Cemented carbide additive manufacturing method

Abstract

A cemented carbide additive manufacturing method, comprising the specific steps of: (1) preparing uniformly dispersed cemented carbide powder by ball milling; (2) preparing a printing feed by internal mixing; (3) preparing a printing green body by means of fused deposition modeling of the feed; and (4) carrying out degreasing and vacuum pressure sintering on the green body to obtain a cemented carbide product. A cemented carbide solid part which is free of pores, cracks and decarburization, is free of harmful phases such as free carbon and brittle phase, and has simple phase composition, high relative density and excellent comprehensive mechanical properties is prepared by means of green body printing in cooperation with two-step degreasing of solvent degreasing and thermal degreasing and vacuum pressure sintering. Therefore, the present invention effectively solves the problems of cracking, pores, decarburization, brittle phase and deformation, low relative density, poor comprehensive mechanical properties, etc. which make troubles in cemented carbide additive manufacturing for a long time and are difficult to solve by existing additive manufacturing technology. The cemented carbide powder raw material used in an existing powder metallurgy process can be adopted. The prepared cemented carbide product has excellent hardness, strength and fracture toughness. The method is simple, low-cost, and suitable for large-scale production.

Description

A cemented carbide additive manufacturing method Technical Field

[0001] The present invention relates to a method for manufacturing cemented carbide additive materials with excellent comprehensive mechanical properties, and in particular to a method for manufacturing cemented carbide additive materials with high hardness, high bending strength and high fracture toughness, belonging to the technical field of cemented carbide and additive manufacturing. Background Art

[0002] Cemented carbide is a composite material composed of a refractory metal hard compound and a binder metal. It possesses excellent mechanical properties such as high hardness, wear resistance, compressive strength, and elastic modulus. Known as the "teeth of industry," it is a key material in manufacturing, resource extraction, transportation, electronics, and infrastructure construction. It is produced using powder metallurgy. Additive manufacturing currently offers a new technological approach for the preparation of complex cemented carbide components.

[0003] Powder Bed Fusion (PBF) is the main method currently used in cemented carbide additive manufacturing, including selective laser sintering (SLS), selective laser melting (SLM), and selective electron beam melting (SEBM). It can directly produce cemented carbide parts with complex shapes. It requires the raw material powder to have excellent properties, including sphericity, particle size distribution, bulk density, tap density, and fluidity. The products produced are prone to difficult-to-eliminate pores and cracks, abnormal grain growth, oxidation and decarburization, and the formation of brittle phases. They have low relative density and poor mechanical properties. Kumar et al. [S Kumar, et al., Optimization of parameters for SLS of WC-Co [J]. Rapid Prototyping Journal, 2017, 23 (6): 1202-1211] used SLS to prepare WC-17% Co cemented carbide with a large number of pores and large-sized cracks, and no strength data was reported. Fries et al. [S Fries, et al., Influence of post heat treatment on microstructure and fracture strength of cemented carbides manufactured using laser-based additive manufacturing [J]. International Journal of Refractory Metals and Hard Materials, 111 (2023) 106085] used LPBF (Laser Powder Bed Fusion) to prepare WC-12Co cemented carbide, which cracked severely and showed η phase or ternary phase, and had low mechanical properties. Kim et al. [KW Kim, et al. Microstructural and wear properties of WC-12Co cemented carbide fabricated by direct energy deposition [J]. Wear, 518-519 (2023) 204653] used DED (direct energy deposition) to prepare WC-12Co cemented carbide, but no flexural strength and fracture toughness were reported.Wang et al. [J Wang, et al. Microstructure and properties of WC-12Co cemented carbide fabricated via selective electron beam melting [J]. International Journal of Refractory Metals and Hard Materials, 106 (2022) 105847] prepared WC-12Co cemented carbide using SEBM, which showed the appearance of Co3W3C ternary phase, with a compressive strength of 1770 MPa and a compressive strength of 1839 MPa after heat treatment. No fracture toughness data was reported. Xing et al. [M Xing, et al. Additive manufacturing of cemented carbides inserts with high mechanical performance[J]. Materials Science and Engineering: A, 861(2022)144350] also showed brittle Co3W3C ternary phase in the WC-12Co cemented carbide prepared by LPBF. The compressive strength of the printed state was 998 MPa. After heat treatment at 1390℃ and 1480℃, the compressive strength reached 3426 MPa and 3802 MPa, respectively. No fracture toughness data was reported.

[0004] Recently, Mariani et al. [M Mariani, et al., Mechanical and microstructural characterization of WC-Co consolidated by binder jetting additive manufacturing[J], International Journal of Refractory Metals&Hard Materials.100(2021)105639] used BJAM (binder jetting additive manufacturing)-debinding-vacuum sintering to prepare WC-12%Co cemented carbide with a relative density of 97.4%. After hot isostatic pressing (HIP) treatment, a sample with a relative density of 99.3% was obtained, and the microhardness and fracture strength were 1205HV and 2257MPa, respectively. Enneti et al. [RK Enneti, et al., Wear properties of sintered WC-12%Co processed via Binder Jet 3D Printing (BJ3DP) [J], International Journal of Refractory Metals & Hard Materials. 78 (2019) 228-232] used BJ3DP-vacuum sintering to prepare WC-12Co hard alloy with a maximum relative density of 94%, and the relative density of the sintered-HIP sample reached 99%. No strength data was reported. Wolfe et al. [TA Wolfe, et al. Binder jetting 3D printed cemented carbide: Mechanical and wear properties of medium and coarse grades [J]. International Journal of Refractory Metals and Hard Materials, 113 (2023) 106197] used BJ3DP-sintering-HIP to prepare WC-(10, 12, 17) Co cemented carbide, with microhardness, transverse fracture strength and fracture toughness of 990–1300 HV30, 814–2684 MPa and 17–23 MN·m -3 / 2Cramer et al. [CL Cramer, et al. Binder jet printed WC infiltrated with pre-made melt of WC and Co [J]. International Journal of Refractory Metals and Hard Materials, 87 (2020) 105137] used BJAM to prepare WC-Co cemented carbide with a hardness of 8.34 GPa and a fracture toughness of 24.7 MPa·m 1 / 2 , but no flexural strength data was reported. Lengauer et al. [W Lengauer, et al., Fabrication and properties of extrusion-based 3D-printed hardmetal and cermet components [J], International Journal of Refractory Metals & Hard Materials. 82 (2019) 141-149.] used EBAM (extrusion-based additive manufacturing) and debinding sintering to produce WC-10% Co carbide indexable inserts. The printed green samples showed dense pores in the build direction (Z direction), but the relative density and mechanical properties of the sintered samples were not reported. Zhao et al. [Z Zhao, et al., Additive manufacturing of cemented carbide using analogous powder injection molding feedstock[J], International Journal of Refractory Metals and Hard Materials. 111(2023)106095] used EBAM (Extrusion-based additive manufacturing)-debinding sintering process to prepare WC-10Co cemented carbide with a relative density of 99.3%. The hardness, fracture strength and fracture toughness of the sintered sample were 1350±20HV30, 1695±30MPa and 7.27MPa·m, respectively. 1 / 2 In the aforementioned processes, the BJAM method utilizes a powder bed method similar to PBF, with the same raw material powder performance requirements as PBF. The resulting cemented carbide parts have simpler shapes and lower relative density. The EBAM-debinding sintering process is prone to large wedge-shaped pores and interlaminar cracks, resulting in lower relative density.

[0005] To address the above issues, the present invention proposes a cemented carbide additive manufacturing method. First, ball milling is used to prepare uniformly dispersed cemented carbide powder; second, a printing feed with a high powder loading is prepared; third, the feed is printed to prepare cemented carbide green bodies, eliminating the porosity defects of the printed green bodies; fourth, the green bodies are subjected to two-step degreasing and vacuum pressure sintering to obtain cemented carbide products with excellent comprehensive mechanical properties.

[0006] Summary of the Invention

[0007] The present invention provides a method for additive manufacturing of cemented carbide with excellent comprehensive mechanical properties. First, ball milling is performed to prepare uniformly dispersed cemented carbide powder; second, internal mixing is performed to prepare a printing feed with a high powder loading; third, the feed is printed to prepare a cemented carbide green body; fourth, the green body is degreased and vacuum pressure sintered to obtain a cemented carbide product with excellent comprehensive mechanical properties; during pressure sintering, the pressure is controlled to be greater than or equal to 5MPa.

[0008] The specific steps include:

[0009] (1) Preparation of cemented carbide powder by ball milling:

[0010] Hard raw material powder WC, or WC and at least one of TiC, Ti(C,N), (W,Ti)C, (W,Ti,Ta)C; or hard powder WC and at least one of VC, Cr3C2, TaC, (Ta,Nb)C; or hard powder WC and at least one of TiC, Ti(C,N), (W,Ti)C, (W,Ti,Ta)C, and at least one of VC, Cr3C2, TaC, (Ta,Nb)C;

[0011] At least one of the bonding metal raw material powders Co and Ni;

[0012] Mix and ball mill according to the designed ratio to prepare uniformly dispersed cemented carbide powder;

[0013] (2) Mixing and preparing printing feed:

[0014] The cemented carbide powder and the organic binder are placed in a mixing chamber according to a designed ratio and mixed to obtain a uniform mixed material of the cemented carbide powder and the organic binder;

[0015] The prepared banburying mixture is fed into a granulator to prepare granular printing feed with a particle size of 1-4 mm;

[0016] (3) Additive manufacturing to prepare green parts:

[0017] Using the granular printing feed obtained in step (2) as a raw material, a fused deposition modeling (FDM) device is used to print and prepare a cemented carbide green body;

[0018] (4) Solvent degreasing of cemented carbide green body: first, degreasing by soaking in n-heptane, then degreasing by soaking in gasoline and / or kerosene, and then vacuum drying to obtain solvent degreased green body; wherein, the soaking and degreasing time is determined according to the size of the green body; the degreasing temperature, drying temperature and time are determined according to the characteristic temperatures of the organic binder and the solvent;

[0019] Among them, the characteristic temperatures of organic binders and solvents refer to melting / melting temperature and volatilization temperature.

[0020] (5) Thermal debinding-sintering: The green body obtained by solvent debinding in step (4) is subjected to thermal debinding-vacuum pressure sintering to obtain a cemented carbide solid part. During pressure sintering, the pressure is controlled to be greater than or equal to 5 MPa.

[0021] In which, the hard raw material and the bonding metal Co and Ni raw material powders in step (1) are powders that meet the requirements of commercial powder metallurgy cemented carbide, and the ball milling can adopt the ball milling process used in the existing cemented carbide powder metallurgy preparation technology; in addition to the raw material powder, paraffin is further added, and the amount of paraffin added accounts for 0.5 to 5% of the total mass of the raw material powder.

[0022] In the printing feed in step (2), the volume proportion of the cemented carbide powder is 40-70%, and the volume proportion of the organic binder is 60-30%. The volume proportion of the cemented carbide powder in the organic binder is defined as the powder loading amount.

[0023] The difficulty in designing the organic binder in step (2) is that the printing feed has a high loading capacity while having the shear thinning characteristics of a pseudoplastic fluid, good temperature stability and thermoplasticity, ensuring that the printing feed has a wide printing process window and the printed green body has high strength to avoid defects such as degreasing cracks and swelling. The present invention optimizes the design of the composition of the organic binder, and the organic binder includes a skeleton component, a plasticizing component and a dispersing component; the skeleton component is at least one of polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polymethyl methacrylate, polystyrene, polyacetal, etc.; the plasticizing component includes at least one of paraffin wax, microcrystalline wax, beeswax, palm wax, etc.; the dispersing component is at least one of stearic acid and stearate. The volume proportion of the plasticizing component in the organic binder is 35-65%, the volume of the skeleton component is 30-50%, and the volume proportion of the dispersing component is 1-15%.

[0024] The banburying parameters of step (2) are as follows: banburying temperature is 100-200° C., rotation speed is 30-100 rpm, and banburying time is 30-300 min.

[0025] The preparation parameters of the printing feed in step (2) are: screw speed 30-100 rpm, screw pressure 3-10 kg, and the obtained particle diameter is 1-4 mm.

[0026] The amount of paraffin wax in step (2) includes the amount of paraffin wax added in the ball milling process in step (1), that is, the amount of paraffin wax in the organic binder in step (2), which is composed of the sum of the amount of paraffin wax in the ball milling process in step (1) and the amount of paraffin wax added subsequently.

[0027] Preferably, the organic binder contains stearic acid, polyethylene, polypropylene, and paraffin, and the volume ratio is stearic acid: polyethylene: polypropylene: paraffin = 7-12:18-22:18-22:40-55.

[0028] As a further preference, the organic binder is composed of stearic acid, polyethylene, polypropylene, and paraffin, and the volume ratio is stearic acid: polyethylene: polypropylene: paraffin = 8-12:18-22:18-22:45-55.

[0029] Preferably, the organic adhesive contains stearic acid, polyethylene, polypropylene, polymethyl methacrylate, polystyrene, and paraffin wax; calculated by volume, the wax-based adhesive comprises stearic acid: polyethylene: polypropylene: polymethyl methacrylate: polystyrene: paraffin wax in a ratio of 7-12:7-12:7-12:6-12:6-12:40-55.

[0030] As a further preferred embodiment, the organic binder is composed of stearic acid, polyethylene, polypropylene, polymethyl methacrylate, polystyrene, and paraffin; by volume ratio,

[0031] Stearic acid: polyethylene: polypropylene: polymethyl methacrylate: polystyrene: paraffin = 8-10:9-11:9-11:7-9:7-9:43-48. Or

[0032] The organic binder is composed of stearic acid, polyethylene, polypropylene, polymethyl methacrylate, polystyrene, and paraffin wax; calculated by volume, stearic acid: polyethylene: polypropylene: polymethyl methacrylate: polystyrene: paraffin wax = 10-12:10-12:10-12:10-12:10-12:53-58. Or

[0033] The organic adhesive consists of stearic acid, polyethylene, polypropylene, polymethyl methacrylate, polystyrene and paraffin wax; calculated by volume, the ratio of stearic acid: polyethylene: polypropylene: polymethyl methacrylate: polystyrene: paraffin wax is 7.5-8.5:7.5-8.5:7.5-8.5:7.5-8.5:7.5-8.5:40-42.

[0034] The organic adhesive consists of stearic acid, paraffin wax, microcrystalline wax, ethylene-vinyl acetate copolymer and low-density polyethylene in a volume ratio of 4-6:42-48:12-17:18-22:22-28.

[0035] Among them, the cemented carbide green body described in step (3) is made by printing with FDM equipment using the granular printing feed prepared in step (2) as raw material, and the printing process is as follows: the three-dimensional CAD model of the part is sliced ​​and layered using the printing software of the additive manufacturing system, and imported into the additive manufacturing system; after heating the granular printing feed, according to the slice and layer data of the imported three-dimensional CAD model of the part, the granular material is extruded by a screw and printed layer by layer according to the slice data to obtain a printed green body.

[0036] Wherein, the green body printing technology described in step (3) is FDM, and the difficulty lies in reducing or eliminating the defects of cemented carbide green body printing (such as wedge-shaped or diamond-shaped pores, interlayer cracks, etc.). After optimization, the cemented carbide green body printing process parameters that can be selected in the present invention are: nozzle diameter of 0.1-1.0mm, printing temperature of 100-220℃, layer thickness of 0.08-0.5mm, printing speed of 10-80mm / s, filling rate of 50-100%, microwire overlap ratio of 0-60%, preferably 0-30%, filling mode of [0,90°], [45°,-45°], or a combination of the two filling modes, and substrate temperature of 50-150℃. Under the synergistic effect of the above parameters, green body defects can be eliminated.

[0037] The microfilament overlap ratio described in the present invention is defined as the ratio of the overlap amount of two adjacent feeding extrusion belts to the bandwidth, where the bandwidth is the inner diameter of the nozzle.

[0038] The difficulty of the solvent degreasing process described in step (4) is that the degreasing process needs to be designed according to the composition and performance of the organic binder to avoid swelling of the printed green body due to the high molecular components in the binder and cracking of the green body, while ensuring the degreasing rate. The solvent degreasing process designed by the present invention is a two-step solvent degreasing process using n-heptane, gasoline and / or kerosene: the cemented carbide green body prepared in step (3) is immersed in n-heptane for degreasing for 4-30 hours; then taken out and immersed in gasoline and / or kerosene for degreasing for 1-10 hours; finally, it is dried in a vacuum drying oven to obtain a solvent-degreased green body; wherein: the degreasing temperature of n-heptane is 5-50°C, preferably 20-35°C; the immersion time is 4-30 hours, preferably 8-20 hours; the degreasing temperature of gasoline and / or kerosene is 10-55°C, preferably 20-40°C; the immersion time is 1-10 hours, preferably 2-6 hours; the drying temperature is 40-80°C, preferably 40-60°C; and the drying time is 3-14 hours, preferably 6-8 hours. The purpose of designing the two-step solvent degreasing process is to control the degreasing rate and prevent the green body from producing defects such as degreasing bulges and cracks.

[0039] Or: Use a mixed solvent of n-heptane and gasoline and / or kerosene as the degreasing solvent. The purpose is to control the degreasing rate and prevent defects such as degreasing bulging and cracking in the green body. The optional immersion extraction degreasing is usually 4-60 hours, and the specific degreasing time can be adjusted according to actual conditions.

[0040] Among them, the step (5) of hot debinding and sintering of the green body is an integrated process of hot debinding and vacuum pressure sintering: the first step is to perform hot debinding of the green body: evacuate the sintering chamber to a pressure of less than 1000Pa, fill it with reducing gas, heat it from room temperature to a debinding temperature of 400-750°C at a heating rate of 0.1-3°C / min, and debind it for 60-120min; the second step is to perform vacuum pressure sintering: the sintering temperature is 750-1500°C, first evacuate the sintering chamber to a pressure of less than 1000Pa, heat it from the debinding temperature to the sintering temperature at a heating rate of 0.5-10°C / min, pressurize it to 5-10MPa with inert gas, and sinter it for 60-180min.

[0041] More preferably, in the first step, the heating rate of the green body thermal debinding is 0.1-1.5°C / min; in the second step, the heating rate of the vacuum pressure sintering is 0.5-8°C / min; more preferably, the heating rate of the first step is 0.3-1.5°C / min, and the heating rate of the second step is 1-5°C / min.

[0042] The present invention proposes a cemented carbide additive manufacturing preparation method, which combines a polymer plasticizing component, a skeleton component, and a dispersed component to prepare a printing feed using cemented carbide powder as a raw material. The prepared printing feed has high temperature stability and can be used for green body printing within a wide temperature range. The plasticizing component designed in the organic binder can increase the loading capacity of the printing feed powder. By optimizing the printing process parameters, the porosity and crack defects of the cemented carbide printed green body can be reduced. By designing a suitable degreasing-sintering process according to the composition of each component of the organic binder, a cemented carbide solid part with high relative density and excellent comprehensive mechanical properties can be produced.

[0043] Advantages and positive effects of the present invention:

[0044] (1) The present invention provides a cemented carbide additive manufacturing method that can produce cemented carbide complex structure products with excellent comprehensive mechanical properties. The prepared cemented carbide product has no pores, no cracks, no harmful phases such as decarburization phase, free carbon and brittle phase, has a simple phase composition and high relative density, and effectively solves the problems of cracking, pores, decarburization, brittle phase and deformation that are difficult to solve in the existing PBF additive manufacturing process, as well as the problems of pores, deformation, low relative density and poor comprehensive mechanical properties that are difficult to solve in the existing green additive manufacturing-debinding sintering (GAM-DS) process. The cemented carbide powder raw materials and ball milling process used in the existing powder metallurgy process can be used. The prepared cemented carbide product has excellent hardness, strength and fracture toughness, and the preparation method is simple, low cost, and easy to scale production.

[0045] (2) The present invention adds paraffin wax during the process of mixing raw material powders and ball milling to prepare cemented carbide powder, which fully coats the powder and prevents the powder from absorbing oxygen during ball milling, thereby preparing cemented carbide powder with low oxygen content and uniform dispersion, which can effectively eliminate the oxidation and decarburization of cemented carbide in subsequent processes.

[0046] (3) The skeleton component, plasticizing component and dispersing component used in the organic binder of the present invention can reduce the requirements for cemented carbide raw material powder, which is beneficial to the degreasing of printed green bodies. In addition, the raw materials are easy to obtain and low in cost, making them suitable for industrial promotion and application.

[0047] (4) In order to solve the problem that the green body printed by the fused deposition modeling process is prone to forming wedge-shaped or diamond-shaped pores and cracks, the present invention eliminates the wedge-shaped or diamond-shaped pores and cracks in the green body through the synergistic effect of printing process parameters and organic binders, and prepares a cemented carbide green body with high relative density.

[0048] (5) The two-step solvent degreasing + thermal degreasing process designed in this invention avoids the degreasing defects caused by the excessive speed of conventional solvent degreasing. By combining two-step solvent degreasing with thermal degreasing with appropriate parameters, degreasing defects of the green body can be effectively eliminated, and the effective degreasing rate can be improved. Further, by combining it with the sintering process, sintering defects and harmful phases can be eliminated, and the product phase composition is simple.

[0049] (6) The integrated process of thermal degreasing and vacuum pressure sintering is used to prepare cemented carbide products that are nearly fully dense, free of metallurgical defects, cracks, low porosity, and free of harmful phases such as decarburization phase, free carbon, and brittle phase. The product quality and comprehensive mechanical properties are superior to those of existing additive manufacturing processes and are comparable to those of cemented carbides prepared by powder metallurgy processes.

[0050] The prepared WC-9Co cemented carbide product is a two-phase cemented carbide with no pores or cracks and a uniform microstructure. After optimization, the relative density of the obtained WC-9Co cemented carbide product is greater than 99.6%, and the microhardness, flexural strength and fracture toughness are greater than or equal to 1522HV30, 3447Mpa and 19.92MPa·m, respectively. 1 / 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0051] FIG1 is a diagram showing the internal microstructure of a cemented carbide printed green body subjected to two-step solvent degreasing in accordance with the first embodiment of the present invention, showing no degreasing swelling or cracks;

[0052] FIG2 is an XRD phase analysis result of a sintered cemented carbide sample of Example 1 of the present invention, which is composed of two phases, WC and Co, without harmful phases such as free carbon, decarburized phase, ternary or multi-element brittle phase, etc.;

[0053] FIG3 is an SEM microstructure of a sintered cemented carbide sample of Example 1 of the present invention, showing no Co magnetism, no free carbon, no decarburized phase, and no brittle phase (before corrosion);

[0054] FIG4 is a Micro-CT scan result of the internal structure of a cemented carbide sintered sample according to Example 1 of the present invention, showing no defects such as voids and cracks.

[0055] The present invention will be described in further detail below with reference to specific embodiments. However, it should be understood that these embodiments are intended to illustrate and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims of this application.

[0056] The present invention proposes a cemented carbide additive manufacturing method, which combines additive manufacturing with powder metallurgy sintering technology to prepare high-performance cemented carbide complex structure products. First, by adopting step (2) of the present invention, a printing feed with high powder loading and good printability can be prepared; by adopting the optimized process parameters in step (3) of the present invention, wedge-shaped or diamond-shaped holes, cracks, etc. of the printed green body can be eliminated; by adopting the two-step solvent degreasing of the green body in step (4) of the present invention, solvent degreasing defects, especially cracking, can be eliminated. Step (5) of the present invention performs a hot degreasing-vacuum pressure sintering integrated process, which can prepare a cemented carbide product with uniform microstructure, no decarburization phase, no free carbon, no brittle phase, no cracks and other metallurgical defects, high relative density (greater than 99.6% after optimization), and excellent mechanical properties. DETAILED DESCRIPTION

[0057] Example 1:

[0058] (1) Preparation of WC-Co cemented carbide powder: WC (particle size less than 5 μm) and Co powder were weighed according to the mass ratio of WC to 9 wt.% Co, paraffin wax was weighed according to 0.5% of the mass of (WC-9 wt.% Co), and anhydrous ethanol was used as the ball milling medium. The mixture was loaded into a drum ball mill and ball milled for 60 h, and then vacuum dried for 10 h and sieved to obtain WC-9 wt.% Co cemented carbide powder;

[0059] (2) An organic binder consisting of stearic acid, paraffin wax, microcrystalline wax, ethylene-vinyl acetate copolymer and low-density polyethylene in a volume ratio of 5:45:15:20:25 and WC-9wt.%Co cemented carbide powder were mixed in an open-close internal mixer at a speed of 30 r / min, a mixing temperature of 150°C and a mixing time of 2 h to obtain a mixed material with a powder loading of 54 Vol.%; and then, a granulator was used for granulation, with the heating chamber and discharge port temperatures of the granulator being 140°C and 110°C, respectively, the rotation speed being 60 r / min and the screw pressure being 10 kg to obtain a printing feed with a particle size of 1.5-3.5 mm.

[0060] (3) Preparation of cemented carbide green body by fused deposition modeling printing: Using the granular printing feed prepared in step (2) as raw material, the cemented carbide green body was prepared by fused deposition modeling equipment printing, and the printing parameters were: nozzle diameter of 0.4 mm, printing temperature of 150 ° C, layer thickness of 0.1 mm, printing speed of 30 mm / s, microfilament overlap ratio of 30%, extrusion flow rate of 60%, [0,90°] as the 3D printing routing mode, and substrate temperature of ; the relative density of the printed cemented carbide green body was about 98.4%;

[0061] (4) Solvent degreasing: The printed green body was solvent degreased using a two-step solvent degreasing process of n-heptane extraction degreasing and kerosene extraction degreasing: In the first step, the printed green body was immersed in n-heptane for extraction degreasing, the degreasing time was 12 hours, and the degreasing temperature was 30°C; In the second step, the green body sample degreased by n-heptane was immersed in 30°C kerosene for extraction degreasing for 1 hour; the degreasing solvent was heated in a water bath; after the green body was solvent degreased, it was dried in a drying oven at 45°C for 5 hours;

[0062] (5) Hot debinding + sintering: A debinding-sintering integrated furnace is used to perform continuous hot debinding + vacuum pressure sintering on the green body that has completed solvent debinding: the first step is to perform hot debinding of the green body: evacuate the sintering chamber to a pressure of less than 100Pa, fill it with reducing gas H2, and use a gradient heating / insulation process to heat from room temperature to debinding temperatures of 450℃, 550℃, and 650℃ at a heating rate of 0.1-3℃ / min, and keep it warm for 60min; the second step is to directly heat the debinded green body that has completed hot debinding and perform vacuum-pressure sintering: first, evacuate the sintering chamber to a pressure of less than 100Pa, heat from the debinding temperature of 650℃ to the sintering temperature of 1430℃ at a heating rate of 0.5-10℃ / min, pressurize it to 5MPa with argon, and sinter for 115min to obtain a WC-9Co cemented carbide sintered sample.

[0063] The WC-9Co cemented carbide sintered samples prepared using the above process had a relative density of 99.7%, porosity of A02B00, free carbon of C00, and η phase of E00. They also exhibited uniform dimensional shrinkage in all directions, with no cracks, warping, or deformation. Among the samples prepared, the best test indicators were: microhardness of 1528HV30, flexural strength of 3537MPa, and fracture toughness of 20.92MPa·m 1 / 2 .

[0064] Example 2:

[0065] Other conditions were the same as those in Example 1, except that the microfilament overlap rate was 15%, the printing layer thickness was 0.1 mm, and the relative density of the printed green body was about 98.1-98.2%.

[0066] Example 3:

[0067] Other conditions were the same as those in Example 1, except that the microfilament overlap rate was 30%, the printing layer thickness was 0.2 mm, and the relative density of the printed green body was about 97.6-97.8%.

[0068] As a comparative example, the following are the relative density and mechanical properties of WC-Co cemented carbides prepared by powder metallurgy, as well as green additive manufacturing-debinding and sintering processes such as BJAM-debinding-sintering-hot isostatic pressing (HIP), 3DGP-debinding-sintering, and FDM-debinding-sintering reported in the literature.

[0069] Comparative Example 1:

[0070] [1]J.Jiang,S.Ouyang,H.Chen,S.Guo,L.Yin,Z.Tan,H.Shi,Z.Zhong,L.Qiu,Effect of MWCNTs on microstructure and properties ofWC-9Co gradient cemented carbides,Ceramics International,48(2022)19295-19304

[0071] Jiang et al. [1] prepared WC-9Co cemented carbide by powder pressing, degreasing and sintering. The relative density, microhardness, flexural strength and fracture toughness are shown in Table 1, which are 99.57%, 1227HV respectively. 20 , 2519MPa and 12-12.5MPa·m 1 / 2 .

[0072] Comparative Example 2:

[0073] [2]M.Mariani,I.Goncharov,D.Mariani,GPDe Gaudenzi,A.Popovich,N.Lecis,M.Vedani,Mechanical and microstructural characterization of WC-Co consolidated by binder jetting additive manufacturing,International Journal of Refractory Metals&Hard Materials,100(2021)105639

[0074] Mariani et al. [2] used the BJAM-Debinding-Sintering-HIP process to prepare WC-12Co cemented carbide. The relative density, microhardness and flexural strength are shown in Table 1, which are 99.3%, 1205±12HV respectively. 10 and 2257 ± 28 MPa, with no fracture toughness data.

[0075] Comparative Example 3:

[0076] [3]T.Wolfe, R.Shah, K.Prough, JLTrasorras, Coarse cemented carbide produced via binder jetting 3D printing, International Journal of Refractory Metals and Hard Materials, 110 (2023) 106016

[0077] Wolfe et al. [3] used the BJAM-debinding-sintering-HIP process to prepare WC-10Co and WC-12Co cemented carbides. The relative density and mechanical properties are shown in Table 1. Among them, the microhardness, flexural strength and fracture toughness of WC-10Co cemented carbide are 1119HV 30 , 2231MPa and 18.8MPa·m 1 / 2 The microhardness, flexural strength and fracture toughness of WC-12Co cemented carbide are 1050HV 30 , 2684MPa and 19.4MPa·m 1 / 2 .

[0078] Comparative Example 4:

[0079] [4]

[0080] Zhang et al. [4] used the 3DGP-debinding-sintering process to prepare WC-20Co cemented carbide. The relative density, hardness and flexural strength are shown in Table 1, which are 99.9%, 87.7HRA and 2612.8MPa respectively. There is no fracture toughness data.

[0081] Comparative Example 5:

[0082] [5] Z. Zhao, R. Liu, J. Chen, X. Xiong, Additive manufacturing of cemented carbide using analogous powder injection molding feedstock, International Journal of Refractory Metals and Hard Materials, 111 (2023) 106095

[0083] Zhao et al. [5] used FDM-debinding-sintering (Fused Deposition Molding-Debinding-Sintering) to prepare WC-8Co cemented carbide. The relative density, microhardness, flexural strength and fracture toughness are shown in Table 1, which are 99.3%, 1350±20HV30, 1695±30MPa and 7.27±0.5MPa·m 1 / 2 .

[0084] Compared with the WC-Co cemented carbide prepared by the powder metallurgy process reported in the comparative example, BJAM-degreasing-sintering-HIP, 3DGP-degreasing-sintering and FDM-degreasing-sintering green body additive manufacturing-degreasing and sintering processes, the present invention has obvious advantages in relative density and comprehensive mechanical properties.

[0085] Table 1 Mechanical properties of WC-Co cemented carbide prepared by different processes

[0086] Obviously, the above embodiments and comparative examples are merely examples for clarity of explanation and are not intended to limit the embodiments. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A cemented carbide additive manufacturing method, characterized in that The method comprises the following steps: first, preparing uniformly dispersed cemented carbide powder by ball milling; second, preparing cemented carbide printing feed by internal mixing; third, preparing cemented carbide green body by feed printing; and fourth, degreasing and vacuum pressure sintering the green body to obtain a cemented carbide product with excellent comprehensive mechanical properties.

2. A cemented carbide additive manufacturing method according to claim 1, characterized in that: The steps include: (1) Preparation of cemented carbide powder by ball milling: Hard raw material powder WC, or WC and at least one of TiC, Ti(C,N), (W,Ti)C, (W,Ti,Ta)C; or hard powder WC and at least one of VC, Cr3C2, TaC, (Ta,Nb)C; or hard powder WC and at least one of TiC, Ti(C,N), (W,Ti)C, (W,Ti,Ta)C, and at least one of VC, Cr3C2, TaC, (Ta,Nb)C; At least one of the bonding metal raw material powders Co and Ni; Mixing and ball milling are performed according to the designed ratio to prepare uniformly dispersed cemented carbide powder; (2) Mixing and preparing printing feed: The cemented carbide powder and the organic binder are placed in a mixing chamber of a mixer according to a designed ratio for mixing to obtain a mixed material in which the cemented carbide powder and the organic binder are mixed evenly; The prepared banburying mixture is loaded into a granulator to prepare a granular printing feed with a particle size of 1-4 mm; (3) Additive manufacturing to prepare green parts: Using the granular printing feed obtained in step (2) as a raw material, a fused deposition modeling (FDM) device is used to print and prepare a cemented carbide green body; (4) Solvent degreasing of cemented carbide green body: first, degreasing by immersion in n-heptane, then degreasing by immersion in gasoline or kerosene, and then vacuum drying to obtain solvent degreasing green body; wherein, the immersion degreasing time is determined according to the size of the green body; the degreasing temperature, drying temperature and time are determined according to the characteristic temperatures of the organic binder and the solvent; (5) Thermal debinding-sintering: The solvent-debinded green body of step (4) is subjected to thermal debinding-vacuum pressure sintering to obtain a cemented carbide solid part; during pressure sintering, the pressure is controlled to be greater than or equal to 5 MPa.

3. A cemented carbide additive manufacturing method according to claim 2, characterized in that: The hard raw material and the bonding metal Co and Ni raw material powders in step (1) are powders that meet the requirements of commercial powder metallurgy cemented carbide.

4. A cemented carbide additive manufacturing method according to claim 2, characterized in that: In step (1), in addition to the hard raw material and the bonding metal Co and Ni raw material powders, paraffin is further added, and the amount of the added paraffin accounts for 0.5-5% of the total mass of the raw material powders.

5. A cemented carbide additive manufacturing method according to claim 2, characterized in that: In the printing feed described in step (2), the volume proportion of cemented carbide powder is 40-70%, and the volume proportion of organic binder is 60-30%; The banburying parameters of step (2) are: banburying temperature is 100-200° C., rotation speed is 30-100 rpm, and banburying time is 30-300 min.

6. A cemented carbide additive manufacturing method according to claim 2, characterized in that: The preparation parameters of the printing feed in step (2) are: screw speed 30-100 rpm, screw pressure 3-10 kg, and the obtained particle diameter 1-4 mm.

7. A cemented carbide additive manufacturing method according to claim 2, characterized in that: The cemented carbide green body printing process parameters of step (3) are: nozzle diameter of 0.1-1.0 mm, printing temperature of 100-220 ° C, layer thickness of 0.08-0.5 mm, printing speed of 10-80 mm / s, filling rate of 50-100%, microwire overlap ratio of 0-60%, preferably 0-30%, more preferably 0-15%, filling mode of [0, 90 °], [45 °, -45 °], or a combination of the two filling modes, and substrate temperature of 50-150 ° C.

8. A cemented carbide additive manufacturing method according to claim 2, characterized in that: In the solvent degreasing process of step (4), the cemented carbide green body prepared in step (3) is immersed in n-heptane for degreasing for 4-30 hours; then taken out and immersed in gasoline and / or kerosene for degreasing for 1-10 hours; finally, it is dried in a vacuum drying oven to obtain a solvent degreased green body; wherein: the degreasing temperature of n-heptane is 5-50°C, preferably 20-35°C; the immersion time is 4-30 hours, preferably 8-20 hours; the degreasing temperature of gasoline or kerosene is 10-55°C, preferably 20-40°C; the immersion time is 1-10 hours, preferably 2-6 hours; the drying temperature is 40-80°C, preferably 40-60°C; the drying time is 3-14 hours, preferably 6-8 hours; Or: Use a mixed solvent of n-heptane, gasoline and / or kerosene to soak, extract and degrease for 4-60 hours.

9. A cemented carbide additive manufacturing method according to claim 2, characterized in that: The step (5) of hot debinding and sintering of the green body is an integrated process of hot debinding and vacuum pressure sintering: the first step is to hot debind the green body: evacuate the sintering chamber until the pressure is less than 1000Pa, fill it with reducing gas, heat it from room temperature to the debinding temperature of 400-750°C at a heating rate of 0.1-3°C / min, and debind for 60-120min; the second step is to vacuum pressure sintering: the sintering temperature is 750-1500°C, first evacuate the sintering chamber until the pressure is less than 1000Pa, heat it from the debinding temperature to the sintering temperature at a heating rate of 0.5-10°C / min, pressurize it to 5-10MPa with inert gas, and sinter for 60-180min.

10. A cemented carbide additive manufacturing method according to claim 1 or claim 2, characterized in that: The prepared cemented carbide product is a two-phase WC-Co cemented carbide with low porosity, no cracks, no decarburization, no brittle phase, and uniform microstructure, or a cemented carbide without harmful phases.

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