A method for preparing a polymer-derived ceramic coating

Abstract

This invention discloses a method for preparing a polymer-derived ceramic coating, belonging to the field of coating materials technology. The method first obtains a ceramic bulk by cross-linking and pyrolysis of a polymer precursor, then prepares a suitable ceramic powder through ball milling, sieving, spray granulation, and high-temperature debinding. After pretreatment of the substrate by sandblasting, cleaning, and drying, the powder is deposited onto the substrate surface using an atmospheric plasma spraying process to form a polymer-derived ceramic coating. This invention achieves rapid coating formation through plasma spraying, allows for flexible control of coating thickness, and produces a dense coating with no obvious defects and good adhesion to the substrate. It effectively solves the problems of easy cracking, difficult thickness control, and long preparation cycle in existing technologies. The process is simple and efficient, suitable for high-temperature protection of high-temperature alloys, ceramics, and ceramic matrix composites, especially meeting the engineering application needs of aerospace hot-end components.

Description

Technical Field

[0001] This invention relates to the field of coating materials technology, and more specifically, to a method for preparing a polymer-derived ceramic coating. Background Technology

[0002] With the rapid development of high-end equipment technologies such as aerospace, the service environment of key hot-end components such as turbine blades and combustion chambers inside aero-engines and other equipment is becoming increasingly harsh. Applying ceramic protective coatings to the surface of these components can effectively improve their high-temperature resistance, oxidation resistance, and resistance to extreme environments, which is of great significance for ensuring the reliability of equipment during service.

[0003] Polymer-derived ceramics are novel ceramic materials derived from polymers through high-temperature cross-linking and pyrolysis. They possess excellent high-temperature stability and designability in composition and structure, making them ideal candidate materials for high-temperature protective coatings. Therefore, developing efficient preparation technologies for polymer-derived ceramic coatings suitable for engineering applications has significant application value and engineering implications.

[0004] Existing polymer-derived ceramic coatings are mainly prepared using the following methods: Relevant literature describes the preparation of antioxidant coatings using precursor slurry spraying combined with high-temperature pyrolysis. The resulting coatings exhibit good antioxidant properties at 1200℃, but they are prone to cracking defects, and the coating thickness is difficult to control precisely.

[0005] Chinese patent application CN116065209A discloses a method for preparing polymer-derived ceramic coatings on alloy surfaces. The SiOC ceramic coating is prepared by multiple electrodeposition combined with pyrolysis process. The coating has good adhesion and oxidation resistance. However, this method requires the preparation of precursor electrolyte and multiple electrodeposition processes, which are complex and have a long preparation cycle.

[0006] Chinese patent application CN113564560A discloses a coating preparation method based on chemical vapor deposition, which obtains a dense and well-bonded SiOC ceramic coating on the alloy surface. However, this process has shortcomings such as low deposition efficiency, high production cost, and slow coating growth rate, making it difficult to meet the requirements of efficient large-scale preparation.

[0007] In summary, existing polymer-derived ceramic coating preparation technologies generally suffer from problems such as difficulty in thickness control, long preparation cycles, low molding efficiency, and poor process adaptability. Therefore, there is an urgent need to develop a novel polymer-derived ceramic coating preparation method that is simple to implement, fast to form, and easily controls thickness, to meet the protection application requirements of high-temperature hot-end components in aerospace and other fields. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, the present invention provides a method for preparing a polymer-derived ceramic coating. The method involves cross-linking and pyrolyzing a polymer precursor, ball milling and sieving, and spray granulation to remove adhesive to obtain a sprayable powder. Then, atmospheric plasma spraying is used to form a film on the substrate surface. This method solves the problems of difficult thickness control, long preparation cycle, and low forming efficiency of existing coatings, and achieves rapid coating formation, precise thickness adjustment, and a dense surface without obvious defects.

[0009] The first objective of this invention is to provide a method for preparing a polymer-derived ceramic coating, the method specifically comprising the following steps: Step S1: After the polymer precursor is subjected to cross-linking and pyrolysis treatment in sequence, a ceramic block is obtained. The ceramic block is then ball-milled and sieved to obtain polymer-derived ceramic powder. Step S2: The polymer-derived ceramic powder obtained in step S1 is subjected to spray granulation and high-temperature debinding in sequence to obtain polymer-derived ceramic spray powder. Step S3: Using atmospheric plasma spraying, the polymer-derived ceramic powder prepared in step S2 is sprayed onto the substrate surface to obtain a polymer-derived ceramic coating.

[0010] Compared with existing technologies, this invention constructs a novel polymer-derived ceramic coating preparation path through a complete process flow of precursor crosslinking and pyrolysis powdering, spray granulation and degumming, and atmospheric plasma spraying film formation. This effectively overcomes the limitations of traditional methods on coating formation, significantly improves coating preparation efficiency and engineering application level, enables rapid coating formation and flexible thickness control, and ensures a stable and reliable bonding state between the coating and the substrate. Overall, it improves the coating's service performance in harsh environments such as high temperature and oxidation, meeting the actual use requirements of high-temperature protective coatings for high-end equipment such as aerospace.

[0011] In one possible implementation, in step S1, the polymer precursor is selected from one of polysiloxane, polycarbosilane, polynitrosilane, polyborosilicate, and polysiloxane. This invention, by employing a specific type of polymer precursor, enables the coating to be stably transformed into a ceramic phase with uniform structure and excellent performance during subsequent high-temperature treatment. This ensures the coating possesses excellent high-temperature stability, structural integrity, and environmental adaptability, making it less prone to phase transformation, cracking, and performance degradation during long-term high-temperature service. This effectively improves the coating's resistance to oxidation, ablation, and extreme environments.

[0012] In one possible implementation, in step S1, the crosslinking treatment is performed under vacuum conditions, and the parameters of the crosslinking treatment are as follows: crosslinking temperature is 120-150℃, and crosslinking time is 2-4 hours. This invention performs crosslinking treatment on the precursor under vacuum conditions, which allows the polymer precursor to be fully crosslinked and cured, avoiding internal defects caused by insufficient crosslinking or uneven heating, improving the molding quality and structural uniformity of the precursor, and providing a stable and reliable preform for subsequent pyrolysis processes.

[0013] In one possible implementation, in step S1, the pyrolysis treatment is carried out in a tube furnace, specifically as follows: using nitrogen or argon as a protective atmosphere, the temperature is raised to 900-1200℃ at a rate of 1-5℃ / min and held at that temperature for 2-4 hours, followed by cooling to room temperature at a rate of 1-2℃ / min. This invention, through a pyrolysis process using a controlled atmosphere and programmed temperature rise and fall, effectively avoids oxidation, component segregation, and abnormal grain growth of the ceramic phase at high temperatures, resulting in a ceramic bulk with a pure phase, dense structure, and uniform composition. This improves the compositional consistency and high-temperature stability of the ceramic powder, thereby ensuring the uniformity of the prepared coating's composition and stable performance, and enhancing the reliability of the coating under high-temperature service conditions.

[0014] In one possible implementation, the parameters for ball milling and sieving in step S1 are as follows: ball milling speed is 200-500 r / min, and ball milling time is 24-30 h. The average particle size of the polymer-derived ceramic powder obtained in step S1 is 8-15 μm.

[0015] Compared with existing technologies, this invention obtains ceramic fine powder with uniform particle size distribution and good dispersibility through reasonable ball milling and sieving parameters, effectively reducing powder agglomeration, large particles and impurity residues, improving the overall quality of powder, providing high-quality raw materials for subsequent spray granulation and plasma spraying, making the spraying process more stable, the coating formation more dense and smooth, and reducing the probability of defects such as pores and cracks in the coating.

[0016] In one possible implementation, the specific steps of spray granulation in step S2 are as follows: polymer-derived ceramic powder, polyvinyl alcohol, deionized water and anhydrous ethanol are mixed and ball-milled at a speed of 80-120 r / min in a mass ratio of (40-45):(40-45):(5-10):(5-10) to obtain a multiphase mixture. The multiphase mixture is fed into a spray granulator for granulation and drying. The inlet temperature of the spray granulator is 270-300℃, the outlet temperature is 100-120℃, the nozzle speed is 33-35 r / min, and the peristaltic pump speed is 13-15 r / min.

[0017] Compared with existing technologies, the present invention employs an optimized spray granulation process that allows ceramic powder and binder components to be fully and uniformly mixed, producing granulated powder with excellent flowability, dispersibility, and spray applicability. This significantly improves powder delivery stability and deposition efficiency during plasma spraying, resulting in a more uniform coating thickness, a denser structure, and effectively improved coating surface quality and overall protective performance.

[0018] In one possible implementation, in step S2, the high-temperature degumming is carried out in a tube furnace, and the specific process is as follows: using nitrogen or argon as a protective atmosphere, the temperature is raised to 200-300℃ at a rate of 1-5℃ / min and held at that temperature for 2-3 hours, and then cooled to room temperature at a rate of 1-2℃ / min. The average particle size of the polymer-derived ceramic spray powder obtained in step S2 is 20-30 μm.

[0019] Compared with existing technologies, this invention can completely remove residual organic binders and other components in powder by using a controlled atmosphere and high temperature to remove adhesives. This avoids defects such as pores and cracks caused by the decomposition of organic matter during the spraying process, improves the purity and flowability of the sprayed powder, ensures a strong interface bond and dense internal structure of the coating, and enhances the bonding strength and high-temperature service stability of the coating.

[0020] In one possible implementation, in step S3, the substrate is a high-temperature alloy, ceramic, or ceramic matrix composite material, and the substrate is pre-treated with a surface, which includes sandblasting, cleaning, and drying in sequence. The cleaning process is as follows: the substrate after sandblasting is placed in an ethanol or acetone solution for ultrasonic cleaning for 30-60 minutes. The drying process is carried out in a vacuum oven with the following parameters: drying temperature of 80-100℃ and drying time of 1-3h.

[0021] Compared with existing technologies, the present invention can effectively improve the surface roughness and cleanliness of the substrate by performing systematic pretreatment of sandblasting, cleaning and drying, remove surface oil, oxide scale and impurities, significantly enhance the mechanical and interfacial bonding between the coating and the substrate, reduce the risk of coating peeling and flaking, and improve the overall bonding reliability and service life of the coating.

[0022] In one possible implementation, the substrate is further coated with a transition layer after surface pretreatment. The thickness of the transition layer is 80-240 μm, and the material is 3YSZ, 8YSZ, or NiCrAlY. The transition layer is prepared by atmospheric plasma spraying with the following parameters: argon flow rate of 56-60 L / min, hydrogen flow rate of 14-18 L / min, spraying current of 500-600 A, spraying power of 51-53 kW, spraying distance of 90-110 mm, and number of spraying layers of 2-5.

[0023] Compared with the prior art, the present invention can effectively alleviate the mismatch of thermal expansion coefficients between the substrate and the ceramic coating by setting a transition layer between the substrate and the ceramic coating, reduce the residual stress at the interface, optimize the stress distribution of the coating, improve the interfacial bonding strength and thermal shock resistance, and make the coating less prone to cracking and peeling in high temperature alternating environment, thereby further improving the long-term service stability of the coating system.

[0024] In one possible implementation, the parameters of the atmospheric plasma spraying method in step S3 are: argon flow rate of 40-44 L / min, hydrogen flow rate of 6-10 L / min, carrier gas flow rate of 5-8 L / min, spraying current of 500-600 A, spraying power of 30-32 kW, spraying distance of 90-110 mm, and number of sprayed layers of 2-10. This invention, by optimizing the atmospheric plasma spraying parameters, enables the sprayed powder to fully melt and uniformly deposit, forming a dense, continuous ceramic coating without obvious defects. This achieves rapid coating formation and precise thickness control, ensuring coating uniformity and stability, and improving the coating's high-temperature resistance, oxidation resistance, and impact resistance, meeting the requirements of high-end equipment hot-end components for high-performance protective coatings. Attached Figure Description

[0025] Figure 1 These are the surface SEM and EDS images of the polymer-derived ceramic coating prepared in Example 5 of this invention; Figure 2 These are cross-sectional SEM and EDS images of the polymer-derived ceramic coating prepared on a substrate with a YSZ transition layer according to Example 1 of the present invention. Figure 3 This is an XPS image of the polymer-derived ceramic coating prepared on a substrate with a YSZ transition layer according to Example 1 of the present invention. Detailed Implementation

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0027] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0029] The following description is based on specific embodiments.

[0030] Example 1

[0031] This embodiment provides a method for preparing a polymer-derived ceramic coating, as detailed below: Step S1: Crosslink the polysiloxane in a vacuum oven at 120℃ for 2 hours. Then, pyrolyze the crosslinked block in a tube furnace under argon atmosphere at 900℃ for 2 hours. The heating rate is 5℃ / min, and the cooling rate is 2℃ / min to obtain a ceramic block. The ceramic block is then subjected to planetary ball milling at 300 r / min for 24 hours to obtain polymer-derived ceramic powder with an average particle size of approximately 10.5 μm. Step S2: Polymer-derived ceramic powder is ball-milled with polyvinyl alcohol, deionized water, and anhydrous ethanol to obtain a SiOC-based multiphase mixture, wherein the ratio of polymer-derived ceramic powder:polyvinyl alcohol:deionized water:anhydrous ethanol is 40:40:10:10, and the ball milling speed is 80-120 r / min. The SiOC-based multiphase mixture is then granulated and dried in a spray granulator. The spray granulation inlet temperature is 290℃, the outlet temperature is 115℃, the nozzle speed is 34 r / min, and the peristaltic pump speed is 15 r / min, resulting in granulated SiOC spray-coated ceramic powder. The granulated SiOC spray-coated ceramic powder is then degummed in a tube furnace under argon atmosphere at 200℃ for 2 hours, with a heating rate of 5℃ / min and a cooling rate of 2℃ / min. The average particle size of the polymer-derived ceramic spray-coated powder obtained after degumming is 21.3 μm. Step S3: After sandblasting the nickel-based superalloy, it is ultrasonically cleaned in an ethanol solution for 30 minutes, and then vacuum dried at 80°C for 2 hours for later use. 8YSZ powder is sprayed onto the roughened nickel-based alloy surface using an atmospheric plasma spraying device. The argon flow rate is 58 L / min, the hydrogen flow rate is 16 L / min, the spraying current is 500 A, the spraying power is 51 kW, the spraying distance is 90 mm, and the number of spraying layers is 2, resulting in a YSZ transition layer. Step S4: Using an atmospheric plasma spraying device, spray the polymer-derived ceramic powder obtained in step S2 onto the YSZ transition layer obtained in step S3. The argon flow rate used in the spraying process is 42L / min, the hydrogen flow rate is 8L / min, the carrier gas flow rate is 6L / min, the spraying current is 500A, the spraying power is 30kW, the spraying distance is 90mm, and the number of spraying layers is 2, to obtain the polymer-derived ceramic coating.

[0032] Characterization showed that the thickness of the YSZ transition layer obtained in this embodiment was 157.12 μm, and the thickness of the polymer-derived ceramic coating was 9.45 μm.

[0033] Figure 2 These are cross-sectional SEM and EDS images of the polymer-derived ceramic coating prepared on a substrate with a YSZ transition layer in this embodiment. Figure 2 It can be seen that the polymer-derived ceramic coating prepared in this embodiment has good bonding with the transition layer and no internal pores; Figure 3 This is an XPS image of the polymer-derived ceramic coating prepared on a substrate with a YSZ transition layer in this embodiment. Figure 3 It can be proven that the coating is polymer-derived SiOC.

[0034] Example 2

[0035] This embodiment provides a method for preparing a polymer-derived ceramic coating, as detailed below: Step S1: Crosslink the polysiloxane in a vacuum oven at 120℃ for 2 hours. Then, pyrolyze the crosslinked block in a tube furnace under argon atmosphere at a pyrolysis temperature of 1000℃ for 2 hours. The heating rate is 5℃ / min, and the cooling rate is 2℃ / min, yielding a ceramic block. The ceramic block is then subjected to planetary ball milling at 250 r / min for 24 hours to obtain polymer-derived ceramic powder with an average particle size of approximately 10.3 μm. Step S2: Polymer-derived ceramic powder is ball-milled with polyvinyl alcohol, deionized water, and anhydrous ethanol to obtain a SiOC-based multiphase mixture, wherein the ratio of polymer-derived ceramic powder:polyvinyl alcohol:deionized water:anhydrous ethanol is 40:40:10:10, and the ball milling speed is 80-120 r / min. The SiOC-based multiphase mixture is then granulated and dried in a spray granulator. The spray granulation inlet temperature is 290℃, the outlet temperature is 115℃, the nozzle speed is 34 r / min, and the peristaltic pump speed is 15 r / min, resulting in granulated SiOC spray-coated ceramic powder. The granulated SiOC spray-coated ceramic powder is then degummed in a tube furnace under argon atmosphere at 200℃ for 2 hours, with a heating rate of 5℃ / min and a cooling rate of 2℃ / min. The average particle size of the polymer-derived ceramic spray-coated powder obtained after degumming is 21.3 μm. Step S3: After sandblasting the nickel-based superalloy, it is ultrasonically cleaned in an ethanol solution for 30 minutes, and then vacuum dried at 80°C for 2 hours for later use. 8YSZ powder is sprayed onto the roughened nickel-based alloy surface using an atmospheric plasma spraying device. The argon flow rate is 58 L / min, the hydrogen flow rate is 16 L / min, the spraying current is 500 A, the spraying power is 51 kW, the spraying distance is 90 mm, and the number of spraying layers is 4, resulting in a YSZ transition layer. Step S4: Using an atmospheric plasma spraying device, spray the polymer-derived ceramic powder obtained in step S2 onto the YSZ transition layer obtained in step S3. The argon flow rate used in the spraying process is 42L / min, the hydrogen flow rate is 8L / min, the carrier gas flow rate is 6L / min, the spraying current is 500A, the spraying power is 30kW, the spraying distance is 90mm, and the number of spraying layers is 4, to obtain the polymer-derived ceramic coating.

[0036] Characterization showed that the thickness of the YSZ transition layer obtained in this embodiment was 310.02 μm, and the thickness of the polymer-derived ceramic coating was 17.26 μm.

[0037] Example 3

[0038] This embodiment provides a method for preparing a polymer-derived ceramic coating, as detailed below: Step S1: Crosslink polycarbosilane in a vacuum oven at 150℃ for 2 hours. Then, pyrolyze the crosslinked block in a tube furnace under nitrogen atmosphere at 1200℃ for 4 hours, with a heating rate of 1℃ / min and a cooling rate of 1℃ / min, to obtain a ceramic block. The ceramic block is then subjected to planetary ball milling at 200 r / min for 30 hours to obtain polymer-derived ceramic powder. Step S2: The polymer-derived ceramic powder is ball-milled with polyvinyl alcohol, deionized water, and anhydrous ethanol to obtain a SiC-based multiphase mixture, wherein the ratio of polymer-derived ceramic powder:polyvinyl alcohol:deionized water:anhydrous ethanol is 45:45:5:5, and the ball milling speed is 80-120 r / min. The SiC-based multiphase mixture is then granulated and dried in a spray granulator. The spray granulation inlet temperature is 270℃, the outlet temperature is 120℃, the nozzle speed is 33 r / min, and the peristaltic pump speed is 14 r / min, resulting in granulated SiC spray-coated ceramic powder. The granulated SiC spray-coated ceramic powder is then degummed in a tube furnace under a nitrogen atmosphere at 300℃ for 3 hours, with a heating rate of 1℃ / min and a cooling rate of 2℃ / min. Step S3: After sandblasting the ceramic matrix composite material, it is ultrasonically cleaned in an ethanol solution for 60 min, and then vacuum dried at 100℃ for 1 h for later use. 3YSZ powder is sprayed onto the roughened ceramic matrix composite material surface using an atmospheric plasma spraying device. The argon flow rate is 56 L / min, the hydrogen flow rate is 14 L / min, the spraying current is 600 A, the spraying power is 53 kW, the spraying distance is 110 mm, and the number of spraying layers is 3, to obtain the YSZ transition layer. Step S4: Using an atmospheric plasma spraying device, the polymer-derived ceramic powder obtained in step S2 is sprayed onto the YSZ transition layer obtained in step S3. The argon flow rate is 40L / min, the hydrogen flow rate is 6L / min, the carrier gas flow rate is 5L / min, the spraying current is 600A, the spraying power is 32kW, the spraying distance is 110mm, and the number of spraying layers is 4, to obtain a polymer-derived ceramic coating.

[0039] Example 4

[0040] This embodiment provides a method for preparing a polymer-derived ceramic coating, as detailed below: Step S1: Crosslink the polynitrosilane in a vacuum oven at 130℃ for 4 hours. Then, pyrolyze the crosslinked block in a tube furnace under nitrogen atmosphere at 1050℃ for 3 hours, with a heating rate of 3℃ / min and a cooling rate of 1.5℃ / min to obtain a ceramic block. The ceramic block is then subjected to planetary ball milling at 500 r / min for 26 hours to obtain polymer-derived ceramic powder. Step S2: The polymer-derived ceramic powder is ball-milled with polyvinyl alcohol, deionized water, and anhydrous ethanol to obtain a SiCN-based multiphase mixture, wherein the ratio of polymer-derived ceramic powder:polyvinyl alcohol:deionized water:anhydrous ethanol is 42:42:8:8, and the ball milling speed is 80-120 r / min. The SiCN-based multiphase mixture is then granulated and dried in a spray granulator. The spray granulation inlet temperature is 300℃, the outlet temperature is 100℃, the nozzle speed is 35 r / min, and the peristaltic pump speed is 13 r / min, resulting in granulated SiCN-coated ceramic powder. The granulated SiCN-coated ceramic powder is then degummed in a tube furnace under an argon atmosphere at a degumming temperature of 300℃ for 2.5 h, with a heating rate of 3℃ / min and a cooling rate of 1℃ / min. Step S3: After sandblasting the nickel-based superalloy, it is ultrasonically cleaned in an ethanol solution for 45 minutes, and then vacuum dried at 90°C for 3 hours for later use. NiCrAlY powder is sprayed onto the roughened nickel-based alloy surface using an atmospheric plasma spraying device. The argon flow rate is 60 L / min, the hydrogen flow rate is 18 L / min, the spraying current is 550 A, the spraying power is 52 kW, the spraying distance is 100 mm, and the number of spraying layers is 5, to obtain a NiCrAlY transition layer. Step S4: Using an atmospheric plasma spraying device, the polymer-derived ceramic powder obtained in step S2 is sprayed onto the NiCrAlY transition layer obtained in step S3. The argon flow rate is 44 L / min, the hydrogen flow rate is 10 L / min, the carrier gas flow rate is 6 L / min, the spraying current is 550 A, the spraying power is 31 kW, the spraying distance is 100 mm, and the number of spraying layers is 10, thus obtaining a polymer-derived ceramic coating.

[0041] Example 5

[0042] This embodiment provides a method for preparing a polymer-derived ceramic coating, as detailed below: Step S1: Crosslink the polysiloxane in a vacuum oven at 120℃ for 2 hours. Then, pyrolyze the crosslinked block in a tube furnace under argon atmosphere at 900℃ for 2 hours. The heating rate is 5℃ / min, and the cooling rate is 2℃ / min to obtain a ceramic block. The ceramic block is then subjected to planetary ball milling at 300 r / min for 24 hours to obtain polymer-derived ceramic powder with an average particle size of approximately 10.5 μm. Step S2: Polymer-derived ceramic powder is ball-milled with polyvinyl alcohol, deionized water, and anhydrous ethanol to obtain a SiOC-based multiphase mixture, wherein the ratio of polymer-derived ceramic powder:polyvinyl alcohol:deionized water:anhydrous ethanol is 40:40:10:10, and the ball milling speed is 80-120 r / min. The SiOC-based multiphase mixture is then granulated and dried in a spray granulator. The spray granulation inlet temperature is 290℃, the outlet temperature is 115℃, the nozzle speed is 34 r / min, and the peristaltic pump speed is 15 r / min, resulting in granulated SiOC spray-coated ceramic powder. The granulated SiOC spray-coated ceramic powder is then degummed in a tube furnace under argon atmosphere at 200℃ for 2 hours, with a heating rate of 5℃ / min and a cooling rate of 2℃ / min. The average particle size of the polymer-derived ceramic spray-coated powder obtained after degumming is 21.3 μm. Step S3: After sandblasting the ceramic, place it in an ethanol solution for ultrasonic cleaning for 30 minutes, and then vacuum dry it at 80°C for 2 hours for later use. Step S4: Using an atmospheric plasma spraying device, spray the polymer-derived ceramic powder obtained in step S2 onto the ceramic obtained in step S3. The argon flow rate used in the spraying process is 42L / min, the hydrogen flow rate is 8L / min, the carrier gas flow rate is 6L / min, the spraying current is 500A, the spraying power is 30kW, the spraying distance is 90mm, and the number of spraying layers is 2, to obtain a polymer-derived ceramic coating.

[0043] Figure 1 These are the surface SEM and EDS images of the polymer-derived ceramic coating prepared in this embodiment. Figure 1 As can be seen, the coating surface is dense and the element distribution is uniform, indicating that the polymer-derived SiOC coating was successfully sprayed.

[0044] In summary, the present invention has fully verified the feasibility and stability of the polymer-derived ceramic coating preparation method through the above-mentioned embodiments. Using different polymer precursors, ceramic powders meeting the requirements of plasma spraying can be obtained under reasonable crosslinking, pyrolysis, ball milling, granulation, and debinding process conditions. After substrate pretreatment and transition layer preparation, optimized atmospheric plasma spraying parameters enable stable formation on the surfaces of high-temperature alloys, ceramics, and ceramic matrix composites. The prepared coating has a dense surface, uniform element distribution, no obvious internal pores or cracks, good bonding with the transition layer and substrate, and a pure phase composition and stable structure. This method allows for flexible control of coating thickness by adjusting the number of spray layers. The process is simple and efficient, effectively overcoming the shortcomings of traditional methods such as easy cracking, difficulty in thickness control, and long cycle time. It can meet the protective requirements in harsh high-temperature environments and has good engineering applicability and promotional value.

[0045] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method for preparing a polymer-derived ceramic coating, characterized in that, The preparation method specifically includes the following steps: Step S1: After the polymer precursor is subjected to cross-linking and pyrolysis treatment in sequence, a ceramic block is obtained. The ceramic block is then ball-milled and sieved to obtain polymer-derived ceramic powder. Step S2: The polymer-derived ceramic powder obtained in step S1 is subjected to spray granulation and high-temperature debinding in sequence to obtain polymer-derived ceramic spray powder. Step S3: Using atmospheric plasma spraying, the polymer-derived ceramic powder prepared in step S2 is sprayed onto the substrate surface to obtain a polymer-derived ceramic coating.

2. The preparation method according to claim 1, characterized in that, In step S1, the polymer precursor is selected from one of polysiloxane, polycarbosilane, polynitrosilane, polyboroniaborona.

3. The preparation method according to claim 1, characterized in that, In step S1, the crosslinking treatment is carried out under vacuum conditions, and the parameters of the crosslinking treatment are as follows: the crosslinking temperature is 120-150℃, and the crosslinking time is 2-4h.

4. The preparation method according to claim 1, characterized in that, In step S1, the pyrolysis process is carried out in a tube furnace, and the specific process is as follows: using nitrogen or argon as a protective atmosphere, the temperature is raised to 900-1200℃ at a rate of 1-5℃ / min and held at that temperature for 2-4 hours, and then cooled to room temperature at a rate of 1-2℃ / min.

5. The preparation method according to claim 1, characterized in that, In step S1, the parameters for ball milling and sieving are as follows: ball milling speed is 200-500 r / min, and ball milling time is 24-30 h; The average particle size of the polymer-derived ceramic powder obtained in step S1 is 8-15 μm.

6. The preparation method according to claim 1, characterized in that, In step S2, the specific steps of spray granulation are as follows: polymer-derived ceramic powder, polyvinyl alcohol, deionized water and anhydrous ethanol are mixed and ball-milled at a speed of 80-120 r / min according to a mass ratio of (40-45):(40-45):(5-10):(5-10) to obtain a multiphase mixture. The multiphase mixture is fed into a spray granulator for granulation and drying. The inlet temperature of the spray granulator is 270-300℃, the outlet temperature is 100-120℃, the nozzle speed is 33-35 r / min, and the peristaltic pump speed is 13-15 r / min.

7. The preparation method according to claim 1, characterized in that, In step S2, the high-temperature degumming is carried out in a tube furnace, and the specific process is as follows: using nitrogen or argon as a protective atmosphere, the temperature is raised to 200-300℃ at a rate of 1-5℃ / min and held at that temperature for 2-3 hours, and then cooled to room temperature at a rate of 1-2℃ / min. The average particle size of the polymer-derived ceramic spray powder obtained in step S2 is 20-30 μm.

8. The preparation method according to claim 1, characterized in that, In step S3, the substrate is a high-temperature alloy, ceramic or ceramic matrix composite material, and the substrate is pre-treated with surface pretreatment, which includes sandblasting, cleaning and drying in sequence. The cleaning process is as follows: the substrate after sandblasting is placed in an ethanol or acetone solution for ultrasonic cleaning for 30-60 minutes. The drying process is carried out in a vacuum oven with the following parameters: drying temperature of 80-100℃ and drying time of 1-3h.

9. The preparation method according to claim 8, characterized in that, After surface pretreatment, the substrate is coated with a transition layer. The thickness of the transition layer is 80-240 μm, and the material is 3YSZ, 8YSZ or NiCrAlY. The transition layer is prepared by atmospheric plasma spraying with the following parameters: argon flow rate of 56-60 L / min, hydrogen flow rate of 14-18 L / min, spraying current of 500-600 A, spraying power of 51-53 kW, spraying distance of 90-110 mm, and number of spraying layers of 2-5.

10. The preparation method according to claim 1, characterized in that, In step S3, the parameters of the atmospheric plasma spraying method are as follows: argon flow rate of 40-44 L / min, hydrogen flow rate of 6-10 L / min, carrier gas flow rate of 5-8 L / min, spraying current of 500-600 A, spraying power of 30-32 kW, spraying distance of 90-110 mm, and number of spraying layers of 2-10.

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