High-temperature thermal cycle impact resistant yttrium oxide composite coating on surface of refractory metal and preparation method of yttrium oxide composite coating

Abstract

The invention relates to the technical field of metal surface coating preparation, in particular to a high-temperature thermal cycle impact resistant yttrium oxide composite coating on the surface of refractory metal and a preparation method of the yttrium oxide composite coating. The refractory metal composite coating material is composed of a refractory metal matrix and a coating. The coating comprises a bonding layer, a middle layer and a surface layer which are arranged in a contact manner; the bonding layer is composed of the refractory metal and yttrium oxide, and the porosity of the bonding layer is 1%-5%; the middle layer is a pure yttrium oxide layer with the porosity of 5%-10%; the porosity of the surface layer is 1t; 2% of a pure yttrium oxide layer; the melting point of the refractory metal is 2470 DEG C or higher. According to the refractory metal composite coating material and the preparation method and application thereof, the refractory metal coating structure is optimized, the porosity of the coating is further adjusted, the high-temperature molten metal corrosion resistance and the high-temperature thermal shock resistance of the coating are improved, meanwhile, the bonding strength between the coatings is guaranteed, and the service life of the coating is prolonged. The method is expected to be applied to high-melting-point metal smelting equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface coating preparation, in particular to an yttrium oxide composite coating on a refractory metal surface that is resistant to high-temperature thermal cycle shock and a preparation method thereof. Background Art

[0002] Y2O3 is an important rare earth oxide with a high melting point and excellent high-temperature chemical stability, remaining stable in both high-temperature oxidizing and reducing atmospheres. This makes it virtually chemically inert when in contact with various molten metals. Therefore, yttrium oxide can be used in protective coatings to resist corrosion from metal solutions or vapors at high temperatures. It is widely used in fields with extreme environmental demands, such as the metallurgical industry, nuclear industry, and aerospace.

[0003] Refractory metals (such as tungsten, molybdenum, tantalum, and niobium) are used as structural materials in metal smelting equipment due to their extremely high melting points, extremely low ductile-brittle transition temperatures, excellent high-temperature strength, and high resistance to acid and alkali corrosion. They can replace traditional graphite or silicon carbide hot-end structural materials in metal smelting equipment. However, these refractory metal structural materials are susceptible to high-temperature chemical reactions with the molten metal solution or vapor at high temperatures, which can contaminate the metal solution contained within. The resulting refractory metal compounds typically exhibit hard and brittle phases, significantly reducing the service life of the refractory metal structural components. Therefore, specialized coatings are required to protect these refractory metal structural materials. Performance requirements for such protective coatings include excellent bonding strength, high-temperature chemical stability, good resistance to molten metal corrosion, a suitable coefficient of thermal expansion, and thermal shock resistance. Studies have shown that yttrium oxide exhibits excellent high-temperature chemical and phase stability, and offers superior resistance to chemical attack from molten metals, salts, and other agents at high temperatures, making it a suitable material for smelting crucible coatings. However, Y2O3 coatings have low fracture toughness and are susceptible to cracking in practical applications due to the impact of high-temperature cycling (i.e., thermal shock). This phenomenon has become a major obstacle to their engineering applications. The coating's thermal shock resistance has become a major bottleneck restricting the engineering application of Y2O3 coatings, prompting researchers to focus on improving the coating structure and preparation techniques to enhance its durability and thermal shock resistance.

[0004] A search revealed that while there are currently several patents domestically and internationally addressing the preparation technology and specific thermal and mechanical properties of yttrium oxide coatings, most of these are plasma-resistant coatings for etching equipment in the microelectronics industry. Their substrates are typically low-melting-point aluminum alloys, and their application conditions and performance requirements differ significantly from those of the patent. Furthermore, there is a lack of research on the high-temperature thermal cycling shock resistance of yttrium oxide coatings. For example, CN110578143A discloses the preparation of an Al-ZrO2 / Y2O3 composite coating using atmospheric plasma spraying technology, CN118256849A discloses a plasma-resistant yttrium oxide coating and its preparation method, and CN118086820A discloses a method for preparing a low-roughness, etch-resistant Y2O3 coating. While these patent applications mention the use of plasma spraying to prepare yttrium oxide topcoats, the yttrium oxide coatings described are only targeted at low-melting-point aluminum alloy substrates used in the microelectronics industry. Neither the coating's structural design nor the process parameters meet the high-temperature thermal shock requirements of refractory metal substrates in specific industrial applications. In addition, CN118773600A discloses a method for preparing an yttrium oxide ceramic coating on the surface of tantalum metal. Although this patent application is aimed at preparing an yttrium oxide coating on the surface of a tantalum substrate, the coating preparation method is a laser cladding process, and there is still much room for improvement in the thermal shock resistance of the coating.

[0005] In summary, at present, there is no technology in China to prepare yttrium oxide coating on the surface of refractory metal substrates that can resist high-temperature thermal cycling impact. The introduction of this technology will be of great significance to the research and development of engineering technologies for extreme environmental requirements in fields such as metallurgy, nuclear industry, aerospace, etc.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide an yttrium oxide composite coating for refractory metal surfaces that is resistant to high-temperature thermal cycling shock and a preparation method thereof, so as to obtain a coating that has good resistance to high-temperature thermal cycling shock (cooling from a temperature of 1200°C or higher) and sufficient resistance to corrosion from molten metal solutions. The coating can be used in fields with extreme environmental requirements such as metallurgy, nuclear industry, aerospace, etc.

[0008] Based on this, the present invention has the following technical solutions: In a first aspect, the present invention provides a refractory metal composite coating material, which is composed of a refractory metal substrate and a coating; the coating includes a bonding layer, an intermediate layer and a surface layer arranged in contact; The bonding layer is composed of the refractory metal and yttrium oxide, and the porosity of the bonding layer is 1% to 5%; the intermediate layer is a pure yttrium oxide layer with a porosity of 5% to 10%; and the surface layer is a pure yttrium oxide layer with a porosity of less than 2%; The melting point of the refractory metal is above 2470°C.

[0009] In the present invention, the refractory metal may be tungsten, molybdenum, tantalum, niobium metal and high melting point alloys thereof.

[0010] By optimizing the coating structure of refractory metals and further adjusting the porosity of the coating, the present invention is beneficial for improving both the coating's resistance to high-temperature molten metal corrosion and its high-temperature thermal shock performance, while ensuring the bonding strength between the coatings. It is expected to be applied in high-melting-point metal smelting equipment.

[0011] Compared to coatings produced using traditional sintered ceramic processes, the refractory metal composite coating material of the present invention offers a denser coating, higher bonding strength, and superior mechanical properties. Compared to coatings produced using laser cladding processes, the refractory metal composite coating material of the present invention avoids residual stresses caused by rapid cooling, reduces cracking tendency, and helps improve the overall thermal shock resistance of the coating.

[0012] In the present invention, the refractory metal powder in the bonding layer is consistent with the refractory metal matrix material.

[0013] According to a refractory metal composite coating material provided by the present invention, in the bonding layer, the refractory metal powder accounts for 20 vol% to 60 vol% of the total powder volume of the bonding layer.

[0014] The pure yttrium oxide powder used in this invention is a spray-granulated agglomerated powder that enhances fluidity during powder transportation. The powder has a particle size range of 18 to 75 μm and a purity greater than 99.95%. The bonding layer is made by mixing a fine-grained refractory metal powder (particle size <38 μm, 400 mesh) of the same material as the substrate with the yttrium oxide powder.

[0015] In the present invention, the preparation method of the pure yttrium oxide powder comprises the following steps: (1) Crushing micron-sized yttrium oxide powder into a particle size of hundreds of nanometers to obtain nano-yttrium oxide powder; (2) adding 1 wt% to 5 wt% of polyethylene glycol (PEG-10000) to the nano-yttrium oxide powder, and then preparing an yttrium oxide slurry with a solid content of 30 wt% to 50 wt% using deionized water; (3) The yttrium oxide slurry is titrated with ammonia water to adjust the pH value of the slurry to between 8 and 9; then the slurry is atomized and dispersed into very fine droplets, and high-temperature hot air is introduced into the granulation tower at a temperature of 160 to 180°C, so that the atomized droplets are evaporated in a short time to form spherical particles.

[0016] In the present invention, the mixed powder of the bonding layer is prepared by mixing refractory metal powder and pure yttrium oxide powder in proportion, and mixing the powders in a planetary mixer to obtain composite material spraying powder with uniform distribution of the two powder components.

[0017] According to a refractory metal composite coating material provided by the present invention, the purity of the pure yttrium oxide powder used in the bonding layer is greater than 99.9 wt%, and the particle size range is 15~75 μm; the purity of the refractory metal powder is greater than 99.98 wt%, and the particle size is less than 38 μm.

[0018] According to the refractory metal composite coating material provided by the present invention, the thickness of the bonding layer accounts for 15-40% of the total thickness of the coating.

[0019] According to a refractory metal composite coating material provided by the present invention, in the coating, the thickness of the bonding layer is 50-100 μm; And / or, in the coating, the thickness of the intermediate layer is 50-200 μm.

[0020] And / or, in the coating, the surface layer has a thickness of 50 to 200 μm.

[0021] According to a refractory metal composite coating material provided by the present invention, the refractory metal includes one or an alloy of any of tungsten, molybdenum, tantalum, and niobium.

[0022] In a second aspect, the present invention provides a method for preparing the above-mentioned refractory metal composite coating material, comprising: S1: cleaning the surface of the refractory metal substrate and performing sandblasting to obtain a pretreated substrate; S2: spraying the bonding layer on the surface of the pretreated substrate to obtain a bonding layer metal material; preferably, the bonding layer is sprayed on the surface of the pretreated substrate by a low-pressure plasma spraying process or an atmospheric plasma spraying process; S3: spraying the intermediate layer on the surface of the bonding layer metal material to obtain the intermediate layer metal material; preferably, the intermediate layer is sprayed on the surface of the bonding layer metal material by an atmospheric plasma spraying process; S4: spraying the surface layer on the surface of the intermediate layer metal material; preferably, adopting an atmospheric plasma spraying process to spray the surface layer on the surface of the intermediate layer metal material.

[0023] In S1 of the present invention, before preparing the coating, the substrate needs to be strictly cleaned, degreased, and sandblasted to achieve a surface roughness of 5 to 10 μm; and after obtaining a fresh metal surface without an oxide layer, the coating needs to be prepared immediately.

[0024] In a specific implementation process, when cleaning the surface of the refractory metal, an acetone (or alcohol) solution can be used to clean the surface of the substrate to remove surface dust and oil stains, and then dry it.

[0025] In the present invention, the preparation process can adopt a plasma spraying process, including an atmospheric plasma spraying (APS) process and a low-pressure plasma spraying process (LPPS). Among them, the low-pressure plasma spraying process can be applied to the preparation of the bonding layer, and the atmospheric plasma spraying process is suitable for the preparation of the surface layer and the bonding layer. By optimizing the preparation process of the coating, it is beneficial to obtain a coating structure with different porosities, thereby absorbing the stress and strain generated by the high-temperature thermal cycle impact process, thereby improving its thermal shock resistance.

[0026] According to a preparation method of a refractory metal composite coating material provided by the present invention, in S1, the surface of the refractory metal substrate is sandblasted using corundum sand with a particle size of 40-70 mesh, at an air pressure of 0.2-0.4 MPa, an incident angle of 45-75 degrees, and a sandblasting distance of 130-180 mm. After sandblasting, the residual sand on the surface is blown away with compressed air.

[0027] According to a method for preparing a refractory metal composite coating material provided by the present invention, in S1, the spraying parameters include: spraying current 500~650 A, powder feeding rate 15~40 g / min, spraying distance 90~150 mm, argon flow rate 40~80 L / min, and hydrogen flow rate 10~20 L / min.

[0028] According to a method for preparing a refractory metal composite coating material provided by the present invention, in S2, the spraying parameters include: spraying current 450~550 A, powder feeding rate 15~50 g / min, spraying distance 120~180 mm, argon flow rate 30~50 L / min, and hydrogen flow rate 5~15 L / min.

[0029] According to a method for preparing a refractory metal composite coating material provided by the present invention, in S3, the spraying parameters include: spraying current 500~600 A, powder feeding rate 15~50 g / min, spraying distance 100~140 mm, argon flow rate 40~60 L / min, and hydrogen flow rate 10~20 L / min.

[0030] In a fourth aspect, the present invention provides application of the refractory metal composite coating material in refractory metal smelting equipment.

[0031] Based on this, the technical solution of the present invention has the following beneficial effects: The present invention provides an yttrium oxide composite coating on the surface of refractory metals that is resistant to high-temperature thermal cycling shock and a preparation method thereof. By optimizing the coating structure of the refractory metal and further adjusting the porosity of the coating, it is beneficial to simultaneously improve the coating's resistance to high-temperature molten metal corrosion and high-temperature thermal shock performance, while ensuring the bonding strength between the coatings. It is expected to be used in high-melting-point metal smelting equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 This is a scanning electron microscope photograph of the cross section of the three-layer composite yttrium oxide coating on the surface of the tantalum substrate prepared in Example 1 provided by the present invention.

[0034] Figure 2 2 are the temperature curves of the thermal shock test of the coatings in Examples 1 and 2 and Comparative Example 1.

[0035] Figure 3 This is a macroscopic morphology photograph of the coating surface during the thermal shock test in Example 1 of the present invention, where the red numbers represent the corresponding coating cycle times.

[0036] Figure 4 This is an optical microscope photograph of the cross section of the thinner composite coating on the surface of the pure tantalum substrate prepared in Example 2 of the present invention.

[0037] Figure 5 These are photos of the coating surface morphology before and after 40 cycles of the thermal shock test in Example 2 of the present invention.

[0038] Figure 6 Schematic diagram of the metallographic microstructure of the interface of the single-layer yttrium oxide coating on the surface of the pure tantalum substrate in Comparative Example 1.

[0039] Figure 7 This is a macroscopic morphology photograph of the coating surface during the thermal shock test in Comparative Example 1, where the red numbers represent the corresponding coating cycle times. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0041] Unless otherwise specified, the various raw materials used in the examples and comparative examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0042] The porosity of the coating can be measured by the drainage method or microstructure photo image analysis method. The thermal shock resistance of the coating is tested using the following scheme: (1) The specimen specifications are Φ25 mm and 3 to 8 mm thick circular refractory metal substrates (tungsten, molybdenum, tantalum, niobium or their alloys). The edges of the specimens are chamfered to avoid local stress concentration cracking.

[0043] (2) The experiment is carried out in a high-temperature furnace that can be evacuated or filled with inert gas (such as argon). Before the experiment begins, evacuate or pass argon for 20 minutes to clear the air in the furnace tube. Vacuum or pass argon continuously during the entire experiment. The sample is heated to a high temperature zone (1200°C or higher) at a constant heating rate V1 (such as 10°C / min) and then kept at that temperature for 20 minutes. Thereafter, it is cooled to a certain low temperature range at a constant cooling rate V2 (10°C / min) and kept at that temperature for 20 minutes. Then, it is heated to a high temperature zone at V1 again. This is a thermal cycle shock. Perform several thermal cycle shock tests until the coating shows obvious cracking or partial peeling.

[0044] In the following examples and comparative examples, the pure yttrium oxide powder is a spray powder obtained by spray granulation based on original powder particles of 100 nanometers. The powder particle size ranges from 15 to 75 μm, and the median particle size is about 30 μm.

[0045] The specific preparation method comprises the following steps: (1) Using a high-energy ball mill to crush micron-sized yttrium oxide powder into a particle size of hundreds of nanometers; (2) Then, the crushed nano-yttrium oxide powder in the first step is used as a raw material, 1 wt% to 5 wt% of polyethylene glycol (PEG-10000) is added, and then deionized water is used to prepare an yttrium oxide slurry with a solid content of 30 wt% to 50 wt%; (3) Titrate ammonia water to adjust the pH value of the slurry to between 8 and 9; (4) The prepared slurry is dispersed into extremely fine droplets through an atomizer, and high-temperature hot air at a temperature of 160-180°C is passed into the granulation tower to evaporate the water in the atomized droplets in a short time to form spherical particles; (5) The dried powder particles enter the collector at the bottom of the drying tower under the action of gravity and air flow. The lighter or heavier powder particles are separated by a cyclone separator, and the powder balls with suitable particle size are retained.

[0046] (6) The collected powder is sieved with a sieve of a specific mesh size to obtain yttrium oxide spherical powder that meets the spraying requirements.

[0047] In the following examples and comparative examples, the purity of the pure yttrium oxide powder used is greater than 99.9 wt % and the particle size ranges from 15 to 75 μm; the purity of the refractory metal powder is greater than 99.98 wt % and the particle size is less than 38 μm.

[0048] Example 1 This embodiment provides a design and preparation method of a high-temperature thermal cycle-resistant yttria composite coating on a refractory metal surface. In this embodiment, the substrate of the coating is a pure tantalum substrate.

[0049] The preparation method provided in this embodiment comprises the following steps: (1) Clean the surface of pure tantalum metal: Use acetone solution to clean the surface of the substrate to remove surface dust and oil stains, and then dry it.

[0050] (2) Sandblasting of refractory metal substrates: Use 40-mesh corundum sand, 0.4 MPa air pressure, 45-75 degree incident angle, and 150 mm sandblasting distance to sandblast the metal surface. After sandblasting, use compressed air to blow away the remaining sand on the surface. (3) A Ta+Y2O3 powder mixture with a volume ratio of 1:1 was used as the bonding layer. The process parameters were: powder feed rate 30 g / min, current 550 A, spray distance 90 mm, argon 50 L / min, and hydrogen 10 L / min. The bonding layer thickness was approximately 60–80 μm. Image analysis based on 7–10 metallographic photographs revealed a coating porosity of 3.8%.

[0051] (4) Spraying a porous yttrium oxide interlayer. Process parameters: spray current 550 A, powder feed rate 30 g / min, spray distance 140 mm, argon flow rate 40 L / min, hydrogen flow rate 12 L / min. The interlayer thickness was 110-130 μm. Image analysis based on 7-10 metallographic photographs showed a coating porosity of approximately 6.2%.

[0052] (5) Spraying a dense yttrium oxide surface layer: spraying current 600 A, powder feed rate 30 g / min, spraying distance 110 mm, argon flow rate 50 L / min, hydrogen flow rate 15 L / min. Image analysis based on 7-10 metallographic photographs showed that the coating porosity was approximately 1.6%.

[0053] The cross section of the coating obtained in this embodiment was subjected to microscopic morphology analysis, and the metallographic photograph of the cross section of the coating is shown in FIG. Figure 1 . Use Figure 2 The temperature curve shown in the figure is used to conduct thermal shock analysis on the coating. The coating surface does not crack or fall off after 30 cycles. The macroscopic photos of the coating at each stage of the thermal shock process are shown in the figure. Figure 3 shown.

[0054] Example 2 This embodiment provides a design and preparation method for an yttria composite coating on a refractory metal surface that is resistant to high-temperature thermal cycling shock. The coating substrate in this embodiment is also a pure tantalum substrate. The difference from Example 1 lies in the different porosities of the various layers. The thickness of the intermediate and surface layers is thinner than in Example 1, totaling approximately 190 microns, compared to over 300 microns in Example 1.

[0055] The preparation method provided in this embodiment comprises the following steps: (1) Clean the surface of pure tantalum metal: Use acetone (or alcohol) solution to clean the surface of the substrate to remove surface dust and oil stains, and then dry it.

[0056] (2) Sandblasting of refractory metal substrates: Use corundum sand with a particle size of 40~70 mesh, an air pressure of 0.3 MPa, an incident angle of 45~75 degrees, and a sandblasting distance of 130~180 mm to sandblast the metal surface. After sandblasting, use compressed air to blow away the residual sand particles on the surface.

[0057] (3) A Ta+Y2O3 powder mixture with a volume ratio of 1:1 was used as the bonding layer. The process parameters were: powder feed rate 40 g / min, current 600 A, spray distance 110 mm, argon 60 L / min, and hydrogen 10 L / min. The bonding layer thickness was 65 μm. Image analysis based on multiple metallographic photographs showed that the coating had a porosity of approximately 4.6%.

[0058] (4) Spraying a porous yttrium oxide interlayer. Process parameters: spray current 550 A, powder feed rate 25 g / min, spray distance 150 mm, argon flow rate 50 L / min, hydrogen flow rate 12 L / min. The interlayer thickness was 70 μm. Image analysis based on multiple metallographic photographs showed a coating porosity of approximately 8.1%.

[0059] (5) Spraying a dense yttrium oxide surface layer: spraying current 600 A, powder feed rate 30 g / min, spraying distance 110 mm, argon flow rate 50 L / min, hydrogen flow rate 15 L / min. Image analysis based on multiple metallographic photographs showed a coating porosity of 1.5%.

[0060] The cross section of the coating obtained in this embodiment was subjected to microscopic morphology analysis, and the metallographic photograph of the cross section of the coating is shown in FIG. Figure 4 . Use Figure 2 The temperature curve shown in the figure is used to conduct thermal shock analysis on the coating. After 40 cycles, the coating surface does not show any cracking or falling off, indicating that the coating has good thermal shock resistance. The photos of the coating before and after 40 cycles are shown in the figure. Figure 5 shown.

[0061] Comparative Example 1 The substrate of the coating in this comparative example is a pure tantalum substrate. The difference from Example 1 is that there is no bonding layer or intermediate layer in the coating in this example. Only a dense yttrium oxide coating is sprayed on the surface of the tantalum substrate. The coating is subjected to thermal shock under the same conditions. The preparation method provided in this comparative example comprises the following steps: (1) Clean the surface of pure tantalum metal: Use acetone (or alcohol) solution to clean the surface of the substrate to remove surface dust and oil stains, and then dry it.

[0062] (2) Sandblasting of refractory metal substrates: Use corundum sand with a particle size of 40~70 mesh, an air pressure of 0.3 MPa, an incident angle of 45~75 degrees, and a sandblasting distance of 150 mm to sandblast the metal surface. After sandblasting, use compressed air to blow away the residual sand particles on the surface.

[0063] (3) Spraying a dense yttrium oxide surface layer: spraying current 600 A, powder feed rate 30 g / min, spraying distance 110 mm, argon flow rate 50 L / min, hydrogen flow rate 15 L / min. Image analysis based on 7-10 metallographic photographs showed that the coating porosity was approximately 1.6%.

[0064] The cross section of the coating obtained in this comparative example was subjected to microscopic morphology analysis, and the metallographic photograph of the cross section of the coating is shown in FIG. Figure 6 . Use Figure 2 The temperature curve shown in the figure is used to conduct thermal shock analysis on the coating. After 4 thermal shock cycles, the coating edge peels off, proving that the thermal shock resistance of the coating is insufficient. The macroscopic photo of the coating after 4 thermal shock cycles is shown in the figure. Figure 7 As shown in the above comparative examples, it can be seen that for a coating structure different from that defined in the present invention, even if the same process and the same materials are used, it is difficult to meet the thermal cycle shock resistance performance.

[0065] Comparative Example 2 The coating provided in this comparative example differs from Examples 1 and 2 only in that the porosity of the bonding layer, the middle layer, and the surface layer are all the same, namely, 2%.

[0066] After less than 20 cycles, cracks occurred in the yttrium oxide layer and gradually fell off. By comparison, it can be seen that due to the lack of an intermediate layer with a higher porosity, although the coating contains a bonding layer structure composed of refractory metal and yttrium oxide, the overall thermal shock resistance of the coating is still limited.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A refractory metal composite coating material, characterized in that: It consists of a refractory metal matrix and a coating; the coating includes a bonding layer, an intermediate layer and a surface layer arranged in contact; The bonding layer is composed of the refractory metal and yttrium oxide, and the porosity of the bonding layer is 1% to 5%; the intermediate layer is a pure yttrium oxide layer with a porosity of 5% to 10%; and the surface layer is a pure yttrium oxide layer with a porosity of less than 2%; The melting point of the refractory metal is above 2470°C.

2. The refractory metal composite coating material according to claim 1, characterized in that: In the bonding layer, the refractory metal powder accounts for 20 vol% to 60 vol% of the total powder volume of the bonding layer.

3. The refractory metal composite coating material according to claim 1 or 2, characterized in that: The purity of the pure yttrium oxide powder used in the bonding layer is greater than 99.9 wt%, and the particle size ranges from 15 to 75 μm; the purity of the refractory metal powder is greater than 99.98 wt%, and the particle size is less than 38 μm.

4. The refractory metal composite coating material according to any one of claims 1 to 3, characterized in that: The thickness of the bonding layer accounts for 15% to 40% of the total coating thickness.

5. The refractory metal composite coating material according to claim 4, characterized in that: In the coating, the thickness of the bonding layer is 50-100 μm; And / or, in the coating, the thickness of the intermediate layer is 50 to 200 μm; And / or, in the coating, the surface layer has a thickness of 50 to 200 μm.

6. The refractory metal composite coating material according to any one of claims 1 to 5, characterized in that: The refractory metal includes one or an alloy of any of tungsten, molybdenum, tantalum, and niobium.

7. The method for preparing the refractory metal composite coating material according to any one of claims 1 to 6, characterized in that: include: S1: cleaning the surface of the refractory metal substrate and performing sandblasting to obtain a pretreated substrate; S2: spraying the bonding layer on the surface of the pretreated substrate to obtain a bonding layer metal material; preferably, the bonding layer is sprayed on the surface of the pretreated substrate by a low-pressure plasma spraying process or an atmospheric plasma spraying process; S3: spraying the intermediate layer on the surface of the bonding layer metal material to obtain the intermediate layer metal material; preferably, the intermediate layer is sprayed on the surface of the bonding layer metal material by an atmospheric plasma spraying process; S4: spraying the surface layer on the surface of the intermediate layer metal material; preferably, adopting an atmospheric plasma spraying process to spray the surface layer on the surface of the intermediate layer metal material.

8. The method for preparing a refractory metal composite coating material according to claim 7, wherein: In S1, the surface of the refractory metal substrate was sandblasted using corundum sand with a particle size of 40-70 mesh, an air pressure of 0.2-0.4 MPa, an incident angle of 45-75 degrees, and a sandblasting distance of 130-180 mm. After sandblasting, the residual sand on the surface was blown away with compressed air.

9. The method for preparing a refractory metal composite coating material according to claim 7 or 8, characterized in that: In S1, the spraying parameters include: spraying current 500–650 A, powder feed rate 15–40 g / min, spraying distance 90–150 mm, argon flow rate 40–80 L / min, and hydrogen flow rate 10–20 L / min; and / or, in S2, the spraying parameters include: spraying current 450-550 A, powder feeding rate 15-50 g / min, spraying distance 120-180 mm, argon flow rate 30-50 L / min, hydrogen flow rate 5-15 L / min; And / or, in S3, the spraying parameters include: spraying current 500~600 A, powder feeding rate 15~50 g / min, spraying distance 100~140 mm, argon flow rate 40~60 L / min, and hydrogen flow rate 10~20 L / min.

10. Use of the refractory metal composite coating material according to any one of claims 1 to 6 or the refractory metal composite coating material prepared by the preparation method according to any one of claims 7 to 9 in refractory metal smelting equipment.

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