Preparation method of whisker-coated graphene synergistically toughened cobalt-free cemented carbide material

Abstract

The invention discloses a preparation method of whisker-coated graphene synergistically toughened cobalt-free cemented carbide material, which uses single-phase carbide ceramics as hard phase, single-phase oxide ceramics as cobalt-substitute bonding phase, and Al 3+ An Al2O3 whisker precursor is prepared by ionization. By regulating the hydrothermal reaction conditions, it curls onto the graphene surface to form a whisker structure, forming a whisker-coated graphene synergistic phase as a toughening and reinforcing phase. This is then processed using a two-stage hot pressing sintering method. The single-phase carbide ceramic is WC; the single-phase oxide ceramic is Al2O3; and the whisker-coated graphene synergistic phase is an alumina whisker / graphene synergistic phase, an alumina whisker / graphene synergistic phase, or an alumina whisker / redox graphene synergistic phase. The cobalt-free cemented carbide tool material provided by the present invention exhibits excellent properties such as high hardness, high toughness, high flexural strength, high wear resistance, and high corrosion resistance.

Description

Technical Field

[0001] The invention belongs to composite material preparation technology, and specifically relates to a preparation method of whisker-coated graphene synergistically toughened cobalt-free cemented carbide material. Background Art

[0002] As a tool material, cemented carbide is widely used in cutting tools, drawing dies, and rock drilling tools. Traditional cemented carbide contains a metal binder phase (such as cobalt), which ensures the toughness and bending strength of the alloy, but reduces the hardness, wear resistance and chemical stability. Cobalt-free cemented carbide has excellent properties such as high hardness, high temperature resistance, oxidation resistance and corrosion resistance, and is one of the important development directions of cemented carbide.

[0003] However, low toughness is a common issue hindering the development of cobalt-free cemented carbide. To address this performance issue, currently available approaches include: 1) adding grain growth inhibitors to produce fine-grained cemented carbide; 2) adding whiskers to produce whisker-toughened cemented carbide; 3) adding fibers to produce fiber-toughened cemented carbide; and 4) adding carbon materials such as graphene and carbon nanotubes to produce carbon-toughened cemented carbide. However, no cobalt-free cemented carbide material has yet been found that meets these toughness requirements. For example, fiber and whisker toughening requires consideration of the inherent properties of the fibers or whiskers themselves. If their mechanical properties are poor or mismatched with the matrix, the desired toughening effect will not be achieved. Graphene-toughened cobalt-free cemented carbide materials have difficult interface control between graphene and tungsten carbide, resulting in low interface strength. Due to the large density difference between tungsten carbide powder and graphene, graphene is difficult to disperse evenly in tungsten carbide and other powders. Graphene has a large specific surface area, and van der Waals forces easily cause graphene to aggregate, severely weakening the effect of graphene on improving material properties. Summary of the Invention

[0004] In response to the deficiencies in the background technology, the present invention provides a method for preparing a whisker / graphene synergistically toughened cobalt-free cemented carbide material, which can achieve precise control of the interface between graphene and phases such as carbide, effectively solve the graphene agglomeration problem and the stratification problem during powder mixing, thereby ensuring the excellent performance of the cobalt-free cemented carbide material, such as high hardness, high toughness, high flexural strength, high wear resistance, and high corrosion resistance.

[0005] The technical solution adopted by the present invention is: a preparation method of whisker-coated graphene synergistically toughened cobalt-free cemented carbide material, which uses single-phase carbide ceramic as the hard phase, oxide ceramic as the cobalt-substitute bonding phase, and whisker-coated graphene synergistic phase as the toughening and reinforcing phase, and is prepared by a two-stage hot pressing and sintering process.

[0006] On the basis of the above scheme, as a preference, the graphene material is graphene or graphene oxide or redox graphene, and the whiskers are aluminum oxide whiskers (Al2O 3w), the graphene material is graphene or graphene oxide or redox graphene, and the whiskers are Al2O 3w The whiskers and the whisker-coated graphene synergistic phase are aluminum oxide whiskers / graphene synergistic phase, aluminum oxide whiskers / graphene oxide synergistic phase, and aluminum oxide whiskers / redox graphene synergistic phase.

[0007] On the basis of the above scheme, as a preferred method, the preparation process of the whisker / graphene synergistic phase is as follows: dimethylformamide is selected as a dispersant to ultrasonically disperse the graphene, and then hexadecyltrimethylammonium bromide is used for continuous ultrasonic treatment to form a graphene dispersion, which is then mixed with a diluted AlCl3 solution in distilled water, and the pH of the original solution containing graphene is adjusted to 9-10 with diluted NH3•H2O. After mixing, due to the heterogeneous coagulation reaction, the surface of the graphene is coated with a layer of hydrated aluminum oxide, and then a hydrothermal reaction is carried out to form a γ-AlOOH layered structure. The pH value is then adjusted so that the separated layered structure grows into a rod-shaped nanostructure through a curling growth mechanism, and after drying, a composite powder of a whisker-coated graphene structure is formed.

[0008] Whiskers have a certain aspect ratio, and graphene has a certain specific surface area. Both whiskers and graphene have excellent mechanical properties. In theory, whiskers and graphene can improve the toughness and strength of cobalt-free cemented carbide when introduced as phases. However, experiments have found that whiskers are prone to entanglement and agglomeration, and graphene is prone to stacking and agglomeration, resulting in poor dispersion, making it difficult to achieve the expected toughening and strengthening effects. 3w ) doped graphene as a synergistic strengthening phase, graphene has a large specific surface area and can be used as a 3w Provides a support, while Al2O 3w Distributed on the graphene surface, it can hinder the aggregation of graphene and increase the density of graphene to alleviate the problem of stratification and sedimentation, thereby significantly increasing the Al2O 3w -The contact area between graphene and ceramic phase; Experimental findings show that the use of in-situ alumina whiskers (Al2O 3w ), graphene, and WC powder as raw materials, and the in-situ alumina whiskers (Al2O 3w ) / graphene synergistic effect, to achieve precise control of the properties and performance of the interface between graphene and ceramics, and thus give full play to its toughening and strengthening effects on cobalt-free cemented carbide.

[0009] Based on the above solution, preferably, the single-phase carbide ceramic is WC.

[0010] Based on the above solution, preferably, the oxide ceramic is Al2O3 ceramic.

[0011] Based on the above solution, preferably, the mass fraction of the cobalt-substitute binder phase is 10-15%.

[0012] Based on the above solution, preferably, the single-phase carbide ceramic is in the form of powder with an average particle size of 300 to 600 nm.

[0013] Based on the above solution, preferably, the oxide ceramic is in the form of powder with an average particle size of 300 to 600 nm.

[0014] Based on the above scheme, preferably, the graphene is powder with an average thickness of 4 to 9 nm and an average diameter of 5 to 10 μm, and the whiskers are powder with an average diameter of 1 to 3 μm and an average aspect ratio of 10 to 15.

[0015] On the basis of the above scheme, as a preferred embodiment, the process of the two-stage hot pressing sintering method is: while the vacuum degree is maintained below 5 Pa, the temperature is raised to 1550-1650°C at 10-15°C / min, kept warm for 2-6 minutes, and then cooled to 1450-1500°C at 50-60°C / min and kept warm for 4-6 hours, and then cooled to 700-800°C at 50-60°C / min and then cooled with the furnace; during the period from room temperature to 700-800°C, the pressure of the applied pressure is maintained at 5-15MPa, and when from 700-800°C to 1400-1650°C, the pressure of the applied pressure is maintained at 35-45MPa.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention uses Al 3+ Ion preparation of Al2O 3w The precursor is made to curl up and form a whisker structure on the surface of graphene by regulating the hydrothermal reaction conditions to improve the surface state of graphene. Graphene has a large specific surface area and can be used as a precursor for Al2O 3w Provides a support, while Al2O 3w The aluminum oxide whiskers are distributed on the graphene surface to form a graphene structure, which can hinder the aggregation of graphene and significantly increase the Al2O 3w -The contact area between graphene and matrix phase, improve the properties of graphene / matrix interface, strengthen the in-situ Al2O 3w -Graphene synergistic toughening effect.

[0018] (2) The present invention selects WC as the hard phase, selects alumina as the cobalt-replacing binder phase, and selects in-situ alumina whiskers (Al2O 3w ) / graphene as the toughening and reinforcing phase, and a cobalt-free cemented carbide was prepared by two-stage hot pressing sintering, which overcomes the composition barrier of traditional tungsten-cobalt cemented carbide materials and has flexibility and applicability in microstructure control.

[0019] (3) The whisker / graphene synergistic toughening of cobalt-free cemented carbide tool materials prepared by the present invention can achieve in-situ aluminum oxide whiskers (Al2O 3w The whisker / graphene synergistic effect enables precise control of the properties and performance of the graphene-ceramic interface, thereby fully leveraging its toughening and strengthening effects on cobalt-free cemented carbide. Compared to traditional tungsten-cobalt cemented carbide, the hardness, toughness, flexural strength, and wear resistance of the cobalt-free cemented carbide are significantly enhanced by the whisker / graphene synergistic toughening.

[0020] (4) The two-stage hot pressing sintering method adopted in the present invention can achieve near-densification sintering of cobalt-free cemented carbide tool materials while ensuring fine grains. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 This is an SEM image of the microstructure of the whisker / graphene synergistically toughened WC-Al2O3 cobalt-free cemented carbide tool material in Example 1 of the present invention.

[0023] Figure 2 This is an SEM image of the microstructure of the whisker / graphene synergistically toughened WC-Al2O3 cobalt-free cemented carbide tool material in Example 2 of the present invention.

[0024] Figure 3 This is an SEM image of the fracture morphology of the whisker / graphene synergistically toughened WC-Al2O3 cobalt-free cemented carbide tool material in Example 1 of the present invention.

[0025] Figure 4 This is the X-ray diffraction pattern of the whisker / graphene synergistically toughened WC-Al2O3 cobalt-free cemented carbide tool material in Example 1 of the present invention.

[0026] Figure 5 This is the X-ray diffraction pattern of the whisker / graphene synergistically toughened WC-Al2O3 cobalt-free cemented carbide tool material in Example 2 of the present invention.

[0027] Figure 6 This is a Raman spectrum of the whisker / graphene synergistically toughened WC-Al2O3 cobalt-free cemented carbide tool material in Example 1 of the present invention.

[0028] Figure 7 This is a Raman spectrum of the whisker / graphene synergistically toughened WC-Al2O3 cobalt-free cemented carbide tool material in Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to examples, but the scope of the present invention is not limited thereto.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0031] As introduced in the background technology, cobalt-free cemented carbide tool materials have low toughness and are difficult to meet the requirements of high-speed cutting for excellent comprehensive performance of tools (high hardness, high toughness, etc.), which is a common problem restricting its development. The present invention proposes a preparation method for cobalt-free cemented carbide materials that are synergistically toughened by whiskers and graphene.

[0032] A typical embodiment of the present invention provides a method for preparing a whisker / graphene synergistically toughened cobalt-free cemented carbide material (especially a tool material), which is prepared by a two-stage hot pressing and sintering process using a single-phase carbide ceramic as the hard phase, an oxide ceramic as the cobalt-substitute binder phase, and a whisker / graphene synergistic phase as the toughening and reinforcing phase.

[0033] Wherein, the single-phase carbide ceramic is WC;

[0034] The oxide ceramic is Al2O3 ceramic;

[0035] The graphene material is graphene, graphene oxide, or redox graphene;

[0036] The whiskers are Al2O 3w The whiskers and the whisker-coated graphene synergistic phase are aluminum oxide whiskers / graphene synergistic phase, aluminum oxide whiskers / graphene oxide synergistic phase, and aluminum oxide whiskers / redox graphene synergistic phase.

[0037] In some embodiments, the mass fraction of the cobalt-substituted binder phase is 10-15%.

[0038] In some embodiments, the single-phase carbide ceramic is a powder with an average particle size of 300-600 nm.

[0039] In some embodiments, the oxide ceramic is in the form of powder with an average particle size of 300-600 nm.

[0040] In some embodiments, the graphene material is a powder with an average thickness of 4-9 nm and an average diameter of 5-10 μm.

[0041] In some embodiments, the whisker material is powder, has an average diameter of 1-3 μm, and an average aspect ratio of 10-15.

[0042] In some embodiments, the process of the two-stage hot pressing sintering method is as follows: while maintaining the vacuum degree below 5 Pa, the temperature is raised to 1550~1650°C at 10~15°C / min, kept at this temperature for 2~6 minutes, and then cooled to 1450~1500°C at 50~60°C / min and kept at this temperature for 4~6 hours, and then cooled to 700~800°C at 50~60°C / min and then cooled with the furnace; from room temperature to 700~800°C, the pressure of the applied pressure is maintained at 5~15MPa, and from 700~800°C to 1400~1650°C, the pressure of the applied pressure is maintained at 35~45MPa.

[0043] In some embodiments, carbide ceramic powder and substitute "cobalt" oxide ceramic powder are dry-ground to obtain composite powder, whiskers and graphene powder are placed in anhydrous ethanol to ultrasonically disperse the suspension, and then the above suspension and the above composite powder are placed in a mixed solution of anhydrous ethanol and polyethylene glycol for ball milling, and then filtered and vacuum-dried to obtain whisker / graphene synergistically toughened cobalt-free cemented carbide powder, and the whisker / graphene synergistically toughened cobalt-free cemented carbide powder is processed by two-stage hot pressing sintering.

[0044] In some embodiments, WC and Al2O3 composite powders are ball-milled separately for 50 hours, graphene and whiskers are mixed to obtain a graphene / whisker synergistic suspension, and then the suspension, WC, and Al2O3 composite powders are mixed, and 10 vol% polyethylene glycol (molecular weight 200) is mixed with anhydrous ethanol as a dispersant, and planetary ball milling is continued for 4 hours, and finally vacuum drying is performed; a two-stage hot pressing sintering is used to treat the whiskers and graphene synergistically toughened cobalt-free cemented carbide powder.

[0045] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments. Example 1

[0046] Few-layer graphene with an area size of 0.5 μm and an addition amount of 0.4 wt% to the total weight of the composite powder was selected. 1 mg / mL dimethylformamide was used as a dispersant for ultrasonic dispersion at 40°C for 1 hour. Subsequently, the graphene dispersion was formed by continuous ultrasonic treatment with 2 wt% hexadecyltrimethylammonium bromide for 0.5 hours and mechanical ball milling for 1 hour. The dispersed graphene was then mixed with a dilute AlCl₃ solution (0.3 mol / L) in distilled water. The pH of the original graphene-containing solution was adjusted to 9-10 with diluted NH₃•H₂O to promote the coagulation process. After mixing, due to the heterogeneous coagulation reaction, the graphene surface is coated with a layer of hydrated alumina, and then a hydrothermal reaction is carried out at 80°C for 24 hours to form a γ-AlOOH layered structure. The pH value is then adjusted (<5) to allow the separated layered structure to grow into a rod-shaped nanostructure through a curling growth mechanism. After drying, a composite powder with a whisker-coated graphene structure is formed.

[0047] WC and Al2O3 with a mass fraction of 14% were ball-milled separately for 50 hours, and then the whisker-coated graphene, WC, and Al2O3 composite powders were mixed. 10 vol% polyethylene glycol (molecular weight 200) was mixed with anhydrous ethanol as a dispersant, and planetary ball milling was continued for 4 hours. Finally, vacuum drying was performed and then passed through a 120-mesh sieve to obtain the composite powder to be sintered.

[0048] A two-stage hot-pressing sintering process was used to synergistically toughen cobalt-free cemented carbide powder with whiskers and graphene. The two-stage hot-pressing sintering process involved heating to 1600°C at a rate of 13°C / min, holding for 4 minutes, then cooling to 1455°C at a rate of 55°C / min and holding for 5.5 hours. Cooling to 750°C at a rate of 55°C / min was then performed, followed by furnace cooling. From room temperature to 800°C, the applied pressure was maintained at 10.5 MPa, and from 800°C to 1600°C, the applied pressure was maintained at 40 MPa.

[0049] After the sintering process is completed, the hard phase of the whisker / graphene synergistic toughening cobalt-free cemented carbide tool material can be obtained, and its mechanical properties are: Vickers hardness HV 30 18.34 GPa, fracture toughness 11.02 MPa·m 1 / 2 , flexural strength 1340MPa. Example 2

[0050] Few-layer graphene with an area size of 0.5 μm and an addition amount of 0.8 wt% of the total composite powder mass was selected. 1 mg / mL dimethylformamide was used as a dispersant for ultrasonic dispersion at 40°C for 1 hour. Subsequently, the graphene dispersion was formed by continuous ultrasonic treatment with 2 wt% hexadecyltrimethylammonium bromide for 0.5 hours and mechanical ball milling for 1 hour. The dispersed graphene was then mixed with a dilute AlCl₃ solution (0.3 mol / L) in distilled water. The pH of the original graphene-containing solution was adjusted to 9-10 with diluted NH₃•H₂O to promote the coagulation process. After mixing, due to the heterogeneous coagulation reaction, the graphene surface is coated with a layer of hydrated alumina, and then a hydrothermal reaction is carried out at 80°C for 24 hours to form a γ-AlOOH layered structure. The pH value is then adjusted (<5) to allow the separated layered structure to grow into a rod-shaped nanostructure through a curling growth mechanism. After drying, a composite powder with a whisker-coated graphene structure is formed.

[0051] WC and Al2O3 with a mass fraction of 14% were ball-milled separately for 50 hours, and then the whisker-coated graphene, WC, and Al2O3 composite powders were mixed. 10 vol% polyethylene glycol (molecular weight 200) was mixed with anhydrous ethanol as a dispersant, and planetary ball milling was continued for 4 hours. Finally, vacuum drying was performed and then passed through a 120-mesh sieve to obtain the composite powder to be sintered.

[0052] A two-stage hot-pressing sintering process was used to synergistically toughen cobalt-free cemented carbide powder with whiskers and graphene. The two-stage hot-pressing sintering process involved heating to 1600°C at a rate of 13°C / min, holding for 4 minutes, then cooling to 1455°C at a rate of 55°C / min and holding for 5.5 hours. Cooling to 750°C at a rate of 55°C / min was then performed, followed by furnace cooling. From room temperature to 800°C, the applied pressure was maintained at 10.5 MPa, and from 800°C to 1600°C, the applied pressure was maintained at 40 MPa.

[0053] After the sintering process is completed, the hard phase of the whisker / graphene synergistic toughening cobalt-free cemented carbide tool material can be obtained, and its mechanical properties are: Vickers hardness HV 30 17.89 GPa, fracture toughness 10.83 MPa·m 1 / 2 , flexural strength 1275 MPa.

[0054] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it is not intended that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications having the same function.

Claims

1. A method for preparing a whisker-coated graphene synergistically toughened cobalt-free cemented carbide material, characterized in that: The material is prepared by a two-stage hot pressing sintering process using single-phase carbide ceramics as the hard phase, oxide ceramics as the cobalt-substituting bonding phase, and whisker-coated graphene material as the synergistic phase for toughening and reinforcing. The preparation process of the whisker / graphene synergistic phase involves ultrasonically dispersing graphene using dimethylformamide as a dispersant. Subsequently, hexadecyltrimethylammonium bromide is continuously ultrasonically treated to form a graphene dispersion. This dispersion is then mixed with a diluted AlCl3 solution in distilled water. The pH of the original graphene-containing solution is adjusted to 9-10 using diluted NH3·H2O. After mixing, a layer of hydrated aluminum oxide is coated on the graphene surface due to a heterogeneous coagulation reaction. A hydrothermal reaction then occurs to form a γ-AlOOH layered structure. The pH is then adjusted to <5, allowing the separated layered structures to grow into rod-shaped nanostructures through a curling growth mechanism. After drying, a composite powder with a whisker-coated graphene structure is formed.

2. The method for preparing whisker-coated graphene synergistically toughened cobalt-free cemented carbide material according to claim 1, wherein: The graphene material is graphene or graphene oxide or redox graphene, the whiskers are Al2O3 whiskers, and the whisker-coated graphene synergistic phase is aluminum oxide whisker / graphene synergistic phase, aluminum oxide whisker / graphene oxide synergistic phase, and aluminum oxide whisker / redox graphene synergistic phase.

3. The method for preparing whisker-coated graphene synergistically toughened cobalt-free cemented carbide material according to claim 1, wherein: Single-phase carbide ceramics are WC.

4. The method for preparing whisker-coated graphene synergistically toughened cobalt-free cemented carbide material according to claim 1, wherein: The oxide ceramic is Al2O3 ceramic.

5. The method for preparing whisker-coated graphene synergistically toughened cobalt-free cemented carbide material according to claim 1, wherein: The mass fraction of the cobalt-substitute binder phase is 10-15%.

6. The method for preparing whisker-coated graphene synergistically toughened cobalt-free cemented carbide material according to claim 1, characterized in that: The single-phase carbide ceramic is a powder with an average particle size of 300 to 600 nm.

7. The method for preparing whisker-coated graphene synergistically toughened cobalt-free cemented carbide material according to claim 1, characterized in that: The oxide ceramic is in the form of powder with an average particle size of 300 to 600 nm.

8. The method for preparing whisker-coated graphene synergistically toughened cobalt-free cemented carbide material according to claim 1, characterized in that: The graphene is in the form of powder, with an average thickness of 4 to 9 nm and an average diameter of 5 to 10 μm. The whiskers are in the form of powder, with an average diameter of 1 to 3 μm and an average aspect ratio of 10 to 15.

9. The method for preparing whisker-coated graphene synergistically toughened cobalt-free cemented carbide material according to claim 1, characterized in that: The process of the two-stage hot pressing sintering method is as follows: while the vacuum degree is maintained below 5Pa, the temperature is raised to 1550-1650°C at 10-15°C / min, kept warm for 2-6 minutes, and then cooled to 1450-1500°C at 50-60°C / min and kept warm for 4-6 hours, and then cooled to 700-800°C at 50-60°C / min and then cooled with the furnace; from room temperature to 700-800°C, the pressure of the applied pressure is maintained at 5-15MPa, and from 700-800°C to 1400-1650°C, the pressure of the applied pressure is maintained at 35-45Mpa.

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