Preparation method of flame-retardant ceramic coating based on yttria concentration regulation

Abstract

The application belongs to the technical field of surface modification, and relates to a preparation method of a flame-retardant ceramic coating based on yttrium oxide concentration regulation, comprising the following steps: dissolving sodium hydroxide and sodium fluoride with a specific mass ratio into a sodium silicate salt electrolyte, and adding a Y2O3 solution with a specific concentration into the electrolyte to obtain a first mixed solution; then placing a magnesium alloy substrate in the first mixed solution, and performing micro-arc oxidation treatment to obtain a magnesium alloy-flame-retardant ceramic composite, and finally obtaining a flame-retardant ceramic coating on the surface of the magnesium alloy substrate through post-processing. The mass ratio of sodium hydroxide and sodium fluoride, the concentration of the sodium silicate salt electrolyte, and the Y2O3 solution with an appropriate concentration are cooperatively regulated to realize accurate regulation of the performance of the flame-retardant coating on the surface of the magnesium alloy, so as to meet the actual application requirements of the flame-retardant performance of the magnesium alloy material for high-temperature key components, and promote the wide application of the magnesium alloy under high-temperature and flammable working conditions.

Description

Technical Field

[0001] This invention belongs to the field of surface modification technology and relates to a method for preparing flame-retardant ceramic coatings based on the control of yttrium oxide concentration. Background Technology

[0002] Magnesium alloys have broad application prospects in aerospace, automotive, and 3C electronics industries due to their outstanding advantages of being lightweight and high-strength. However, their low ignition point (approximately 550℃) and poor heat resistance and flame retardancy make them prone to violent combustion under high-temperature or friction conditions, posing serious safety hazards and greatly limiting their application in high-temperature critical components such as those around engines.

[0003] Microarc oxidation (MAO), also known as plasma electrolytic oxidation (PEO), is an advanced surface engineering technology based on a high-voltage micro-area discharge mechanism. This technology places metals such as aluminum and titanium, and their alloys, in a specialized electrolyte system. Utilizing the micro-area plasma discharge effect, a reinforced ceramic film layer, primarily composed of a ceramic phase, with a dense structure and metallurgical bonding to the substrate, is generated in situ on the substrate surface. This reinforced ceramic film layer exhibits high bonding strength with the substrate, effectively blocking oxygen and heat sources, significantly improving the substrate's corrosion resistance and wear resistance, and greatly enhancing its flame retardancy and high-temperature oxidation resistance.

[0004] However, existing micro-arc oxidation technology still has many shortcomings in the preparation of flame-retardant coatings for magnesium alloys: First, ceramic films prepared by traditional electrolyte systems are prone to microcrack defects at high temperatures, resulting in damage to the integrity of the film and making it difficult to meet the requirements of harsh high-temperature operating conditions in terms of flame-retardant performance; Second, the existing electrolyte formulation design is relatively simple, lacking reasonable doping of functional components, and the intrinsic correlation between the content of additives and the core properties of ceramic films such as flame retardancy and wear resistance has not been systematically explored, making it difficult to achieve precise control of film performance; Third, rare earth oxides (such as Y2O3) have significant potential in improving the high-temperature resistance and flame-retardant performance of ceramic films due to their excellent high thermal stability, but existing systematic research on the preparation of flame-retardant coatings for magnesium alloys by Y2O3-doped micro-arc oxidation is relatively scarce, especially lacking in-depth exploration of the intrinsic correlation between Y2O3 doping content and the microstructure, ablation resistance, and flame-retardant aging of ceramic films, thus failing to fully utilize the modification advantages of Y2O3. For the reasons mentioned above, it is necessary to systematically study the Y2O3 doping micro-arc oxidation process, explore its influence on the microstructure and flame retardant properties of the ceramic film layer on the surface of magnesium alloys, clarify the regulation mechanism of Y2O3 doping amount, so as to achieve precise control of the flame retardant coating performance of magnesium alloy surfaces, thereby meeting the actual application requirements of high-temperature key components for the flame retardant properties of magnesium alloy materials, and promoting the widespread application of magnesium alloys in high-temperature and flammable conditions.

[0005] Therefore, there is an urgent need to provide a method for preparing flame-retardant ceramic coatings based on the control of yttrium oxide concentration to solve the above problems. Summary of the Invention

[0006] This invention provides a method for preparing a flame-retardant ceramic coating based on yttrium oxide concentration control, aiming to solve the problem of insufficient ablation resistance of magnesium alloys in existing technologies. This method uses magnesium alloy as a substrate and, by controlling the concentration of Y₂O₃ solution and combining it with a micro-arc oxidation process, generates a dense ceramic layer in situ on the substrate surface, thereby preparing a ceramic coating with excellent ablation resistance on the magnesium alloy surface, significantly improving the ablation and corrosion resistance of the magnesium alloy.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a method for preparing a flame-retardant ceramic coating based on yttrium oxide concentration control, comprising the following steps: S1. Dissolve sodium hydroxide and sodium fluoride in a specific mass ratio into a sodium silicate electrolyte of a specific concentration, and add a Y2O3 solution of a specific concentration to obtain a first mixed solution; S2. After pretreatment, the magnesium alloy substrate surface is placed in the first mixed solution and subjected to micro-arc oxidation treatment to obtain a magnesium alloy-flame retardant ceramic composite. Subsequently, the magnesium alloy-flame retardant ceramic composite is post-treated to finally obtain a flame retardant ceramic coating on the magnesium alloy substrate surface.

[0008] Specifically, the sodium silicate electrolyte is prepared by dissolving 20g of sodium silicate in every 1L of deionized water.

[0009] Further, in S1, the mass ratio of sodium hydroxide to sodium fluoride is 1:(3~5).

[0010] Furthermore, the concentration of the Y2O3 solution is 6~10 g / L.

[0011] Furthermore, the concentration of the Y2O3 solution is 7~9 g / L.

[0012] Specifically, the flame-retardant ceramic coating exhibits the best density when the concentration of the Y2O3 solution is 8 g / L.

[0013] Furthermore, in S2, the pretreatment sequentially includes polishing, a first cleaning, and a first drying.

[0014] Specifically, the grinding process involves using sandpaper to grind the surface of the magnesium alloy substrate step by step until the surface is smooth with a roughness Ra ≤ 0.8 μm.

[0015] Specifically, the first cleaning process involves placing the polished magnesium alloy substrate in anhydrous ethanol and ultrasonically cleaning it for 10-15 minutes to remove surface oil and residual particles.

[0016] Specifically, the first drying process uses a hair dryer to dry the product.

[0017] Furthermore, in S2, the micro-arc oxidation treatment uses a unipolar pulse power supply, with the magnesium alloy substrate as the anode and a conventional stainless steel plate as the cathode; the specific steps of the micro-arc oxidation treatment are as follows: first, control the voltage to rise from 0V to the set voltage, and then perform constant voltage treatment for 15~20min.

[0018] Furthermore, the set voltage is 300V, the boost rate is 25~30 V / min, and the current density is 0.1~0.3A / dm³. 2 The duty cycle is 14-16%.

[0019] Furthermore, in S2, the post-processing sequentially includes a second washing and a second drying.

[0020] Specifically, the second cleaning process involves placing the polished magnesium alloy substrate in anhydrous ethanol and ultrasonically cleaning it for 10-15 minutes to remove surface oil and residual particles.

[0021] Specifically, the second drying process uses a hair dryer to dry the product.

[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention optimizes the electrolyte system in the micro-arc oxidation process. Specifically, by controlling the concentration of Y₂O₃, combined with a stable ratio of sodium hydroxide and sodium fluoride and a basic concentration of sodium silicate, the ablation resistance of the flame-retardant ceramic coating is significantly improved. The concentration of yttrium oxide (Y₂O₃) solution is a key process parameter determining the ablation resistance of the flame-retardant ceramic coating. Although Y₂O₃ does not directly participate in the physical composition and chemical reactions of the flame-retardant ceramic coating, it can physically regulate the micro-arc discharge behavior during the micro-arc oxidation process. Y₂O₃ particles can act as a physical barrier and induce nucleation during micro-arc discharge, significantly promoting film densification. As the Y₂O₃ concentration gradually increases, the sealing phenomenon on the coating surface becomes more pronounced, thus significantly affecting the microstructure and ablation resistance of the coating. Furthermore, when the Y₂O₃ concentration is 8 g / L, the coating exhibits optimal ablation resistance, enabling the in-situ preparation of a ceramic coating with good sealing and excellent ablation resistance on magnesium alloy surfaces. The raw materials used in this invention are inexpensive and environmentally friendly, and have good prospects for industrial application. Attached Figure Description

[0023] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart of the preparation method of the present invention; Figure 2 The image shows the morphology of the flame-retardant ceramic coating prepared in Example 1 using a scanning electron microscope (SEM). Figure 3 The image shows the digital morphology of a specific area of ​​the flame-retardant ceramic coating prepared in Example 1 after being subjected to high-temperature (1000°C) flame burning. Figure 4 The image shows the morphology of the flame-retardant ceramic coating prepared in Example 2 using a scanning electron microscope (SEM). Figure 5 The image shows the digital morphology of a specific area of ​​the flame-retardant ceramic coating prepared in Example 2 after being subjected to high-temperature (1000°C) flame burning. Figure 6 The image shows the cross-section of the flame-retardant ceramic coating prepared in Example 2 using a scanning electron microscope (SEM). Figure 7 EDS elemental distribution diagram of the cross section of the flame-retardant ceramic coating prepared in Example 2; Figure 8 The image shows the morphology of the flame-retardant ceramic coating prepared in Example 3 using a scanning electron microscope (SEM). Figure 9 The image shows the digital morphology of a specific area of ​​the flame-retardant ceramic coating prepared in Example 3 after being subjected to high-temperature (1000°C) flame burning. Figure 10 The image shows the morphology of the flame-retardant ceramic coating prepared in Comparative Example 1 using a scanning electron microscope (SEM). Figure 11 The image shows the digital morphology of a specific area of ​​the flame-retardant ceramic coating prepared in Comparative Example 1 after being scorched by a high-temperature (1000℃) flame from a spray gun. Figure 12 The image shows the morphology of the flame-retardant ceramic coating prepared in Comparative Example 2 using a scanning electron microscope (SEM). Figure 13 The image shows the digital morphology of a specific area of ​​the flame-retardant ceramic coating prepared in Comparative Example 2 after being subjected to high-temperature (1000℃) flame burning. Figure 14 The image shows the SEM morphology of a specific area on the surface of the flame-retardant ceramic coating prepared in Comparative Example 2 after being scorched at a high temperature (1000℃) by a spray gun flame. Figure 15 The image shows the scanning electron microscope (SEM) morphology of the flame-retardant ceramic coating prepared in Comparative Example 3. Figure 16 The image shows the digital morphology of a specific area of ​​the flame-retardant ceramic coating prepared in Comparative Example 3 after being scorched by a high-temperature (1000℃) flame from a spray gun. Detailed Implementation

[0026] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0027] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] Example 1 like Figure 1 As shown in the figure, this embodiment provides a method for preparing a flame-retardant ceramic coating on a magnesium alloy surface, including the following steps: S1. Weigh out specific masses of sodium hydroxide and sodium fluoride, wherein the mass ratio of sodium hydroxide to sodium fluoride is 1:3. Then dissolve them in a 20 g / L sodium silicate electrolyte and add 6 g / L Y2O3 solution to obtain a first mixed solution. S2. Polish the surface of the magnesium alloy substrate until smooth, then clean and dry it in sequence; The pretreated magnesium alloy substrate was placed in the first mixed solution. Using the magnesium alloy substrate as the anode and a conventional stainless steel plate as the cathode, micro-arc oxidation was performed. During the micro-arc oxidation process, the voltage was increased from 0V to 300V using an external unipolar pulse power supply at a rate of 25V / min and a current density of 0.1A / dm³. 2 With a duty cycle of 14%, after the voltage was increased to 300V, it was subjected to constant voltage treatment for 15 minutes to obtain a magnesium alloy-flame retardant ceramic composite. The magnesium alloy-flame retardant ceramic composite was then cleaned with deionized water and dried, and finally a flame retardant ceramic coating was obtained on the surface of the magnesium alloy substrate.

[0029] Example 2 The preparation method in this embodiment is the same as that in Example 1, except that: In S1: The mass ratio of sodium hydroxide to sodium fluoride is 1:5; The concentration of the Y2O3 solution is 8 g / L.

[0030] In S2: The unipolar pulse power supply has a boost rate of 27 V / min and a current density of 0.18 A / dm³. 2 The duty cycle is 15%, and after the voltage is increased to 300V, it is subjected to constant voltage treatment for 18 minutes.

[0031] Example 3 The preparation method in this embodiment is the same as that in Example 1, except that: In S1: The mass ratio of sodium hydroxide to sodium fluoride is 1:4; The concentration of the Y2O3 solution is 10 g / L.

[0032] In S2: The unipolar pulse power supply has a boost rate of 30V / min and a current density of 0.3A / dm³. 2 The duty cycle is 16%, and after the voltage is increased to 300V, it is subjected to constant voltage treatment for 20 minutes.

[0033] Comparative Example 1 The preparation method in this embodiment is the same as that in Example 1, except that: In S1: The concentration of the Y2O3 solution is 0 g / L (i.e., no Y2O3 solution is added to the sodium silicate electrolyte).

[0034] Comparative Example 2 The preparation method in this embodiment is the same as that in Example 1, except that: In S1: The mass ratio of sodium hydroxide to sodium fluoride is 1:4; The concentration of the Y2O3 solution is 2 g / L.

[0035] In S2: The unipolar pulse power supply has a boost rate of 27V / min and a current density of 0.3A / dm³. 2 The duty cycle is 16%, and after the voltage is increased to 300V, it is subjected to constant voltage treatment for 17 minutes.

[0036] Comparative Example 3 The preparation method in this embodiment is the same as that in Example 1, except that: In S1: The concentration of the Y2O3 solution is 4 g / L.

[0037] In S2: The unipolar pulse power supply has a boost rate of 28V / min and a current density of 0.15A / dm³. 2 The duty cycle is 15%, and after the voltage is increased to 300V, it is subjected to constant voltage treatment for 16 minutes.

[0038] The flame-retardant ceramic coatings prepared in Examples 1-3 and Comparative Examples 1-3 were characterized by scanning electron microscopy (SEM), and the morphological characteristics obtained are as follows: like Figure 2 The image shown is an SEM image of the flame-retardant ceramic coating prepared in Example 1. From this image, it can be concluded that when 6 g / L of Y2O3 solution is added to the sodium silicate electrolyte, the coating surface enters a significant pore-sealing transition stage. Most of the discharge micropores have been backfilled by the melt, leaving only a small number of shallow depressions. The surface of the ceramic layer exhibits a large-area melting and resolidification platform, and the platform surface is smooth. No open through holes were found, and the coating density was greatly improved.

[0039] like Figure 4 The image shown is an SEM image of the flame-retardant ceramic coating prepared in Example 2. From this image, it can be concluded that when 8 g / L of Y2O3 solution is added to the sodium silicate electrolyte, the sealing degree of the coating surface is further deepened, the original discharge micropores almost completely disappear, the surface of the ceramic layer is mainly composed of a continuously distributed molten solidified layer, and micro-protrusions formed by excessive accumulation of molten material appear in local areas.

[0040] like Figure 8 The image shown is an SEM image of the flame-retardant ceramic coating prepared in Example 3. From this image, it can be concluded that when 10 g / L of Y2O3 solution is added to the sodium silicate electrolyte, the coating surface is completely sealed, the original porous landform of micro-arc oxidation is completely covered, and a large-area continuous molten glass morphology is presented, and the surface of the ceramic layer is smooth and flat.

[0041] like Figure 10 As shown, this is a SEM image of the flame-retardant ceramic coating prepared in Comparative Example 1. From this image, it can be concluded that when no Y2O3 solution is added to the sodium silicate electrolyte, the coating surface exhibits a typical micro-arc oxidation porous structure with a large number of discharge micropores of varying sizes. The micropores are crater-shaped with clear boundaries and obvious openings. The pores are surrounded by molten and solidified ceramic particles with high surface roughness. No obvious signs of molten material backfilling are observed, making it impossible to effectively backfill and repair the pores.

[0042] like Figure 12The image shown is a SEM image of the flame-retardant ceramic coating prepared in Comparative Example 2. From this image, it can be concluded that when 2 g / L of Y2O3 solution is added to the sodium silicate electrolyte, the coating surface is still mainly porous, but local areas show the phenomenon of molten material spreading, and the edges of some discharge micropores begin to be passivated. A small amount of molten oxide flow traces can be seen around the pore openings. At the same time, the number of micropores is slightly reduced, and the pore size distribution range is narrowed. This indicates that the introduction of Y2O3 solution begins to affect the discharge behavior, and the fluidity of the molten material is enhanced.

[0043] like Figure 15 The image shown is a SEM image of the flame-retardant ceramic coating prepared in Comparative Example 3. From this image, it can be concluded that when 4 g / L of Y2O3 solution is added to the sodium silicate electrolyte, the melting degree of the coating surface is significantly improved. Specifically, a large number of discharge micropores are partially filled by molten oxide, the pore depth is significantly shallower, some small pores are completely covered, local smoothing areas begin to appear on the surface of the ceramic layer, exhibiting a wavy morphology after molten flow and solidification, the number of micropores is reduced compared to when no Y2O3 solution is added, and the surface roughness is reduced.

[0044] like Figure 3 , Figure 5 , Figure 9 The figures shown are digital morphology images of specific areas on the surface of each flame-retardant ceramic coating prepared in Examples 1-3 after being ablated by a high-temperature (1000℃) flame from a spray gun. From these images, it can be concluded that: when the amount of Y2O3 solution added is 6 g / L, a continuous and dense glass layer forms on the surface of the magnesium alloy substrate, and the pores disappear; when the amount of Y2O3 solution added is 8 g / L, the flame-retardant ceramic coating has the best structure, with only slight oxidation; when the amount of Y2O3 solution added is 10 g / L, the surface of the flame-retardant ceramic coating can also achieve complete pore sealing, and after ablation, the glass layer slightly exhibits brittle detachment characteristics, which can effectively improve the ablation resistance of the magnesium alloy substrate. Figure 11 , Figure 13 and Figure 16 The figures shown are digital morphology images of the flame-retardant ceramic coatings prepared in Comparative Examples 1 to 3 after being subjected to high-temperature (1000℃) flame burning of specific areas on their surfaces. From the figures, it can be concluded that: when no Y2O3 solution is added, the flame-retardant ceramic coating is severely ablated, resulting in film breakage and substrate detachment; when the amount of Y2O3 solution added is 2 g / L or 4 g / L, the destructiveness of ablation is reduced, but burnt pores still appear.

[0045] like Figure 14The image shows the SEM morphology of a specific area of ​​the flame-retardant ceramic coating prepared in Comparative Example 2 after being scorched by a high-temperature (1000℃) flame gun. The image shows that a clear crack network appears on the surface of the coating, and the coating has peeled off from the substrate in some areas. The interface between the coating and the substrate can be seen at the peeling edge.

[0046] like Figure 6 The image shown is a scanning electron microscope (SEM) morphology image of the cross section of the flame-retardant ceramic coating prepared in Example 2. From the image, it can be seen that the area above the boundary line is the flame-retardant ceramic coating, and the area below the boundary line is the magnesium alloy substrate. The two are tightly bonded, with a thickness of about 38~40μm. There are no obvious cracks or large gaps, indicating that the coating and the substrate are well bonded. The flame-retardant ceramic coating can provide fire resistance and corrosion resistance.

[0047] like Figure 7 The image shows the EDS elemental distribution of the cross-section of the flame-retardant ceramic coating prepared in Example 2, where green represents Na, yellow represents Si, red represents O, and purple represents F. The image shows that the elements are uniformly distributed in the coating, and the high overlap of Si, O, and Na indicates that the coating body is a silicate ceramic phase. F is enriched at the interface, which is beneficial for improving corrosion resistance. An elemental gradient transition layer exists between the coating and the substrate, indicating that the ceramic layer and the magnesium alloy substrate are in-situ grown metallurgically. Furthermore, no Y was detected in the coating, confirming that Y₂O₃ physically controls the micro-arc discharge process and does not directly participate in the formation of the coating composition.

[0048] In addition, to investigate the effect of different concentrations of Y2O3 solution on the protective performance of flame-retardant ceramic coatings, the fire resistance of each post-treated magnesium alloy / flame-retardant ceramic composite prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The specific results are shown in Table 1. Table 1. Combustion parameters of post-treated magnesium alloy-flame-retardant ceramic composites in Examples 1-3 and Comparative Examples 1-3. Table 1 shows that with the increase of Y2O3 solution addition, the density of the flame-retardant ceramic coating structure gradually increases, the ignition time is prolonged, and the duration of open flame is shortened. When the Y2O3 solution addition is 8 g / L, the coating forms a multi-level structure with moderate surface melting and highly dense inner layers. In the 1000℃ burning test, the corresponding flame-retardant ceramic coating did not show open flame combustion, only slight oxidation on the coating surface, and could maintain the flame-retardant state for a long time (>60s), demonstrating excellent high-temperature flame-retardant and protective performance. The protective mechanism is that the dense inner layer structure can effectively reduce ablation pores and delay crack propagation, while also hindering the outward diffusion of molten magnesium and magnesium vapor, thereby blocking the combustion chain reaction, verifying the decisive role of the structural integrity of the flame-retardant ceramic coating in its heat resistance performance.

[0049] In summary, a stable and high-temperature resistant flame-retardant ceramic coating can be constructed when the amount of Y₂O₃ solution added is 6-10 g / L. Conversely, adding too little or too much will lead to excessive sintering and peeling failure of the flame-retardant ceramic coating. In particular, the flame-retardant ceramic coating exhibits optimal ablation resistance when the amount of Y₂O₃ solution added is 8 g / L. This invention achieves a synergistic improvement in the densification and flame-retardant properties of the flame-retardant ceramic coating by controlling the mass ratio of sodium hydroxide and sodium fluoride, the concentration of sodium silicate electrolyte, and by using an appropriate concentration of Y₂O₃ solution.

[0050] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0051] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a flame-retardant ceramic coating based on yttrium oxide concentration control, characterized in that, Includes the following steps: S1. Dissolve sodium hydroxide and sodium fluoride in a specific mass ratio into a sodium silicate electrolyte of a specific concentration, and add a Y2O3 solution of a specific concentration to obtain a first mixed solution; S2. After pretreatment, the magnesium alloy substrate surface is placed in the first mixed solution and subjected to micro-arc oxidation treatment to obtain a magnesium alloy-flame retardant ceramic composite. Subsequently, the magnesium alloy-flame retardant ceramic composite is post-treated to finally obtain a flame retardant ceramic coating on the magnesium alloy substrate surface.

2. The method for preparing a flame-retardant ceramic coating based on yttrium oxide concentration control according to claim 1, characterized in that, In S1, the mass ratio of sodium hydroxide to sodium fluoride is 1:(3~5).

3. The method for preparing a flame-retardant ceramic coating based on yttrium oxide concentration control according to claim 1, characterized in that, The concentration of the Y2O3 solution is 6~10 g / L.

4. The method for preparing a flame-retardant ceramic coating based on yttrium oxide concentration control according to claim 1, characterized in that, The concentration of the Y2O3 solution is 7~9 g / L.

5. The method for preparing a flame-retardant ceramic coating based on yttrium oxide concentration control according to claim 1, characterized in that, In S2, the pretreatment includes polishing, first cleaning, and first drying in sequence.

6. The method for preparing a flame-retardant ceramic coating based on yttrium oxide concentration control according to claim 1, characterized in that, In S2, the micro-arc oxidation process uses a unipolar pulse power supply, with the magnesium alloy substrate as the anode and a conventional stainless steel plate as the cathode. The specific steps of the micro-arc oxidation process are as follows: first, the voltage is controlled to rise from 0V to the set voltage, and then constant voltage treatment is performed for 15~20 minutes.

7. The method for preparing a flame-retardant ceramic coating based on yttrium oxide concentration control according to claim 6, characterized in that, The set voltage is 300V, the boost rate is 25~30 V / min, and the current density is 0.1~0.3A / dm³. 2 The duty cycle is 14-16%.

8. The method for preparing a flame-retardant ceramic coating based on yttrium oxide concentration control according to claim 1, characterized in that, In S2, the post-processing includes a second washing and a second drying.

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