Molybdenum or molybdenum alloy surface oxidation resistant coating and method of making same

Abstract

The application discloses a molybdenum or molybdenum alloy surface oxidation-resistant coating and a preparation method thereof, and relates to the technical field of surface treatment. The molybdenum or molybdenum alloy surface oxidation-resistant coating comprises the following components: a silicon-containing and molybdenum compound, a boride, a carbon- or oxygen-containing compound and silicon; wherein the boride comprises at least one of zirconium boride, hafnium boride or titanium boride, and the carbon- or oxygen-containing compound comprises at least one of silicon carbide, hafnium carbide, zirconium carbide or hafnium oxide. The preparation method of the molybdenum or molybdenum alloy surface oxidation-resistant coating comprises the following steps: mixing coating powder, a binder and a solvent to obtain mixed slurry; performing spray drying on the mixed slurry to prepare powder; and depositing the powder on the surface of molybdenum or molybdenum alloy by using a plasma physical vapor deposition process to form an oxidation-resistant coating on the surface of molybdenum or molybdenum alloy. The application can solve the problems of poor thermal adaptability and insufficient oxidation resistance of the current single molybdenum silicide coating, and the problem that the current molybdenum alloy surface coating cannot be prepared in a large size.

Description

Technical Field

[0001] This application belongs to the field of surface treatment technology, specifically relating to an anti-oxidation coating for molybdenum or molybdenum alloy surfaces and its preparation method. Background Technology

[0002] Molybdenum (Mo) and its alloys are important high-temperature structural materials. Molybdenum and its alloys possess a series of excellent properties, such as a high melting point (2620℃), good electrical and thermal conductivity, good thermal shock resistance, and thermal fatigue resistance, making them widely used as high-temperature structural or functional materials in fields such as electronics, glass, and aerospace. However, the Mo element in molybdenum alloys begins to react with oxygen at 300℃ to form MoO3, which lacks oxidation resistance. Furthermore, the oxidation rate increases with temperature, and the MoO3 formed above 700℃ is volatile, causing a significant decrease in workpiece quality and a severe imbalance in precision, thus limiting its feasibility as a standalone high-temperature structural material.

[0003] In related technologies, anti-oxidation coatings on the surface of molybdenum and its alloys are generally single-component molybdenum disilicide (MoSi2) coatings. However, the mismatch in the coefficient of thermal expansion between the single molybdenum disilicide coating and the alloy leads to coating detachment, powdering, and failure, making current anti-oxidation coatings on molybdenum alloy surfaces unable to meet the requirements of relevant working conditions. Furthermore, current methods generally employ infiltration to prepare anti-oxidation coatings on the surface of molybdenum and its alloys, such as embedding infiltration and sintering methods. However, due to the process limitations of embedding infiltration and sintering methods, it is impossible to effectively prepare anti-oxidation coatings on large-size sample surfaces.

[0004] Therefore, improving the oxidation resistance of molybdenum and its alloys is key to ensuring their long-term safe application, and there is an urgent need to develop high-temperature oxidation-resistant coating materials and their preparation methods that can be used under high-temperature conditions. Summary of the Invention

[0005] The purpose of this application is to provide an anti-oxidation coating for molybdenum or molybdenum alloy surfaces and a method for preparing the same, which can alleviate the problems of poor thermal adaptability and insufficient anti-oxidation performance of existing single molybdenum silicide coatings, and can also alleviate the problem that current molybdenum and its alloy surface coatings cannot be prepared in large sizes.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows:

[0007] According to one aspect of this application, an embodiment of this application provides an anti-oxidation coating for the surface of molybdenum or molybdenum alloys, the anti-oxidation coating comprising the following components:

[0008] Silicon and molybdenum compounds, borides, carbon or oxygen-containing compounds, and silicon;

[0009] The boride includes at least one of zirconium boride, hafnium boride, or titanium boride, and the carbon- or oxygen-containing compound includes at least one of silicon carbide, hafnium carbide, zirconium carbide, or hafnium oxide.

[0010] In some alternative embodiments, the silicon- and molybdenum-containing compound includes molybdenum disilicide.

[0011] In some alternative embodiments, the boride is selected from zirconium boride.

[0012] In some alternative embodiments, the carbon- or oxygen-containing compound is selected from silicon carbide.

[0013] In some alternative embodiments, the mass ratio of the silicon and molybdenum compound, the boride, the carbon or oxygen compound and silicon is (60-90):(2-30):(5-15):(0.1-5).

[0014] In some alternative embodiments, the thickness of the antioxidant coating is 60 μm to 150 μm.

[0015] In some alternative embodiments, the porosity of the antioxidant coating is less than 2%.

[0016] According to another aspect of this application, embodiments of this application provide a method for preparing an anti-oxidation coating on a molybdenum or molybdenum alloy surface, the method comprising:

[0017] The coating powder, binder, and solvent are mixed to obtain a mixed slurry;

[0018] The mixed slurry was spray-dried to obtain a powder.

[0019] The powder is deposited on the surface of molybdenum or molybdenum alloy using a plasma spraying-physical vapor deposition process, forming an anti-oxidation coating on the surface of molybdenum or molybdenum alloy mainly composed of silicon and molybdenum compounds, borides, carbon or oxygen compounds and silicon.

[0020] The boride includes at least one of zirconium boride, hafnium boride, or titanium boride, and the carbon- or oxygen-containing compound includes at least one of silicon carbide, hafnium carbide, zirconium carbide, or hafnium oxide.

[0021] In some optional embodiments, the coating powder comprises molybdenum disilicide, zirconium boride, and silicon carbide; the mass ratio of molybdenum disilicide, zirconium boride, silicon carbide, and binder is (60-90):(2-30):(5-15):(0.2-1.5).

[0022] In some alternative embodiments, the adhesive includes at least one of polyvinyl alcohol, polyethylene glycol, polyacrylic acid, or carboxymethyl cellulose.

[0023] In some alternative embodiments, the particle size of the mixed slurry reaches D. max <1μm.

[0024] In some alternative embodiments, the solid content of the mixed slurry ranges from 30% to 70%.

[0025] In some alternative embodiments, the spray drying is performed using a two-fluid spray dryer.

[0026] In some alternative embodiments, after the powder is prepared and before the plasma spraying-physical vapor deposition process is performed, the steps of drying and sieving the powder are further included.

[0027] In some optional embodiments, the spray drying process conditions include: a total spray drying temperature of ≤200℃, a gas pressure of 0.2 MPa to 0.4 MPa, a peristaltic pump speed of 15 to 30 r / min, and an outlet temperature of 100℃ to 150℃.

[0028] In some alternative embodiments, the drying and sieving processes involve a drying temperature of 60°C to 75°C and a drying time of 2 hours to 6 hours.

[0029] In some alternative embodiments, during the drying and sieving process, the particle size of the sieved powder ranges from 1 μm to 30 μm.

[0030] In some alternative embodiments, after the powder is prepared and before the plasma spraying-physical vapor deposition process is performed, a roughening treatment step is further included on the surface of the molybdenum or molybdenum alloy.

[0031] In some optional embodiments, the process conditions of the plasma spraying-physical vapor deposition process include: power of 60-80KW, spraying distance of 450mm-550mm, ambient pressure of less than 200Pa, and spraying time of 6min-8min.

[0032] In some alternative embodiments, the thickness of the antioxidant coating is 60 μm to 150 μm.

[0033] In some alternative embodiments, the porosity of the antioxidant coating is less than 2%.

[0034] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0035] In the embodiments of this application, the provided anti-oxidation coating for molybdenum or molybdenum alloy surfaces includes silicon and molybdenum compounds, borides, carbon or oxygen-containing compounds, and silicon; wherein the borides include at least one of zirconium boride, hafnium boride, or titanium boride, and the carbon or oxygen-containing compounds include at least one of silicon carbide, hafnium carbide, zirconium carbide, or hafnium oxide. Therefore, by controlling the coating material and designing the coating composition, this application can reduce the thermal mismatch between the coating and the substrate, enhance the adhesion of the coating, improve the bonding strength between the coating and the substrate, and overcome the disadvantages of insufficient thermal adaptability and anti-oxidation performance of current single-component molybdenum silicon carbide coatings.

[0036] The coating of this invention is deposited using a plasma spraying-physical vapor deposition process. Not only does the prepared coating have the advantages of good adhesion to the substrate and being less prone to peeling off, but it also breaks through the limitations of preparing anti-oxidation coatings on molybdenum alloy surfaces using the infiltration method. It also overcomes the problem that conventional methods for preparing anti-oxidation coatings on molybdenum alloy surfaces cannot prepare large-size samples, and has a broader prospect for engineering applications.

[0037] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0038] Figure 1 A scanning electron microscope image of a typical cross-section of an antioxidant coating prepared according to an embodiment of this application;

[0039] Figure 2 X-ray diffraction patterns of typical antioxidant coatings prepared in the embodiments of this application;

[0040] Figure 3 Metallographic images of the anti-oxidation coating prepared on the surface of TZM molybdenum alloy in Example 1 after oxidation at 1600℃ for 10 hours (with and without coating comparison).

[0041] Figure 4 The image shown is a scanning electron microscope image of the anti-oxidation coating prepared on the surface of TZM molybdenum alloy in Example 2 after oxidation at 1600℃ for 4 hours.

[0042] Figure 5 This is a schematic diagram of a typical vapor-deposited coating prepared on the surface of a molybdenum alloy in Comparative Example 1.

[0043] Figure 6 The image shows the macroscopic morphology of the coating prepared on the surface of molybdenum alloy in Comparative Example 1 after treatment at 1600℃ for 10 hours.

[0044] Figure 7 The image shows a scanning electron microscope image of the anti-oxidation coating prepared on the surface of a molybdenum alloy for Comparative Example 1 after oxidation at 1600℃ for 10 hours. Detailed Implementation

[0045] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] 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 ranges, the endpoint values ​​of the ranges, or 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. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following related objects are in an "or" relationship.

[0047] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0048] The embodiments of this application will be described in detail below with reference to the accompanying drawings and specific examples and application scenarios.

[0049] In related technologies, anti-oxidation coatings on molybdenum or molybdenum alloy surfaces are typically single-component MoSi2 coatings. The mismatch in thermal expansion coefficients between the single molybdenum silicide coating and the substrate (molybdenum or molybdenum alloy) leads to easy coating detachment, powdering, and failure, rendering current anti-oxidation coatings on molybdenum or molybdenum alloy surfaces inadequate for relevant operating conditions. Consequently, binary or multi-component silicide coatings have become the main development trend for anti-oxidation coatings. Although some binary or multi-component silicide coatings have been proposed in related technologies, they still suffer from poor adhesion to the substrate or insufficient oxidation resistance.

[0050] Furthermore, current methods for preparing antioxidant coatings typically employ infiltration techniques, such as embedding and sintering, which have limitations in effectively preparing antioxidant coatings on large-sized sample surfaces. The inventors of this application have discovered that using plasma spraying-physical vapor deposition (PS-PVD) can achieve solid-liquid-gas single-phase or multi-phase mixed deposition to meet diverse application requirements. It can also achieve non-visual deposition, satisfying the deposition needs of complex surfaces (including obscured areas); thus providing an effective means to prepare antioxidant coatings for large-sized samples.

[0051] In view of this, the inventors of this application, through extensive research, have proposed new improvement ideas from the aspects of coating composition and coating preparation process. By improving the composition or preparation process of the coating, a coating that can greatly enhance the oxidation resistance of molybdenum or molybdenum alloys is provided. Furthermore, a method for preparing high-temperature oxidation-resistant coatings on the surface of molybdenum or molybdenum alloys that is efficient, rapid, and without size limitations is provided to overcome the aforementioned deficiencies in related technologies. The following is a detailed description of this application.

[0052] In some embodiments, this application provides an anti-oxidation coating for molybdenum or molybdenum alloy surfaces, the anti-oxidation coating comprising the following components:

[0053] The compounds contain silicon and molybdenum, borides, carbon or oxygen-containing compounds, and silicon; wherein the borides include at least one of zirconium boride, hafnium boride, or titanium boride, and the carbon or oxygen-containing compounds include at least one of silicon carbide, hafnium carbide, zirconium carbide, or hafnium oxide.

[0054] The term "boride" refers to boron-containing compounds, such as metal borides.

[0055] The term "silicon and molybdenum compounds" primarily refers to Mo. y Si x In this case, x can be 1 to 3, and y can be 1 to 5; for example, x can be 1, 2, or 3, and y can be 1, 2, 3, 4, or 5. For instance, if x is 2 and y is 1, the silicon and molybdenum compound can be molybdenum disilicide.

[0056] The term "carbon- or oxygen-containing compound" refers to a compound containing carbon or oxygen, that is, a carbide or an oxide.

[0057] In the aforementioned antioxidant coating, silicon and molybdenum compounds are the main components of the coating, while other substances such as borides, carbon or oxygen-containing compounds, and silicon can serve as reinforcing phases.

[0058] The antioxidant coating provided in this application embodiment can be formed on the surface of a molybdenum alloy, or on the surface of molybdenum. That is, the substrate in this application embodiment can be a molybdenum alloy, but it is not limited to this; it can also be molybdenum. For simplicity, the following detailed description mainly uses a molybdenum alloy as an example, but it should be understood that molybdenum with similar requirements is also applicable to this invention.

[0059] The anti-oxidation coating on the surface of molybdenum or molybdenum alloys in this invention is a coating that effectively resists oxidation on the surface of molybdenum alloys, and can be used to solve the problems of poor thermal adaptability and insufficient anti-oxidation performance of current single molybdenum silicon coatings. In detail:

[0060] The phase composition of the antioxidant coating of this application mainly includes silicon and molybdenum compounds, borides, carbon or oxygen-containing compounds, and silicon (Si). The borides include any one or a combination of at least two of zirconium boride (ZrB2), hafnium boride (HfB2), or titanium boride (TiB2). The carbon or oxygen-containing compounds include any one or a combination of at least two of silicon carbide (SiC), hafnium carbide (HfC), zirconium carbide (ZrC), or hafnium oxide (HfO2). As an example, the borides can be ZrB2, HfB2, TiB2, or any two of ZrB2, HfB2, and TiB2, or ZrB2, HfB2, and TiB2. The carbon or oxygen-containing compounds can be SiC, HfC, ZrC, HfO2, or any combination of any two or more of SiC, HfC, ZrC, and HfO2.

[0061] Therefore, in this antioxidant coating, by optimizing the thermal expansion coefficient of the coating components to make them closer to the substrate, such as molybdenum alloys or molybdenum materials, the thermal mismatch between the coating and the substrate is effectively reduced. Furthermore, the addition of silicon- and molybdenum-containing compounds improves antioxidant properties, while the addition of borides and carbon- or oxygen-containing compounds enhances high-temperature performance, reducing the risk of coating cracking during high-temperature cycling. The Si phase absorbs oxygen to generate SiO2, thus providing antioxidant protection. In this embodiment, the Si phase can be a unique precipitated phase prepared during coating preparation, such as in PS-PVD coating preparation. The added silicon-containing compound undergoes certain physicochemical changes during the PS-PVD process, resulting in the formation of the Si phase. Therefore, the antioxidant coating provided by this invention, through optimization of the coating components, reduces the thermal mismatch between the coating and the substrate, improves high-temperature antioxidant properties, enhances coating adhesion, increases the bonding strength between the coating and the substrate, and reduces the risk of cracking during high-temperature cycling, effectively overcoming the shortcomings of current single-component molybdenum silicide coatings in terms of thermal adaptability and antioxidant performance.

[0062] Therefore, the embodiments of the present invention can effectively protect molybdenum alloys and improve the oxidation resistance of the molybdenum alloy substrate. Through component optimization and multiphase synergy, the present invention improves the high-temperature stability and oxidation resistance of the coating. The anti-oxidation coating prepared by the embodiments of the present invention has good adhesion, effectively reducing the risk of coating powdering and peeling, and possesses superior overall performance.

[0063] Furthermore, this invention has a wide range of applications and can be applied to fields involving molybdenum or molybdenum alloys, such as high-temperature hot-end components in aerospace, nuclear industry, machinery, and metallurgy, with a maximum applicable temperature of 1600℃.

[0064] In some embodiments, the silicon and molybdenum compounds include molybdenum disilicide (MoSi2). For example, the antioxidant coating is primarily composed of MoSi2, Si, borides, and carbon- or oxygen-containing compounds.

[0065] In some embodiments, the boride is selected from zirconium boride (ZrB2). In the embodiments of this application, the boride may be selected from one or more of zirconium boride (ZrB2), hafnium boride (HfB2), or titanium boride (TiB2); preferably, ZrB2 is more preferred, as it is more conducive to improving the high-temperature oxidation resistance of the coating, has better practical application value, and is widely available and easy to obtain. For example, the anti-oxidation coating is mainly composed of MoSi2, Si, ZrB2, and carbon- or oxygen-containing compounds.

[0066] In some embodiments, the carbon- or oxygen-containing compound is selected from silicon carbide. In the embodiments of this application, the carbon- or oxygen-containing compound may be selected from one or more of silicon carbide (SiC), hafnium carbide (HfC), zirconium carbide (ZrC), or hafnium oxide (HfO2); preferably, SiC is more preferred, as it is more conducive to improving the high-temperature oxidation resistance of the coating, has better practical application value, and is widely available and easy to obtain.

[0067] As an example, in some embodiments, the antioxidant coating is mainly composed of MoSi2, Si, ZrB2 and SiC.

[0068] In some embodiments, the mass ratio of silicon and molybdenum compounds, borides, carbon or oxygen-containing compounds, and silicon is (60–90):(2–30):(5–15):(0.1–5). As an example, MoSi2, ZrB... 2、 The mass ratio of SiC to Si is (60-90): (2-30): (5-15): (0.1-5).

[0069] It should be noted that the proportion of each substance in the coating is related to the process control and the proportion of powder raw materials. By adjusting the process parameters and the proportion of powder raw materials, the proportion of each substance in the obtained coating can be within the above-mentioned suitable range. This invention does not limit the specific proportion of each substance in the coating, as long as the proportion of powder raw materials is within a suitable range and the relevant performance of the obtained coating meets the actual use requirements.

[0070] It should also be noted that in the above coating, silicon is a naturally occurring phase during the coating production process. In the embodiments of this application, silicon was not added to the raw materials of the coating, so the silicon content in the final coating is trace.

[0071] In some embodiments, the thickness of the antioxidant coating is 60 μm to 150 μm. For example, the thickness of the antioxidant coating is any one of 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 120 μm, and 150 μm, or a range between any two.

[0072] Compared to the shortcomings of traditional diffusion layers, which are basically unable to control thickness or uniformity, the thickness of the anti-oxidation coating in this invention embodiment can be precisely controlled, making the thickness controllable and improving the uniformity of the thickness, thereby improving the quality of the coating.

[0073] In some embodiments, the porosity of the antioxidant coating is less than 2%. For example, the porosity of the antioxidant coating is 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.2%, 1%, or less than 1%.

[0074] It should be understood that the oxidation resistance of a coating is closely related to its density. Traditional MoSi coatings may have high porosity due to insufficient sintering or crack formation during the sintering process, allowing oxygen to diffuse along the defects and reducing oxidation resistance. However, the coating preparation process used in this application controls the porosity of the anti-oxidation coating to below 2%, reducing porosity and improving the density of the coating, thereby enhancing its oxidation resistance.

[0075] Accordingly, in some embodiments, a method for preparing an anti-oxidation coating on the surface of molybdenum or molybdenum alloy is provided, the method comprising the following steps:

[0076] Step S100: The coating powder, binder and solvent are mixed to obtain a mixed slurry;

[0077] Step S200: Spray dry the mixed slurry to obtain powder;

[0078] Step S300: Powder is deposited on the surface of molybdenum or molybdenum alloy using a plasma spraying-physical vapor deposition process to form an anti-oxidation coating on the surface of molybdenum or molybdenum alloy, mainly composed of silicon and molybdenum compounds, borides, carbon or oxygen compounds and silicon.

[0079] The borides include at least one of zirconium boride, hafnium boride, or titanium boride, and the carbon- or oxygen-containing compounds include at least one of silicon carbide, hafnium carbide, zirconium carbide, or hafnium oxide.

[0080] It should be understood that all the features and advantages described above regarding the "anti-oxidation coating on the surface of molybdenum or molybdenum alloy" also apply to the "preparation method of anti-oxidation coating on the surface of molybdenum or molybdenum alloy", and will not be repeated here.

[0081] In this embodiment, a mixed slurry containing coating powder can be prepared first, followed by powder preparation. Then, the powder is deposited onto the surface of molybdenum or a molybdenum alloy using a plasma spraying-physical vapor deposition process, thereby forming an anti-oxidation coating on the molybdenum or molybdenum alloy surface. The coating prepared in this embodiment has the advantages of good adhesion to the substrate and resistance to peeling, overcoming the limitations of preparing anti-oxidation coatings on molybdenum alloy surfaces using the penetration method, and has broader prospects for engineering applications.

[0082] The method provided in this invention is simple to prepare, easy to operate, has a high yield and high efficiency, and overcomes the problem that conventional methods for preparing anti-oxidation coatings on molybdenum alloy surfaces cannot prepare large-sized samples. This invention can effectively protect molybdenum or molybdenum alloy substrates with irregular shapes and large volumes.

[0083] Therefore, the rapid and efficient method for preparing an antioxidant coating provided by the embodiments of the present invention can be used to solve the problem that molybdenum alloy surface coatings cannot be prepared on a large scale at present. In some specific embodiments, the method for preparing the antioxidant coating includes the following steps S100 to S300.

[0084] Step S100: Prepare the mixed slurry: Mix the coating powder, binder and solvent to obtain the mixed slurry.

[0085] In some embodiments, in step S100, the coating powder and binder powder are mixed and added to a solvent, and then ball-milled in proportion until the particle size of the mixed slurry reaches the required particle size.

[0086] Optionally, the coating powder includes silicon and molybdenum compound raw materials, boride raw materials, and carbon or oxygen compound raw materials. As an example, the silicon and molybdenum compound raw material includes molybdenum disilicide; the boride raw material includes one or more of zirconium boride, hafnium boride, or titanium boride, preferably, the boride raw material is selected from zirconium boride; the carbon or oxygen compound raw material includes one or more of silicon carbide, hafnium carbide, zirconium carbide, or hafnium oxide, preferably, the carbon or oxygen compound raw material is selected from silicon carbide.

[0087] Thus, by way of example, the coating powder includes molybdenum disilicide, zirconium boride, and silicon carbide.

[0088] Optionally, the adhesive includes, but is not limited to, at least one of polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyacrylic acid (PAA), or carboxymethyl cellulose (CMC).

[0089] In the above-mentioned mixed slurry, the addition of a binder can play a bonding role. The binder can be a conventional bonding material, such as PVA, PEG, PAA, etc.; preferably, the binder is selected from PVA, which has good adhesion, and is widely available, low in cost, and easy to obtain.

[0090] Optionally, the solvents mentioned above include, but are not limited to, water. Using water as a solvent is low-cost and safe.

[0091] In some alternative embodiments, in step S100 above, the coating powders MoSi2, ZrB2, SiC and binder such as PVA are mixed and then added to a solvent such as water, and mixed in proportion. The mixing method can be ball milling until the particle size of the mixed slurry reaches the required particle size.

[0092] In some embodiments, in step S100, the mass ratio of molybdenum disilicide, zirconium boride, silicon carbide, and binder is (60-90):(2-30):(5-15):(0.2-1.5). That is, the mixing ratio of MoSi2, ZrB2, SiC, and binder powder is: by mass percentage, MoSi2 accounts for 60%-90%, ZrB2 accounts for 2%-30%, SiC accounts for 5%-15%, and PVA accounts for 0.2%-1.5%. Optionally, after adding solvent water, the solid content of the slurry is 30%-70%.

[0093] In the embodiments of this application, the solid content of the mixed slurry ranges from 30% to 70%; for example, the solid content of the mixed slurry can be any one of 30%, 40%, 50%, 60%, 70% or any range between two.

[0094] In some embodiments, in step S100, the particle size of the mixed slurry reaches D. max<1μm. By controlling the particle size of the mixed slurry within this range, the uniform distribution of all components in the powder material preparation process can be ensured, thereby improving the uniformity of the mixed slurry.

[0095] Exemplary, in some embodiments, step S100 includes: mixing coating powders MoSi2, ZrB2, SiC, and a binder such as PVA, then adding the mixture to a solvent such as water, and mixing them according to a ratio, for example, the mixing ratio of MoSi2, ZrB2, SiC, and binder powder is: by mass percentage, MoSi2 accounts for 60%–90%, ZrB2 accounts for 2%–30%, SiC accounts for 5%–15%, and PVA accounts for 0.2%–1.5%, and after mixing, adding the mixture to the solvent water to prepare a slurry with a solid content of 30%–70%, and then ball milling the mixture until the particle size of the slurry reaches D. max <1μm, a mixed slurry was prepared.

[0096] Step S200: Prepare powder: Spray dry the above mixed slurry to obtain powder.

[0097] In some embodiments, in step S200, the spray drying is performed using a two-fluid spray dryer.

[0098] In some embodiments, after obtaining the powder, step S200 further includes drying and sieving the powder.

[0099] Therefore, step S200 includes: preparing powder from the mixed slurry using a two-fluid spray dryer, and drying and sieving the prepared powder.

[0100] Optionally, in step S200, the spray drying process conditions include: a total temperature of ≤200℃ throughout the spray drying preparation process, a gas pressure of 0.2 MPa to 0.4 MPa, a peristaltic pump speed of 15 to 30 r / min, and an outlet temperature of 100℃ to 150℃. As an example, the gas pressure can be any one of 0.2 MPa, 0.3 MPa, or 0.4 MPa, or a range between any two; the peristaltic pump speed can be any one of 15 r / min, 20 r / min, 25 r / min, or 30 r / min, or a range between any two; and the outlet temperature can be any one of 100℃, 110℃, 120℃, 130℃, 140℃, or 150℃, or a range between any two.

[0101] Optionally, in step S200, during drying and sieving, the drying temperature is 60℃~75℃, and the drying time is 2h~6h. As an example, the drying temperature is any one of 60℃, 62℃, 65℃, 70℃, 75℃, or a range between any two; the drying time is any one of 2h, 3h, 4h, 5h, 6h, or a range between any two.

[0102] Optionally, in step S200, during drying and sieving, the particle size of the sieved powder ranges from 1 μm to 30 μm. As an example, the particle size of the sieved powder is any one of 1 μm, 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, and 30 μm, or a range between any two.

[0103] By controlling the particle size range of the powder after sieving to between 1μm and 30μm, it is beneficial to the subsequent deposition process, which can ensure the gas-liquid co-deposition of the coating and guarantee the quality of the coating preparation.

[0104] Step S300: Prepare an antioxidant coating: Deposit powder onto the surface of molybdenum or molybdenum alloy using a plasma spraying-physical vapor deposition process to form an antioxidant coating on the surface of molybdenum or molybdenum alloy.

[0105] In some embodiments, step S300, prior to the plasma spraying-physical vapor deposition process, further includes roughening the surface of the molybdenum or molybdenum alloy. Optionally, the roughening process can be performed by sandblasting.

[0106] Optionally, step S300 includes: roughening the surface of molybdenum or molybdenum alloy by sandblasting, and then depositing powder on the surface of molybdenum or molybdenum alloy by plasma spraying-physical vapor deposition process.

[0107] Optionally, in step S300, the process conditions for the plasma spraying-physical vapor deposition process include: power of 60-80 kW, spraying distance of 450-550 mm, ambient pressure of less than 200 Pa, and spraying time of 6-8 min. As an example, the power of the plasma physical vapor deposition system can be any one of 60 kW, 65 kW, 70 kW, 75 kW, or 80 kW, or a range between any two; the spraying distance can be any one of 450 mm, 480 mm, 500 mm, 520 mm, or 550 mm, or a range between any two; the ambient pressure can be 180 Pa, 170 Pa, 160 Pa, 150 Pa, or 100 Pa; and the spraying time can be any one of 6 min, 7 min, or 8 min, or a range between any two.

[0108] By controlling parameters such as power, spraying distance, ambient pressure, and spraying time in the plasma spraying-physical vapor deposition process within the above range, a gas-liquid co-deposition state can be generated. The bottom of the coating can protect the substrate, and the top of the coating can isolate oxygen. As a result, the prepared antioxidant coating has good density and good high-temperature antioxidant capacity.

[0109] In some embodiments, the thickness of the antioxidant coating prepared by the present invention is 60 μm to 150 μm.

[0110] In some embodiments, the porosity of the antioxidant coating prepared by the present invention is less than 2%.

[0111] In some embodiments, the antioxidant coating prepared by the present invention is mainly composed of a composite phase of Si, MoSi2, ZrB2, and SiC. The adhesion between this antioxidant coating and the substrate is greater than 30 MPa, indicating good adhesion.

[0112] Figure 1 The image shows a scanning electron microscope image of a typical cross-section of the antioxidant coating prepared according to an embodiment of the present invention; Figure 2 The X-ray diffraction patterns of typical antioxidant coatings prepared according to embodiments of the present invention are shown. Figure 1 It can be seen that the antioxidant coating prepared in the embodiments of the present invention is dense and uniform internally, and the coating has a good bonding effect with the substrate. From Figure 2 It can be seen that the phase composition of the coating obtained in a typical embodiment of the present invention is as follows.

[0113] Therefore, based on the above settings, this invention mainly controls the coating material, the coating preparation process, and the thickness. It prepares powder with a particle size range of 1–30 μm (such as MoSi+ZrB2+SiC powder) using a two-fluid spray dryer, and then deposits a dense anti-oxidation coating (such as a MoSi2+ZrB2+SiC coating) using a plasma spraying-physical vapor deposition system. The method of this invention can conveniently prepare an anti-oxidation coating usable at 1600℃ on the surface of molybdenum or molybdenum alloys. The coating prepared by this invention has the advantages of good adhesion to the substrate and resistance to peeling, overcoming the limitations of preparing anti-oxidation coatings on molybdenum alloy surfaces using the infiltration method, and has broader prospects for engineering applications.

[0114] The following describes the implementation methods of this application. The implementation methods described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the implementation methods, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents, materials, or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0115] Example 1

[0116] A method for preparing an anti-oxidation coating on a molybdenum or molybdenum alloy surface, comprising:

[0117] By weight percentage, 70% MoSi2, 20% ZrB2, 9% SiC, and 1% PVA (binder) powders were mixed and then dissolved in water to prepare a slurry with a solid content of 50%. The mixture was then ball-milled until the particle size of the slurry reached D... max <1μm. The mixed slurry was then powdered using a two-fluid spray dryer. Throughout the process, the temperature was controlled at a maximum of 190℃, the gas pressure at 0.2MPa, the peristaltic pump speed at 20r / min, and the outlet temperature at 120℃. The powder was then dried and sieved. The drying conditions were 75℃ for 4 hours, resulting in a powder particle size range of 5~25μm. The molybdenum alloy surface was then roughened using white corundum sandblasting at 0.2MPa, followed by plasma spraying-physical vapor deposition (PVD). The PPVD system power was 70KW, the spraying distance was 500mm, the ambient pressure was less than 200Pa, and the spraying time was 6min.

[0118] Thus, the thickness of the resulting anti-oxidation coating is between 60 and 80 μm, and the porosity of the coating is about 1%. The anti-oxidation coating on the surface of this molybdenum alloy is mainly composed of a composite phase of Si, MoSi2, ZrB2, and SiC.

[0119] According to the test (the test method refers to the national standard GB8642-2002, the same below), the adhesion between the antioxidant coating and the substrate prepared in this embodiment is 55MPa, which is a good adhesion.

[0120] Figure 3 The image shows a metallographic photograph of the anti-oxidation coating prepared on the surface of TZM molybdenum alloy in this embodiment after oxidation at 1600℃ for 10 hours (with and without coating); the metallographic photograph after oxidation at 1600℃ for 10 hours (with and without coating) is shown below. Figure 3 As shown, the substrate in the uncoated area exhibits obvious ablation, while the substrate in the coated area is well preserved, demonstrating the protective effect of the coating on the substrate.

[0121] Example 2

[0122] A method for preparing an anti-oxidation coating on a molybdenum or molybdenum alloy surface, comprising:

[0123] By weight percentage, 70% MoSi2, 25% ZrB2, 4% SiC, and 1% PVA (binder) powders were mixed and then dissolved in water to prepare a slurry with a solid content of 50%. The mixture was then ball-milled until the particle size of the slurry reached D... max<1μm. The mixed slurry was then powdered using a two-fluid spray dryer. Throughout the process, the temperature was controlled at a maximum of 190℃, the gas pressure at 0.2MPa, the peristaltic pump speed at 20r / min, and the outlet temperature at 120℃. The powder was then dried and sieved. The drying conditions were 75℃ for 4 hours, resulting in a powder particle size range of 5~25μm. The molybdenum alloy surface was then roughened using white corundum sandblasting at 0.2MPa, followed by plasma spraying-physical vapor deposition (PVD). The PPVD system power was 70KW, the spraying distance was 500mm, the ambient pressure was less than 200Pa, and the spraying time was 8min.

[0124] Thus, the thickness of the resulting antioxidant coating is between 100 and 120 μm, and the porosity of the coating is about 1%.

[0125] Tests showed that the adhesion between the antioxidant coating and the substrate obtained in this embodiment was 40 MPa, indicating good adhesion.

[0126] Figure 4 The image shown is a scanning electron microscope (SEM) image of the anti-oxidation coating prepared on the surface of TZM molybdenum alloy in this embodiment after oxidation at 1600℃ for 4 hours; the SEM image after oxidation at 1600℃ for 4 hours is as follows. Figure 4 As shown, a continuous and dense SiO2 coating is formed on the surface of the coating, which can effectively block the intrusion of oxygen and thus effectively improve the oxidation resistance of the substrate.

[0127] Example 3

[0128] A method for preparing an anti-oxidation coating on a molybdenum or molybdenum alloy surface, comprising:

[0129] By weight percentage, 80% MoSi2, 15% ZrB2, 4% SiC, and 1% PEG (binder) powders were mixed and then dissolved in water to prepare a slurry with a solid content of 50%. The mixture was then ball-milled until the particle size of the slurry reached D... max <1μm. The mixed slurry was then powdered using a two-fluid spray dryer. Throughout the process, the temperature was controlled at a maximum of 190℃, the gas pressure at 0.2MPa, the peristaltic pump speed at 20r / min, and the outlet temperature at 120℃. The powder was then dried and sieved. The drying conditions were 75℃ for 4 hours, resulting in a powder particle size range of 5~25μm. The molybdenum alloy surface was then roughened using white corundum sandblasting at 0.2MPa, followed by plasma spraying-physical vapor deposition (PVD). The PPVD system power was 70KW, the spraying distance was 500mm, the ambient pressure was less than 200Pa, and the spraying time was 8min.

[0130] Thus, the thickness of the resulting antioxidant coating is between 100 and 120 μm, and the porosity of the coating is about 1%.

[0131] Tests showed that the adhesion between the antioxidant coating and the substrate obtained in this embodiment was 40 MPa, indicating good adhesion.

[0132] Example 4

[0133] A method for preparing an anti-oxidation coating on a molybdenum or molybdenum alloy surface, comprising:

[0134] By weight percentage, 70% MoSi2, 20% ZrB2, 9% SiC, and 1% PVA (binder) powders were mixed and then dissolved in water to prepare a slurry with a solid content of 50%. The mixture was then ball-milled until the particle size of the slurry reached D... max <1μm. The mixed slurry was then powdered using a two-fluid spray dryer. Throughout the process, the temperature was controlled at a maximum of 190℃, the gas pressure at 0.4MPa, the peristaltic pump speed at 30r / min, and the outlet temperature at 150℃. The powder was then dried and sieved. The drying conditions were 75℃ for 4 hours, resulting in a powder particle size range of 5~25μm. The molybdenum alloy surface was then roughened using white corundum sandblasting at 0.2MPa, followed by plasma spraying-physical vapor deposition (PVD) technology. The PPVD system power was 60KW, the spraying distance was 450mm, the ambient pressure was less than 200Pa, and the spraying time was 7min.

[0135] Thus, the thickness of the resulting antioxidant coating is between 80 and 100 μm, and the porosity of the coating is about 1%.

[0136] Tests showed that the adhesion between the antioxidant coating and the substrate obtained in this embodiment was 40 MPa, indicating good adhesion.

[0137] Comparative Example 1

[0138] A method for preparing an anti-oxidation coating on a molybdenum or molybdenum alloy surface, comprising:

[0139] By weight percentage, 99% MoSi2 and 1% PVA (binder) powders were mixed and then dissolved in water to prepare a slurry with a solid content of 50%. The mixture was then ball-milled until the particle size of the slurry reached D. max<1μm. The mixed slurry was then powdered using a two-fluid spray dryer. Throughout the process, the temperature was controlled at a maximum of 190℃, the gas pressure at 0.2MPa, the peristaltic pump speed at 20r / min, and the outlet temperature at 120℃. The powder was then dried and sieved. The drying conditions were 75℃ for 4 hours, resulting in a powder particle size range of 5~25μm. The molybdenum alloy surface was then roughened using white corundum sandblasting at 0.2MPa, followed by plasma spraying-physical vapor deposition (PVD). The PPVD system power was 80KW, the spraying distance was 500mm, the ambient pressure was less than 200Pa, and the spraying time was 8min.

[0140] Thus, the thickness of the resulting antioxidant coating is between 100 and 120 μm.

[0141] Figure 5 The typical vapor-deposited coating produced by the process in Comparative Example 1 is shown. Figure 6 The image shows the macroscopic morphology of the coating in Comparative Example 1 after treatment at 1600℃ for 10 hours. Figure 5 As can be seen from the comparison, the coating prepared in this example is a vapor-deposited state, with feather-like columnar crystals forming on the surface. Figure 6 It is quite obvious that the oxidized coating has produced obvious pores between the substrate and the coating, and the substrate has not been effectively protected, resulting in volatilization.

[0142] Figure 7 The image shows a scanning electron microscope (SEM) image of the anti-oxidation coating prepared on the surface of the molybdenum alloy in this comparative example after oxidation at 1600℃ for 10 hours; the SEM image after oxidation at 1600℃ for 10 hours is shown below. Figure 7 As shown, it can be observed that after oxidation, pores appear inside the coating, the coating swells severely, and severe powdering occurs in some areas. Pores caused by the volatilization of the substrate are formed between the coating and the substrate, and the coating fails to provide protection.

[0143] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0144] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An anti-oxidation coating for molybdenum or molybdenum alloy surfaces, characterized in that, The antioxidant coating is composed of the following components: Molybdenum disilicide, borides, carbon or oxygen-containing compounds, and silicon; The borides include at least one of zirconium boride, hafnium boride, or titanium boride, and the carbon- or oxygen-containing compounds include at least one of silicon carbide, hafnium carbide, zirconium carbide, or hafnium oxide. The antioxidant coating is deposited using a plasma spraying-physical vapor deposition process. In the deposition process, the mixed slurry is first spray-dried to obtain powder; then the powder is deposited on the surface of molybdenum or molybdenum alloy using a plasma spraying-physical vapor deposition process.

2. The anti-oxidation coating on the surface of molybdenum or molybdenum alloy according to claim 1, characterized in that, The boride is selected from zirconium boride; And / or, the carbon- or oxygen-containing compound is selected from silicon carbide.

3. The anti-oxidation coating on the surface of molybdenum or molybdenum alloy according to claim 1, characterized in that, The mass ratio of the silicon- and molybdenum-containing compounds, borides, carbon- or oxygen-containing compounds and silicon is (60–90): (2–30): (5–15): (0.1–5).

4. The anti-oxidation coating on the surface of molybdenum or molybdenum alloy according to any one of claims 1 to 3, characterized in that, The thickness of the antioxidant coating is 60μm to 150μm; And / or, the porosity of the antioxidant coating is less than 2%.

5. A method for preparing an anti-oxidation coating on the surface of molybdenum or molybdenum alloy, characterized in that, The method includes: The coating powder, binder, and solvent are mixed to obtain a mixed slurry; The mixed slurry was spray-dried to obtain a powder. The powder is deposited on the surface of molybdenum or molybdenum alloy using a plasma spraying-physical vapor deposition process, forming an anti-oxidation coating on the surface of molybdenum or molybdenum alloy composed of molybdenum disilicide, boride, carbon or oxygen-containing compounds and silicon. The boride includes at least one of zirconium boride, hafnium boride, or titanium boride, and the carbon- or oxygen-containing compound includes at least one of silicon carbide, hafnium carbide, zirconium carbide, or hafnium oxide.

6. The method for preparing an anti-oxidation coating on the surface of molybdenum or molybdenum alloy according to claim 5, characterized in that, The coating powder includes molybdenum disilicide, zirconium boride, and silicon carbide; The mass ratio of molybdenum disilicide, zirconium boride, silicon carbide, and binder is (60–90): (2–30): (5–15): (0.2–1.5). And / or, the adhesive comprises at least one of polyvinyl alcohol, polyethylene glycol, polyacrylic acid, or carboxymethyl cellulose; And / or, the particle size of the mixed slurry reaches Dmax < 1 μm; And / or, the solid content of the mixed slurry ranges from 30% to 70%.

7. The method for preparing an anti-oxidation coating on the surface of molybdenum or molybdenum alloy according to claim 5, characterized in that, The spray drying process is performed using a two-fluid spray dryer; And / or, after obtaining the powder and before performing the plasma spraying-physical vapor deposition process, the process further includes steps of drying and sieving the powder.

8. The method for preparing an anti-oxidation coating on the surface of molybdenum or molybdenum alloy according to claim 7, characterized in that, The spray drying process conditions include: The entire spray drying process is carried out at a temperature of ≤200℃, a gas pressure of 0.2 MPa~0.4 MPa, a peristaltic pump speed of 15~30 r / min, and an outlet temperature of 100℃~150℃. And / or, in the drying and sieving process, the drying temperature is 60℃~75℃ and the drying time is 2h~6h; And / or, in the drying and sieving process, the particle size of the sieved powder ranges from 1 μm to 30 μm.

9. The method for preparing an anti-oxidation coating on the surface of molybdenum or molybdenum alloy according to any one of claims 5 to 8, characterized in that, After the powder is prepared, and before the plasma spraying-physical vapor deposition process is performed, the process further includes a roughening treatment of the surface of the molybdenum or molybdenum alloy. And / or, the process conditions for the plasma spraying-physical vapor deposition process include: The power is 60-80KW, the spraying distance is 450mm-550mm, the ambient pressure is less than 200Pa, and the spraying time is 6min-8min.

10. The method for preparing an anti-oxidation coating on the surface of molybdenum or molybdenum alloy according to any one of claims 5 to 8, characterized in that, The thickness of the antioxidant coating is 60μm to 150μm; And / or, the porosity of the antioxidant coating is less than 2%.

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