A method for preparing a gradient structure polycrystalline diamond compact substrate by additive manufacturing and application thereof

Abstract

The present application relates to a kind of gradient structure polycrystalline diamond compact substrate preparation method and application based on powder extrusion printing forming;Belong to PDC design preparation technical field.The present application first attempts to prepare gradient cemented carbide close to interface layer Co-poor, away from interface layer Co-rich as PDC substrate by extrusion type additive manufacturing, improve PDC impact resistance and service life.The present application is obtained by the synergy of each parameter of extrusion type additive manufacturing process, with special structure design, first with outer layer Co-poor, inner layer Co-rich or with obvious Co gradient upper and lower structure.The present application is simple and controllable, and the performance of the product obtained after diamond combination is excellent, especially in wear resistance while having very high impact resistance;Convenient for industrial application.

Description

Technical Field

[0001] This invention relates to a method for preparing gradient-structure polycrystalline diamond composite substrates based on powder extrusion printing and its application; it belongs to the field of PDC design and fabrication technology. Background Technology

[0002] Polycrystalline diamond (PCD) composites are ideal materials for manufacturing cutting tools, drilling bits, and other wear-resistant tools. They combine the high hardness, high wear resistance, and thermal conductivity of diamond with the strength and impact toughness of cemented carbide. Currently, the substrates used for PCD are mainly homogeneous cemented carbide. During the high-temperature, high-pressure synthesis process, Co in the cemented carbide matrix melts and diffuses throughout the diamond micron powder layer, partially dissolving the diamond. After cooling, the dissolved diamond reprecipitates, forming D-D bonds. During this process, excess Co diffused into the diamond micron powder layer tends to accumulate at the interface of the composite. Furthermore, the significant difference in elastic modulus and thermal expansion coefficient between metallic Co and diamond results in severe residual stress at the interface. This leads to a decrease in the bonding strength between the PCD layer and the cemented carbide substrate, causing the diamond layer to easily detach during service and resulting in composite failure.

[0003] Gradient cemented carbide can be designed with specific gradient distributions based on the characteristics of its service conditions. This can be achieved relatively easily by controlling the liquid phase volume fraction, solid phase grain size, liquid phase composition, and carbon content, resulting in cemented carbide products with gradient distributions of performance and composition. Therefore, by pre-setting a Co content gradient in the cemented carbide substrate of a polycrystalline diamond composite sheet, the cemented carbide substrate becomes cobalt-poor near the polycrystalline diamond region and cobalt-rich further away from the diamond region. This can appropriately suppress Co migration during the composite process of the polycrystalline diamond composite sheet, solve the problem of Co enrichment at the composite sheet interface, and alleviate the residual thermal stress inside the composite sheet.

[0004] Traditional methods for preparing gradient cemented carbide typically involve sequentially loading cemented carbide powders of different contents, particle sizes, or carbon contents into a mold, followed by sintering in a vacuum or a specific atmosphere; or pre-preparing cemented carbide powders with low stoichiometric carbon content, and then obtaining a gradient cemented carbide with a central η-rich phase through sintering and carburizing. However, these methods generally suffer from limitations such as high cost, complex operation, and difficulty in designing and preparing macroscopic and microscopic structures, making it difficult to prepare high-performance gradient cemented carbides and achieve mass production.

[0005] The search revealed that there are no existing reports on using additively manufactured gradient cemented carbide as a substrate for polycrystalline diamond composite sheets. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention first designs a gradient structure PDC substrate, which is a gradient hard alloy with Co-depleted and Co-rich regions. Simultaneously, a matching 3D printing and sintering process has been developed.

[0007] This invention utilizes the dual-nozzle feature of an extrusion 3D printer to mix two types of cemented carbide with different Co contents and particle sizes with a polymer binder to form a feedstock, thereby preparing gradient cemented carbide with upper and lower / or inner and outer structures. This simplifies the preparation process of gradient cemented carbide and allows for the adjustment of gradient layer thickness, cemented carbide component distribution, and internal structure according to actual production needs, enabling the personalized production of polycrystalline diamond composite substrates.

[0008] This invention addresses the problems of high Co content and severe residual stress at the interface of polycrystalline diamond composite sheets obtained from traditional homogeneous cemented carbide substrates. This invention uses extrusion additive manufacturing to prepare a gradient cemented carbide substrate with low Co content near the interface layer and high Co content far from the interface layer, thereby improving the impact resistance and service life of PDC.

[0009] This invention discloses a method for preparing additively manufactured gradient structure polycrystalline diamond composite substrates, comprising the following steps:

[0010] Step 1

[0011] N types of cemented carbide powders with different Co contents are selected; where N is a positive integer greater than or equal to 2; the cemented carbide powders with different Co contents in N are used to prepare P types of feedstocks with different Co contents; where P is a positive integer; the feedstocks contain cemented carbide powder and organic polymer binders; the powder loading in the feedstocks is set to 51~61 vol.%, preferably 55~59 vol.%.

[0012] Organic polymer binders include fillers, skeletons, plasticizers, and surfactants, with a mass ratio of 50-70:20-45:3-7:1-5.

[0013] 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, a mass ratio of PW:MW = 4~5:1.

[0014] The skeleton comprises 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, in a mass ratio of HDPE : EVA = 0.5~1.5 : 0.5~1.5.

[0015] The plasticizer is selected from at least one of dioctyl phthalate (DOP), dibutyl phthalate (DBP), trimethylol phosphate (TCP), and tributyl citrate (TBC), preferably DOP.

[0016] The surfactant is selected from at least one of stearic acid (SA) and oleic acid, preferably SA;

[0017] Step 2

[0018] At least two of the P types of feedstocks are extruded and printed according to the designed structure to obtain a printed blank; the printed blank contains a Co-depleted layer and a Co-rich layer, wherein the Co content in the Co-depleted layer is less than the Co content in the Co-rich layer;

[0019] Step 3

[0020] The printed blank obtained in step 2 is degreased and sintered to obtain a hard alloy sintered blank with a gradient distribution of Co content; that is, a gradient structure polycrystalline diamond composite substrate is obtained.

[0021] The cemented carbide powder is WC-Co cemented carbide with a particle size of 0.5~3μm and a Co content of 7~20wt.%.

[0022] In industrial applications, before 3D printing, a model is created based on the target three-dimensional structure, and slicing software is used to convert the three-dimensional structure into a multi-layer two-dimensional structure diagram that can be recognized by the printing equipment.

[0023] Preferably, the organic polymer binder is composed of paraffin wax, microcrystalline wax, vegetable oil, ethylene-vinyl acetate copolymer, high-density polyethylene, dioctyl phthalate, and stearic acid in a mass ratio of paraffin wax: microcrystalline wax: vegetable oil: ethylene-vinyl acetate copolymer: high-density polyethylene: dioctyl phthalate: stearic acid = 45-47:10-11:4-6:15-17:17:4-6:2. Alternatively, the organic polymer binder is composed of PW, MW, EO, EVA, HDPE, DOP, and SA in a mass ratio of PW:MW:EO:EVA:HDPE:DOP:SA = 45-47:10-11:4-6:15-17:17:4-6:2.

[0024] This invention discloses a method for preparing gradient-structured polycrystalline diamond composite substrates using additive manufacturing. During extrusion printing, the cemented carbide feedstocks obtained in steps 1) and 2) are placed into different hoppers of an extrusion 3D printer. The nozzle size and layer thickness are selected based on the target structural accuracy. Printing strategy parameters such as extrusion temperature, printing platform temperature, and infill flow rate are set. The modeling and slicing file is imported, and printing is performed according to the set program to obtain a cemented carbide composite green blank with a gradient distribution of Co content. In industrial applications, the following parameters are generally controlled: nozzle size 0.1~0.8mm, layer thickness 0.1~0.2mm, extrusion temperature 120~180℃, infill flow rate 50~100%, printing platform temperature 70~100℃, infill speed 10~40mm / s, trace width consistent with nozzle diameter, single-layer trace pattern is straight, and the uppermost layer trace direction is [0, 90°]. The infill flow rate is adjusted on the printer control panel based on the percentage of the inherent extrusion flow rate in the slicing software.

[0025] Preferably, the nozzle size is 0.4 mm, the layer thickness is 0.15 mm, the extrusion temperature is 165°C, the filling flow rate is 90%, the printing platform temperature is 80°C, the filling speed is 30 mm / s, the line width is 0.4 mm, the single-layer line routing is straight, and the upper layer line routing direction is [0, 90°].

[0026] This invention discloses a method for preparing additively manufactured gradient structure polycrystalline diamond composite substrates, including degreasing and sintering, comprising solvent degreasing and thermal degreasing-vacuum sintering; wherein solvent degreasing uses n-heptane as the degreasing solvent, the temperature is 30~60℃, the degreasing time is 12~36h, and PW, MW, and SA are removed to obtain a degreased green blank.

[0027] The hot debinding-vacuum sintering process is as follows: the cemented carbide green blank after solvent debinding is placed in a vacuum furnace for hot debinding. The temperature is slowly raised to 800-1000℃ in an H2 atmosphere with a flow rate of 40-60 L / min and held for 40-90 min to completely remove the polymer binder. Then, the temperature is continuously raised to 1400-1500℃ under vacuum, and 3-6 bar high-pressure argon gas is introduced and held for 20-50 min. The sample is then cooled with the furnace to obtain a gradient PDC substrate sintered body.

[0028] This invention discloses a method for preparing additive manufacturing gradient structure polycrystalline diamond composite substrates, wherein the resulting substrates have upper and lower structures or inner and outer structures depending on the cobalt content.

[0029] In the aforementioned inner and outer structures, the Co content of the outer layer is less than that of the inner layer.

[0030] Preferably, when the substrate has an upper and lower structure, during the printing process, the total height of the Co-depleted layer / total height of the printed blank is controlled to be 1-4:8, preferably 1-3.5:10; such a design is beneficial for obtaining products with high wear ratio and strong impact toughness.

[0031] As a further preferred formulation, two groups of organic polymer binders, group a and group b, were prepared according to the mass ratios of PW:MW:EO:EVA:HDPE:DOP:SA = 47:10:4:16:17:4:2 and 45:11:5:15:17:5:2, respectively; and according to the volume ratio, group a binder:YG10 raw material = 43:57; group b binder: YG15 raw material ratio: 43:57; Printing material C and printing material D are obtained. The particle size of YG10 raw material is less than 1.0 μm, and the particle size of YG15 raw material is greater than that of YG10 raw material, preferably 1.1-1.8 μm. Printing materials C and D are used to print the upper and lower structures according to the set printing parameters. During printing, the nozzle size is controlled at 0.4 mm, the layer thickness at 0.15 mm, the extrusion temperature at 165℃, the filling flow rate at 90%, the printing platform temperature at 80℃, the filling speed at 30 mm / s, the line width at 0.4 mm, the single-layer line routing is straight, and the upper layer line routing direction is [0, 90°]. A printing blank is obtained, and then degreased and sintered to obtain the product. In the printing blank, the ratio of the total thickness of the layer containing YG15 raw material to the total thickness of the printing blank is 0.1~0.35. At this time, under the same degreasing and sintering conditions, the obtained product has the best toughness and the best wear performance.

[0032] As a preferred option, when the substrate has an internal and external structure, during the printing process, the total thickness of the Co-depleted layer / total thickness of the printed blank is controlled to be 25-35:100, preferably 32-33:100; such a design is beneficial for obtaining products with high wear ratio and strong impact toughness.

[0033] During the exploration process, it was discovered that when the sintered product is designed with an internal and external structure, i.e., the cobalt content of the inner layer is greater than that of the outer layer, if high-cobalt raw materials with high cobalt content and large particle size and low-cobalt raw materials with small particle size and low cobalt content are used, then when designing the printing blank, the outer layer needs to be designed as a high-cobalt layer and the inner layer as a low-cobalt layer; otherwise, the desired product cannot be obtained. This point has not been reported before this invention.

[0034] As a further preferred formulation, two groups of organic polymer binders, group a and group b, were prepared according to the mass ratios of PW:MW:EO:EVA:HDPE:DOP:SA = 47:10:4:16:17:4:2 and 45:11:5:15:17:5:2, respectively; and according to the volume ratio, group a binder:YG10 raw material = 43:57; group b binder: YG15 raw material ratio: 43:57; Printing material C and printing material D are obtained, wherein the particle size of YG10 raw material is less than 1.0 μm, and the particle size of YG15 raw material is greater than that of YG10 raw material, preferably 1.1-1.8 μm; Printing materials C and D are used to print the internal and external structures according to the set printing parameters. During printing, the nozzle size is controlled at 0.4 mm, the layer thickness at 0.15 mm, the extrusion temperature at 165℃, the filling flow rate at 90%, the printing platform temperature at 80℃, the filling speed at 30 mm / s, the line width at 0.4 mm, the single-layer line routing is straight, and the upper layer line routing direction is [0, 90°]; a printed blank is obtained, and then degreased and sintered to obtain the product. In the printed blank, the layer containing YG15 raw material is on the outer layer. YG10 raw material is in the inner layer, and the height of the inner layer / the height of the printed blank = 8.9-9.1:13.3-13.5; the equivalent diameter of the inner layer / the equivalent diameter of the printed blank = 6-6.5:8.

[0035] This invention relates to an additive manufacturing method for preparing a gradient-structured polycrystalline diamond composite substrate. The method involves taking a cemented carbide sintered blank obtained in step (3) with a gradient Co content, contacting the low-Co content region with diamond, and assembling it into a sample to be synthesized. The sample is then synthesized at 1400-1700℃, preferably 1450-1550℃, under a pressure of 5-7.5 GPa, preferably 7-7.5 GPa, to obtain a polycrystalline diamond composite with a gradient-structured substrate. A hexahedral press is commonly used in this process.

[0036] Principles and advantages

[0037] This invention is the first attempt to use extrusion additive manufacturing to prepare a gradient hard alloy with a Co-poor surface near the interface layer and a Co-rich surface far from the interface layer as a PDC substrate, thereby improving the impact resistance and service life of PDC.

[0038] This invention, through the synergy of various parameters in the extrusion additive manufacturing process and in conjunction with a special structural design, has for the first time obtained an upper and lower structure with an outer cobalt-poor layer and an inner cobalt-rich layer or a significant cobalt gradient.

[0039] This invention configures a suitable polymer binder to be mixed with powder to form a feedstock based on the characteristics of powder composition, morphology and particle size, and selects a suitable nozzle; sets a suitable printing path and parameters, starts the nozzle and extrudes the feedstock to prepare a green body with a complex structure of multiple materials; then removes the polymer binder in the green body in an orderly manner from low melting point to high melting point through a specific debinding and sintering process to ensure the consistency of the structure of the prepared material; finally, a sintered body with a complex structure of multiple materials is obtained by high-temperature sintering.

[0040] This invention utilizes the multi-nozzle and high structural design flexibility of powder extrusion additive manufacturing to form gradient structure polycrystalline diamond composite substrates. By rationally designing various cemented carbide material feed formulations, printing strategies, debinding and sintering processes, it controls the forming and bonding of cemented carbide layers with different components and the shrinkage during debinding and sintering, providing a new solution for forming high-toughness PDC substrates. This can suppress the large-scale migration of Co in cemented carbide and assist in the rapid development of high-performance PDC products. Attached Figure Description

[0041] Figure 1 The printing model and printing path used in Example 2 are shown, where (a) is the printing model and (b) is the printing path.

[0042] Figure 2 These are macroscopic and microscopic morphology diagrams of the sintered body in Example 2; where AD represents the macroscopic structure; A outer to D outer represents the microscopic morphology of the outer side; A inner to D inner represents the microscopic morphology of the core; and A interface to D interface represents the microscopic morphology of the interface.

[0043] Figure 3 The curve showing the Co content distribution from the core to the surface of the sintered sample described in Example 2;

[0044] Figure 4 The curve showing the hardness distribution from the core to the surface of the vacuum sintered sample described in Example 2;

[0045] Figure 5 This is a macroscopic morphology diagram of the vacuum sintered blank with the side and top wrapping structure described in Example 3;

[0046] Figure 6 The curves showing the Co content distribution (left) and hardness distribution (right) of the vacuum sintered blank described in Example 3 are shown. Detailed Implementation

[0047] Example 1---Preparation of a top-bottom structure gradient cemented carbide, which is then combined with diamond to form PDC;

[0048] Step 1

[0049] The diameter × height dimensions of the additively manufactured gradient structure PDC substrate are designed to be Φ13.6 × 8 mm, with the upper layer heights set to 0.9 mm (Group A), 1.8 mm (Group B), 2.7 mm (Group C), and 3.6 mm (Group D), representing a 128% scaling-up in the additive manufacturing green stage. In the green stage of the gradient structure polycrystalline diamond substrate, the lower layer is mainly composed of YG10 with a particle size of 0.7 μm, while the upper layer is mainly composed of YG15 with a particle size of 1.2 μm.

[0050] Step Two

[0051] Two groups of organic polymer binders, group a and group b, were prepared according to the mass ratios of PW:MW:EO:EVA:HDPE:DOP:SA:47:10:4:16:17:4:2 and 45:11:5:15:17:5:2, respectively. The volume ratios of binder group a and YG10 raw material powder were 43:57, and the ratio of binder group b to YG15 raw material powder was 43:57. The powders and binders were placed in an internal mixer and heated to 150°C for uniform mixing. During this process, the mixture was cooled to allow for thorough shearing and kneading of the powder 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°C for 30 minutes, and the total mixing time was 2 hours. The internally mixed feed pellets were then fed into a granulator for granulation to obtain the molded material.

[0052] Step 3: Import the designed double-layer cemented carbide model into the printing and slicing software. Set two extruders for each layer, and configure the printing strategy parameters for each extruder in the software: nozzle size 0.4mm, layer thickness 0.15mm, extrusion temperature 165℃, infill flow rate 90%, printing platform temperature 80℃, infill speed 30mm / s, line width 0.4mm, single-layer line routing as a straight line, and upper layer line routing direction [0, 90°]. Then, place the prepared YG10 and YG15 cemented carbide feedstocks into the two hoppers of the extrusion 3D printer and print according to the preset parameters.

[0053] Step 4: Degrease the printed preform with solvent at a temperature of 50°C, using n-heptane as the solvent, for 24 hours.

[0054] Step 5: The degreased green compact was placed in an H2 atmosphere furnace at a flow rate of 50 L / min and slowly heated to 550℃, held for 1 hour. Under vacuum, the temperature was continuously increased to 1400℃, and a high-pressure Ar charge of 5.8 bar was introduced for 25 minutes. The sample was then cooled in the furnace to obtain a sintered PDC substrate with a gradient structure. In the obtained sintered PDC substrate with a gradient structure, the lower layer had a Co content of 12–14 wt.%, and the upper layer had a Co content of 9–11 wt.%.

[0055] Step Six

[0056] Diamond-4wt.%Co powder (4% of the total mass of diamond + Co) with an average diamond grain size of 10μm was placed sequentially into a molybdenum cup along with a pre-fabricated gradient structure PDC substrate sintered body (with the upper end of the pre-fabricated gradient structure PDC substrate sintered body in contact with the diamond). NaCl, carbon nanotubes, pyrophyllite, conductive sheets, and graphite sheets were then assembled into a high-temperature, high-pressure composite block and 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.

[0057] The prepared gradient PDC substrate green body exhibited regular morphology with a dimensional deviation of <3%, a relative density of 98%, and was free of blistering and cracking defects after solvent degreasing. After vacuum sintering, the lower layer of the gradient PDC substrate showed a radial dimensional shrinkage of 17.44%, the upper layer a radial dimensional shrinkage of 18.22%, and the axial dimensional shrinkage of 20.31%. Both layers maintained a density >98%. The wear ratio and impact toughness of the PDC obtained after high temperature and high pressure are shown in the table below.

[0058]

[0059] In this embodiment, the wear ratio test was performed on the polycrystalline diamond (PDC) sample using SiC grinding wheels. One point on each PDC was tested with each wheel, with the wheel wear controlled at 110-130 grams. Two corresponding points were tested for each PDC, and the average value was taken. 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 performed; if no damage (cracking, delamination, etc.) was observed, the impact energy was increased to 25J, and ten more tests were performed; if no damage still occurred, the impact energy was increased by another 5J, and ten more tests were performed, gradually accumulating until the sample was damaged. The impact energy multiplied by the number of impacts was the impact energy. Five tests were performed on each layer, and the average value was taken. (The wear ratio and impact toughness testing methods used in subsequent embodiments and comparative examples are consistent). In the above exploration, the effect achieved by Group B far exceeded expectations.

[0060] Comparative Example 1—Homogeneous cemented carbide substrate, control group

[0061] Additive manufacturing was used to prepare YG10 and YG15 cemented carbide green blanks with diameter × height dimensions of Φ13.6 × 8 mm, respectively. All other parameters and procedures remained unchanged, and polycrystalline diamond composite sheets were fabricated using YG10 and YG15 as substrates, respectively. The wear ratios of these two composite sheets were 38.7 × 10⁻⁶ and 38.7 × 10⁻⁶, respectively. 4 38.06×10 4 The impact toughnesses are 868J and 903J, respectively.

[0062] Example 2 – A preliminary experiment on the internal and external structure was conducted. This example was not combined with diamond to form PDC, but was only used as a preliminary experiment. Its structure is that the outer side wraps the core.

[0063] Step 1

[0064] The additive manufacturing gradient structure PDC substrate was designed with a diameter × height of Φ13.4 × 8 mm, with the inner layer measuring Φ9 × 8 mm. The dimensions were scaled up by 120% during the additive manufacturing green stage. In the green of the gradient structure polycrystalline diamond substrate, the inner layer was primarily composed of YG15 with a particle size of 1.2 μm, while the outer layer was primarily composed of YG10 with a particle size of 0.7 μm; the outer layer consisted of the sides enclosing the inner layer. Four groups of samples (A, B, C, and D) were prepared based on different YG15 loadings, as described in step two.

[0065] Step Two

[0066] Based on mass ratios of PW:MW:EO:EVA:HDPE:DOP:SA = 47:10:4:16:17:4:2 and 45:11:5:15:17:5:2, two groups of organic polymer binders, a and b, were prepared respectively. Based on volume ratios, the binder for group a was 43:57 of YG10 raw material powder, and the binder for group b was 45:39:55~61 of YG15 raw material powder. The powder and binder were placed in an internal mixer and heated to 150°C to mix evenly. During the mixing process, the temperature was lowered to allow the powder and organic polymer to be fully sheared and kneaded 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°C for 30 minutes, and the total mixing time was 2 hours. Subsequently, the internally mixed feed was sent to a granulator for granulation to obtain the molded material. By volume ratio, group a organic polymer: YG10 raw material mixed powder = 43:57, group b organic polymer: YG15 raw material mixed powder = 45:55 (group A), 43:57 (group B), 41:59 (group C), 39:61 (group D).

[0067] The powder and binder were placed in a mixer and heated to 150°C to mix evenly. During the mixing process, the powder was cooled down to allow the organic polymer to be fully sheared and kneaded to ensure uniform mixing. The cooled mixer was then crushed and sieved to obtain the target feed pellets. The cooling temperature and time were 125°C for 30 minutes, and the total mixing time was 2 hours. The mixer feed was then fed into a granulator to granulate and obtain the molding material.

[0068] Step 3: Import the designed double-layer cemented carbide model into the printing and slicing software. Set two extruders for each layer, and configure the printing strategy parameters for each extruder in the software: nozzle size 0.4mm, layer thickness 0.15mm, extrusion temperature 165℃, infill flow rate 90%, printing platform temperature 80℃, infill speed 30mm / s, line width 0.4mm, single-layer line routing as a straight line, and upper layer line routing direction [0, 90°]. Then, place the prepared YG10 and YG15 cemented carbide feedstocks into the two hoppers of the extrusion 3D printer and print according to the preset parameters.

[0069] Step 4: Degrease the printed preform with solvent at a temperature of 50°C, using n-heptane as the solvent, for 24 hours.

[0070] Step 5: The degreased green compact was placed in an H2 atmosphere furnace at a flow rate of 50 L / min and slowly heated to 550 °C, held for 1 hour. Under vacuum, the temperature was continuously increased to 1400 °C, and a high-pressure Ar2 pressure of 5.8 bar was introduced for 25 minutes. The sample was then cooled in the furnace to obtain a sintered PDC substrate with an internal and external gradient structure. The macroscopic morphology of the sintered body is shown in [see figure]. Figure 2 Co gradient distribution is shown in Figure 3 Hardness distribution is shown in Figure 4 .

[0071] In groups A, B, C, and D, the powder loading of YG15 on the inner side increases sequentially, with a slightly smaller change in radial shrinkage rate, ranging from 16.41% to 17.44%. However, the axial shrinkage rate decreases significantly with the change in the inner YG15 loading, with inner shrinkage rates of 31.78%, 29.08%, 26.42%, and 25.86%, and outer shrinkage rates of 17.44%, 17.57%, 17.16%, and 17.96%, respectively. Therefore, it can be observed that the outer shrinkage rate is significantly lower than the inner shrinkage rate in the axial direction. This is mainly due to the influence of Co migration and sintering shrinkage. Co migrates from the inner layer to the outer layer, increasing the interparticle spacing in the inner layer, while the interparticle spacing in the outer layer is filled with more Co. During the sintering densification process, this results in increased internal shrinkage and decreased external shrinkage. As the YG15 powder loading increases, the interparticle spacing in the inner layer decreases, and the driving force for Co migration decreases, reducing the amount of Co migrating from the inner layer to the outer layer. The combined effect of these two factors significantly reduces the inner layer shrinkage rate and slightly increases the outer layer shrinkage rate.

[0072] Furthermore, the Co content and hardness from the core to the side surface both show a gradient distribution, indicating that this example successfully prepared a side-wrapped internal and external gradient hard alloy. This example lays the foundation for the subsequent preparation of internal and external gradient structure substrates adapted to polycrystalline diamond composite sheets. For details of the subsequent PDC preparation scheme, please refer to Example 3.

[0073] This exploratory experiment revealed that Co was not distributed according to the original design structure. The cobalt distribution was reversed in the printed and sintered blanks.

[0074] Example 3---The side wrapping structure of the preliminary experiment in Example 2 was changed to side and top wrapping, and then combined with diamond to form PDC.

[0075] Step 1

[0076] Using the same cemented carbide powder and organic polymer binder as in Example 2, a PDC substrate with an inner and outer gradient structure was designed with a diameter × height of Φ13.4 × 8 mm. The inner layer has a size of Φ9 × 6.2 mm (the inner layer is located in the center of the substrate, and the inner layer in the printed blank is a cobalt-poor layer). The outer layer wraps around the sides and top of the inner layer. The thickness of the outer layer's side portion is (13.4-9) / 2 = 2.2 mm, and the thickness of the top portion is 8-6.2 = 1.8 mm. YG10 with a particle size of 0.7 μm was placed in the inner layer (i.e., by volume ratio, group a binder: YG10 raw material powder = 43:57); YG15 with a particle size of 1.2 μm was placed in the outer layer (i.e., by volume ratio, group b binder: YG15 raw material powder = 43:57). The inner and outer gradient structure PDC substrate with a Co-poor outer layer and a Co-rich inner layer was prepared according to the same molding, debinding, and sintering steps and parameters as in Example 2. The morphology of the substrate with an outer Co-depleted layer and an inner Co-rich layer is shown in the figure. Figure 5 As shown, the hardness changes as follows Figure 6 As shown.

[0077] Step Two

[0078] Diamond-4wt.%Co powder (4% of the total mass of diamond + Co) with an average diamond grain size of 10μm was placed sequentially into a molybdenum cup along with a pre-fabricated gradient structure PDC substrate sintered body (with the upper end of the pre-fabricated gradient structure PDC substrate sintered body in contact with the diamond). NaCl, carbon nanotubes, pyrophyllite, conductive sheets, and graphite sheets were then assembled into a high-temperature, high-pressure composite block and 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.

[0079] The prepared gradient structure PDC substrate green blank has a regular morphology with a dimensional deviation of <5% and a relative density of 97%. Solvent degreasing showed no blistering or cracking defects. After vacuum sintering, the bottom inner side of the gradient structure PDC substrate slightly bulges, with a bulge height of less than 1 mm. The axial dimension shrinkage is approximately 20.73%, the upper layer radial dimension shrinkage is 18.37%, and the lower layer radial dimension shrinkage is 17.29%, with a density >98%. The PDC wear ratio obtained after high temperature and high pressure is 38.3 × 10⁻⁶. 4Its impact toughness is 1280J.

[0080] Comparative Example 2---Increasing the YG10 loading to 64 vol.% resulted in excessive loading of the feed.

[0081] YG10 powder and YG15 powder were selected, with particle sizes of 0.7μm and 1.2μm, respectively.

[0082] Two groups of organic polymer binders, group a and group b, were prepared according to the following mass ratios: PW:MW:EO:EVA:HDPE:DOP:SA = 47:10:4:16:17:4:2 and 45:11:5:15:17:5:2, respectively. According to the volume ratio, group a organic polymer:YG10 raw material powder = 36:64; group b organic polymer:YG15 raw material powder = 43:57. PW, MW, EO, EVA, HDPE, and DOP were added to a mixer in descending order of melting point and heated until homogeneous. SA was added simultaneously with the powder in three batches, with cooling during this period to allow for thorough shearing and kneading of the powder and organic polymers to ensure uniform mixing. The cooled mixer was then crushed and sieved to obtain the target feed particles. The mixing temperature was 150℃, the cooling time was 125℃-30min, the total mixing time was 2h, and the feed particle size was 6-12 mesh.

[0083] A sample with an inner and outer structure, measuring Φ13.4×8mm in diameter × height, was prepared. The inner layer dimensions were Φ9×8mm (scaled up 120% during additive manufacturing green body stage). The inner layer composition was YG15 (1.2μm), and the outer layer composition was YG10 (0.7μm). The printing temperature was set to 165℃, and the fill flow rate to 90%. YG15 printed normally; however, adjusting parameters such as flow rate, layer thickness, and nozzle size resulted in inconsistent extrusion of the YG10. Increasing the printing temperature to 175℃ resulted in smooth extrusion, but significant overflow was observed near the nozzle, and the extrusion volume was unstable. This was due to excessive feed rate; the viscosity was high at normal printing temperatures, and increasing the printing temperature caused phase separation during extrusion.

[0084] Comparative Example 3—Increasing the YG15 loading to 64 vol.% resulted in samples that could be printed normally, but their stability decreased.

[0085] Step 1

[0086] The diameter × height dimensions of the additively manufactured gradient structure PDC substrate are designed to be Φ13.4 × 8 mm, with the inner layer dimensions being Φ9 × 8 mm. The dimensions are scaled up by 120% during the additive manufacturing green stage. In the green stage of the gradient structure polycrystalline diamond substrate, the outer layer is mainly composed of YG10 with a particle size of 0.7 μm, and the inner layer is mainly composed of YG15 with a particle size of 1.2 μm.

[0087] Step Two

[0088] Two groups of organic polymer binders, group a and group b, were prepared according to the following mass ratios: PW:MW:EO:EVA:HDPE:DOP:SA = 47:10:4:16:17:4:2 and 45:11:5:15:17:5:2, respectively. The volume ratios were: group a:YG10 raw material powder = 43:57, and group b:YG15 raw material powder = 36:64. PW, MW, EO, EVA, HDPE, and DOP were added sequentially to a mixer in descending order of melting point and heated until homogeneous. SA was added simultaneously with the powder in three separate additions, with cooling during this process to allow for thorough shearing and kneading of the powder and organic polymers to ensure uniform mixing. The cooled mixer was then crushed and sieved to obtain the target feed particles. The mixing temperature was 150℃, the cooling time was 125℃-30min, the total mixing time was 2h, and the feed particle size was 6-12 mesh.

[0089] Step 3

[0090] The designed double-layer cemented carbide model with inner and outer side wrapping was imported into the printing and slicing software. Two extruders were set for each of the upper and lower layers, and the printing strategy parameters for each extruder were configured in the software: nozzle size 0.4mm, layer thickness 0.15mm, extrusion temperature 175℃, infill flow rate 90%, printing platform temperature 80℃, infill speed 30mm / s, trace width 0.4mm, single-layer trace pattern straight line, and upper layer trace direction [0, 90°]. The prepared YG10 and YG15 cemented carbide feedstocks were then placed into the two hoppers of the extrusion 3D printer, and printing was performed according to the preset parameters. YG10 printed normally; YG15 printing progressed well initially, but as the number of layers increased, a significant amount of feedstock remained at the end of the nozzle printing path for each layer. This residue accumulated into small spheres during the middle of sample preparation and collapsed due to the back-and-forth compression by the nozzles, resulting in sample failure, with a failure rate of approximately 55%.

[0091] Comparative Example 4 – The degreasing parameters were changed (30~60℃ beyond the protection range), and their impact on performance was investigated.

[0092] In step four of Example 1, the degreasing temperature was adjusted to 80℃, and degreasing was performed for 18 hours, while other steps and parameters remained unchanged. The prepared multi-material PDC substrate sintered green body blistered and cracked during solvent degreasing due to excessively high temperature and rapid degreasing rate.

[0093] Comparative Example 5 – The extrusion temperature of YG10 was changed to 190℃, and the extrusion temperature of YG15 was changed to 185℃, which exceeded the protection range.

[0094] Step 1

[0095] The PDC substrate with an inner and outer gradient structure has a diameter × height of Φ13.4 × 8 mm, where the inner layer has a size of Φ9 × 6.2 mm. The outer layer wraps around the sides and top of the inner layer. The thickness of the outer layer's side portion is (13.4-9) / 2 = 2.2 mm, and the thickness of the top portion is 8-6.2 = 1.8 mm. YG10 particles with a particle size of 0.7 μm are placed in the inner layer, and YG15 particles with a particle size of 1.2 μm are placed in the outer layer.

[0096] Step Two

[0097] Two groups of organic polymer binders, group a and group b, were prepared according to the following mass ratios: PW:MW:EO:EVA:HDPE:DOP:SA = 47:10:4:16:17:4:2 and 45:11:5:15:17:5:2, respectively. The volume ratios were: group a:YG10 raw material powder = 43:57, and group b:YG15 raw material powder = 36:64. PW, MW, EO, EVA, HDPE, and DOP were added sequentially to a mixer in descending order of melting point and heated until homogeneous. SA was added simultaneously with the powder in three separate additions, with cooling during this process to allow for thorough shearing and kneading of the powder and organic polymers to ensure uniform mixing. The cooled mixer was then crushed and sieved to obtain the target feed particles. The mixing temperature was 150℃, the cooling time was 125℃-30min, the total mixing time was 2h, and the feed particle size was 6-12 mesh.

[0098] Step 3

[0099] The designed double-layer cemented carbide model, encompassing the inner and outer structures on the sides and top, was imported into the printing and slicing software. Two extruders were set for each of the upper and lower layers, and the printing strategy parameters for each extruder were configured in the software: nozzle size 0.4mm, layer thickness 0.15mm, infill flow rate 90%, printing platform temperature 80℃, infill speed 30mm / s, trace width 0.4mm, single-layer trace pattern straight line, and upper layer trace direction [0, 90°]. The extrusion temperature for YG10 was 190℃, and for YG15, it was 185℃. The prepared YG10 and YG15 cemented carbide feedstocks were then placed into the two hoppers of the extrusion 3D printer, and printing was performed according to the preset parameters.

[0100] When the nozzle temperature exceeds 185℃, the YG15 feed nozzle uncontrollably flows out molten filaments due to the excessive temperature, making normal printing impossible; the YG10 feed nozzle can print, but the nozzle extrusion flow is large during the printing process, and after printing one layer, a ring of feed material sticks to the nozzle, significantly reducing the stability of feed extrusion.

[0101] Comparative Example 6—Increasing the nozzle size of YG10 and the filling speed of YG15 (both exceeding the protection range) resulted in large deviations in the dimensional properties of the green body and a significant decrease in its impact resistance.

[0102] Step 1

[0103] The PDC substrate with an inner and outer gradient structure has a diameter × height of Φ13.4 × 8 mm, where the inner layer has a size of Φ9 × 6.2 mm. The outer layer wraps around the sides and top of the inner layer. The thickness of the outer layer's side portion is (13.4-9) / 2 = 2.2 mm, and the thickness of the top portion is 8-6.2 = 1.8 mm. YG10 particles with a particle size of 0.7 μm are placed in the inner layer, and YG15 particles with a particle size of 1.2 μm are placed in the outer layer.

[0104] Step Two

[0105] Two groups of organic polymer binders, group a and group b, were prepared according to the following mass ratios: PW:MW:EO:EVA:HDPE:DOP:SA = 47:10:4:16:17:4:2 and 45:11:5:15:17:5:2, respectively. The volume ratios were: group a:YG10 raw material powder = 43:57, and group b:YG15 raw material powder = 36:64. PW, MW, EO, EVA, HDPE, and DOP were added sequentially to a mixer in descending order of melting point and heated until homogeneous. SA was added simultaneously with the powder in three separate additions, with cooling during this process to allow for thorough shearing and kneading of the powder and organic polymers to ensure uniform mixing. The cooled mixer was then crushed and sieved to obtain the target feed particles. The mixing temperature was 150℃, the cooling time was 125℃-30min, the total mixing time was 2h, and the feed particle size was 6-12 mesh.

[0106] Step 3

[0107] The designed double-layer cemented carbide model, encompassing the inner and outer structures on the sides and top, was imported into the printing and slicing software. Two extruders were assigned to each of the upper and lower layers, and the printing strategy parameters for each extruder were set in the software: layer thickness 0.15mm, extrusion temperature 165℃, infill flow rate 90%, printing platform temperature 80℃, and straight-line routing for each layer, with the upper layer routing direction [0, 90°]. The YG10 nozzle size was 1.0mm, with an infill speed of 30mm / s; the YG15 nozzle size was 0.4mm, with an infill speed of 60mm / s, and the routing width was consistent with the nozzle diameter. The prepared YG10 and YG15 cemented carbide feedstocks were then placed into the two hoppers of the extrusion 3D printer, and printing was performed according to the preset parameters.

[0108] Step Four

[0109] Following the same molding, degreasing, and sintering steps and parameters as in Example 2, 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.

[0110] The prepared gradient structure PDC substrate green blank exhibits unstable depressions and protrusions on its sides, with a dimensional deviation >8%. The green blank has a relative density of 97%, and solvent degreasing shows no blistering or cracking defects. After vacuum sintering, the bottom inner side of the gradient structure PDC substrate bulges out, with a protrusion height of 2-3 mm, while the top is slightly concave. The axial dimension shrinkage is approximately 23.14%, the upper layer radial dimension shrinkage is 21.47%, and the lower layer radial dimension shrinkage is 18.38%, with a density >98%. The PDC wear ratio obtained after high temperature and high pressure is 36.7 × 10⁻⁶. 4 Its impact toughness is 936J.

Claims

1. A method for preparing additively manufactured gradient structure polycrystalline diamond composite substrates, characterized in that, Includes the following steps: Step 1 N types of cemented carbide powders with different Co contents are selected; where N is a positive integer greater than or equal to 2; the N types of cemented carbide powders with different Co contents are used to prepare P types of feedstocks with different Co contents; where P is a positive integer; the feedstocks contain cemented carbide powder and organic polymer binders; the powder loading in the feedstocks is set to 51~61 vol.%. Organic polymer binders include fillers, skeletons, plasticizers, and surfactants, with a mass ratio of 50-70:20-45:3-7:1-5. The fillers include solid paraffin wax (PW) and microcrystalline wax (MW), mixed at a mass ratio of PW:MW = 4~5:

1. The skeleton includes one or more of the following: vegetable oil EO, high-density polyethylene HDPE, low-density polyethylene LDPE, polypropylene PP, and ethylene-vinyl acetate copolymer EVA; The plasticizer is selected from at least one of dioctyl phthalate (DOP), dibutyl phthalate (DBP), trimethylol phosphate (TCP), and tributyl citrate (TBC). The surfactant is selected from at least one of stearic acid (SA) and oleic acid; Step 2 At least two of the feed materials in type P are extruded and printed according to the designed structure to obtain a printed blank; the printed blank contains a Co-poor layer and a Co-rich layer, wherein the Co content in the Co-poor layer is less than the Co content in the Co-rich layer; during printing, the nozzle size is 0.1~0.8mm, the layer thickness is 0.1~0.2mm, the extrusion temperature is 120~180℃, the filling flow rate is 50~100%, the printing platform temperature is 70~100℃, the filling speed is 10~40mm / s, the line width is consistent with the nozzle diameter, the single-layer line routing is straight, and the upper limit layer line routing direction is [0, 90°]; Step 3 The printed blank obtained in step 2 is degreased and sintered to obtain a cemented carbide sintered blank with a gradient distribution of Co content; that is, a gradient structure polycrystalline diamond composite substrate is obtained. Debinding and sintering include solvent debinding and hot debinding-vacuum sintering; among which solvent debinding uses n-heptane as the debinding solvent, the temperature is 30~60℃ and the debinding time is 12~36h to obtain debinded green body; The hot debinding-vacuum sintering process is as follows: The cemented carbide green blank after solvent debinding is placed in a vacuum furnace for hot debinding. The temperature is slowly raised to 800-1000℃ in an H2 atmosphere with a flow rate of 40-60 L / min and held for 40-90 min to completely remove the polymer binder. Then, the temperature is continuously raised to 1400-1500℃ under vacuum, and Ar2 at a high pressure of 3-6 bar is introduced and held for 20-50 min. The sample is then cooled with the furnace to obtain a gradient PDC substrate sintered body. Depending on the cobalt content, the resulting substrates may have an upper and lower structure or an inner and outer structure. In the substrate having an inner and outer structure, the Co content of the outer layer is less than that of the inner layer; When the substrate has a top-bottom structure, during the printing process, the total height of the Co-depleted layer / the total height of the printed blank should be controlled to be 1-4:

8. When the substrate has an internal and external structure, during the printing process, the total thickness of the Co-depleted layer / the total thickness of the printed blank should be controlled to be 25-35:

100.

2. The method for preparing an additive manufacturing gradient structure polycrystalline diamond composite substrate according to claim 1, characterized in that: During extrusion printing, the nozzle size is controlled at 0.4mm, the layer thickness at 0.15mm, the extrusion temperature at 165℃, the filling flow rate at 90%, the printing platform temperature at 80℃, the filling speed at 30mm / s, the line width at 0.4mm, the single-layer line routing is straight, and the upper layer line routing direction is [0, 90°].

3. The method for preparing an additive manufacturing gradient structure polycrystalline diamond composite substrate according to claim 1, characterized in that: Based on mass ratios of PW:MW:EO:EVA:HDPE:DOP:SA = 47:10:4:16:17:4:2 and 45:11:5:15:17:5:2, two groups of organic polymer binders, a and b, were prepared respectively; based on volume ratios, group a binder:YG10 raw material = 43:57; group b binder: YG15 raw material = 43:57; to obtain printing material C and printing material D, wherein the particle size of YG10 raw material is less than 1.0μm and the particle size of YG15 raw material is 1.1-1.8μm; printing materials C and D are used to print the upper and lower structures according to the set printing parameters. During printing, the nozzle size is controlled at 0.4mm, the layer thickness is 0.15mm, the extrusion temperature is 165℃, the filling flow rate is 90%, the printing platform temperature is 80℃, the filling speed is 30mm / s, the line width is 0.4mm, the single layer line method is straight, and the upper layer line direction is [0, 90°]; to obtain the printing blank, and then the product is obtained by degreasing and sintering. In the printing blank, the ratio of the total thickness of the layer containing YG15 raw material to the total thickness of the printing blank is 0.1~0.

35.

4. The method for preparing an additively manufactured gradient structure polycrystalline diamond composite substrate according to claim 1, characterized in that: When the substrate has an internal and external structure, during the printing process, the total thickness of the Co-depleted layer / the total thickness of the printed blank is controlled to be 32-33:

100.

5. The method for preparing an additively manufactured gradient structure polycrystalline diamond composite substrate according to claim 1, characterized in that: When the sintered product is designed with an internal and external structure, that is, the cobalt content of the inner layer is greater than that of the outer layer, high cobalt raw materials with high cobalt content and large particle size and low cobalt raw materials with small particle size and low cobalt content are used. Therefore, when designing the printing blank, the outer layer is designed as a high cobalt layer and the inner layer is designed as a low cobalt layer.

6. A method for preparing additively manufactured gradient structure polycrystalline diamond composite substrates, characterized in that: Based on mass ratios of PW:MW:EO:EVA:HDPE:DOP:SA = 47:10:4:16:17:4:2 and 45:11:5:15:17:5:2, two groups of organic polymer binders, a and b, were prepared respectively; based on volume ratios, group a binder:YG10 raw material = 43:57; group b binder: YG15 raw material = 43:57; Printing material C and printing material D are obtained, wherein the particle size of YG10 raw material is less than 1.0μm and the particle size of YG15 raw material is 1.1-1.8μm; Printing materials C and D are used to print the internal and external structures according to the set printing parameters. During printing, the nozzle size is controlled at 0.4mm, the layer thickness at 0.15mm, the extrusion temperature at 165℃, the filling flow rate at 90%, the printing platform temperature at 80℃, the filling speed at 30mm / s, the line width at 0.4mm, the single-layer line routing is straight, and the upper layer line routing direction is [0, 90°]; A printing blank is obtained, and then the product is obtained by degreasing and sintering. In the printing blank, the YG15 raw material is in the outer layer, and the YG10 raw material is in the inner layer, and the height of the inner layer / the height of the printing blank = 8.9-9.1:13.3-13.5; the diameter of the inner layer / the diameter of the printing blank = 6-6.5:

8.

7. An application of the additive manufacturing method for preparing gradient-structure polycrystalline diamond composite substrates as described in any one of claims 1-6, characterized in that: The obtained cemented carbide sintered blank with a gradient Co content was brought into contact with diamond in the low Co content region and assembled into a sample to be synthesized. The sample was then synthesized at 1400-1700℃ under a pressure of 5-7.5 GPa to obtain a polycrystalline diamond composite sheet with a gradient structure substrate.

Images