A method for producing a cemented carbide with low porosity defects and a cemented carbide produced thereby

Abstract

This invention discloses a method for preparing low-porosity cemented carbide, relating to the field of alloy technology. The method involves sequentially subjecting cemented carbide raw materials to selective laser melting (SLM) forming and microwave heat treatment, followed by cooling. The cemented carbide is WC-AlCoCrFeNi, and the mass content of AlCoCrFeNi in the WC-AlCoCrFeNi is 10-14%. This invention utilizes a novel high-entropy alloy binder instead of a Co binder, controls the appropriate energy density, and employs efficient microwave heat treatment to reduce porosity and increase hardness. This invention enables SLM-formed WC-AlCoCrFeNi cemented carbide to achieve a relative density of 96.37% and a hardness of 1777.8 HV. 10 Furthermore, the porosity of the formed material is relatively low.

Description

Technical Field

[0001] This invention relates to the field of alloy technology, and specifically to a method for preparing low-porosity cemented carbide and the cemented carbide prepared therefrom. Background Technology

[0002] Cemented carbide is a key material in modern industry, and its excellent comprehensive performance relies on the synergistic effect of the WC hard phase and the binder phase. Cemented carbide is widely used in the manufacture of wear-resistant parts and key components such as drill bits, cutting inserts, and probes, playing an indispensable role in many fields including military, mold manufacturing, machining, oil drilling, mining tools, and geological exploration. Traditional WC-Co cemented carbide is widely used due to cobalt's excellent wettability, wear resistance, and high strength; however, the scarcity of cobalt resources, price volatility, and performance degradation at high temperatures have become bottlenecks restricting the application of cemented carbide. Therefore, researchers have begun to focus on the development and application of novel binders.

[0003] Currently, researchers have conducted extensive research in existing technologies, for example: (1) They first explored transition metal elements and prepared WC-Fe hard alloys with different Fe contents through spark plasma sintering. The study found that the relative density increases with the increase of Fe binder content, and the hardness is mainly controlled by WC content and grain size. The hardness of the fine-grained 30wt% Fe sample is the highest at 60.5HRC. The bending strength is dominated by the relative density, while that of the coarse-grained 70wt% Fe sample is the highest. The maximum strength of the Fe sample was 1851 MPa; (2) Since the WC grain size of the cemented carbide is large when a single metal is used as a binder, some researchers have added metal oxides to inhibit grain growth. By microwave sintering and adding La2O3, the grain size of WC-Ni cemented carbide was inhibited, and the hardness of the alloy sample produced could reach 1955 HV; Nano WC and WC-Al2O3 composite materials were prepared by high frequency induction heating sintering technology. The results showed that Al2O3 can significantly promote sintering, inhibit WC grain growth and increase relative density; (3) In 2004, Ye Junwei et al. first proposed the concept of high entropy alloy (HEA). High entropy alloy is an alloy formed by five or more metals in equal or approximately equal amounts. High entropy alloy has high entropy effect, lattice distortion effect, hysteresis diffusion effect and "cocktail effect". High entropy alloys (HCIs) exhibit excellent tunability of microstructure and good thermal stability, thus attracting widespread attention from researchers in the field of cemented carbide research. Compared with traditional metals, HCIs demonstrate superior high-temperature performance and corrosion resistance, a characteristic that significantly improves the wear resistance, high-temperature oxidation resistance, and corrosion resistance of WC-HEA cemented carbide. For example, the NiFeCrWMo binder, through the multi-principal element effect, not only significantly inhibits the abnormal growth of WC grains but also achieves simultaneous improvement in hardness and fracture toughness through the formation of interfacial composite carbides, resulting in a performance improvement of approximately 15% compared to traditional WC-8Co alloys. Furthermore, WC-HEA cemented carbide exhibits superior stability in extreme environments such as seawater corrosion and high-temperature oxidation, providing a new direction for high-end tool materials in marine engineering and aerospace fields.

[0004] Selective laser melting (SLM), a key branch of additive manufacturing, is widely used in aerospace, biomedicine, and other fields due to its advantages in complex structure forming and high material utilization. However, various defects inevitably occur during the SLM process, which severely restrict the performance of additive parts and become a bottleneck limiting the large-scale application of SLM. For example, porosity is one of the most common defect types in SLM-made additive parts, and its formation mechanism is closely related to process parameters, powder characteristics, and molten pool dynamics. When the laser energy density is insufficient, the powder cannot be completely melted, resulting in unfused pores. On the other hand, excessively high laser power may cause violent evaporation and splashing of powder material, forming pores. Studies have shown that even a porosity as low as 1% in additive parts can significantly reduce their tensile strength and fatigue life. In the manufacturing of high-temperature alloy components for aero-engines, unfused defects may cause sudden failure of parts under high temperature and high pressure environments, seriously threatening flight safety.

[0005] Currently, defect control has become a key bottleneck restricting the engineering application of SLM technology in the field of precision manufacturing of cemented carbide. Therefore, providing a method for preparing low-porosity cemented carbide using selective laser melting is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the above problems, the present invention provides a method for preparing cemented carbide with low porosity defects.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing low-porosity cemented carbide, wherein the cemented carbide raw material is subjected to laser selective melting forming and microwave heat treatment in sequence, followed by cooling; The cemented carbide is WC-AlCoCrFeNi, and the mass content of AlCoCrFeNi in WC-AlCoCrFeNi is 10-14%.

[0009] This invention provides a novel method for forming low-defect, high-hardness cemented carbide through selective laser melting (SLM) and microwave heat treatment. By using a high-entropy alloy binder instead of a Co binder and controlling the appropriate energy density, efficient microwave heat treatment is employed to reduce porosity and increase hardness. This invention enables SLM-formed WC-AlCoCrFeNi cemented carbide to achieve a relative density of 96.37% and a hardness of 1777.8 HV. 10 Furthermore, the porosity of the formed material is relatively low.

[0010] Preferably, in the laser selective melting and forming process: the laser power is 180-200W, the scanning speed is 530-640mm / s, and the energy density is 125-135J / mm². 3 The diameter of the light spot is 0.1 mm.

[0011] Preferably, the microwave heat treatment conditions are as follows: microwave frequency of 2450MHz, microwave power of 2kW, temperature control accuracy of ±1℃; maximum heat treatment temperature of 1400-1450℃, heating rate of 40-50℃ / min, and holding time of 20-25min.

[0012] Preferably, the cemented carbide raw material is W, C, Al, Co, Cr, Fe, and Ni; Wherein, the mass percentage of C is 5.5-6.0% of the total mass of the cemented carbide raw material, the mass percentage of Al is 1.0-1.5% of the total mass of the cemented carbide raw material, the mass percentage of Co is 2.5-3.0% of the total mass of the cemented carbide raw material, the mass percentage of Cr is 2.0-2.5% of the total mass of the cemented carbide raw material, the mass percentage of Fe is 2.5-3.0% of the total mass of the cemented carbide raw material, the mass percentage of Ni is 2.5-3.0% of the total mass of the cemented carbide raw material, and the balance is W.

[0013] Preferably, the balance does not exclude other elements besides those mentioned in this invention, such as O and N, which may also be included in the cemented carbide raw material, with a mass fraction not exceeding 0.01%. When the cemented carbide raw material also includes other elements besides those mentioned in this invention, the amount of W is adjusted accordingly so that the mass percentage of elements other than W in the cemented carbide raw material is within the range defined by this invention.

[0014] Preferably, the mass percentage of C is 5.8% of the total mass of the cemented carbide raw material, the mass percentage of Al is 1.28% of the total mass of the cemented carbide raw material, the mass percentage of Co is 2.8% of the total mass of the cemented carbide raw material, the mass percentage of Cr is 2.47% of the total mass of the cemented carbide raw material, the mass percentage of Fe is 2.65% of the total mass of the cemented carbide raw material, the mass percentage of Ni is 2.79% of the total mass of the cemented carbide raw material, and the balance is W.

[0015] Preferably, the particle size distribution range of the cemented carbide raw material is 50-150 μm; Among them, D10 is 60-70μm, D50 is 90-100μm, and D90 is 140-160μm.

[0016] Preferably, according to conventional practice in the art, D10 generally refers to the particle size corresponding to a cumulative particle size distribution volume percentage of 10% for WC-AlCoCrFeNi cemented carbide raw materials; D50 generally refers to the particle size corresponding to a cumulative particle size distribution volume percentage of 50% for WC-AlCoCrFeNi cemented carbide raw materials, i.e., the median particle size or the median particle size of the volume distribution; D90 generally refers to the particle size corresponding to a cumulative particle size distribution volume percentage of 90% for WC-AlCoCrFeNi cemented carbide raw materials.

[0017] Preferably, the laser selective melting forming process is carried out in an argon atmosphere with an oxygen content of less than 300 ppm.

[0018] Preferably, the purity of the argon gas is 99.99 wt% or higher.

[0019] Preferably, the powder layer thickness in the laser selective melting forming process can be 40-60 μm, and the scanning interval can be 40-50 μm.

[0020] Preferably, the microwave heat treatment is performed under vacuum conditions or a protective atmosphere.

[0021] Preferably, the cooling is performed by furnace cooling for 2-3 hours.

[0022] Hard alloys obtained by any of the methods described above.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The preparation method of WC-AlCoCrFeNi cemented carbide of the present invention adopts SLM technology, which realizes the short cycle manufacturing of complex WC-AlCoCrFeNi cemented carbide components. (2) In the preparation method of WC-AlCoCrFeNi cemented carbide of the present invention, SLM forming effect is good, the formed WC-AlCoCrFeNi cemented carbide has low porosity, and high hardness and relative density. (3) The microwave heat treatment process in the preparation method of WC-AlCoCrFeNi cemented carbide of the present invention is simple, fast, efficient, uniform and energy-saving. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings in this description are merely embodiments of the present invention.

[0025] Figure 1 The images show the microstructure (a) and grain size histogram (b) of the WC-AlCoCrFeNi cemented carbide before heat treatment in Example 1 of this invention. Figure 2 The images show the microstructure (a) and grain size histogram (b) of the WC-AlCoCrFeNi cemented carbide after heat treatment in Example 1 of this invention. Figure 3 This is a pore diagram of the WC-AlCoCrFeNi cemented carbide before heat treatment in Example 1 of the present invention; Figure 4 This is a pore diagram of the WC-AlCoCrFeNi cemented carbide after heat treatment in Example 1 of the present invention; Figure 5 The images show a comparison of the grain structure of WC-HEA cemented carbide before and after heat treatment in Example 1 of the present invention, and with that prepared by conventional microwave sintering. (a) is a microstructure of the WC-AlCoCrFeNi cemented carbide before heat treatment in Example 1, (b) is a microstructure of the WC-AlCoCrFeNi cemented carbide after heat treatment in Example 1, and (c) is a microstructure of the comparative cemented carbide. Detailed Implementation

[0026] Embodiments of the present invention are described below, examples of which are shown in the accompanying drawings. The embodiments described with reference to the drawings are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0027] Additive manufacturing technology, also known as 3D printing technology, mainly uses powder, granules or metal wires as raw materials. Through pre-layer processing of CAD models, high-energy laser beams are used to melt and deposit the materials to grow them (additive manufacturing), directly completing the near-net-shape of high-performance components from the CAD model in one step. Selective laser melting: an additive manufacturing technology that uses laser melting of pre-placed metal powder to form parts; Example 1 This invention provides a method for preparing low-porosity cemented carbide, specifically comprising the following steps: (1) Weigh the raw materials according to the mass percentage of each component in the total mass of WC-AlCoCrFeNi cemented carbide powder: C 5.8%, Al 1.26%, Co 2.82%, Cr 2.38%, Fe 2.75%, Ni 2.49%, W balance; use AlCoCrFeNi high entropy alloy and WC ball milling compound powder, 1.25kg / can, four cans planetary ball mill, the ball milling bead material is ZrO2, the ball-to-material ratio is 4:1, the rotation speed is 200r / min, the ball milling time is 3h, and the characteristic parameters of the powder are shown in Table 1; Table 1 Characteristic parameters of cemented carbide powder

[0028] (2) According to the required features of the formed part, a three-dimensional model is built on the computer and saved as an STL file. It is then imported into the construction software of the laser selective melting forming equipment for layer processing. The forming chamber substrate is made of stainless steel and the substrate is leveled. Then, the WC-AlCoCrFeNi hard alloy powder obtained in step (1) is loaded into the powder supply cylinder of the selective laser melting forming equipment. The powder is evenly spread on the forming substrate using a scraper, and the equipment door is closed. (3) Introduce a protective atmosphere and set the melting and forming parameters: continuously introduce high-purity argon gas (purity of 99.99wt%) for protection, control the oxygen content in the cavity to be less than 300ppm, and set the forming chamber pressure to 13-20Mpa; set the solid forming parameters: laser power of 180W, spot diameter of 100μm, scanning speed of 530mm / s, scanning interval of 50μm, powder layer thickness of 50μm, interlayer rotation of 67°, zigzag scanning, initial scanning direction of 0°, clockwise rotation of 67° for each layer, no partition scanning or other auxiliary scanning, and the overlap rate between melt channels of 50%; after melting and forming, clean the residual powder of the formed sample, and then separate the substrate and the part by wire cutting; use an electron microscope (TESCAN, GAIA3, Czech Republic), the microstructure morphology of the part obtained by laser selective melting is shown in the figure. Figure 1 As shown in (a) above, the porosity diagram of the laser selective melting formed part is as follows: Figure 3 As shown, a small number of porosity defects are visible in its structure; (4) The additive part was microwave-heated to 1400℃ in an argon protective atmosphere at a heating rate of 40℃ / min, held for 20min, cooled to 100℃ in the furnace, and then air-cooled to room temperature to obtain WC-AlCoCrFeNi cemented carbide; an electron microscope (TESCAN, GAIA3, Czech Republic) was used to examine the parts, such as... Figure 2 Image (a) shows the microstructure of WC-AlCoCrFeNi cemented carbide after heat treatment via laser selective melting, as shown in image (a). Figure 4 A porosity diagram of WC-AlCoCrFeNi cemented carbide after heat treatment by selective laser melting was obtained, showing that some pores were filled. The Vickers hardness, relative density, and average grain size of WC obtained by the WC-AlCoCrFeNi cemented carbide in the above embodiments are compared with those of the comparative example (Chen W, Yin Z, Yuan J. Microwavesintering of WC-HEA cemented carbide: Sintering process, microstructure and mechanical properties[J]. International Journal of Refractory Metals and HardMaterials, 2024, 123: 106789.) as shown in Table 2. Figure 1 , 3 (b) and Figure 5 As shown in Table 3, the porosity results before and after microwave heat treatment are as follows: Table 2 Results of Vickers hardness, relative density and WC average grain size of cemented carbide in Example 1

[0029] Table 3 Porosity of WC-AlCoCrFeNi cemented carbide before and after microwave heat treatment in Example 1

[0030] As can be seen from the above, in terms of grain shape, WC grains exhibit an elongated shape under laser selective melting (SDM), while WC grains after microwave heat treatment are angular polygons, triangles, or rectangular blocks. The biggest difference between SDM, traditional sintering, and microwave heat treatment lies in the cooling rate. SDM has a very high cooling rate, while traditional sintering has a longer holding time and a lower cooling rate. This is the main reason for the significant difference in WC grain shape between the two processes. The microwave heat treatment used in this invention has advantages such as fast heating, uniform temperature, low energy consumption, and environmental friendliness, which other heat treatment methods do not possess.

[0031] In terms of grain size, the average grain size of WC in WC-AlCoCrFeNi cemented carbide prepared by laser selective melting process is 0.60 μm. However, after microwave heat treatment, the average grain size of WC increased significantly to 2.09 μm. This is because during microwave heat treatment, WC grains agglomerate, and smaller, fragmented grains gradually aggregate and fuse to form larger grains, thus leading to a significant increase in the average grain size of WC. After microwave heat treatment, both the relative density and Vickers hardness improved to some extent. The increase in relative density was relatively small, with a 0.13% increase compared to before heat treatment. However, the increase in Vickers hardness was larger, with an 11.1% increase. From the perspective of relative density, the increase in Vickers hardness was not due to the densification of the sample. According to the Hall-Page relationship, grain coarsening leads to a decrease in hardness. After microwave heat treatment, the average grain size of WC in Example 1 increased significantly, but the Vickers hardness increased instead. Analysis of the microstructure revealed that the increase in hardness was mainly due to the change in the shape of the WC grains, from an unstable elongated shape to a stable, angular shape.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing low-porosity cemented carbide, characterized in that, The method involves sequentially subjecting the cemented carbide raw material to laser selective melting and microwave heat treatment, followed by cooling. The cemented carbide is WC-AlCoCrFeNi, and the mass content of AlCoCrFeNi in WC-AlCoCrFeNi is 10-14%.

2. The method for preparing low-porosity cemented carbide according to claim 1, characterized in that, In the laser selective melting and forming process: the laser power is 180-200W, the scanning speed is 530-640mm / s, and the energy density is 125-135J / mm². 3 The diameter of the light spot is 0.1 mm.

3. The method for preparing low-porosity cemented carbide according to claim 1, characterized in that, The conditions for microwave heat treatment are as follows: microwave frequency is 2450MHz, microwave power is 2kW, temperature control accuracy is ±1℃; maximum heat treatment temperature is 1400-1450℃, heating rate is 40-50℃ / min, and holding time is 20-25min.

4. The method for preparing low-porosity cemented carbide according to claim 1, characterized in that, The cemented carbide raw materials are W, C, Al, Co, Cr, Fe, and Ni; Wherein, the mass percentage of C is 5.5-6.0% of the total mass of WC-AlCoCrFeNi, the mass percentage of Al is 1.0-1.5% of the total mass of the cemented carbide raw material, the mass percentage of Co is 2.5-3.0% of the total mass of the cemented carbide raw material, the mass percentage of Cr is 2.0-2.5% of the total mass of the cemented carbide raw material, the mass percentage of Fe is 2.5-3.0% of the total mass of the cemented carbide raw material, the mass percentage of Ni is 2.5-3.0% of the total mass of the cemented carbide raw material, and the balance is W.

5. The method for preparing low-porosity cemented carbide according to claim 4, characterized in that, The mass percentage of C is 5.8% of the total mass of the cemented carbide raw material, the mass percentage of Al is 1.28% of the total mass of the cemented carbide raw material, the mass percentage of Co is 2.8% of the total mass of the cemented carbide raw material, the mass percentage of Cr is 2.47% of the total mass of the cemented carbide raw material, the mass percentage of Fe is 2.65% of the total mass of the cemented carbide raw material, the mass percentage of Ni is 2.79% of the total mass of the cemented carbide raw material, and the balance is W.

6. The method for preparing low-porosity cemented carbide according to claim 1, characterized in that, The particle size distribution range of the cemented carbide raw material is 50-150 μm; Among them, D10 is 50-60μm, D50 is 100-110μm, and D90 is 140-160μm.

7. The method for preparing low-porosity cemented carbide according to claim 1, characterized in that, The laser selective melting and forming process is carried out in an argon atmosphere with an oxygen content of less than 300 ppm.

8. The method for preparing low-porosity cemented carbide according to claim 1, characterized in that, In the laser selective melting forming process, the powder layer thickness can be 40-60μm, and the scanning interval is 40-50μm.

9. The method for preparing low-porosity cemented carbide according to claim 1, characterized in that, The cooling process involves in-furnace cooling for 2-3 hours.

10. The cemented carbide obtained by the method according to any one of claims 1-9.

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