An anti-oxidation coating for molybdenum alloy surface, its preparation method and its application

Abstract

This invention discloses an anti-oxidation coating for molybdenum alloy surfaces, its preparation method, and its application. First, a high-temperature resistant oxidation-resistant powder is prepared. Then, a solution containing polyvinyl alcohol and vinyltrisilane is prepared. The powder and solution are mixed and stirred until homogeneous, forming a slurry. The surface of the molybdenum alloy material is then polished with sandpaper. The slurry is then uniformly coated onto the pretreated surface of the molybdenum alloy material. The coated surface is then dried in an electric furnace and subjected to heat preservation treatment, resulting in a uniform and dense high-temperature anti-oxidation coating. This invention's high-temperature anti-oxidation coating exhibits excellent anti-oxidation effects and can effectively protect irregularly shaped and large-volume molybdenum alloy substrates. This invention has advantages such as simple process, convenient operation, low cost, high yield, and high efficiency, making it suitable for industrial promotion and application. It has significant practical value for the manufacture of high-temperature hot-end components in aerospace, nuclear industry, machinery, and metallurgy.

Description

Technical Field

[0001] This invention relates to a molybdenum alloy coating with good anti-oxidation properties, its preparation method and its application, and more specifically, to a method for preparing an anti-oxidation coating for large, complex-shaped molybdenum alloys by coating. Background Technology

[0002] With the development of aerospace technology, the application of some difficult-to-deform materials is becoming increasingly widespread. Currently, the main deformation method for these materials is high-temperature isothermal forging. Molybdenum-based alloys, due to their excellent high-temperature mechanical properties, good thermal conductivity, and low coefficient of thermal expansion, are often used as dies for high-temperature isothermal forging. Applications of molybdenum products in tooling include piercing mandrels for seamless stainless steel tubes, die-casting dies for ferrous metals, isothermal forging dies, and oscillating rolling dies. The deformation temperatures of high-temperature alloys and intermetallic compounds are mostly above 1000℃, and the forging time is relatively long. Therefore, the die materials must have high yield strength, oxidation resistance, creep resistance, and good thermal fatigue performance. However, molybdenum alloys undergo severe oxidation under high-temperature manufacturing environments, leading to significant quality losses and making normal production impossible. Therefore, the oxidation resistance of molybdenum alloys has always been a research hotspot for scholars both domestically and internationally. Improving the oxidation resistance of molybdenum alloys is key to expanding their applications in the materials field. Currently, the most important way to improve the oxidation resistance of molybdenum alloys is to form an anti-oxidation coating on the surface of the alloy. MoSi2 has a high melting point (2030℃) and a moderate density (6.24 g / cm³). 3 MoSiO2 exhibits excellent oxidation resistance and forms a dense SiO2 protective film over a wide oxidation temperature range, making it widely used in the field of anti-oxidation coatings for molybdenum alloys. However, due to the mismatch in the coefficient of thermal expansion (CTE) between Mo and SiO2 (8.5 × 10⁻⁶), the coating... -6 / K) and Mo matrix (5.8×10 -6 During the process of cooling from the operating temperature to room temperature, cracks form perpendicular to the Mo matrix along the grain boundaries of the MoSi2 coating, leading to coating failure.

[0003] Therefore, in applied research, patent CN201610501780.7 discloses a method for preparing a molybdenum alloy anti-oxidation coating from waste stone. Waste granite powder is added to a standard coating powder, and after preparation, calcination forms a glaze, resulting in good anti-oxidation effects. Patent CN86103384 discloses a method for infiltrating an anti-oxidation coating of molybdenum or molybdenum alloy. This coating is made by uniformly mixing silicon powder, chromium powder, and iron powder (particle size less than 500 mesh), or silicon powder, chromium powder, and vanadium powder, or silicon powder, chromium powder, and titanium powder with a certain proportion of nitrocellulose lacquer and ethyl acetate, then spraying the mixture onto molybdenum or molybdenum alloy parts, followed by drying and vacuum high-temperature heat treatment to form the coating. Patent CN202110229234.3 discloses a molybdenum alloy with an anti-oxidation composite coating and its preparation method. The coating prepared by this method has a double-layer structure, with the outer layer containing at least (Mo,X)Si2 phase and (Cr,X)Si2 phase, and the inner layer containing at least (Mo,X)5Si3 phase; wherein X in (Mo,X)Si2 represents Cr, Ti, or W, and X in (Cr,X)Si2 represents Mo, Ti, or W. This coating has excellent anti-oxidation capabilities at medium and high temperatures. Patent CN202010402959.3 discloses a method for depositing an Al2O3 ceramic layer. This method optimizes the cathode micro-arc deposition pretreatment technology and, for the first time, uses cathode micro-arc plasma electrolytic deposition technology to prepare an Al2O3 ceramic layer on the surface of molybdenum or tantalum alloys. The Al2O3 ceramic grows in situ on the surface of molybdenum or tantalum alloys, providing physical isolation for molybdenum and tantalum alloy parts operating in environments above 1250℃. It also improves the oxidation resistance of molybdenum alloy tooling and increases the service life of molybdenum alloy parts. Patent CN201811625855.8 discloses a method for preparing an anti-oxidation coating on the surface of a molybdenum-based material. This method involves coating the surface of the molybdenum-based material with a silicon-infiltrating slurry, drying it, and then holding it at a temperature of 600–1300°C before cooling, resulting in a coating with rapid reaction and high raw material utilization. Patent CN201811212909.8 discloses a method for preparing a MoSi2 coating on a molybdenum alloy surface by laser cladding. This method first sputters a 20–30 μm thick Si layer on the surface of the molybdenum alloy, then pre-places silicide alloy powder. Laser scanning is used to combine the molybdenum alloy, the sputtered Si layer, and the pre-placed silicide alloy powder, resulting in a MoSi2 coating with good adhesion to the molybdenum alloy. Patent CN201711395404.5 discloses a Mo5Si3-MoSi2-SiO2 high-temperature protective composite coating for the surface of molybdenum and molybdenum alloy electrodes and its preparation method.This invention utilizes a vacuum activation infiltration method to prepare a Mo5Si3-MoSi2 composite coating. The surface MoSi2 layer provides a Si source for subsequent oxidation processes. During the subsequent high-temperature oxidation process, the MoSi2 undergoes oxidation, forming a dense SiO2 coating on the surface. This fills the pores and cracks in the MoSi2 coating, improving the overall density of the coating system and thus enhancing its resistance to high-temperature oxidation. Patent CN201710791688.3 discloses a method for preparing a molybdenum silicide coating on the surface of molybdenum or molybdenum alloys. Using silicon powder as a raw material, a silicon coating is prepared on the surface of a molybdenum or molybdenum alloy substrate using plasma spraying technology. The substrate is then heat-treated in an inert atmosphere at 1000–1500°C for 1–10 hours to form a molybdenum silicide coating on the surface of the molybdenum or molybdenum alloy substrate.

[0004] With the rapid development of some difficult-to-deform materials, the requirements for the high-temperature oxidation resistance of molybdenum alloy and other dies are becoming increasingly stringent. The aforementioned coatings all suffer from high manufacturing costs and significant disadvantages for large or complex-shaped workpieces. Therefore, finding a coating preparation method with low production costs and less stringent requirements on workpiece size and shape, and streamlining the high-temperature manufacturing process for high-temperature isothermal forging dies, could provide enormous development potential for difficult-to-deform materials. Summary of the Invention

[0005] To address the problems of existing technologies, the present invention aims to overcome the shortcomings of existing technologies and provide an anti-oxidation coating for molybdenum alloy surfaces, its preparation method, and its application. Addressing the challenges of complex processes, high costs, and stringent requirements on the shape and dimensions of molybdenum alloys used in high-temperature anti-oxidation coating preparation, this invention provides a method suitable for preparing anti-oxidation coatings on molybdenum alloy surfaces at temperatures above 1100℃. This method is suitable for preparing anti-oxidation coatings on large, complex-shaped molybdenum alloys. The preparation method of this invention has advantages such as simple process, low cost, high efficiency, and suitability for large-sized, complex parts in factories.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An anti-oxidation coating for molybdenum alloy surface has a perovskite structure and a lamellar structure parallel to the substrate surface, forming a barrier layer on the molybdenum alloy surface to block gas transmission.

[0008] Preferably, the anti-oxidation coating on the surface of the molybdenum alloy of the present invention mainly comprises MoO3 phase, Al2O3 phase, SiO2 phase, Na2O phase, ZrO2 phase, Mo5Si2 phase, TiO2 phase, MoO2 phase, CaO phase and CaZrTi2O7 phase.

[0009] Preferably, the anti-oxidation coating on the surface of the molybdenum alloy of the present invention is a borosilicate glass ceramic surface layer containing SiO2, Al2O3, CaO and B2O3 formed on the surface of the molybdenum alloy at a sintering temperature of 1100 to 1300°C, thereby forming a uniform and dense glaze protective layer on the surface of the molybdenum alloy.

[0010] Preferably, when the boron powder added to the antioxidant coating of the present invention is sintered at a temperature of 1100 to 1300°C, the boron diffuses into the molybdenum alloy substrate and reacts with the Mo on the surface of the molybdenum alloy substrate to generate a Mo-B compound, forming a gradient composition transition layer at the interface between the molybdenum alloy substrate and the antioxidant coating.

[0011] Preferably, the Al powder and Mo5Si2 phase added to the antioxidant coating of the present invention can react with the oxygen transported inward through the antioxidant coating to generate alumina ceramic and SiO2, thereby blocking the oxygen transport path and forming a component phase combination for self-healing of microcracks and self-repair of the antioxidant coating.

[0012] A method for preparing an anti-oxidation coating on a molybdenum alloy surface according to the present invention includes the following steps:

[0013] (1) Preparation of high-temperature resistant oxidation powder:

[0014] The raw materials were weighed and proportioned according to the mass percentage composition of the high-temperature resistant oxidation powder. The raw materials were then placed in a ball mill and ball-milled to prepare a uniformly mixed powder, thus obtaining the high-temperature resistant oxidation powder. The composition and mass fraction of the high-temperature resistant oxidation powder are as follows:

[0015] TiO2: 10-25%;

[0016] Al2O3: 10-25%;

[0017] CaO: 10-15%;

[0018] MoSi2: 5-15%;

[0019] Na2O: 5-15%;

[0020] Aluminum powder: 5-15%;

[0021] ZrO2: 1-5%;

[0022] B2O3: 0.1–2%;

[0023] Boron powder: 0.1-1%;

[0024] The balance is SiO2;

[0025] (2) Preparation of slurry:

[0026] Prepare a solution containing 5-10% polyvinyl alcohol and 1-5% vinyltrisilane by mass. Mix the prepared high-temperature resistant oxidation powder with the solution at a mass ratio of 1:3 and stir until uniformly mixed to form a slurry.

[0027] (3) Preparation of anti-oxidation coating on molybdenum alloy surface:

[0028] The surface of the molybdenum alloy material is polished with sandpaper to remove the oxide layer, thus performing surface pretreatment. The slurry is then uniformly coated onto the pretreated surface of the molybdenum alloy material. The coating is then dried in an electric furnace at 500–600°C, and finally kept at 1100–1300°C to obtain a uniform and dense high-temperature anti-oxidation coating.

[0029] Preferably, in step (3), the surface of the molybdenum alloy material is polished with 1000# sandpaper.

[0030] Preferably, in step (3), after the surface of the molybdenum alloy material is polished with sandpaper, the surface of the molybdenum alloy material is cleaned with ultrasound and then dried for later use, thus completing the pretreatment process.

[0031] Preferably, in step (3), the coating is subjected to heat preservation treatment for 1-4 hours.

[0032] Preferably, in step (3), the high-temperature antioxidant coating obtained is a glazing protective layer.

[0033] Preferably, in step (3), the obtained high-temperature antioxidant coating forms a perovskite structure and has a lamellar structure parallel to the substrate surface, forming a barrier layer that blocks gas transmission.

[0034] An application of the anti-oxidation coating on the surface of the molybdenum alloy described in this invention, wherein the anti-oxidation coating on the surface of the molybdenum alloy is used to form an anti-oxidation glazing protective layer on the molybdenum alloy workpiece substrate under service conditions of not less than 1100°C.

[0035] Compared with the prior art, the present invention has the following obvious and prominent substantive features and significant advantages:

[0036] 1. The present invention adds SiO2 and Al2O3 and pre-sintersects them to form borosilicate glass ceramics with CaO and B2O3 on the surface of molybdenum alloy. At the same time, B2O3 will be incorporated into the borosilicate glass, which can reduce the viscosity of SiO2 and the porosity of the coating, thereby forming a uniform and dense glaze protective layer at the sintering temperature.

[0037] 2. The boron powder added in this invention diffuses into the matrix at high temperature and reacts with Mo to generate Mo-B compound. The presence of this compound will hinder the diffusion of Si element into the matrix. While ensuring the formation of an excellent protective layer, it prevents the reaction at the interface between the matrix and the coating, ensuring that the matrix material is not corroded by the coating and maintains excellent mechanical properties.

[0038] 3. The addition of ZrO2 and TiO2 in this invention will react at high temperature to form a perovskite structure. This layered structure is parallel to the matrix surface, which effectively reduces the oxygen transport process.

[0039] 4. The method of the present invention uses the addition of MoSi2 and Al powder to achieve multiple protective effects. When oxygen is transported inward through the surface layer, MoSi2 reacts with oxygen to generate alumina ceramic and SiO2, thereby blocking the oxygen transport path and achieving the self-healing effect of cracks and the self-repairing effect of coating.

[0040] 5. The high-temperature anti-oxidation coating of the present invention has excellent anti-oxidation effect and can effectively protect molybdenum alloy substrates with irregular shapes and large volumes;

[0041] 6. This invention has the advantages of simple process, convenient operation, low cost, high yield and high efficiency. It is suitable for industrial promotion and application and has important practical value for the preparation of high temperature hot end components in aerospace, nuclear industry, machinery, metallurgy and other fields. Attached Figure Description

[0042] Figure 1 This is the cross-sectional morphology of the coating in Embodiment 1 of the present invention.

[0043] Figure 2 This is the cross-sectional morphology of the coating in Embodiment 2 of the present invention.

[0044] Figure 3 The phase composition of the coating in Example 2 of this invention.

[0045] Figure 4 The surface morphology of the coating in Embodiment 3 of the present invention.

[0046] Figure 5 The coating cross-sectional morphology is shown as a comparative example.

[0047] Figure 6 The surface morphology of the comparative sample is shown as an oxidation surface. Detailed Implementation

[0048] The above solution will be further described below with reference to specific embodiments. The preferred embodiments of the present invention are described in detail below:

[0049] Example 1

[0050] In this embodiment, an anti-oxidation coating for a molybdenum alloy surface has a perovskite structure and a lamellar structure parallel to the substrate surface, forming a barrier layer on the molybdenum alloy surface that blocks gas transmission.

[0051] In this embodiment, a method for preparing an anti-oxidation coating on a molybdenum alloy surface includes the following steps:

[0052] The raw materials were weighed and proportioned according to the mass percentage composition of the high-temperature resistant oxide powder. The raw materials were then placed in a ball mill and ball-milled to prepare a powder with uniformly mixed components, thus obtaining the high-temperature resistant oxide powder. The composition and mass fraction of the high-temperature resistant oxide powder were as follows: 10% TiO2, 5% MoSi2, 10% Al2O3, 15% CaO, 15% aluminum powder, 10% Na2O, 5% ZrO2, 2% B2O3, 1% boron powder, and the balance being SiO2.

[0053] The above-mentioned high-temperature resistant oxide powder was weighed and proportioned according to requirements, and then ball-milled in a ball mill to obtain a uniformly mixed powder. A solution containing 10% polyvinyl alcohol and 1% vinyltrisilane was prepared. The prepared powder and solution were mixed at a ratio of 1:3 and stirred until a slurry was formed. The surface of the molybdenum alloy material was polished with 1000# sandpaper to remove the oxide layer and increase the adhesion of the slurry. Then, it was ultrasonically cleaned and dried. The slurry was uniformly coated onto the surface of the molybdenum alloy, dried in an electric furnace at 600℃, and then held at 1100℃ for 1 hour to obtain a high-temperature anti-oxidation coating. The cross-sectional microstructure is shown in the figure. Figure 1 As can be seen, the protective film is uniform and dense, forming a high-performance glaze protective layer. In this embodiment, the Al powder and Mo5Si2 phase added to the antioxidant coating can react with the oxygen transported inward through the antioxidant coating to generate alumina ceramic and SiO2, thereby blocking the oxygen transport path and forming a component phase combination that enables self-healing of microcracks and self-repair of the antioxidant coating.

[0054] Example 2

[0055] This embodiment is basically the same as Embodiment 1, except that:

[0056] In this embodiment, an anti-oxidation coating for a molybdenum alloy surface has a perovskite structure and a lamellar structure parallel to the substrate surface, forming a barrier layer on the molybdenum alloy surface that blocks gas transmission.

[0057] In this embodiment, a method for preparing an anti-oxidation coating on a molybdenum alloy surface includes the following steps:

[0058] The raw materials were weighed and proportioned according to the mass percentage composition of the high-temperature resistant oxide powder. The raw materials were then placed in a ball mill and ball-milled to prepare a powder with uniformly mixed components, thus obtaining the high-temperature resistant oxide powder. The composition and mass fraction of the high-temperature resistant oxide powder were as follows: 25% TiO2, 15% MoSi2, 15% Al2O3, 10% CaO, 5% aluminum powder, 5% Na2O, 1% ZrO2, 0.1% B2O3, 0.1% boron powder, with the balance being SiO2.

[0059] The above-mentioned high-temperature resistant oxidation powder was weighed and proportioned according to requirements, and then ball-milled in a ball mill to obtain a uniformly mixed powder. A solution containing 5% polyvinyl alcohol and 5% vinyltrisilane was prepared. The prepared powder and solution were mixed at a ratio of 1:3 and stirred until a slurry was formed. The surface of the molybdenum alloy material was polished with 1000# sandpaper to remove the oxide layer and increase the adhesion of the slurry. Then, it was ultrasonically cleaned and dried. The slurry was uniformly coated onto the surface of the molybdenum alloy, dried in an electric furnace at 500℃, and then held at 1200℃ for 2 hours to obtain a high-temperature anti-oxidation coating. The cross-sectional microstructure is shown in [Figure showing...]. Figure 2 As can be seen, the coating reacts at high temperatures to form a perovskite structure. Figure 3 Phase analysis revealed that this layered structure, parallel to the matrix surface, effectively reduces oxygen transport.

[0060] In addition, by Figure 3 It is known that the phase composition of the anti-oxidation coating on the molybdenum alloy surface in this embodiment mainly includes MoO3 phase, Al2O3 phase, SiO2 phase, Na2O phase, ZrO2 phase, Mo5Si2 phase, TiO2 phase, MoO2 phase, CaO phase, and CaZrTi2O7 phase. In this embodiment, a borosilicate glass-ceramic surface layer containing SiO2, Al2O3, CaO, and B2O3 is formed on the molybdenum alloy surface through sintering at 1200℃, thereby bonding a uniform and dense glaze protective layer to the molybdenum alloy surface. Boron powder added to the anti-oxidation coating diffuses into the molybdenum alloy substrate at sintering temperature of 1200℃, reacting with Mo on the surface of the molybdenum alloy substrate to generate Mo-B compounds, forming a gradient composition transition layer at the interface between the molybdenum alloy substrate and the anti-oxidation coating. In this embodiment, the Al powder and Mo5Si2 phase added to the antioxidant coating can react with the oxygen transported inward through the antioxidant coating to generate alumina ceramic and SiO2, thereby blocking the oxygen transport path and forming a component phase combination that enables the antioxidant coating to self-heal microcracks and self-repair.

[0061] Example 3

[0062] This embodiment is basically the same as the previous embodiments, except that:

[0063] In this embodiment, a method for preparing an anti-oxidation coating on a molybdenum alloy surface includes the following steps:

[0064] The raw materials were weighed and proportioned according to the mass percentage composition of the high-temperature resistant oxide powder. The raw materials were then placed in a ball mill and ball-milled to prepare a powder with uniformly mixed components, thus obtaining the high-temperature resistant oxide powder. The composition and mass fraction of the high-temperature resistant oxide powder were as follows: 15% TiO2, 10% MoSi2, 25% Al2O3, 15% CaO, 10% aluminum powder, 15% Na2O, 2% ZrO2, 2% B2O3, 0.1% boron powder, and the balance was SiO2.

[0065] The above-mentioned high-temperature resistant oxide powder was weighed and proportioned according to requirements, and then ball-milled in a ball mill to obtain a uniformly mixed powder. A solution containing 10% polyvinyl alcohol and 1% vinyltrisilane was prepared. The prepared powder and solution were mixed at a ratio of 1:3 and stirred until a slurry was formed. The surface of the molybdenum alloy material was polished with 1000# sandpaper to remove the oxide layer and increase the adhesion of the slurry. Then, it was ultrasonically cleaned and dried. The slurry was uniformly coated onto the surface of the molybdenum alloy, dried in an electric furnace at 600℃, and then held at 1200℃ for 4 hours to obtain a high-temperature anti-oxidation coating. The surface morphology is shown in [Figure showing surface morphology]. Figure 4 As can be seen, the protective film is uniform and dense, and the glazing effect is good.

[0066] Example 4

[0067] This embodiment is basically the same as the previous embodiments, except that:

[0068] In this embodiment, a method for preparing an anti-oxidation coating on a molybdenum alloy surface includes the following steps:

[0069] The raw materials were weighed and proportioned according to the mass percentage composition of the high-temperature resistant oxide powder. The raw materials were then placed in a ball mill and ball-milled to prepare a powder with uniformly mixed components, thus obtaining the high-temperature resistant oxide powder. The composition and mass fraction of the high-temperature resistant oxide powder were as follows: 10% TiO2, 8% MoSi2, 25% Al2O3, 5% CaO, 10% aluminum powder, 10% Na2O, 5% ZrO2, 1% B2O3, 0.1% boron powder, and the balance was SiO2.

[0070] The above-mentioned high-temperature resistant oxide powder was weighed and proportioned according to the requirements, and then ball-milled in a ball mill to obtain a powder with uniformly mixed components. A solution containing 10% polyvinyl alcohol and 1% vinyltrisilane was prepared, and the prepared powder and solution were mixed at a ratio of 1:3 and stirred evenly to form a slurry. The surface of the molybdenum alloy material was polished with 1000# sandpaper to remove the oxide layer on the surface of the molybdenum alloy and increase the adhesion of the slurry. Then, it was cleaned by ultrasonication and dried for later use. The slurry was evenly coated on the surface of the molybdenum alloy and dried in an electric furnace at 500℃. Then, it was kept at 1300℃ for 2 hours to obtain a high-temperature anti-oxidation coating. It can be seen that the protective film is uniform and dense, and the glazing effect is good.

[0071] Comparative Example

[0072] In this comparative example, a method for preparing a molybdenum alloy surface coating includes the following steps:

[0073] The surface of the molybdenum alloy material was polished with 1000# sandpaper. A silicon coating was then prepared on the surface of the molybdenum alloy substrate sample using plasma spraying. (See attached image.) Figure 5 After heating to 1200℃ in a resistance furnace and holding for 2 hours, a lamellar MoO3 structure with matrix oxidation appeared on the surface of the molybdenum alloy matrix sample. Figure 6 It failed to achieve the effect of high-temperature anti-oxidation.

[0074] As can be seen from Examples 1-4 and the comparative examples above, the above embodiments have a rich combination of functional phases and functional additives, forming a functional phase combination of SiO2, Al2O3, CaO, and B2O3 glazing protective layer. It also includes a Mo-B compound interface layer, and ZrO2 and TiO2 react at high temperatures to form a perovskite structure. Furthermore, it includes a Mo-containing composite phase combination of MoO3, MoO2, and Mo5Si2 phases, and a composite phase combination of CaO, ZrO2, TiO2, and CaZrTi2O7 phases. This coating has outstanding self-healing capabilities for micro-defects and micro-cracks, achieving intelligent repair under high-temperature service conditions, thus forming a self-healing surface layer. This results in excellent high-temperature oxidation resistance and improved service life of the coating. The anti-oxidation coating in Examples 1-4 of the present invention can provide effective anti-oxidation protection for molybdenum alloys at 1100–1300℃, exhibiting significant anti-oxidation effects. In Examples 1-4, the addition of SiO2 and Al2O3, followed by pre-sintering, forms borosilicate glass ceramics on the molybdenum alloy surface with CaO and B2O3. Simultaneously, B2O3 integrates into the borosilicate glass, reducing the viscosity of SiO2 and the porosity of the coating, thus forming a uniform and dense glaze protective layer at the sintering temperature. The boron powder added in Examples 1-4 diffuses into the substrate at high temperatures and reacts with Mo to form Mo-B compounds. The presence of these compounds hinders the diffusion of Si into the substrate, ensuring the formation of an excellent protective layer while preventing reactions at the substrate-coating interface, thus ensuring the substrate material remains uncorroded by the coating and maintains excellent mechanical properties. The addition of ZrO2 and TiO2 in Examples 1-4 reacts at high temperatures to form a perovskite structure. This lamellar structure, parallel to the substrate surface, effectively reduces oxygen transport. The addition of MoSi2 and Al powder in Examples 1-4 above provides multiple protective effects. When oxygen is transported inward through the surface layer, MoSi2 reacts with oxygen to generate alumina ceramic and SiO2, thus blocking the oxygen transport path and achieving self-healing of cracks and self-repairing of the coating. The high-temperature anti-oxidation coating prepared by the methods in Examples 1-4 above has excellent anti-oxidation effects and can effectively protect irregularly shaped and large-volume molybdenum alloy substrates. The methods in the above embodiments of the present invention have the advantages of simple process, convenient operation, low cost, high yield, and high efficiency, making them suitable for industrial promotion and application. They have important practical value for the preparation of high-temperature hot-end components in aerospace, nuclear industry, machinery, metallurgy and other fields.

[0075] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of the present invention shall be equivalent substitutions. As long as they meet the purpose of the invention and do not deviate from the technical principle and inventive concept of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. An anti-oxidation coating for molybdenum alloy surfaces, characterized in that: It has a perovskite-zircon structure and a lamellar structure parallel to the matrix surface, forming a barrier layer on the surface of the molybdenum alloy to block gas transmission. The anti-oxidation coating on the molybdenum alloy surface is a borosilicate glass ceramic surface layer containing SiO2, Al2O3, CaO, and B2O3, formed on the surface of the molybdenum alloy at a sintering temperature of 1100~1300℃, thereby bonding a uniform and dense glaze protective layer on the surface of the molybdenum alloy.

2. The anti-oxidation coating on the molybdenum alloy surface according to claim 1, characterized in that: Its phase composition mainly includes MoO3 phase, Al2O3 phase, SiO2 phase, Na2O phase, ZrO2 phase, Mo5Si2 phase, TiO2 phase, MoO2 phase, CaO phase and CaZrTi2O7 phase.

3. The anti-oxidation coating on the molybdenum alloy surface according to claim 1, characterized in that: When the boron powder added to the antioxidant coating is sintered at a temperature of 1100~1300℃, the boron diffuses into the molybdenum alloy matrix and reacts with the molybdenum alloy matrix surface to form a Mo-B compound, forming a gradient composition transition layer at the interface between the molybdenum alloy matrix and the antioxidant coating.

4. The anti-oxidation coating on the molybdenum alloy surface according to claim 2, characterized in that: The Al powder and Mo5Si2 phase added to the antioxidant coating can react with the oxygen transported inward through the antioxidant coating to generate alumina ceramics and SiO2, thereby blocking the oxygen transport path and forming a component phase combination that enables the antioxidant coating to self-heal microcracks and self-repair.

5. A method for preparing the anti-oxidation coating on the surface of a molybdenum alloy as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of high-temperature resistant oxidation powder: The raw materials were weighed and proportioned according to the mass percentage composition of the high-temperature resistant oxidation powder. The raw materials were then placed in a ball mill and ball-milled to prepare a uniformly mixed powder, thus obtaining the high-temperature resistant oxidation powder. The composition and mass fraction of the high-temperature resistant oxidation powder are as follows: TiO2: 10~25%; Al2O3: 10~25%; CaO: 10~15%; MoSi2: 5~15%; Na2O: 5~15%; Aluminum powder: 5~15%; ZrO2: 1~5%; B2O3: 0.1~2%; Boron powder: 0.1~1%; The balance is SiO2; (2) Preparation of slurry: Prepare a solution containing 5-10% polyvinyl alcohol and 1-5% vinyltrisilane by mass. Mix the prepared high-temperature resistant oxidation powder with the solution at a mass ratio of 1:3 and stir until homogeneous to form a slurry. (3) Preparation of anti-oxidation coating on molybdenum alloy surface: The surface of the molybdenum alloy material is polished with sandpaper to remove the oxide layer, thus performing surface pretreatment. The slurry is then uniformly coated onto the pretreated surface of the molybdenum alloy material. The coating is then dried in an electric furnace at 500-600°C, and finally kept at 1100-1300°C to obtain a uniform and dense high-temperature anti-oxidation coating.

6. The method for preparing the anti-oxidation coating on the surface of the molybdenum alloy according to claim 5, characterized in that: In step (3), the surface of the molybdenum alloy material is polished with 1000# sandpaper; Alternatively, in step (3), after polishing the surface of the molybdenum alloy material with sandpaper, the surface of the molybdenum alloy material is cleaned by ultrasound and then dried for later use, thus completing the pretreatment process. Alternatively, in step (3), the coating is heat-insulated for 1-4 hours.

7. The application of the anti-oxidation coating on the surface of the molybdenum alloy as described in claim 1, characterized in that: The anti-oxidation coating on the molybdenum alloy surface is used to form an anti-oxidation surface glaze protective layer for the molybdenum alloy workpiece substrate under service conditions of not less than 1100°C.

Images