Preparation method of Ni-CNTs / WC-based composite spraying powder and related powder of Ni-CNTs / WC-based composite spraying powder

Abstract

The invention discloses a preparation method of Ni-CNTs / WC-based composite spraying powder for spraying and related powder of the Ni-CNTs / WC-based composite spraying powder. The preparation method of the composite spraying powder comprises the steps of preparation of nickel-coated carbon nanotube particles, preparation of mixed slurry and preparation of spraying powder. In the preparation of the nickel-coated carbon nanotube particles, the surface of the carbon nanotube is coated with nickel by adopting a microwave method, so that the wettability with a matrix is improved, and the interface bonding is enhanced; according to the Ni-CNTs / WC-based composite powder prepared through the method, the carbon nanotubes are evenly distributed, the content is controllable, powder particles are compact, the sphericity degree is good, the surface quality is high, the problem that the carbon nanotubes are prone to agglomeration is solved, and the method which is easy and convenient to operate and low in cost is provided for preparation of CNTs enhanced WC-Co, WC-Ni, WC-CoCr and other system composite spraying powder and coatings.

Description

Technical Field

[0001] This invention relates to a method for preparing Ni-CNTs / WC-based composite powder for spraying and the resulting Ni-CNTs / WC-based composite spraying powder. The Ni-CNTs / WC-based spraying powder prepared by this method can be used as a surface spraying material for components such as large aircraft landing gear, automobile engine blocks, oil drilling bits, steel metallurgical submerged rolls, and cardboard corrugated rolls. Background Technology

[0002] Surface coating technology, as an advanced material protection method, utilizes thermodynamics to propel powder at high speed onto the surface of a substrate material under specific temperature conditions. The molten particles rapidly solidify to form a dense protective layer several hundred micrometers thick, significantly improving the wear resistance and chemical stability of mechanical components. Tungsten carbide-based composite coatings, due to their excellent resistance to fretting wear and media corrosion, have been widely applied in high-end equipment in aerospace, automotive manufacturing, oil and gas transportation, and mining machinery. This environmentally friendly coating technology exhibits significant advantages over traditional electroplated hard chromium coatings and has become an important development direction in modern remanufacturing engineering.

[0003] Carbon nanotubes (CNTs) have become the preferred nanomaterial for reinforcing metal / ceramic composite systems due to their superior mechanical parameters, high thermal conductivity, and excellent electrical conductivity. In metal-ceramic composite coating systems, CNTs significantly improve the fracture toughness of the coating mainly through multi-scale strengthening mechanisms such as debonding and pull-out, crack path deflection, and crack bridging. Experimental studies have shown that the introduction of appropriate amounts of CNTs can improve the crack propagation resistance of the composite coating by 40%-65% while maintaining the matrix strength, effectively extending the service life of the protective material under harsh conditions. However, the strong van der Waals forces between carbon nanotubes easily induce self-aggregation, leading to a non-uniform distribution of nanoscale aggregates in the matrix. This not only reduces stress transfer efficiency but also restricts the practical application of the theoretical reinforcement effect. This bottleneck problem has become a key technical obstacle restricting the engineering application of CNT-reinforced coatings.

[0004] In the preparation of tungsten carbide-based composite coating materials, the traditional method of introducing carbon nanotubes mainly relies on mechanical mixing technology. Existing preparation processes typically employ physical dispersion methods such as high-energy ball milling and ultrasonic vibration to incorporate carbon nanotubes into WC-based powders. However, these dispersion methods have significant limitations. Studies have shown that mechanically driven mixing processes struggle to overcome the strong interfacial forces between nanomaterials, leading to the incorporation of carbon nanotubes into WC-based powders. SLocalized aggregation occurs within the matrix powder, and this microscopic non-uniformity not only reduces the effective load-bearing area of ​​the composite material but also easily induces stress concentration effects. However, surface modification of carbon nanotubes can solve these problems.

[0005] Surface modification of carbon nanotubes involves controlling their surface structure and state through physical or chemical methods, effectively improving dispersibility, surface activity, and interfacial compatibility. Nickel coating technology improves the dispersion characteristics of carbon nanotubes in composite systems by reducing surface activation energy. Its strengthening mechanism stems from the energy optimization of the interfacial structure caused by the interaction between nickel atoms and carbon nanotubes, reducing the binding energy by 15-20%, thereby forming a highly stable chemically bonded interface. This enhances the interfacial bonding strength of the composite material and significantly improves tensile strength and durability. Furthermore, the nickel coating layer can inhibit the thermal degradation of carbon nanotube structures in high-temperature processing environments, effectively preventing structural damage and performance degradation of carbon nanotubes. Summary of the Invention

[0006] The primary technical problem to be solved by this invention is to provide a method for preparing nickel-coated CNTs / WC-based composite powder for spraying. The Ni-CNTs / WC-based composite powder obtained by this method has high sphericity, good flowability, uniform distribution of carbon nanotubes and controllable content, which can improve the spraying process performance of the powder.

[0007] Another technical problem to be solved by the present invention is to provide a Ni-CNTs / WC-based composite spray powder prepared by the above method, which has high sphericity, good flowability, uniform distribution of carbon nanotubes and controllable content, and can improve the spraying process performance of the spray powder.

[0008] The technical solution of this invention to solve the primary technical problem is to provide a method for preparing Ni-CNTs / WC-based composite spray powder, characterized by the following steps:

[0009] (1) After immersing the carbon nanotubes in an oxidizing solution and sonicating them at 50±5℃ for 30±3 minutes, they were washed with deionized water by centrifugation at 3000~8000 rpm.

[0010] (2) Disperse the pretreated carbon nanotubes in a plating solution with pH 7.0~9.0, place them in a microwave device for heating, microwave heating time is 5~15 minutes, power is controlled at 300~700 W;

[0011] (3) The obtained product was washed with deionized water and then vacuum dried at 60~80℃ for 1~3 h. Under inert gas protection, the temperature was increased to 350±50℃ at 5±1℃ / min and held for 0.5~1.5 h to obtain nickel-coated carbon nanotubes.

[0012] (4) Mix nickel-coated carbon nanotubes with a dispersant at a mass ratio of 1:0.1~0.5, add to deionized water, and perform intermittent ultrasonic treatment for a total of 30~50 minutes; after centrifuging the dispersion at 1800~2200 rpm for 25~35 min, remove the agglomerates to obtain a stable dispersion system;

[0013] (5) Using WC powder, Ni-CNTs dispersion and metal powder as raw materials, after mixing in proportion, they are wet ball milled with binder under inert gas protection. The proportion of WC is 83~87 wt.%, the proportion of Ni-CNTs is 1~6 wt.%, the proportion of metal powder is 10~16 wt.%, the ball-to-material ratio is 2.5~3.5:1, the ball milling speed is 240~260 rpm, and the ball milling time is 1~2 h.

[0014] (6) After adding deionized water to the ball mill product, spray granulation is carried out using a closed-loop spray dryer. Then, the temperature is raised to 1240~1260℃ for 0.5~1.5 h under hydrogen atmosphere at 10±1℃ / min. Finally, 15~45 μm spherical spray powder is obtained by crushing and sieving.

[0015] Furthermore, the process parameters for the step are as follows:

[0016] (1) After immersing the carbon nanotubes in an oxidizing solution and sonicating them at 50°C for 30 minutes, they were washed with deionized water by three-stage gradient centrifugation at 3000→5000→8000 rpm.

[0017] (2) Disperse the pretreated carbon nanotubes in a plating solution with pH 8.0, place them in a microwave device for heating, and microwave heating time is 10 minutes with power controlled at 500~600W;

[0018] (3) The obtained product was washed with deionized water and then vacuum dried at 70°C for 2 h. Under inert gas protection, the temperature was increased to 350°C at 5°C / min and held for 1 h to obtain nickel-coated carbon nanotubes.

[0019] (4) Mix nickel-coated carbon nanotubes with a dispersant at a mass ratio of 1:0.3, add to deionized water, and perform intermittent ultrasonic treatment for a total of 30-50 minutes. After centrifuging the dispersion at 2000 rpm for 30 minutes, remove the agglomerates and obtain a stable dispersion system.

[0020] (5) Using WC powder and Ni-CNT S The dispersion and metal powder were used as raw materials, and after being mixed in a specific ratio, they were wet ball-milled with a binder under inert gas protection. The WC content was 84.75 wt.%, and the Ni-CNT content was [missing information]. SThe content of the powder was 1.25 wt.%, the content of the metal powder was 14 wt.%, the ball-to-material ratio was 3:1, the ball milling rate was 250 rpm, and the ball milling time was 1~2 h;

[0021] (6) After adding deionized water to the ball milling product, spray granulation was carried out using a closed-loop spray dryer. Then, the product was sintered at 1250℃ for 1 h under a hydrogen atmosphere at a rate of 10℃ / min. Finally, 15~45 μm spherical spray powder was obtained by crushing and sieving.

[0022] Furthermore, in step (1), the oxidizing solution is prepared from 0.5±0.05 mol / L HNO3 and 0.1±0.01 mol / L H2O2.

[0023] Furthermore, in step (2), the plating solution is prepared from 20~30 g / L NiSO4·6H2O, 25~35 g / L NaH2PO2·H2O and 35~45 g / L Na3C6H5O7.

[0024] Furthermore, in steps (3) and (5), the inert gas is either nitrogen or argon.

[0025] Furthermore, in step (5), the WC powder is of one of the following scales: nano, submicron, or micron powder, and has a single-peak, double-peak, or multi-peak distribution.

[0026] Furthermore, in step (5), the metal powder is one or more of Co powder, Cr powder, and Ni powder.

[0027] Finally, in step (5), the adhesive is a variety of polyethylene glycol 4000, 6000 and polyacrylic acid, with a mass ratio of 30%-35%, 40%-45% and 25%-30%.

[0028] The technical solution of this invention to solve another technical problem is to provide a Ni-CNTs / WC-based composite spray powder, characterized in that it is prepared by any of the above-mentioned methods for preparing Ni-CNTs / WC-based composite spray powder, wherein the Ni-CNTs in the composite spray powder are uniformly distributed with a deviation ≤0.5%.

[0029] Compared with existing technologies, the advantages of this invention are as follows: A nickel coating layer is constructed on the surface of carbon nanotubes through a nickel metal surface modification process, forming a nickel-based carbon nanotube composite (Ni-CNTs) with a core-shell structure. This composite is then used as a reinforcing phase and combined with WC-based powder to ultimately prepare a Ni-CNTs / WC-based sprayable powder with an innovative structure. This technical solution significantly improves the interfacial wettability between carbon nanotubes and the metal matrix through the metallurgical bonding characteristics between metallic nickel and the WC matrix, enabling the reinforcing phase to form a stable chemical bond interface with the matrix. This structural design effectively solves the problem of carbon nanotube dispersion in the metal matrix in traditional processes, achieving a three-dimensional uniform distribution of the nanoscale reinforcing phase in the composite powder system. Simultaneously, the spatial barrier effect of the nickel coating layer effectively suppresses the agglomeration of carbon nanotubes caused by van der Waals forces, significantly improving the flowability and thermal spraying adaptability of the composite powder. This provides a simple and low-cost solution for the preparation of CNTs-reinforced WC-Co, WC-Ni, and WC-CoCr composite sprayable powders and high-performance coatings. Attached Figure Description

[0030] Figure 1 Scanning electron microscope (SEM) images of Ni-CNTs prepared in Example 1;

[0031] Figure 2 The image shows the EDS spectrum of the Ni-CNTs surface micro-regions prepared in Example 1.

[0032] Figure 3 This is a 4000x scanning electron microscope image of the Ni-CNTs / WC-CoCr composite powder prepared in Example 1;

[0033] Figure 4 This is a 100,000x scanning electron microscope image of the surface of the Ni-CNTs / WC-CoCr composite powder prepared in Example 1. Detailed Implementation

[0034] The present application will be described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0035] Example 1

[0036] Carbon nanotubes were immersed in a mixture of 0.5 mol / L HNO3 + 0.1 mol / L H2O2 and sonicated at 50℃ for 30 minutes. Afterward, they were washed with deionized water by a three-stage gradient centrifugation (3000→5000→8000 rpm). The pretreated carbon nanotubes were then dispersed in a plating solution at pH 8.0, prepared from 25 g / L NiSO4·6H2O, 30 g / L NaH2PO2·H2O, and 40 g / L Na3C6H5O7. The solution was then heated in a microwave oven for 10 minutes at 500W. The resulting product was washed with deionized water, vacuum dried at 70℃ for 2 h, and then heated to 350℃ at a rate of 5℃ / min under argon protection and held for 1 hour. Nickel-coated carbon nanotubes were obtained. The nickel-coated carbon nanotubes were mixed with XFZ20 dispersant at a mass ratio of 1:0.3 and added to deionized water. Intermittent ultrasonic treatment was performed (5 min × 6 times, with ice water cooling and defoaming intervals), for a total of 30 minutes. The dispersion was centrifuged at 2000 rpm for 30 min to remove agglomerates, resulting in a stable dispersion system. Nano-WC powder, Ni-CNTs, Co powder, and Cr powder were mixed as raw materials, with mass percentages of 84.75 wt.%, 1.25 wt.%, 10 wt.%, and 4 wt.%, respectively. The mixed powder and binder (33%, 42%, 25%) were wet-milled under argon protection at a ball-to-material ratio of 3:1, a milling rate of 250 rpm, and for 2 h, using ethanol as the solvent. The milled product was added to deionized water and spray-dried using a closed-loop spray dryer. Subsequently, it was sintered at 1250 °C for 1 h under a hydrogen atmosphere with a heating rate of 10 °C / min. After crushing and sieving, 15-45 μm spherical Ni-CNTs / WC-CoCr composite spraying powder was obtained, in which Ni-CNTs... S Distribution deviation 0.1%. Powder sphericity 0.98±0.01, flowability 17.0 s / 50g. The microstructure of nickel-coated carbon nanotubes is as follows. Figure 1 As shown, Figure 2 for Figure 1 The EDS spectrum of the red micro-region mainly contains C and Ni elements. Figure 3 The image shows the microstructure of Ni-CNTs / WC-CoCr powder. The powder has good sphericity and no hollow particles. Figure 4 The image shows the surface microstructure of Ni-CNTs / WC-CoCr powder under high magnification, indicating that the nickel-coated carbon nanotubes are uniformly distributed in the powder.

[0037] Example 2

[0038] Carbon nanotubes were immersed in a mixture of 0.5 mol / L HNO3 + 0.1 mol / L H2O2 and sonicated at 50℃ for 30 minutes. Afterward, they were washed with deionized water by a three-stage gradient centrifugation (3000→5000→8000 rpm). The pretreated carbon nanotubes were then dispersed in a plating solution at pH 9.0, prepared from 25 g / L NiSO4·6H2O, 30 g / L NaH2PO2·H2O, and 40 g / L Na3C6H5O7. The solution was then heated in a microwave oven for 8 minutes at 600W. The resulting product was washed with deionized water, vacuum dried at 70℃ for 2 h, and then heated to 350℃ at a rate of 5℃ / min under argon protection and held for 1 hour. Nickel-coated carbon nanotubes were obtained. The nickel-coated carbon nanotubes were mixed with XFZ20 dispersant at a mass ratio of 1:0.3 and added to deionized water. Intermittent ultrasonic treatment was performed (5 min × 6 times, with ice water cooling and defoaming intervals), for a total of 50 minutes. The dispersion was centrifuged at 2000 rpm for 30 min to remove agglomerates, resulting in a stable dispersion system. Micron-sized WC powder, Ni-CNTs, and Co powder were mixed as raw materials, with mass percentages of 86.5 wt.%, 1.5 wt.%, and 12 wt.%, respectively. The mixed powder and binder (35%, 45%, 20%) were then wet-milled under argon protection at a ball-to-material ratio of 3:1, a milling rate of 250 rpm, and for 1 h. The milled product was added to deionized water and spray-dried using a closed-loop spray dryer. Subsequently, it was sintered at 1250 °C for 1 h under a hydrogen atmosphere with a heating rate of 10 °C / min. Spherical Ni-CNTs / WC-Co composite spraying powder with a diameter of 15-45 μm was obtained by crushing and sieving, with a Ni-CNTs distribution deviation of 0.5%. The powder sphericity was 0.97±0.01 and the flowability was 17.5 s / 50g.

[0039] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or direct or indirect substitutions made by those skilled in the art within the scope of the technology disclosed in the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing Ni-CNTs / WC-based composite spray powder, characterized in that... Includes the following steps: (1) After immersing the carbon nanotubes in an oxidizing solution and sonicating them at 50±5℃ for 30±3 minutes, they were washed with deionized water by centrifugation at 3000~8000rpm. (2) Disperse the pretreated carbon nanotubes in a plating solution with pH 7.0~9.0, place them in a microwave device for heating, microwave heating time is 5~15 minutes, power is controlled at 300~700 W; (3) The obtained product was washed with deionized water and then vacuum dried at 60~80℃ for 1~3 h. Under inert gas protection, the temperature was increased to 350±50℃ at 5±1℃ / min and held for 0.5~1.5 h to obtain nickel-coated carbon nanotubes. (4) Mix nickel-coated carbon nanotubes with a dispersant at a mass ratio of 1:0.1~0.5, add to deionized water, and perform intermittent ultrasonic treatment for a total of 30~50 minutes; after centrifuging the dispersion at 1800~2200 rpm for 25~35 min, remove the agglomerates to obtain a stable dispersion system; (5) Using WC powder, Ni-CNTs dispersion and metal powder as raw materials, after mixing in proportion, they are wet ball milled with binder under inert gas protection. The proportion of WC is 83~87 wt.%, the proportion of Ni-CNTs is 1~6 wt.%, the proportion of metal powder is 10~16 wt.%, the ball-to-material ratio is 2.5~3.5:1, the ball milling speed is 240~260 rpm, and the ball milling time is 1~2 h. (6) After adding deionized water to the ball mill product, spray granulation is carried out using a closed-loop spray dryer. Then, the temperature is raised to 1240~1260℃ for 0.5~1.5 h under hydrogen atmosphere at 10±1℃ / min. Finally, 15~45 μm spherical spray powder is obtained by crushing and sieving.

2. The method according to claim 1, characterized in that, The process parameters for the aforementioned steps are as follows: (1) After immersing the carbon nanotubes in an oxidizing solution and sonicating them at 50°C for 30 minutes, they were washed with deionized water by three-stage gradient centrifugation at 3000→5000→8000 rpm. (2) Disperse the pretreated carbon nanotubes in a plating solution with pH 8.0, place them in a microwave device for heating, and microwave heating time is 10 minutes with power controlled at 500~600W; (3) The obtained product was washed with deionized water and then vacuum dried at 70°C for 2 h. Under inert gas protection, the temperature was increased to 350°C at 5°C / min and held for 1 h to obtain nickel-coated carbon nanotubes. (4) Mix nickel-coated carbon nanotubes with a dispersant at a mass ratio of 1:0.3, add to deionized water, and perform intermittent ultrasonic treatment for a total of 30-50 minutes. After centrifuging the dispersion at 2000 rpm for 30 minutes, remove the agglomerates and obtain a stable dispersion system. (5) Using WC powder, Ni-CNTs dispersion and metal powder as raw materials, after mixing in proportion, they are wet ball-milled with binder under inert gas protection. The WC content is 84.75 wt.%, and the Ni-CNTs content is 84.75 wt.%. S The content of the powder was 1.25 wt.%, the content of the metal powder was 14 wt.%, the ball-to-material ratio was 3:1, the ball milling rate was 250 rpm, and the ball milling time was 1~2 h; (6) After adding deionized water to the ball milling product, spray granulation was carried out using a closed-loop spray dryer. Then, the product was sintered at 1250℃ for 1 h under a hydrogen atmosphere at a rate of 10℃ / min. Finally, 15~45 μm spherical spray powder was obtained by crushing and sieving.

3. The method according to claim 1, characterized in that, In step (1), the oxidation solution is prepared from 0.5±0.05 mol / L HNO3 and 0.1±0.01 mol / L H2O2.

4. The method according to claim 1, characterized in that, In step (2), the plating solution is prepared from 20~30 g / L NiSO4·6H2O, 25~35 g / L NaH2PO2·H2O and 35~45 g / L Na3C6H5O7.

5. The method according to claim 1, characterized in that, In steps (3) and (5), the inert gas is either nitrogen or argon.

6. The method according to claim 1, characterized in that, In step (5), the WC powder is one of nano, submicron, or micron powder, and has a single-peak, double-peak, or multi-peak distribution.

7. The method according to claim 1, characterized in that, In step (5), the metal powder is one or more of Co powder, Cr powder, and Ni powder.

8. The method according to claim 1, characterized in that, In step (5), the adhesive is a variety of polyethylene glycol 4000, 6000 and polyacrylic acid, with a ratio of 30%-35%, 40%-45% and 25%-30%.

9. A Ni-CNTs / WC-based composite spray powder, characterized in that, The composite spray powder is prepared by any one of the preparation methods of Ni-CNTs / WC based according to claims 1 to 8, wherein the Ni-CNTs in the composite spray powder are uniformly distributed with a deviation of ≤0.5%.

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