheet. The high-temperature, high-pressure process was performed at 1500℃-9.0GPa for 10 minutes to obtain the polycrystalline diamond composite (PDC) product.

[0106] The prepared multi-material alternating-encapsulation PDC substrate green body exhibited regular morphology and dimensional deviation <9%, with no blistering or cracking defects after solvent degreasing. After vacuum sintering, the radial dimension shrank by 17.58%, the axial dimension shrank by 18.77%, and the density was approximately 98%. No significant dimensional change was observed after high temperature and high pressure. The wear ratio of the polycrystalline diamond sample was tested using a SiC grinding wheel, and its impact resistance was tested using a PDC dynamic load resistance tester. The testing method was as follows: starting with an impact energy of 20J, ten tests were conducted; if no damage (cracking, delamination, etc.) was observed, the impact energy was increased to 25J, and ten more tests were conducted; if no damage still occurred, the impact energy was increased to 30J, and ten more tests were conducted, gradually accumulating until the sample was damaged and the testing was stopped. The impact energy multiplied by the number of impacts was the impact energy. Five tests were conducted per layer, and the average value was taken. The obtained novel PDC wear ratio was 34.2 × 10⁻⁶. 4 The impact toughness is 974J. Due to the high filling speed of the nozzle corresponding to YG13, the dimensional accuracy, relative density, and bonding strength of the green body all decrease to varying degrees, ultimately resulting in a significant impact on performance.

[0107] Comparative Example 5—The axial thickness is set to 0.05 or 0.08 mm;

[0108] Step 1

[0109] Commercial YG13 cemented carbide powder, alumina powder, and Co powder were prepared. The WC particle size of the commercial YG13 powder was 1.2~1.6μm, and the density was 14.2g / cm3. The average particle size of the alumina was 1.2μm, and the average particle size of the Co powder was 1.5μm. The alumina and Co were weighed and mixed at a mass ratio of 87:13 to obtain Al2O3-13Co mixed powder.

[0110] Step Two

[0111] Organic polymers were formulated with a mass ratio of PW:MW:EO:EVA:HDPE:DOP:SA = 47:11:4:15:16:5:2 to obtain a binder; by volume ratio, the binder:YG13 powder = 43:57, and the binder:Al2O3-13Co mixed powder = 45:55. The powders and binder were placed in an internal mixer and heated to 145~160℃ for uniform mixing. During this process, the mixture was cooled to allow for thorough shearing and kneading of the powders and organic polymers to ensure uniform mixing. The cooled internally mixed material was then crushed and sieved to obtain the target feed pellets. The cooling temperature-time was 125℃-30min, and the total internal mixing time was 2h. The internally mixed feed was then fed into a granulator for granulation to obtain two types of molding feeds.

[0112] Step 3: Design a globally distributed multi-material alternating wrapping model. This model consists of alternating wrappings of YG13 and Al2O3-13Co, with Al2O3-13Co layers sandwiched between YG13 layers. The model dimensions are φ17.6 × 8.6 mm (diameter × height). The axial thickness of the Al2O3-13Co layers is 0.05 mm (group a) and 0.08 mm (group b), and the radial thickness is 0.2 mm (derived from its axial thickness × total model diameter / total height). The ratio of the axial thickness of the YG13 layers to the axial thickness of the Al2O3-13Co layers is set to 5:1. The two materials are arranged alternately from the outside to the inside, with YG13 layers on the outside and Al2O3-13Co layers on the inside, until the core of the model is filled. When the last Al2O3-13Co layer is arranged, if there is enough space in the model for one but not two YG13 layers, the remaining space in the core is filled entirely with YG13.

[0113] The designed globally distributed multi-material alternating wrapping model was imported into the corresponding slicing software and extrusion printer. YG13 and Al2O3-13Co were each assigned to two extrusion heads, and the printing strategy parameters for each head were set in the software: nozzle size 0.1 mm, layer thickness 0.1 mm, extrusion temperature 165℃, infill flow rate 90%, printing platform temperature 80℃, infill speed 30 mm / s, line width 0.1 mm, single-layer line routing as a straight line, and upper layer line routing direction [0, 90°]. The prepared YG13 and Al2O3-13Co materials were then fed into the two hoppers of the extrusion 3D printer, and printing was performed according to the preset parameters.

[0114] During the printing process, the extruded filaments of the nozzles corresponding to the Al2O3-13Co layers in groups a and b were not smooth, but rather distributed in a wavy pattern, and the line width was also uneven. After adjusting the filling flow rate and base temperature, the problem was improved to some extent. However, after the green body was printed to a certain height, the nozzles easily scraped the molten printing material of the previous layer, resulting in material shortage or even deformation of the green body, making it impossible to complete the printing normally. At the same time, due to the small layer thickness, the green body of group a was printed slowly, making it difficult to apply in batches.

Claims

1. A method of extrusion-based additive manufacturing of a multi-material alternating wrapped PDC substrate, characterized by: In this alternating-wrap PDC substrate, hard alloy layers and soft layers alternate and wrap around each other from the core to the surface, with soft layers sandwiched between the hard alloy layers, forming an approximate concentric sphere or concentric cylinder structure; the multi-material alternating-wrap PDC substrate contains a working part; the preparation of the multi-material alternating-wrap PDC substrate containing the working part includes the following steps: Step 1: Preparation of Soft Material Feed The soft material has an elastic modulus lower than that of the hard alloy, a thermal expansion coefficient of 3-15x10 -6 / ℃, a melting point not lower than 1300℃, and a volume fraction not higher than 50vol.% in the total volume of the matrix. A soft material feedstock is prepared by mixing and granulation using organic polymer binders, soft material powders, and metal binders as raw materials. The soft material and metal binder are pre-mixed mechanically to a uniform mass ratio of 80-90:10-20. The loading of the soft material powder + metal binder powder is 48-62 vol.%; the d90 of the soft material powder and the metal binder is <50 μm. The soft material is ceramic particles, and the metal binder is Co. The particle size of the soft particles is 0.8-2.5 μm; the particle size of the Co powder mixed with it is 0.8-1.2 times the particle size of the soft particles. The Co content in the soft material feed is 0.95 to 1.05 times that in the cemented carbide; the ceramic particles are selected from at least one of alumina, zirconium oxide, and yttrium oxide; Step 2: Preparation of cemented carbide feedstock Prepare cemented carbide powder, wherein the cemented carbide is WC-Co, and the mass fraction of Co is 8~20 wt.% and the mass fraction of WC is 80~92 wt.%; use organic polymer binder and cemented carbide powder as raw materials, and prepare cemented carbide feed through mixing, kneading and granulation; the volume percentage of cemented carbide powder in the cemented carbide feed is 48-62 vol.%; the particle size of cemented carbide powder is 0.5-3 μm; In steps one and two, the organic polymer adhesive includes filler, skeleton, plasticizer, and surfactant, with a mass ratio of 50-75:15-35:5-20:1-8, respectively. Fillers include one or more of solid paraffin, liquid paraffin, and microcrystalline wax; The skeleton includes one or more of vegetable oil, high-density polyethylene, low-density polyethylene, polypropylene, and ethylene-vinyl acetate copolymer; The plasticizer is selected from at least one of dioctyl phthalate, dibutyl phthalate, tricresyl phosphate, and tributyl citrate. The surfactant is selected from at least one of stearic acid and oleic acid; Step 3: Two-dimensional structure construction Based on the target 3D structure model, the 3D structure is converted into a multi-layer 2D structure diagram that can be recognized by the printing equipment using slicing software. The model consists of a cemented carbide layer and a soft layer. The two materials alternate from the core to the surface and wrap around each other layer by layer. The soft layer is sandwiched between the cemented carbide layers. Any soft layer and its corresponding cemented carbide layer have similar shapes. The number of soft layers is greater than or equal to 2, and the number of cemented carbide layers is greater than or equal to 3. The outermost layer of the model is a cemented carbide layer. Step 4: Printing Preparation Place the soft material feedstock and hard alloy feedstock obtained in steps one and two into different hoppers of the extrusion 3D printer; select printing strategy parameters according to the target structure accuracy, and import the modeling and slicing file; Step 5: Extrusion Printing The cemented carbide preform with a multi-material alternating wrapping structure is extruded and printed. During extrusion printing, the nozzle size is 0.1-0.8mm. During printing, the single layer thickness is 0.1-0.2mm. The extrusion temperature is set to 140-180℃, the printing platform temperature is 70-100℃, and the filling flow rate is 50-100%. Other parameters are as follows: filling speed 10-40mm / s, the line width is consistent with the nozzle size, the upper and lower layer line direction is [0, 90°], and the single layer line method is one of straight line, serrated, or concentric circle. In the multi-material alternating-wrap type cemented carbide green blank, the axial thickness of both the hard layer and the soft layer is not less than 0.1 mm, and the radial thickness is greater than or equal to the nozzle diameter. The relationship between the radial thickness and the axial thickness of a single layer is: axial thickness = radial thickness × total model height / total diameter. Step 6: Solvent Degreasing Degreasing was performed on a PDC substrate green body with alternating multi-material encapsulation structure. Using n-heptane as the degreasing solvent, PW, MW, and SA were removed by degreasing at 45~55℃ for 20-28h to obtain the degreased composite green body. Step 7: Hot degreasing and vacuum sintering The composite preform after degreasing in step six was placed in a vacuum furnace for thermal degreasing. The temperature was slowly raised to 400-550°C in an H2 atmosphere furnace with a flow rate of 45-55 L / min and held for 30-90 min to completely remove the polymer binder. Subsequently, the temperature was continuously raised to 1200-1500°C under vacuum, and Ar high pressure of 3-6 bar was introduced and held for 40-90 min. The sample was then cooled in the furnace to obtain a PDC substrate with a multi-material alternating encapsulation structure. The equivalent diameter of the cemented carbide core is 1-2 times the radial thickness of other cemented carbide layers wrapped in soft materials. Apart from the core material, the ratio of the axial thickness of the single-layer cemented carbide layer to the axial thickness of the single-layer soft material is 3~6:

1.

2. The method of claim 1, wherein: The soft particles have a particle size of 1-2 μm.

3. The method of claim 1, wherein: In the soft layer, the ratio of ceramic particles to Co is less than or equal to the Co content in the cemented carbide used.

4. The method of claim 1, wherein: The organic polymer adhesive is composed of PW, MW, EO, EVA, HDPE, DOP, and SA in a mass ratio of PW:MW:EO:EVA:HDPE:DOP:SA = 47:11:4:15:16:5:

2.

5. An application of a method for extrusion additive manufacturing of multi-material alternating encapsulated PDC substrates, characterized in that: The process involves assembling the working part of the prepared multi-material alternating-wrap type PDC substrate sintered body with the polycrystalline diamond layer into a high-temperature and high-pressure synthesis block, and then placing it in a hexahedral press for high-temperature and high-pressure synthesis; the synthesis process is: pressure: 5-7.5GPa, temperature: 1400-1700℃.

6. The application of the method for extrusion additive manufacturing of multi-material alternating encapsulation PDC substrate according to claim 5, characterized in that: The PDC wear ratio of the product is greater than or equal to 37.1 x 10 4 The average impact toughness is greater than or equal to 972 J.

7. The application of the method for extrusion additive manufacturing of multi-material alternating encapsulation PDC substrate according to claim 6, characterized in that: The PDC wear ratio of the product is greater than or equal to 37.4 x 10 4 The average impact toughness is greater than or equal to 1097 J.

Images