Preparation method of carbon fiber / polyetherketoneketone composite coating and coating thereof

Abstract

The invention discloses a preparation method of a carbon fiber / polyetherketoneketone composite coating and a coating thereof, and the preparation method specifically comprises the following operation steps: dissolving polyetherketoneketone in a strong polar solvent to prepare a homogeneous solution; according to the carbon fiber / polyetherketoneketone composite coating, double-layer electrostatic spraying is combined with hot rolling and surface polishing treatment, and the compactness, uniformity and tribological performance of the coating are improved. According to the invention, the problems of non-uniform carbon fiber dispersion, too low resistivity of the carbon fiber composite coating and insufficient compactness of the composite coating in the traditional coating process are solved. The invention provides an efficient and controllable technical approach for preparing the high-performance carbon fiber / polyether ketone ketone composite coating and coating, and is suitable for the surfaces of robot joints, bearings, aerospace precision transmission parts and medical instrument wear-resistant components.

Description

Technical Field

[0001] This invention relates to the field of high-performance composite coating preparation technology, and in particular to a method for preparing carbon fiber / polyether ketone ketone composite coating and its coating. Background Technology

[0002] Polymer coatings bond to material surfaces through chemical bonding or physical adsorption, forming a protective barrier that significantly improves the wear resistance, corrosion resistance, and aging resistance of materials, making it a key technology for extending material lifespan. Common wear-resistant coatings include polyurethane and polyimide coatings; corrosion-resistant coatings include epoxy resin and polytetrafluoroethylene coatings; and anti-aging coatings include polysiloxane and acrylic resin coatings.

[0003] Currently, high-end manufacturing, electronic packaging, marine engineering, and aerospace industries are placing increasingly stringent comprehensive performance requirements on coating materials, including adaptability to extreme environments (such as high temperature resistance, strong corrosion resistance, high wear resistance, and strong radiation resistance), multifunctionality (such as superhydrophobicity, self-cleaning, electrical and thermal conductivity, and electromagnetic shielding), and long service life. However, traditional polymer coatings still face some challenges and limitations: their temperature resistance is generally low, typically applicable to temperatures not exceeding 200 °C; their mechanical strength is limited, making them susceptible to scratches; and the significant difference in thermal expansion coefficients between the polymer coating and the substrate material can easily induce coating cracking, peeling, and other failure phenomena under thermal cycling conditions. Therefore, developing high-performance polymer coatings with higher mechanical strength, excellent chemical stability, and superior weather resistance has become an important research direction. Among these, introducing reinforcing phases such as nanoparticles, whiskers, fibers, or lamellar structures into polymers to prepare composite coatings can effectively utilize the high hardness and high modulus properties of the reinforcing phases, significantly improving the overall performance of the coating.

[0004] Among numerous polymers, polyaryletherketones (PAEKs) exhibit broad application prospects in the coating field due to their unique molecular structure and excellent comprehensive properties. These polymers are semi-crystalline aromatic thermoplastic polymers composed of phenylene rings linked by ether bonds and ketone groups, mainly including polyetheretherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK), and polyetherketoneetherketoneketone (PEKEKK). These materials possess excellent high-temperature resistance, chemical corrosion resistance, high mechanical strength, good electrical insulation, low coefficient of thermal expansion, and high dimensional stability, maintaining stable performance even under harsh environments, providing key material support for the development of high-performance polymer coatings. Several publicly available patents already disclose preparation techniques for PAEK coatings. For example, Chinese invention patent ZL2013101134140 proposes a flame spraying process suitable for polyetheretherketone powder; Chinese invention patent ZL2015108344967 proposes a thick-film polyetheretherketone composite coating preparation technology based on electrostatic spraying and thermal spraying processes; and Chinese invention patent ZL2017100628052 proposes a method for preparing polyetheretherketone electrostatic spraying powder coating with crosslinking properties.

[0005] In reinforced material systems, carbon fiber possesses significant advantages due to its high specific strength, high specific modulus, and excellent tribological properties. It can effectively improve the mechanical strength, stiffness, and deformation resistance of coatings, while reducing the coefficient of friction and wear rate. Studies have shown that compared to pure polyetheretherketone (PEEK), carbon fiber-reinforced PEEK composites can reduce the coefficient of friction by approximately 37% (Reference: Tribological performance of 3D printed neat and carbon fiber reinforced PEEK composites, Tribology International, 2024, 193, 109356). However, key challenges remain in the preparation of carbon fiber / PEEK composite coatings: First, the high melt viscosity of PEEK easily induces carbon fiber agglomeration during traditional dry melt lamination, leading to uneven fiber dispersion and reduced interfacial stress transfer efficiency. Second, electrostatic spraying requires the composite powder to be within a suitable resistivity window (approximately 5–50 MΩ·cm) to ensure electrical stability. However, the low resistivity of carbon fiber weakens the insulation properties of the composite powder, severely interfering with the electrostatic spraying process; therefore, effective control of resistivity is urgently needed.

[0006] Research has made some progress in the preparation of polyetherketoneketone (PEKK) / carbon fiber composite systems. For example, Chinese invention patent ZL2022104019270 reports a liquid-phase mixing process for preparing chopped carbon fiber / PEKKK composite powder. This method effectively avoids fiber agglomeration caused by excessively high melt viscosity of PEVKKK during melt mixing and overcomes the limitation of mechanical mixing methods in achieving sufficient polymer coating on the carbon fiber surface, thereby improving the uniformity of carbon fiber dispersion in the matrix. This patent provides a new approach for preparing composite coatings suitable for electrostatic spraying; however, to meet the actual requirements of electrostatic spraying processes, further optimization is needed on key parameters such as particle morphology, powder flowability, and resistivity.

[0007] The key to preparing high-performance carbon fiber / polyether ketone ketone composite coatings suitable for electrostatic spraying lies in the precise control of resistivity. Based on the aforementioned liquid-phase mixing process, this goal can be achieved by adjusting the length, volume fraction, and particle morphology of the carbon fibers. Carbon fiber length is a crucial parameter affecting the resistivity and mechanical properties of the composite coating. A suitable critical length needs to be determined to ensure the coating balances reinforcement and electrical insulation. The volume fraction of carbon fibers also affects the conductivity threshold and dispersibility, requiring a balance between reinforcement and insulation. For irregular particles formed during the pulverization process, appropriate heat treatment can induce localized melting and flow of polymer segments to repair cracks, cover exposed fiber ends, and improve particle smoothness and overall insulation performance.

[0008] To address the problems of fiber agglomeration, irregular particle morphology, excessively low resistivity, and insufficient coating density in the preparation of carbon fiber / polyether ketone ketone composite coatings, this invention proposes a method for preparing carbon fiber / polyether ketone ketone composite coatings suitable for electrostatic spraying. This method first controls the length of the carbon fibers through physical shearing or airflow pulverization, then controls the volume fraction of the carbon fibers through solution dispersion and proportioning. Furthermore, the liquid-phase mixing process is optimized to ensure that the polyether ketone ketone fully coats the carbon fiber surface, thereby significantly improving the volume resistivity of the composite powder and ensuring that it maintains the optimal charging window during electrostatic spraying.

[0009] In terms of powder morphology and particle size control, ball milling is used to improve particle size distribution and morphological uniformity, and enhance powder flowability. Through heat treatment, localized melting of chain segments repairs defects generated during the grinding process and covers exposed carbon fiber ends, making the particle surface denser and smoother, thus enhancing the powder's electrical properties. In the coating preparation stage, a two-layer spraying strategy is adopted: the bottom layer has reinforcing and conductivity regulation functions, while the top layer serves as an insulating and surface protective layer, supplemented by post-processing techniques such as hot rolling and grinding to reduce porosity and improve smoothness and density.

[0010] Ultimately, this method achieves uniform dispersion of carbon fibers in the coating and controllable adjustment of resistivity, providing an efficient and feasible technical path for the preparation of high-performance carbon fiber / polyether ketone ketone composite coatings. Summary of the Invention

[0011] Technical Problem Solved: To address the shortcomings of existing technologies, this invention provides a method for preparing carbon fiber / polyether ketone ketone composite coatings and the coating itself. By precisely controlling the length, aspect ratio, and volume fraction of carbon fibers, combined with a solution dispersion drying process, the uniform distribution of carbon fibers and the polymer coating effect are improved, enhancing the insulation and stability of the powder. Furthermore, a combination of airflow milling, ball milling, and heat treatment is employed to effectively improve the particle morphology, flowability, and volume resistivity of the composite powder. Finally, through double-layer electrostatic spraying combined with hot rolling and surface polishing, the density, uniformity, and tribological properties of the coating are improved, effectively solving the problems in the background technology.

[0012] Technical Solution: To achieve the above objectives, the technical solution adopted by this invention is: a method for preparing a carbon fiber / polyether ketone composite coating, specifically including the following steps: S1: Selection and pretreatment of carbon fiber parameters: Select carbon fibers with appropriate parameters, perform heat treatment on the carbon fibers under an inert atmosphere, and then perform low-temperature plasma activation. S2: Preparation of polyether ketone solution: Dissolve polyether ketone in a strongly polar solvent to prepare a homogeneous solution; S3: Dispersion preparation: The activated carbon fibers are added to the obtained polyether ketone homogeneous solution, and then subjected to ultrasonic treatment and mechanical stirring to obtain a uniform dispersion; S4: Composite particle forming: The dispersion is subjected to gradient heating and drying to slowly remove the solvent and form composite particles in which carbon fibers are uniformly coated with polyether ketone ketone. S5: Powder preparation and heat treatment repair: The composite is crushed, ball-milled and heat-treated to partially melt and recrystallize the polyether ketone ketone, repair the crushed cracks and cover the ends of the carbon fibers to obtain a composite powder with suitable resistivity. S6: Electrostatic spraying and consolidation: The composite powder is divided into a base coat and a top coat according to the carbon fiber content, and the two layers are formed by electrostatic spraying and then consolidated at a certain temperature. S7: Crystallization control and hot rolling densification: The solidified double-layer coating is subjected to gradient cooling and held at a certain temperature for a certain time to control the crystallinity, and then hot rolling is carried out under a certain temperature and pressure. S8: Coating surface treatment: Grind or sandblast the coating surface to complete the preparation of the carbon fiber / polyether ketone ketone composite coating.

[0013] As a preferred technical solution of this application, in step S1, the average length of the carbon fiber is 50-200μm, the diameter is 5-10μm, the aspect ratio is 10-30, the heat treatment temperature is 400-600℃, the heat treatment time is 0.5-2h, the power used for low-temperature plasma activation is 100-300W, the gas is one of oxygen and argon-oxygen mixture, and the activation time is 10-30min.

[0014] As a preferred technical solution of this application, the solvent of the polyether ketone solution in step S2 is at least one or more mixed solvents selected from trifluoroacetic acid, dichloroethane, p-chlorophenol, dichloroacetic acid, and dichloropropionic acid, the dissolution temperature is controlled at 40-60℃, and the polyether ketone content of the homogeneous solution is 5-25wt%.

[0015] As a preferred technical solution of this application, in step S3, the ultrasonic power of the dispersion is 300-800W, the ultrasonic time is 30-60min, the stirring speed is 800-1500rpm, the stirring time is 1-2h, and the temperature is kept below 60℃.

[0016] As a preferred technical solution of this application, the composite drying process in step S4 includes first raising the temperature to 40-80℃ at 1-3℃ / min and holding it for 1-3 hours, then raising the temperature to 200-260℃ at 2-5℃ / min and holding it for 24-48 hours to ensure complete drying.

[0017] As a preferred technical solution of this application, in step S5, the particle size of the composite is 15-65μm, the heat treatment temperature after ball milling is 250-350℃, and the time is 10-30min.

[0018] As a preferred technical solution of this application, in step S6, the fiber content of the base coat is 10-30%, the fiber content of the top coat is 1-10%, the thickness of the base coat is 80-150μm, the spraying voltage is 60-70kV, the substrate temperature is 100-120℃, the total thickness of the top coat is 200-300μm, the spraying voltage is 75-90kV, the substrate temperature is 80-100℃, and the consolidation temperature is 300-400℃.

[0019] As a preferred technical solution of this application, in step S7, the gradient cooling temperature is 250-280℃, the holding time is 0.5-2h, the crystallinity is controlled at 10-40%, the hot rolling conditions are 260-320℃, the pressure is 0.5-5MPa, and the action time is 5-30min.

[0020] As a preferred technical solution of this application, the surface treatment method in step S8 is to uniformly polish with 180-400 grit sandpaper and then clean the surface with compressed air, or to uniformly sandblast with 180-400 grit white corundum sand at an appropriate distance and angle under a pressure of 2-6 bar.

[0021] A carbon fiber / polyetherketone ketone composite coating comprises a two-layer gradient structure consisting of a base layer and a top layer. The carbon fiber mass fraction is 10-30%, and the carbon fiber mass fraction of the top layer is 1-10%. The coefficient of friction of the base layer is ≤0.15, and the coating is suitable for the surfaces of robot joints, bearings, aerospace precision transmission components, and wear-resistant components of medical devices.

[0022] Beneficial Effects: Compared with existing technologies, this invention provides a method for preparing carbon fiber / polyether ketone ketone composite coatings and the coating itself, which has the following beneficial effects: This invention improves the uniform distribution of carbon fibers and the polymer coating effect by precisely controlling the length, aspect ratio, and volume fraction of carbon fibers, combined with a solution dispersion and drying process, thereby enhancing the insulation and stability of the powder. Furthermore, it effectively improves the particle morphology, flowability, and volume resistivity of the composite powder by employing a combination of airflow milling, ball milling, and heat treatment. Finally, it enhances the density, uniformity, and tribological properties of the coating through double-layer electrostatic spraying combined with hot rolling and surface polishing. The prepared composite coating exhibits uniform carbon fiber dispersion and stable powder resistivity control within the range required for electrostatic spraying, solving the problems of fiber agglomeration, irregular particle morphology, excessively low resistivity, and insufficient coating density in traditional processes. This method provides an efficient and controllable technical approach for preparing high-performance carbon fiber / polyether ketone ketone composite coatings and coatings, applicable to the surfaces of robot joints, bearings, aerospace precision transmission components, and wear-resistant components of medical devices. Controllable resistivity adjustment: By precisely controlling the carbon fiber parameters, the resistivity of the composite powder is kept stable within the window required for electrostatic spraying, thus avoiding the formation of conductive paths; Coating and dispersion optimization: The solution dispersion-drying process significantly improves the uniform distribution of carbon fibers and the polymer coating effect, thereby enhancing the insulation and stability of the powder; Improved particle morphology: The synergistic effect of air jet milling-ball milling-heat treatment process eliminates the problems of irregular particle morphology and exposed fibers, making the powder particles more dense and smooth, with good flowability and electrical properties; Improved coating quality: The combination of double-layer spraying and hot rolling / grinding post-treatment effectively reduces coating porosity, enhances interfacial adhesion, and ensures coating density and overall performance. The entire preparation method of carbon fiber / polyether ketone composite coating is simple in structure, easy to operate, and has better results than traditional methods. Attached Figure Description

[0023] Figure 1This is a schematic diagram of the preparation method of a carbon fiber / polyether ketone composite coating and the overall process of the coating.

[0024] Figure 2 This is a schematic diagram of a method for preparing a carbon fiber / polyether ketone composite coating and the double-layer coating structure in the coating.

[0025] Figure 3 This invention provides a method for preparing a carbon fiber / polyether ketone composite coating and an electron microscope image of the double-layer coating structure in the coating.

[0026] Figure 4 This invention provides a method for preparing a carbon fiber / polyether ketone ketone composite coating and an electron microscope image of the polyether ketone ketone / carbon fiber pre-composite undercoat.

[0027] Figure 5 This is an electron microscope image of a method for preparing a carbon fiber / polyether ketone ketone composite coating according to the present invention, and the carbon fiber fully coated by polyether ketone ketone in the bottom layer of the coating.

[0028] Figure 6 This invention provides a method for preparing a carbon fiber / polyether ketone composite coating and an electron microscope image of the coating surface after hot rolling.

[0029] Figure 7 This invention provides a method for preparing a carbon fiber / polyether ketone composite coating and an electron microscope image of the coating surface after surface treatment. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0031] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] like Figure 1-7 As shown, a method for preparing a carbon fiber / polyether ketone composite coating specifically includes the following steps: S1: Selection and pretreatment of carbon fiber parameters: Select carbon fibers with appropriate parameters, perform heat treatment on the carbon fibers under an inert atmosphere, and then perform low-temperature plasma activation. S2: Preparation of polyether ketone solution: Dissolve polyether ketone in a strongly polar solvent to prepare a homogeneous solution; S3: Dispersion preparation: The activated carbon fibers are added to the obtained polyether ketone homogeneous solution, and then subjected to ultrasonic treatment and mechanical stirring to obtain a uniform dispersion; S4: Composite molding: The dispersion is dried by gradient heating to slowly remove the solvent and form a composite in which carbon fibers are uniformly coated with polyether ketone ketone. S5: Powder preparation and heat treatment repair: The composite is crushed, ball-milled and heat-treated to partially melt and recrystallize the polyether ketone ketone, repair the crushed cracks and cover the ends of the carbon fibers to obtain a composite powder with suitable resistivity. S6: Electrostatic spraying and consolidation: The composite powder is divided into a base coat and a top coat according to the carbon fiber content. The two coats are formed by electrostatic spraying and then consolidated at a certain temperature. S7: Crystallization control and hot rolling densification: The solidified double-layer coating is subjected to gradient cooling and held at a certain temperature for a certain time to control the crystallinity, and then hot rolling is carried out under a certain temperature and pressure. S8: Coating surface treatment: Grind or sandblast the coating surface to complete the preparation of the carbon fiber / polyether ketone ketone composite coating.

[0034] Furthermore, in step S1, the average length of the carbon fiber is 50-200μm, the diameter is 5-10μm, the aspect ratio is 10-30, the heat treatment temperature is 400-600℃, the heat treatment time is 0.5-2h, the low-temperature plasma activation power is 100-300W, the gas is one of oxygen and argon-oxygen mixture, and the activation time is 10-30min.

[0035] Furthermore, in step S2, the solvent for the polyether ketone solution is at least one or more mixed solvents selected from trifluoroacetic acid, dichloroethane, p-chlorophenol, dichloroacetic acid, and dichloropropionic acid. The dissolution temperature is controlled at 40-60℃, and the polyether ketone content of the homogeneous solution is 5-25wt%.

[0036] Furthermore, in step S3, the ultrasonic power of the dispersion is 300-800W, the ultrasonic time is 30-60min, the stirring speed is 800-1500rpm, the stirring time is 1-2h, and the temperature is kept below 60℃.

[0037] Furthermore, the composite drying process in step S4 includes first raising the temperature to 40-80℃ at 1-3℃ / min and holding it for 1-3 hours, then raising the temperature to 200-260℃ at 2-5℃ / min and holding it for 24-48 hours to ensure complete drying.

[0038] Furthermore, in step S5, the particle size of the composite is pulverized to 15-65 μm, and the heat treatment temperature after ball milling is 250-350℃ for 10-30 min.

[0039] Furthermore, in step S6, the fiber content of the base coat is 10-30%, the fiber content of the top coat is 1-10%, the base coat thickness is 80-150μm, the spraying voltage is 60-70kV, the substrate temperature is 100-120℃, the total thickness of the top coat is 200-300μm, the spraying voltage is 75-90kV, the substrate temperature is 80-100℃, and the consolidation temperature is 300-400℃.

[0040] Furthermore, in step S7, the gradient cooling temperature is 250-280℃, the holding time is 0.5-2h, the crystallinity is controlled at 10-40%, the hot rolling conditions are 260-320℃, the pressure is 0.5-5MPa, and the action time is 5-30min.

[0041] Furthermore, in step S8, the surface treatment method involves uniformly sanding with 180-400 grit sandpaper, then cleaning the surface with compressed air, or uniformly sandblasting with 180-400 grit white corundum sand at an appropriate distance and angle under a pressure of 2-6 bar.

[0042] A carbon fiber / polyetherketone-ketone composite coating comprises a two-layer gradient structure consisting of a base layer and a top layer. The carbon fiber mass fraction of the base layer is 10-30%, and the carbon fiber mass fraction of the top layer is 1-10%. The coefficient of friction is ≤0.15, and the coating is suitable for the surfaces of robot joints, bearings, precision transmission components in aerospace, and wear-resistant components in medical devices.

[0043] Working principle: Step 1: Selection and pretreatment of carbon fiber parameters Short-cut carbon fibers with an average length of 50–200 μm and a diameter of 5–10 μm are selected, with their aspect ratio controlled within the range of 10–30 to avoid the formation of conductive networks through overlap within or between particles. Depending on design requirements, the volume fraction of the carbon fiber is controlled at 1–30%, with the undercoat at 10–30% and the topcoat at 1–10%. The fibers are heat-treated at 400–600 ℃ for 0.5–2 h in an inert atmosphere to remove the sizing agent, and then activated by low-temperature plasma (100–300 W, oxygen / argon-oxygen mixture) for 10–30 min to introduce oxygen-containing functional groups to improve wettability and interfacial bonding. Step 2: Preparation of polyetherketone solution Polyetherketoneketone (PEKK) was dissolved in a highly polar solvent (trifluoroacetic acid, dichloroethane, etc.) to prepare a homogeneous solution of 5–25 wt%. The dissolution temperature was controlled at 40–60 °C, and the solvent was selected to balance the solubility and evaporation rate of PEVKK. Step 3: Dispersion Preparation Activated carbon fibers were added to a polyether ketone solution in a specific ratio, and the solution was dispersed and prevented from agglomerating by ultrasonic treatment (300–800 W, 30–60 min). Mechanical stirring (800–1500 rpm, 1–2 h) was then used to maintain solution stability, resulting in a uniform dispersion. The dispersion process was carried out at a temperature below 60 ℃ to avoid rapid solvent evaporation that could lead to film defects. Step 4: Composite Molding The dispersion was subjected to gradient temperature drying: the temperature was increased to 40–80 °C at 1–3 °C / min and held for 1–3 h to allow polyether ketone ketone to be gradually deposited on the fiber surface; then the temperature was increased to 200–260 °C at 2–5 °C / min to completely remove the solvent, resulting in a composite in which the fibers were uniformly coated. Step 5: Powder preparation and heat treatment repair The composite was air-jet milled to obtain initial powder, which was then sieved to control the particle size distribution. Subsequently, it was ball-milled for 1–2 h to concentrate the particle size within the 15–65 μm range, improving powder flowability and sprayability. The powder was then heat-treated at 250–350 °C under an inert atmosphere to partially melt and recrystallize the polyetherketone, repairing cracks caused by milling, covering exposed fiber ends, further enhancing the coating effect and increasing the powder's volume resistivity. Step 6: Electrostatic spraying and consolidation A two-layer spraying strategy is adopted: Undercoat: As a reinforcing and conductive transition layer, the carbon fiber content is 10–30%, the thickness is 80–150 μm, the spraying voltage is 60–70 kV, and the substrate is preheated to 100–120 ℃; after spraying, it is cured at 300–350 ℃ for 5–10 min.

[0044] Topcoat spraying: As an insulating and surface functional layer, the carbon fiber content is 1–10%, the total thickness is 200–300 μm, the spraying voltage is 75–90 kV, and the substrate is preheated to 80–100 ℃; finally, it is solidified at 380–400 ℃ for 10–30 min to form a dense coating structure.

[0045] Step 7: Crystallization control and hot rolling densification The consolidated coating is then subjected to gradient cooling (10–15 ℃ / min) to 250–280 ℃ and held for 0.5–2 h to control the crystallinity at 10–40%, balancing toughness and heat resistance. Subsequently, it is hot-rolled at 260–320 ℃ and 0.5–5 MPa to further reduce porosity, enhance interfacial bonding, and improve coating density. Step 8: Surface Treatment The coated surface is uniformly sanded with 180-400 grit sandpaper, then cleaned with compressed air; alternatively, 180-400 grit white corundum abrasive is used for uniform sandblasting at an appropriate distance and angle under a pressure of 2-6 bar. This improves tribological properties and wear resistance while ensuring surface smoothness and insulation.

[0046] Step 1: Selection of carbon fiber parameters and pretreatment Short-cut carbon fibers with an average length of 100 μm and a diameter of 5 μm were selected to maintain an aspect ratio of 20. The bottom coating consisted of 20% carbon fiber by volume, and the top coating consisted of 5%. The carbon fibers were heat-treated at 500 °C for 1 h in an inert atmosphere to remove surface sizing agent and improve interfacial bonding. Subsequently, low-temperature plasma activation (200 W, oxygen / argon-oxygen mixture) was performed for 20 min to introduce oxygen-containing functional groups, thereby improving fiber surface polarity and polymer wettability.

[0047] Step 2: Preparation of polyetherketone solution A 20 wt% homogeneous solution of polyether ketone ketone was prepared by dissolving it in trifluoroacetic acid. The dissolution temperature was controlled at 50 °C to ensure complete dissolution and no degradation of the polyether ketone ketone.

[0048] Step 3: Dispersion Preparation Activated carbon fibers were added to a polyether ketone solution at a predetermined ratio. The solution was then ultrasonically treated (500 W, 60 min) to disperse the fibers and prevent agglomeration, while mechanical stirring (1000 rpm, 2 h) was performed simultaneously to maintain the uniformity and stability of the dispersion. The solution temperature was controlled below 60 ℃ during dispersion to avoid uneven solvent evaporation.

[0049] Step 4: Composite Molding The dispersion was placed in a temperature-controlled reactor for gradient heating and drying: the temperature was increased to 60 ℃ at 2 ℃ / min and held for 2 h to allow polyether ketone ketone to gradually deposit on the fiber surface; then the temperature was increased to 250 ℃ at 5 ℃ / min to completely remove the solvent, resulting in composite particles with the fibers uniformly coated.

[0050] Step 5: Powder preparation and heat treatment The composite was initially powdered by air jet milling, and the particle size distribution was controlled by sieving. Subsequently, it was ball-milled for 2 hours to concentrate the particle size within the range of 15–65 μm, improving powder flowability. The powder was then heat-treated at 320 °C under an inert atmosphere to partially melt and recrystallize the polyetherketoneketone, repairing cracks and covering fiber ends, thereby improving the coating effect and volume resistivity.

[0051] Step 6: Electrostatic spraying and consolidation A two-layer spraying strategy is adopted: Underlying coating: as a reinforcing and conductive control layer, 100 μm thick, spraying voltage 60 kV, substrate preheating 120℃, curing 350℃, 5 min; Topcoat spraying: as an insulating and surface protective layer, with a total thickness of 200 μm, spraying voltage of 80 kV, substrate preheating of 80℃, and final curing at 400℃ for 10 min.

[0052] Step 7: Crystallization Control and Hot Rolling After consolidation, the double-layer coating was subjected to gradient cooling (10 °C / min) to 250–280 °C and held for 1 h to control the crystallinity at 20%. Subsequently, it was hot rolled at 320 °C and 5 MPa to improve the coating density and interfacial adhesion.

[0053] Step 8: Surface Treatment Sand evenly with 180-400 grit sandpaper, then clean the surface with compressed air.

[0054] Performance testing: Wear rate is reduced by 40% compared to traditional coatings, and surface roughness meets the requirements of precision parts.

[0055] Step 1: Selection of carbon fiber parameters and pretreatment Short-cut carbon fibers with an average length of 150 μm and a diameter of 6 μm (aspect ratio = 25) were selected. The bottom coating had a carbon fiber volume fraction of 15%, and the top coating had an 8% carbon fiber volume fraction.

[0056] The sizing agent was removed by heat treatment at 450 °C for 1 h under a nitrogen atmosphere. Subsequently, it was activated by low-temperature plasma treatment with a 250 W oxygen / argon-oxygen mixture for 15 min.

[0057] Step 2: Preparation of polyetheretherketone solution Polyetheretherketone powder is dissolved in dichloroethane (25°C) to form a 10% (w / w) solution.

[0058] Step 3: Dispersion Preparation Activated carbon fibers were added, and the mixture was ultrasonically treated at 600 W for 40 min and maintained at 1200 rpm for 1.5 h.

[0059] Step 4: Composite molding and solvent removal Gradient heating: The temperature was increased to 70 ℃ at 1.5 ℃ / min and held for 2 h, then increased to 220 ℃ at 3 ℃ / min to obtain uniformly coated composite particles.

[0060] Step 5: Powder preparation and heat treatment After air jet milling, the particle size is concentrated in 15–65 μm. After ball milling for 1.5 h, heat treatment at 300 ℃ for 1 h under an inert atmosphere is performed to repair cracks and regulate resistivity.

[0061] Step 6: Electrostatic spraying and consolidation Base layer: 120 μm thickness, spraying voltage 65 kV, substrate preheating 110 ℃, consolidation temperature 330 ℃, 5 min; Topcoat: 220 μm thickness, spraying voltage 85 kV, substrate preheating 90 ℃, final curing 380 ℃, 8 min.

[0062] Step 7: Crystallization Control and Hot Rolling Gradient cooling to 260 °C, holding at that temperature for 1.5 h, crystallinity approximately 15%; then hot rolling at 280 °C and 3 MPa for 20 min.

[0063] Step 8: Surface Treatment Use 180-400 mesh white corundum abrasive and blast it evenly at an appropriate distance and angle under a pressure of 2-6 bar.

[0064] Performance: Wear rate is reduced by 35% compared to the untreated composite coating.

[0065] Step 1: Carbon fiber parameters and pretreatment 80 μm in length and 5 μm in diameter (aspect ratio = 16). The bottom layer has a carbon fiber volume fraction of 25%, and the top layer has a volume fraction of 3%.

[0066] The sample was heat-treated at 550 °C for 2 h in an argon atmosphere, followed by activation with 150 W plasma for 30 min.

[0067] Step 2: Preparation of polyetherketone solution A 25 wt% solution was prepared using p-chlorophenol as the solvent at a dissolution temperature of 60 °C.

[0068] Step 3: Dispersion Preparation Ultrasonic power 700 W, 45 min, stirring speed 1500 rpm, time 2 h.

[0069] Step 4: Composite molding and solvent removal Gradient heating: First, the temperature is increased to 80℃ at 2℃ / min and held for 1 h, then increased to 260℃ at 4℃ / min to obtain coated particles.

[0070] Step 5: Powder preparation and heat treatment Air jet milling and ball milling for 2 h resulted in a particle size distribution of 20–60 μm. The powder was then heat-treated at 340 °C for 0.5 h to improve coating and resistivity.

[0071] Step 6: Electrostatic spraying and consolidation The base layer thickness is 150 μm, the spraying voltage is 70 kV, the substrate is preheated to 100 ℃, the solidification temperature is 350 ℃, and the curing time is 6 min.

[0072] Topcoat spraying: Topcoat thickness 200 μm, spraying voltage 90 kV, substrate preheating 85 ℃, final curing 390 ℃, 10 min.

[0073] Step 7: Crystallization Control and Hot Rolling Cool to 280 ℃ and hold for 0.5 h, crystallinity is about 10%; then hot roll at 300 ℃ and 4 MPa for 10 min.

[0074] Step 8: Surface Treatment Sand evenly with 180-400 grit sandpaper, then clean the surface with compressed air.

[0075] Performance: Wear rate is reduced by 37% compared to conventional PEKK coatings.

[0076] Comparative Example 1: Powder particle size too large: Insufficient crushing and ball milling, powder particle size distribution 100–220 μm, the rest is the same as in Example 1.

[0077] Results: The powder had poor flowability, low deposition efficiency during spraying, and a surface roughness Ra = 2.5 μm, which did not meet the requirements for precision parts.

[0078] Comparative Example 2: Short-cut carbon fibers with an average length of <10 μm (diameter of 5–10 μm and aspect ratio <6) were used, and other process parameters were the same as in Example 1.

[0079] Results: The reinforcing effect of fibers on the matrix decreased, the coating’s crack resistance and peel resistance decreased, and the wear rate decreased by 30%.

[0080] Comparative Example 3: The coating was directly cooled naturally after solidification, without heat preservation and crystallization control, and was not hot rolled.

[0081] Results: The coating has many internal pores, crystallinity of less than 30%, poor interfacial bonding, wear rate reduction of 25%, and poor impact resistance. It should be noted that, in this document, relational terms such as first and second (number one, number two), etc., are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0082] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a carbon fiber / polyether ketone composite coating, characterized in that: Specifically, the following steps are included: S1: Selection and pretreatment of carbon fiber parameters: Select carbon fibers with appropriate parameters, perform heat treatment on the carbon fibers under an inert atmosphere, and then perform low-temperature plasma activation. S2: Preparation of polyether ketone solution: Dissolve polyether ketone in a strongly polar solvent to prepare a homogeneous solution; S3: Dispersion preparation: The activated carbon fibers are added to the obtained polyether ketone homogeneous solution, and then subjected to ultrasonic treatment and mechanical stirring to obtain a uniform dispersion; S4: Composite molding: The dispersion is subjected to gradient heating and drying to slowly remove the solvent and form a composite in which carbon fibers are uniformly coated with polyether ketone ketone. S5: Powder preparation and heat treatment repair: The composite is crushed, ball-milled and heat-treated to partially melt and recrystallize the polyether ketone ketone, repair the crushed cracks and cover the ends of the carbon fibers to obtain a composite powder with suitable resistivity. S6: Electrostatic spraying and consolidation: The composite powder is divided into a base coat and a top coat according to the carbon fiber content, and the two layers are formed by electrostatic spraying and then consolidated at a certain temperature. S7: Crystallization control and hot rolling densification: The solidified double-layer coating is subjected to gradient cooling and held at a certain temperature for a certain time to control the crystallinity, and then hot rolling is carried out under a certain temperature and pressure. S8: Coating surface treatment: Grind or sandblast the coating surface to complete the preparation of the carbon fiber / polyether ketone ketone composite coating.

2. The method for preparing a carbon fiber / polyether ketone composite coating according to claim 1, characterized in that: In step S1, the average length of the carbon fiber is 50-200 μm, the diameter is 5-10 μm, the aspect ratio is 10-30, the heat treatment temperature is 400-600℃, the heat treatment time is 0.5-2h, the low-temperature plasma activation power is 100-300W, the gas is one of oxygen and argon-oxygen mixture, and the activation time is 10-30min.

3. The method for preparing a carbon fiber / polyether ketone composite coating according to claim 1, characterized in that: In step S2, the solvent for the polyether ketone solution is at least one or more mixed solvents selected from trifluoroacetic acid, dichloroethane, p-chlorophenol, dichloroacetic acid, and dichloropropionic acid. The dissolution temperature is controlled at 40-60℃, and the polyether ketone content of the homogeneous solution is 5-25wt%.

4. The method for preparing a carbon fiber / polyether ketone composite coating according to claim 1, characterized in that: In step S3, the ultrasonic power of the dispersion is 300-800W, the ultrasonic time is 30-60min, the stirring speed is 800-1500rpm, the stirring time is 1-2h, and the temperature is kept below 60℃.

5. The method for preparing a carbon fiber / polyether ketone composite coating according to claim 1, characterized in that: The composite drying process in step S4 includes first raising the temperature to 40-80℃ at 1-3℃ / min and holding it for 1-3 hours, then raising the temperature to 200-260℃ at 2-5℃ / min and holding it for 24-48 hours to ensure complete drying.

6. The method for preparing a carbon fiber / polyether ketone composite coating according to claim 1, characterized in that: In step S5, the particle size of the composite is 15-65 μm, and the heat treatment temperature after ball milling is 250-350℃ for 10-30 min.

7. The method for preparing a carbon fiber / polyether ketone composite coating according to claim 1, characterized in that: In step S6, the fiber content of the base coat is 10-30%, the fiber content of the top coat is 1-10%, the thickness of the base coat is 80-150μm, the spraying voltage is 60-70kV, the substrate temperature is 100-120℃, the total thickness of the top coat is 200-300μm, the spraying voltage is 75-90kV, the substrate temperature is 80-100℃, and the consolidation temperature is 300-400℃.

8. The method for preparing a carbon fiber / polyether ketone composite coating according to claim 1, characterized in that: In step S7, the gradient cooling temperature is 250-280℃, the holding time is 0.5-2h, the crystallinity is controlled at 10-40%, the hot rolling conditions are 260-320℃, the pressure is 0.5-5MPa, and the action time is 5-30min.

9. The method for preparing a carbon fiber / polyether ketone composite coating according to claim 1, characterized in that: The surface treatment method in step S8 is to uniformly polish with 180-400 grit sandpaper and then clean the surface with compressed air, or to uniformly sandblast with 180-400 grit white corundum sand at an appropriate distance and angle under a pressure of 2-6 bar.

10. A carbon fiber / polyetherketone-ketone composite coating, comprising a two-layer gradient structure of a base layer and a top layer, characterized in that: The carbon fiber mass fraction of the bottom layer is 10-30%, the carbon fiber mass fraction of the top layer is 1-10%, the coefficient of friction is ≤0.15, and the coating is suitable for the surface of robot joints, bearings, aerospace precision transmission components, and wear-resistant components of medical devices.

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