A method of infiltrating diamond nanoparticles into a cemented carbide and the composite material produced thereby

Abstract

The present application relates to a kind of diamond nanoparticles infiltrates the method for reinforcing hard alloy and the composite material made, belongs to hard alloy strengthening field.The method is first mixed, dry screen powder by ball milling under argon protection to WC, Co, VC powder, then preliminary WC-Co hard alloy sample is prepared by spark plasma sintering process.The key step is to uniformly coat nano diamond dispersion liquid after the surface of sintered sample is polished, and cover protection plate, be placed in the crucible covered with diamond powder, in argon atmosphere, stage heating to 1250 DEG C and heat preservation 3h are carried out heat treatment, so that diamond nanoparticles infiltrate matrix, finally by ultrasonic cleaning to remove residue.The method significantly improves the hardness of hard alloy, the sample after processing significantly increases the vickers hardness compared with untreated sample without reducing core fracture toughness, effectively enhances the wear resistance of material, process is simple and controllable, suitable for high stress working condition tool material.

Description

Technical Field

[0001] The present invention relates to the field of hard alloy strengthening, and particularly relates to a method for enhancing a hard alloy by diamond nanoparticle infiltration and a composite material obtained thereby. Background Art

[0002] Due to its excellent hardness, wear resistance, strength, as well as good heat resistance and corrosion resistance, hard alloy is widely used in high-stress and high-wear working condition fields such as cutting tools, molds, and mining tools. Among them, hardness and fracture toughness, as core performance indicators, directly determine the wear resistance and service life of the material under harsh service conditions. Traditional hard alloys are restricted by the problem that hardness and toughness cannot be兼顾 simultaneously (that is, high hardness means low toughness, and high toughness means low hardness), which restricts their service performance and thus cannot meet the development needs of today's industry. Therefore, how to increase hardness without changing fracture toughness has become an urgent problem to be solved.

[0003] There has been no public report on the research and practice of applying diamond nanoparticle infiltration technology to hard alloys (especially the tungsten carbide-cobalt (WC-Co) system) to improve their comprehensive performance. Hard alloy has a complex multiphase structure different from pure metals (hard phase tungsten carbide (WC) and binder phase cobalt (Co)), as well as higher melting points and sintering temperatures. There are unknown challenges in the infiltration behavior, strengthening mechanism, and process adaptability of diamond nanoparticles inside it. Summary of the Invention

[0004] The technical problem to be solved by the present invention is how to solve the problem of poor hardness and toughness existing in existing hard alloy materials.

[0005] The present invention solves the above technical problems through the following technical means:

[0006] The first aspect of the present invention proposes a method for enhancing a hard alloy by diamond nanoparticle infiltration, including the following steps: (1) Load tungsten carbide (WC), cobalt (Co), and vanadium carbide (VC) into a ball milling tank; inject absolute ethanol; after filling with inert gas, seal the tank body, ball mill, dry, screen, put it into a mold for pre-pressing, and then sinter to obtain a preliminary sample; (2) Disperse nano-diamond particles in water and ultrasonicate to obtain a nano-diamond dispersion; evenly apply the nano-diamond dispersion on the preliminary sample, sinter, and ultrasonicate to obtain a strengthened sample.

[0007] WC: Chinese name is tungsten carbide, CAS registration number 12070-12-1.

[0008] Co: Chinese name is cobalt, CAS registration number 7440-48-4.

[0009] VC: Its Chinese name is vanadium carbide, and its CAS number is 12070-10-9.

[0010] Preferably, in step (1), the mass ratio of tungsten carbide, cobalt, and vanadium carbide is (45~48):(2.5~3.5):(0.1~0.3); more preferably, it is 46.8:3.0:0.2.

[0011] Preferably, the particle size of tungsten carbide in step (1) is selected as 0.3~0.5µm, the particle size of cobalt is selected as 0.8~1.2µm, and the particle size of vanadium carbide is selected as 0.05~0.15µm; more preferably, the particle size of tungsten carbide is selected as 0.4µm, the particle size of cobalt is selected as 1µm, and the particle size of vanadium carbide is selected as 0.1µm.

[0012] Preferably, in step (1), grinding balls are added to the ball mill jar, and anhydrous ethanol is injected to immerse the powder and grinding balls.

[0013] Preferably, the grinding ball is a cemented carbide grinding ball.

[0014] Preferably, the grinding balls are a mixture of φ7mm and φ8mm small balls; more preferably, the mass ratio of the φ7mm and φ8mm small balls is 1:1.

[0015] Preferably, the ratio of the mass of the grinding ball to the total mass of tungsten carbide, cobalt, and vanadium carbide (i.e., the ball-to-material ratio) is (5~7):1.

[0016] Preferably, in step (1), filling with inert gas specifically involves moving the ball mill jar into an argon glove box, where vacuuming and argon replacement are performed.

[0017] Preferably, in step (1), ball milling specifically refers to wet ball milling performed on a planetary ball mill.

[0018] Preferably, in step (1), the ball milling conditions are: time of 22-26 hours and ball milling speed of 230-270 r / min; more preferably 24 hours and 250 r / min.

[0019] Preferably, the drying in step (1) is specifically drying in a vacuum drying oven.

[0020] Preferably, the drying conditions are: temperature 70~90℃, time 5~7 hours; more preferably 80℃, 6 hours.

[0021] Preferably, in step (1), the mesh size of the sieve is 80~120 mesh (i.e. 0.125~0.180mm); more preferably, it is 100 mesh (i.e. 0.150mm).

[0022] Preferably, in step (1), the mold is a graphite mold with a diameter of 15~30mm, more preferably 20mm.

[0023] Preferably, the pre-compression in step (1) is 15~25MPa; more preferably 20MPa.

[0024] Preferably, in step (1), the sintering specifically refers to discharge plasma sintering after vacuuming.

[0025] Preferably, in step (1), the sintering conditions are as follows: first, the temperature is raised from room temperature to 500-700℃ in 7-9 minutes, held at 500-700℃ for 4-6 minutes, and the pressure is slowly increased to 30-50 MPa during the holding process, the temperature is raised to 1100-1200℃ at 90-110℃ / min, and then raised to 1250-1350℃ at 10℃ / min, and held for 4-6 minutes; more preferably, the temperature is raised from room temperature to 600℃ in 8 minutes, held at 600℃ for 5 minutes, and the pressure is slowly increased to 40 MPa during the holding process, the temperature is raised to 1200℃ at 100℃ / min, and then raised to 1250℃ at 10℃ / min, and held for 5 minutes.

[0026] Preferably, in step (2), the ultrasound is performed for 2 to 4 hours, and more preferably for 3 hours.

[0027] Preferably, in step (2), the concentration of the nanodiamond dispersion is 0.1~0.3g / ml.

[0028] Preferably, in step (2), the preliminary sample is pretreated by grinding, mirror polishing and cleaning the surface of the preliminary sample.

[0029] Preferably, in step (2), before sintering, a layer of hard alloy sheet is placed on top of the sample, the sample is placed in a crucible and covered with diamond powder.

[0030] Preferably, in step (2), the sintering conditions are as follows: heating to 900-1000°C at a rate of 9-11°C / min under an argon atmosphere, then heating to 1200-1300°C at a rate of 4-6°C / min, maintaining the target temperature for 2-4 hours, and then cooling to room temperature in the furnace; more preferably, heating to 1000°C at a rate of 10°C / min under an argon atmosphere, then heating to 1250°C at a rate of 5°C / min, maintaining the target temperature for 3 hours, and then cooling to room temperature in the furnace.

[0031] Preferably, in step (2), the ultrasound is specifically performed in ethanol for 20 to 40 minutes; more preferably, for 30 minutes.

[0032] A second aspect of the present invention provides a cemented carbide composite material prepared by the above method.

[0033] The beneficial effects of this invention are as follows: (1) This invention modifies the surface of WC-6Co cemented carbide by introducing a diamond nanoparticle infiltration process. During the heat treatment process, the particles are uniformly distributed on the surface of the cemented carbide, which effectively improves the hardness of the cemented carbide. The hardness and fracture toughness of the obtained cemented carbide sample can reach 2393.6 HV and 10.25 MPa·m, respectively. 1 / 2 Compared to the sample without heat treatment (2301.1 HV and 10.08 MPa·m), 1 / 2 Without sacrificing the fracture toughness of the sample core, the Vickers hardness was significantly improved compared to the untreated sample.

[0034] (2) This process can be implemented without relying on complex equipment, and has good process adaptability and scalability. It can be effectively extended to various cemented carbide systems such as WC-TiC. This technology provides a highly versatile solution for the design and preparation of tool materials under high stress conditions. While ensuring the high hardness of the material, it significantly improves its wear resistance, thus providing a reliable technical path for the service performance and life of tools under extreme conditions.

[0035] (3) This method first involves ball milling and mixing WC, Co, and VC powders under argon protection, followed by drying and sieving. Then, a preliminary WC-Co cemented carbide sample is prepared by spark plasma sintering. The key step is to uniformly coat the sintered sample with a nano-diamond dispersion and cover it with a protective plate. The sample is then placed in a crucible covered with diamond powder and heat-treated in stages to 1250℃ under an argon atmosphere for 3 hours to allow the diamond nanoparticles to penetrate the matrix. Finally, the residue is removed by ultrasonic cleaning. This method significantly improves the hardness of cemented carbide. The treated sample shows a significantly higher Vickers hardness than the untreated sample without reducing the core fracture toughness, effectively enhancing the wear resistance of the material. The process is simple and controllable, and suitable for tool materials under high stress conditions.

[0036] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0037] Figure 1 The image shows the microstructure and energy dispersive spectroscopy (EDS) of the cemented carbide composite material in Example 1 of this invention. Figure 2 The image shows the microstructure and energy dispersive spectroscopy (EDS) of the cemented carbide composite material in Comparative Example 1. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art.

[0039] Unless otherwise specified, the test materials and reagents used in the following examples are commercially available or prepared by known methods.

[0040] Unless otherwise specified, all techniques or conditions described in the embodiments can be performed in accordance with the techniques or conditions described in the literature in this field or in the product manual. Unless otherwise specified, the quantitative experiments in the following embodiments are all repeated three times or more, and the results are averaged.

[0041] Example 1: A method for reinforcing cemented carbide with diamond nanoparticles includes the following steps: (1) Preparation of preliminary samples: S1 Ball Milling: The following ingredients were prepared: 46.8g WC powder, 3.0g Co powder, and 0.2g VC powder (WC particle size selected as 0.4µm, Co particle size selected as 1µm, and VC particle size selected as 0.1µm). Carbide grinding balls were added, and anhydrous ethanol was used as the medium to immerse the powder and grinding balls. The ball-to-powder ratio was 6:1. The mixture was placed in a ball mill jar, which was then transferred to an argon-filled glove box. After vacuuming and argon purging within the box, the jar was sealed and removed. Finally, wet ball milling was performed for 24 hours on a planetary ball mill at a speed of 250 rpm.

[0042] S2 Drying: Dry the ball-milled mixture at 80℃ for 6 hours.

[0043] S3 Sieving: The dried composite powder is sieved through a 100-mesh sieve.

[0044] S4 Sintering: The sieved powder is placed into a mold and pre-pressed using a hydraulic press. Then, it is placed in a sintering furnace, and the air inside is evacuated. Subsequently, spark plasma sintering is performed. The pre-pressure is 20 MPa. The temperature is first increased from room temperature to 600°C in 8 minutes, held at 600°C for 5 minutes, and then the pressure is slowly increased to 40 MPa. The temperature is then increased to 1200°C at a rate of 100°C / min, and then to 1250°C at a rate of 10°C / min, and held for 5 minutes. Finally, the sample is cooled in the furnace to obtain a preliminary sample.

[0045] (2) Apply diamond particles: Preliminary sample surface pretreatment: Take out the preliminary sample and grind, mirror polish and clean the surface; Coating: Nanodiamond particles were dispersed in water and ultrasonically dispersed for 3 hours to obtain a nanodiamond dispersion. The well-dispersed nanodiamond dispersion (concentration 0.2 g / ml) was uniformly coated onto the preliminary sample, and a layer of cemented carbide sheet was placed on top for protection. The sample was placed in an alumina crucible and covered with diamond powder to prevent oxidation. The crucible was transferred to a tube furnace and heated to 1000℃ at a rate of 10℃ / min under an argon atmosphere, then heated to 1250℃ at a rate of 5℃ / min, maintaining the target temperature for 3 hours. The sample was then cooled to room temperature in the furnace. Afterward, the reinforced sample was removed and ultrasonicated in ethanol for 30 minutes to remove residual diamond nanoparticles and other contaminants, yielding a cemented carbide composite material. (The microstructure and energy dispersive spectroscopy of the prepared cemented carbide composite material are shown in the figure.) Figure 1 (As shown) Example 2: The difference between this embodiment and embodiment 1 is that in step (2), the concentration of the nanodiamond dispersion is 0.1 g / ml, and the rest is the same as in embodiment 1.

[0046] Example 3: The difference between this embodiment and embodiment 1 is that in step (2), the concentration of the nanodiamond dispersion is 0.3 g / ml, and the rest is the same as in embodiment 1.

[0047] Example 4: The difference between this embodiment and embodiment 1 is that in step (2), the temperature is heated to 1200°C at a rate of 5°C / min, and the rest is the same as in embodiment 1.

[0048] Example 5: The difference between this embodiment and embodiment 1 is that in step (2), the temperature is heated to 1300°C at a rate of 5°C / min, and the rest is the same as in embodiment 1.

[0049] Example 6: A method for reinforcing cemented carbide with diamond nanoparticles includes the following steps: (1) Preparation of preliminary samples: S1 Ball Milling: Prepare the following mixture: 45g WC powder, 2.5g Co powder, and 0.1g VC powder (WC particle size selected: 0.5µm, Co particle size: 1.2µm, VC particle size: 0.15µm). Add cemented carbide grinding balls, and immerse the powder and grinding balls in anhydrous ethanol at a ball-to-powder ratio of 5:1. Place the mixture in a ball mill jar and transfer the jar to an argon-filled glove box. After vacuuming and purging with argon gas inside the box, seal the jar and remove it. Finally, perform wet ball milling for 22 hours on a planetary ball mill at a speed of 270 rpm.

[0050] S2 Drying: Dry the ball-milled mixture at 70℃ for 7 hours.

[0051] S3 Sieving: The dried composite powder is sieved through a 120-mesh sieve.

[0052] S4 Sintering: The sieved powder is placed into a mold and pre-pressed using a hydraulic press. Then, it is placed in a sintering furnace, and the air inside is evacuated. Subsequently, spark plasma sintering is performed. The pre-pressure is 15 MPa. The temperature is first increased from room temperature to 700℃ over 7 minutes, held at 700℃ for 4 minutes, and then the pressure is slowly increased to 30 MPa. The temperature is then increased to 1100℃ at 90℃ / min, and then to 1300℃ at 10℃ / min, held for 6 minutes. Finally, the sample is cooled in the furnace to obtain a preliminary sample.

[0053] (2) Apply diamond particles: Preliminary sample surface pretreatment: Take out the preliminary sample and grind, mirror polish and clean the surface; Coating: Nanodiamond particles were dispersed in water and ultrasonically dispersed for 2 hours to obtain a nanodiamond dispersion. The well-dispersed nanodiamond dispersion (concentration 0.2 g / ml) was uniformly coated onto the preliminary sample, and a layer of cemented carbide sheet was placed on top for protection. The sample was placed in an alumina crucible and covered with diamond powder to prevent oxidation. The crucible was transferred to a tube furnace and heated to 900°C at a rate of 9°C / min under an argon atmosphere, then heated to 1200°C at a rate of 4°C / min, and maintained at the target temperature for 4 hours. The sample was then cooled to room temperature in the furnace. Afterward, the reinforced sample was removed and ultrasonicated in ethanol for 20 minutes to remove residual diamond nanoparticles and other contaminants, resulting in a cemented carbide composite material.

[0054] Example 7: A method for reinforcing cemented carbide with diamond nanoparticles includes the following steps: (1) Preparation of preliminary samples: S1 Ball Milling: Prepare the following mixture: 48g WC powder, 3.5g Co powder, and 0.3g VC powder (WC particle size selected: 0.3µm, Co particle size: 0.8µm, VC particle size: 0.05µm). Add cemented carbide grinding balls, using anhydrous ethanol as the medium to immerse the powder and grinding balls (powder-to-powder ratio: 7:1). Place the mixture in a ball mill jar and transfer the jar to an argon-filled glove box. After vacuuming and argon purging within the box, seal the jar and remove it. Finally, perform wet ball milling for 26 hours on a planetary ball mill at a speed of 230 rpm.

[0055] S2 Drying: Dry the ball-milled mixture at 90℃ for 5 hours.

[0056] S3 Sieving: The dried composite powder is sieved through an 80-mesh sieve.

[0057] S4 Sintering: The sieved powder is placed into a mold and pre-pressed using a hydraulic press. Then, it is placed in a sintering furnace, and the air inside is evacuated. Subsequently, spark plasma sintering is performed. The pre-pressure is 25 MPa. The temperature is first increased from room temperature to 500°C in 9 minutes, held at 500°C for 6 minutes, and then the pressure is slowly increased to 50 MPa. The temperature is then increased to 1200°C at 110°C / min, and then to 1250°C at 10°C / min, held for 4 minutes. Finally, the sample is cooled in the furnace to obtain a preliminary sample.

[0058] (2) Apply diamond particles: Preliminary sample surface pretreatment: Take out the preliminary sample and grind, mirror polish and clean the surface; Coating: Nanodiamond particles were dispersed in water and ultrasonically dispersed for 4 hours to obtain a nanodiamond dispersion. The well-dispersed nanodiamond dispersion (concentration 0.2 g / ml) was uniformly coated onto the preliminary sample, and a layer of cemented carbide sheet was placed on top for protection. The sample was placed in an alumina crucible and covered with diamond powder to prevent oxidation. The crucible was transferred to a tube furnace and heated to 1000°C at a rate of 11°C / min under an argon atmosphere, then heated to 1300°C at a rate of 6°C / min, and held at the target temperature for 2 hours. The sample was then cooled to room temperature in the furnace. After that, the reinforced sample was removed and ultrasonicated in ethanol for 40 minutes to remove residual diamond nanoparticles and other contaminants, resulting in a cemented carbide composite material.

[0059] Comparative Example 1: Infiltration process without nanodiamond particles S1 Ball Milling: Prepare the following mixture: WC 46.8g, Co 3g, VC 0.2g, using anhydrous ethanol as the medium. The ball-to-material ratio is 6:1. Place the mixture into a ball mill jar and transfer the jar into an argon glove box. After vacuuming and purging with argon gas inside the box, seal the jar and remove it. Finally, perform wet ball milling for 24 hours on a planetary ball mill at a speed of 250 rpm.

[0060] S2 Drying: Dry the ball-milled mixture at 80℃ for 6 hours.

[0061] S3 Sieving: The dried composite powder is sieved through a 100-mesh sieve.

[0062] S4 Sintering: The sieved powder is placed into a mold and pre-pressed using a hydraulic press. Then, it is placed in a sintering furnace, and the air inside is evacuated. Subsequently, spark plasma sintering is performed. The pre-pressure is 20 MPa. The temperature is first increased from room temperature to 600°C over 8 minutes, held at 600°C for 5 minutes, and then the pressure is slowly increased to 40 MPa. The temperature is then increased to 1200°C at a rate of 100°C / min, and then to 1250°C at a rate of 10°C / min, held for 5 minutes. Finally, the material is cooled in the furnace. (The microstructure and energy dispersive spectroscopy (EDS) of the obtained material are shown in the figure.) Figure 2 (As shown) Table 1 Performance test results of Examples 1-5 and Comparative Example 1

[0063] As shown in Table 1, the diamond nanoparticle infiltration process (step (2)) significantly improves the performance of cemented carbide: when the VC content is 0.4% and the heat treatment temperature is 1250℃, the Vickers hardness of the sample treated in step (2) (Example 1) reaches 2393.6 HV, which is 92.5 HV higher than the untreated group (Comparative Example 1) without sacrificing the fracture toughness of the sample core. Moreover, comparing the various experiments, the nanodiamond dispersion at a heat treatment temperature of 1250℃ and a concentration of 0.2 g / ml has the best effect.

[0064] This is because when the concentration is low, the number of nanodiamond particles coated on the sample surface is small. Even if they are evenly dispersed by ultrasound for 3 hours, the total amount of "reinforcing phase" that can migrate into the matrix during the heat treatment is limited, and it is impossible to form dense and uniform reinforcing sites in the WC-Co matrix. When the concentration is high, the van der Waals forces and hydrogen bonds between particles are significantly enhanced. Due to agglomeration, the diamond particles cannot migrate into the matrix through heat treatment. Most of them are only attached to the sample surface, and subsequent ultrasonic cleaning with ethanol (30 min) will remove them. The actual number of "effective particles" participating in the reinforcement does not increase proportionally with the concentration.

[0065] At lower temperatures, the atomic thermal motion intensity of nanodiamond particles is insufficient to effectively overcome the interfacial resistance of the WC-Co matrix, resulting in shallow penetration depth and a narrow range. Most particles merely adhere to the sample surface (easily removed by subsequent ultrasonic cleaning), and the number of "effective particles" actually participating in the strengthening process is small. At higher temperatures, abnormal growth of WC grains is promoted, leading to a decrease in hardness. This process achieves a breakthrough in hardness improvement, providing a solution for high-stress cutting / mining tools that combines high hardness and reliability.

[0066] 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 reinforcing cemented carbide with diamond nanoparticles, characterized in that, This includes the following steps: (1) Tungsten carbide, cobalt and vanadium carbide are loaded into a ball mill jar; anhydrous ethanol is injected; after filling with inert gas, the jar is sealed, ball milled, dried, sieved, placed in a mold for pre-pressing, and then sintered to obtain a preliminary sample; (2) Disperse the nanodiamond particles in water and sonicate to obtain a nanodiamond dispersion; apply the nanodiamond dispersion evenly to the preliminary sample, sinter, and sonicate to obtain the final product.

2. The method according to claim 1, characterized in that, In step (1), the mass ratio of tungsten carbide, cobalt, and vanadium carbide is (45~48):(2.5~3.5):(0.1~0.3).

3. The method according to claim 1, characterized in that, In step (1), the particle size of tungsten carbide is selected as 0.3~0.5µm, the particle size of cobalt is selected as 0.8~1.2µm, and the particle size of vanadium carbide is selected as 0.05~0.15µm.

4. The method according to claim 1, characterized in that, The ball milling conditions are: time 22~26h, ball milling speed 230~270r / min.

5. The method according to claim 1, characterized in that, In step (1), the pre-compression is 15~25MPa.

6. The method according to claim 1, characterized in that, In step (1), the sintering conditions are as follows: first, the temperature is raised from room temperature to 500-700℃ in 7-9 minutes, and then held at 500-700℃ for 4-6 minutes. During the holding process, the pressure is slowly increased to 30-50 MPa, the temperature is raised to 1100-1200℃ at 90-110℃ / min, and then raised to 1250-1350℃ at 10℃ / min, and held for 4-6 minutes.

7. The method according to claim 1, characterized in that, In step (2), the ultrasound is performed for 2 to 4 hours.

8. The method according to claim 1, characterized in that, In step (2), the concentration of the nanodiamond dispersion is 0.1~0.3g / ml.

9. As described in claim 1, characterized in that, The sintering conditions are as follows: heating to 900-1000°C at a rate of 9-11°C / min under an argon atmosphere, then heating to 1200-1300°C at a rate of 4-6°C / min, maintaining the target temperature for 2-4 hours, and then cooling to room temperature in the furnace.

10. The diamond nanoparticle-infiltrated reinforced cemented carbide composite material obtained by the method of any one of claims 1-9.

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