Double-layer Si-Zr self-reaction coating and preparation method thereof

Abstract

The invention relates to a double-layer Si-Zr self-reaction coating and a preparation method thereof, and belongs to the technical field of carbon ceramic ablative materials. B4C powder is subjected to ball milling and crushed until the diameter is smaller than 100 nm, ZrSi2 alloy is added and evenly mixed with B4C subjected to ball milling, a polycarbosilane solution is added for ball milling, ZrSi2 slurry wrapped by B4C is obtained and dried, and ZrSi2 powder wrapped by B4C is obtained; adding the powder into a polysiloxane solution containing SiC powder, and mechanically and sufficiently mixing to obtain slurry; spraying the slurry on the surface of the C / C material through pressurization, and drying to obtain the coating material. The coating comprises the polysiloxane-containing SiC layer on the outer layer and the B4C-ZrSi2 layer on the inner layer, in the oxidation ablation process, the crack effect of the coating on the surface layer can be achieved within a certain time, and the oxidation rate of the material is greatly decreased.

Description

Technical Field

[0001] This invention belongs to the field of carbon ceramic ablation materials technology, specifically relating to a double-layer Si-Zr self-reactive coating and its preparation method. Background Technology

[0002] C / C composite materials possess excellent high-temperature stability and good structural strength, and are widely used in the aerospace field. Their application characteristics and suitability have been verified. Carbon materials can be used at temperatures of 2000℃ or even 3000℃, but their oxidation resistance is weak, and oxidation begins at 400℃.

[0003] With advancements in engine technology, engine combustion generates high-temperature corrosive gases containing condensed particles. Thermal protection materials face extreme environmental challenges, including high heat flux density, high heat load, high-pressure airflow and high temperature / stress gradients, high-temperature oxidation, and ablation. This necessitates that thermal structural materials withstand ultra-high temperatures, possess wide-temperature-range oxidation and ablation resistance, and resist strong particle erosion. C / C composite materials are no longer sufficient to meet the requirements of lightweight, high-temperature resistant thermal protection materials. Therefore, to meet the requirements of next-generation thermal protection materials, it is essential to improve their high-temperature oxidation resistance. Applying a coating to the material surface can effectively enhance its oxidation resistance. Currently, a mature method involves preparing a SiC coating on the C / C material surface. The SiO2 obtained from SiC oxidation fills the surface voids, hindering further oxidation by oxygen. However, above 1650℃, SiC transitions from inert oxidation to active oxidation, increasing its oxidation and ablation rate, and SiO2 is eroded and peeled off by the high-temperature combustion gases. Introducing ZrB2 to form a multiphase ceramic coating with SiC further improves the material's temperature resistance range. The main function of introducing ZrC is to utilize the pinning effect of ZrO2 particles, slowing down the SiO2 peeling rate. However, the ZrO2 particle packing morphology contains large voids, and with prolonged ablation, SiO2 undergoes oxidation, ablation, and exfoliation, resulting in a high ablation rate for the material. Therefore, increasing the molten ceramic content between ZrO2 particles to leverage the pinning effect of ZrO2 on the molten phase is key to improving the coating's oxidation resistance. Summary of the Invention

[0004] The purpose of this invention is to provide a double-layer Si-Zr self-reactive coating and its preparation method. The coating includes an outer polysiloxane-containing SiC layer and an inner B4C-ZrSi2 layer, which can effectively heal surface coating cracks within a certain time during the oxidation and ablation process, thereby greatly reducing the oxidation rate of the material.

[0005] The above-mentioned objectives of the present invention are mainly achieved through the following technical solutions: A method for preparing a bilayer Si-Zr self-reactive coating includes the following steps: (1) High-energy ball milling of B4C powder; (2) Mix the ZrSi2 alloy powder with the B4C powder obtained in step (1) to obtain B4C-coated ZrSi2 powder; (3) Prepare a xylene solution of polycarbosilane, wherein the mass percentage of polycarbosilane is 30-40%; (4) The B4C-coated ZrSi2 powder obtained in step (2) is mixed with the xylene solution obtained in step (3) and ball-milled to obtain ZrSi2 slurry, which is then heated to obtain powder. (5) Add the powder obtained in step (4) to a xylene solution of polysiloxane containing SiC powder, and mix thoroughly by mechanical stirring to obtain a coating slurry; (6) Apply the coating slurry obtained in step (5) to the surface of the material and dry it to obtain the coating material.

[0006] In step (1), the ball-to-material ratio is 1:3-5, and the diameter of the B4C powder after ball milling is less than 100nm.

[0007] In step (2), the particle size of ZrSi2 alloy powder is 2-10µm, and the thickness of the B4C-coated ZrSi2 powder layer is not less than 3µm.

[0008] In step (2), the mass ratio of ZrSi2 to B4C is 1:1-1.5.

[0009] In step (4), the heating treatment method is as follows: heat from room temperature to 60°C at a heating rate of 10-20°C / min, then heat from 60°C to 100°C at a heating rate of 1-10°C / min, then heat from 100°C to 200°C at a heating rate of 1-5°C / min, and keep warm for 2-8 hours.

[0010] In step (4), the ball milling parameters are as follows: ball-to-material ratio is 2-6:1, ball milling rate is 70-150 r / min, and ball milling time is 3-10 h.

[0011] In step (4), the mass ratio of B4C-coated ZrSi2 powder to xylene solution is 1~2:1.

[0012] In step (5), the mass ratio of polysiloxane to xylene is 2:7-10, and the mass percentage of SiC powder is 13-20%.

[0013] In step (6), the coating method is spraying, the number of spraying times is 1-5, the spraying pressure is 0.2-8MPa, and the drying temperature is 80-300℃.

[0014] A bilayer Si-Zr self-reactive coating was prepared according to the above preparation method.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: (1) Compared with existing coatings, the material prepared by this invention has unique high-temperature self-healing properties. Through the first layer of polysiloxane SiC coating on the surface of the material, oxygen is consumed. As the combustion time increases, the surface layer is oxidized to form SiO2, while the temperature transfer inner layer ZrSi2 reacts with B4C in situ to form ZrB2-SiC antioxidant multiphase coating.

[0016] (2) Compared with the uniformly distributed ZrB2-SiC multiphase ceramic coating, the present invention has the advantage of gradually filling the voids by self-reaction with temperature. At 1000℃ to 1600℃, when the surface is oxidized, the high temperature transfer causes the inner layer to endothermic reaction to form a new ceramic layer, which also reduces the temperature of the outer SiOC-SiC and slows down the active oxidation process of the outer SiO2. As the temperature further increases to 2000℃, the outer SiO2 is consumed and lost, and the inner layer still has a relatively complete ZrB2-SiC phase that can consume oxygen, so the oxidation rate is low.

[0017] (3) Compared with the SiC-ZrB2 internal and external structure coating prepared by CVI, the coating of this invention is a micron-scale spherical shell two-layer structure. A large number of double-layer spherical shells are densely packed in the coating. After the outer SiO2 layer melts and is eroded by ablation, the inner ZrB2-SiC can still continue to form borosilicate glass with oxygen. Therefore, after a long ablation time, the content of molten phase between the accumulated spherical shells is still high, forming B2O3-SiO2 borosilicate glass between the spherical shells. The ZrO2 inside the spherical shell acts as a skeleton to anchor the borosilicate glass, which stabilizes the coating, weakens the ablation effect, and reduces the ablation rate of the material. In contrast, the SiC-ZrB2 internal and external structure coating is prone to severe ablation of the outer layer, while the inner layer has not yet formed an effective molten state, resulting in oxygen penetration into the coating voids and ablation of the substrate.

[0018] Compared with the B4C-ZrSi2 sintered coating, this invention uses ball milling to uniformly distribute B4C at the nanoscale on the outer edge of ZrSi2 particles. Therefore, compared with the traditional mixing, it has a large contact area and high reactivity at high temperatures. The reaction can occur under high-temperature transport during the oxidation of the outer SiOC-SiC layer. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the coating of the present invention; Figure 2 This is the morphology of the material after ablation in Example 3 of the present invention; Figure 3 This is the microscopic morphology of the cross-section of the material after ablation in Example 3 of the present invention. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments: A double-layer Si-Zr self-reactive coating and its preparation method are disclosed. The coating includes an outer polysiloxane-containing SiC layer and an inner B4C-ZrSi2 layer. The oxidation and ablation process is as follows: the surface SiOC-SiC undergoes oxidation to form SiO2. As the ablation time increases, the high temperature is simultaneously transferred to the inner B4C layer encapsulating ZrSi2 powder, thereby causing an in-situ reaction to form ZrB2 and SiC. The corresponding volume expands and fills the voids in the surface SiO2 liquid film. With further temperature increase and airflow ablation, the ZrB2-SiC formed in situ after the surface SiO2 is ablated continues to consume the oxidizing atmosphere to form a B2O3-SiO2 glass phase, which can continue to effectively fill the ZrO2 skeleton and effectively heal the surface coating cracks within a certain period of time, greatly alleviating the oxidation rate of the material.

[0021] A method for preparing a self-healing coating includes the following steps: S1, B4C powder is subjected to high-energy ball milling, and the diameter of B4C powder after ball milling is less than 100nm; S2, add ZrSi2 alloy powder and mix with ball-milled B4C to obtain B4C-coated ZrSi2 powder, ball milling speed 50-200 r / min; S3, prepare a xylene solution of 30~40 wt% polycarbosilane. S4. Add S2 powder to S3, ball mill at low speed, keep warm at RT-200℃ for 2-8 hours in steps to obtain uniformly coated ZrSi2 powder. S5, SiC powder is added to a polysiloxane solution and mechanically stirred until fully mixed to obtain a solution; S6. Add the powder from S4 to the solution in S5 and mix thoroughly by mechanical stirring to obtain the spraying slurry. S7, the above slurry is sprayed onto the surface of the C / C material under pressure, the spraying is repeated, and then dried to obtain the desired result. Figure 1 The coating shown.

[0022] Preferably, in step S1, the ball-to-material ratio is 1:3-5.

[0023] Preferably, in step S2, the ZrSi2 alloy powder has a particle size of 2-10µm, and the thickness of the B4C powder layer after coating is not less than 3µm. The ZrSi2:B4C mass ratio is 1:1-1.5.

[0024] Preferably, in step S4, the mass ratio of S2 powder to the polycarbosilane solution is (2-4):2, the ball-to-material ratio is 2-6:1, the ball milling rate is 70-150 r / min, and the ball milling time is 3-10 h.

[0025] Preferably, the heating treatment in step S4 is 25℃ to 60℃, with a heating rate of 10-20℃ / min; 60℃ to 100℃, 1-10℃ / min; 100℃ to 200℃, 1-5℃ / min.

[0026] Preferably, in step S5, polysiloxane and xylene are mixed at a mass ratio of 2:7-10 to obtain a solution, and the SiC powder content is 13-20%.

[0027] Preferably, in step S7, the number of spraying passes is 1-5, the drying temperature is 80-300℃, and the spraying pressure is 0.2-8MPa.

[0028] Example 1 In this embodiment, preliminary powders were prepared using ZrSi2 and B4C. Preparation method: B4C powder was subjected to high-energy ball milling to a particle size of 60 nm, with a ball-to-particle ratio of 1:3; ZrSi2 alloy powder was added and mixed with the ball-milled B4C, and the ball milling speed was 70 r / min to obtain B4C-coated ZrSi2 powder with a particle size of 7 µm. A sprayable powder was manufactured using impregnation and coating. Preparation method: The above-mentioned B4C-coated ZrSi2 powder was added to a polycarbosilane solution and held at RT-200℃ for 3 hours in stages to obtain the sprayable powder. The heating rate was 20℃ / min from 25℃ to 60℃, 7℃ / min from 60℃ to 100℃, and 5℃ / min from 100℃ to 200℃. The mass ratio of ZrSi2 powder to polycarbosilane solution was 2:2, the ball-to-powder ratio was 4:1, the ball milling rate was 70 r / min, and the milling time was 4 hours. In this embodiment, a spray coating slurry is prepared using polysiloxane and xylene. Preparation method: Polysiloxane and xylene are mixed at a mass ratio of 2:10 to obtain a solution. SiC powder is added to the solution and mechanically stirred until fully mixed to obtain the final solution. The SiC powder content is 20%. The powder is then added to the solution and mechanically stirred until fully mixed to obtain the spray coating slurry.

[0029] The coating was prepared by atmospheric pressurized spraying. The spraying solution was prepared by placing the composite material on a spraying support and spraying it onto the C / C material surface under atmospheric pressure. After each spraying, a 10-minute interval was observed, and the spraying was repeated five times. The coating was then dried at 300℃. An oxy-acetylene ablation test was conducted using the composite material at 2300℃ for 60 seconds, resulting in a linear ablation rate of 0.0009 mm / s.

[0030] Example 2 In this embodiment, preliminary powders were prepared using ZrSi2 and B4C. Preparation method: B4C powder was subjected to high-energy ball milling to a particle size of 80 nm, with a ball-to-particle ratio of 1:4. ZrSi2 alloy powder was added and mixed with the ball-milled B4C, followed by low-speed ball milling at 80 r / min to obtain B4C-coated ZrSi2 powder with a particle size of 5 µm. A sprayable powder was manufactured using an impregnation and coating method. Preparation method: The B4C-coated ZrSi2 powder was added to a polycarbosilane solution and held at RT-200℃ for 4 hours in stages to obtain the sprayable powder. The heating rate was 10℃ / min from 25℃ to 60℃, 10℃ / min from 60℃ to 100℃, and 4℃ / min from 100℃ to 200℃. The mass ratio of ZrSi2 powder to the polycarbosilane solution was 4:2, the ball-to-powder ratio was 2:1, the ball milling rate was 150 r / min, and the milling time was 10 hours. In this embodiment, a spray coating slurry is prepared using polysiloxane and xylene. Preparation method: Polysiloxane and xylene are mixed at a mass ratio of 2:9 to obtain a solution. SiC powder is added to the solution and mechanically stirred until fully mixed to obtain the final solution. The SiC powder content is 13%. The powder is then added to the solution and mechanically stirred until fully mixed to obtain the spray coating slurry.

[0031] The coating was prepared by atmospheric pressurized spraying. The spraying solution was prepared by placing the composite material on a spraying support and spraying it onto the C / C material surface under atmospheric pressure. After each spraying, a 10-minute interval was observed, and the spraying was repeated five times. The coating was then dried at 270℃. An oxy-acetylene ablation test was conducted using the composite material at 2200℃ for 60 seconds, resulting in a linear ablation rate of 0.0002 mm / s.

[0032] Example 3 In this embodiment, preliminary powders were prepared using ZrSi2 and B4C. Preparation method: B4C powder was subjected to high-energy ball milling to a particle size of 40 nm, with a ball-to-particle ratio of 1:5; ZrSi2 alloy powder was added and mixed with the ball-milled B4C, and the mixture was rapidly milled at 130 r / min to obtain B4C-coated ZrSi2 powder with a particle size of 6 µm. A sprayable powder was prepared by impregnation and coating. Preparation method: The B4C-coated ZrSi2 powder was added to a polycarbosilane solution and held at RT-200℃ for 8 hours in stages to obtain the sprayable powder. The heating rate was 20℃ / min from 25℃ to 60℃, 5℃ / min from 60℃ to 100℃, and 3℃ / min from 100℃ to 200℃. The mass ratio of ZrSi2 powder to the polycarbosilane solution was 3:2, the ball-to-powder ratio was 6:1, the ball milling rate was 150 r / min, and the milling time was 10 hours. In this embodiment, a spray coating slurry is prepared using polysiloxane and xylene. Preparation method: A solution is prepared by mixing polysiloxane and xylene at a mass ratio of 2:7. SiC powder is then added to the solution and mechanically stirred until fully mixed to obtain the final solution. The SiC powder content is 20%. The powder is then added to the solution and mechanically stirred until fully mixed to obtain the spray coating slurry. The coating was prepared by atmospheric pressurized spraying. The spraying solution was prepared by placing the composite material on a spraying support and spraying it onto the C / C material surface under atmospheric pressure. After each spraying, a 10-minute interval was observed, and the spraying was repeated five times. The coating was then dried at 300℃. An oxy-acetylene ablation test was conducted using the composite material at 2600℃ for 60 seconds, resulting in a linear ablation rate of 0.0009 mm / s.

[0033] A schematic diagram of the coating powder structure is shown below. Figure 1 As shown, it consists of three layers: the innermost layer is ZrSi2, the second layer is B4C, and the third layer is a polysiloxane layer containing SiC particles. The microstructure of the material prepared by this invention after ablation is as follows. Figure 2 As shown, ablation forms a liquid film filling a white skeleton protective layer, indicating that the structure coating can protect the substrate, reduce the surface ablation rate, and improve the material's resistance to high-temperature oxidation.

[0034] Figure 3 The image shows the microscopic morphology of the coating cross-section after ablation. The white dense phase is an oxidation product of the coating after ablation. The coating is relatively thick, and the substrate under the coating has not undergone obvious oxidation. The interface between the substrate and the coating is intact, and the coating provides good protection for the substrate.

[0035] The above description is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

[0036] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for preparing a double-layer Si-Zr self-reactive coating, characterized in that: Includes the following steps: (1) High-energy ball milling of B4C powder; (2) Mix the ZrSi2 alloy powder with the B4C powder obtained in step (1) to obtain B4C-coated ZrSi2 powder; (3) Prepare a xylene solution of polycarbosilane, wherein the mass percentage of polycarbosilane is 30-40%; (4) The B4C-coated ZrSi2 powder obtained in step (2) is mixed with the xylene solution obtained in step (3) and ball-milled to obtain ZrSi2 slurry, which is then heated to obtain powder. (5) Add the powder obtained in step (4) to a xylene solution of polysiloxane containing SiC powder, and mix thoroughly by mechanical stirring to obtain a coating slurry; (6) Apply the coating slurry obtained in step (5) to the surface of the material and dry it to obtain the coating material.

2. The method for preparing a double-layer Si-Zr self-reactive coating according to claim 1, characterized in that: In step (1), the ball-to-material ratio is 1:3-5, and the diameter of the B4C powder after ball milling is less than 100nm.

3. The method for preparing a double-layer Si-Zr self-reactive coating according to claim 1, characterized in that: In step (2), the particle size of ZrSi2 alloy powder is 2-10µm, and the thickness of the B4C-coated ZrSi2 powder layer is not less than 3µm.

4. The method for preparing a double-layer Si-Zr self-reactive coating according to claim 1, characterized in that: In step (2), the mass ratio of ZrSi2 to B4C is 1:1-1.

5.

5. The method for preparing a double-layer Si-Zr self-reactive coating according to claim 1, characterized in that: In step (4), the heating treatment method is as follows: heat from room temperature to 60°C at a heating rate of 10-20°C / min, then heat from 60°C to 100°C at a heating rate of 1-10°C / min, then heat from 100°C to 200°C at a heating rate of 1-5°C / min, and keep warm for 2-8 hours.

6. The method for preparing a double-layer Si-Zr self-reactive coating according to claim 1, characterized in that: In step (4), the ball milling parameters are as follows: ball-to-material ratio is 2-6:1, ball milling rate is 70-150 r / min, and ball milling time is 3-10 h.

7. The method for preparing a double-layer Si-Zr self-reactive coating according to claim 1, characterized in that: In step (4), the mass ratio of B4C-coated ZrSi2 powder to xylene solution is 1~2:

1.

8. The method for preparing a double-layer Si-Zr self-reactive coating according to claim 1, characterized in that: In step (5), the mass ratio of polysiloxane to xylene is 2:7-10, and the mass percentage of SiC powder is 13-20%.

9. The method for preparing a double-layer Si-Zr self-reactive coating according to claim 1, characterized in that: In step (6), the coating method is spraying, the number of spraying times is 1-5, the spraying pressure is 0.2-8MPa, and the drying temperature is 80-300℃.

10. A double-layer Si-Zr self-reactive coating, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9.

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