A silicon-chromium-titanium-zirconium-hafnium alloy powder and its preparation method

Abstract

This invention provides a silicon-chromium-titanium-zirconium-hafnium alloy powder and its preparation method, belonging to the field of high-temperature coating technology, to optimize the overall performance of niobium alloy nozzles and improve their operating temperature. The invention proposes a silicon-chromium-titanium-zirconium-hafnium alloy powder, which, based on 100 wt% of powder weight, contains 50-73 wt% silicon, 15-25 wt% chromium, 5-10 wt% titanium, 5-10 wt% zirconium, 1-5 wt% hafnium, and less than 0.315 wt% impurities. This invention yields a high-temperature anti-oxidation coating. The pentaceous alloy system can generate a "high entropy effect," resulting in a composite coating with excellent thermal stability and good adhesion to the niobium alloy matrix. This alloy system possesses good high-temperature strength and oxidation resistance, making it suitable for protective coatings on high-temperature components such as aerospace rocket engines, aircraft engines, and nuclear power equipment.

Description

Technical Field

[0001] This invention relates to the field of metal powder technology, and in particular to a silicon-chromium-titanium-zirconium-hafnium alloy powder and its preparation method. Background Technology

[0002] Niobium has a melting point of 2468℃. Niobium alloys maintain good strength and stability at high temperatures, and can withstand the extremely high temperatures generated during rocket engine operation, ensuring that components do not deform, melt, or fail under extreme conditions. Niobium alloys are used as materials for rocket engine combustion chambers; however, niobium alloys are not resistant to high-temperature oxidation.

[0003] Niobium, upon oxidation, primarily forms niobium pentoxide (Nb₂O₅). The volume of this oxide is larger than that of metallic niobium, generating significant internal stress within the oxide film. This stress easily leads to oxide film rupture. The ruptured oxide film cannot completely cover the niobium alloy surface, failing to prevent oxygen from continuing to react with the internal metal, allowing oxidation to deepen. The oxidation reaction rate is rapid: niobium in niobium alloys exhibits high chemical reactivity at high temperatures, readily reacting with oxygen. When the temperature exceeds 600℃, the niobium alloy begins to oxidize rapidly. Crystal structure and electronic properties: From a crystal structure perspective, niobium's crystal structure allows oxygen atoms to easily diffuse into the interior through intercrystalline channels in a high-temperature, oxygen-rich environment, reacting with niobium atoms. Electronically, the outer electrons of niobium atoms readily interact with electrons of oxygen atoms at high temperatures, forming chemical bonds and initiating the oxidation reaction. Lack of self-healing ability: Unlike some metals with good oxidation resistance, such as aluminum and chromium, the oxide film formed after niobium alloy oxidation lacks self-healing capabilities. When the oxide film is damaged, it cannot repair itself quickly under the influence of the external environment like the oxide films of metals such as aluminum and chromium, and continue to provide protection for the substrate.

[0004] Existing high-temperature anti-oxidation coatings on niobium alloy surfaces are mainly silicide coatings. Under high-temperature conditions, silicides can form a dense and continuous low-oxygen-permeability oxide film, effectively preventing oxygen from contacting the niobium alloy substrate and providing excellent anti-oxidation properties. They possess high melting points, hardness, and chemical stability, maintaining structural stability at high temperatures, and also exhibit certain thermal shock resistance and corrosion resistance. Si-Cr-Ti or Si-Cr-Fe coatings prepared using the slurry melting method can generate multi-component silicide coatings (Nb, Ti, Cr)Si2 or (Nb, Cr, Fe)Si2, providing effective protection for niobium alloys below 1300℃.

[0005] In the 1970s, Sylavania developed two niobium alloy protective coatings: R512A, primarily composed of Si-20Cr-5Ti, and R512E, primarily composed of Si-20Cr-20Fe. The R512A coating achieved a protection life of 100 hours at 1371°C and 1-4 hours at 1649°C, and was successfully applied to the engines of the Apollo lunar module and service module. R512E withstood hundreds of thermal shocks in air or combustion atmospheres at 1400°C with excellent performance and was successfully applied to the niobium nozzle protective coating of the F100 rocket engine. However, there is still a need for improvements in high-temperature protective coatings for niobium alloys, requiring even higher protection temperatures and longer protection lifespans. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, this invention provides a silicon-chromium-titanium-zirconium-hafnium alloy powder and its preparation method, thereby solving the problem that the high-temperature anti-oxidation coatings on the surface of existing niobium alloys still have room for improvement in terms of high-temperature performance. Using this alloy powder to prepare a high-temperature anti-oxidation coating can increase the service temperature of existing niobium alloys and improve the overall performance of rocket nozzles.

[0007] The specific details of the invention are as follows:

[0008] In a first aspect, the present invention provides a silicon-chromium-titanium-zirconium-hafnium alloy powder, wherein, based on 100 wt% of the powder, the alloy powder contains 50-73 wt% silicon, 15-25 wt% chromium, 5-10 wt% titanium, 5-10 wt% zirconium, 1-5 wt% hafnium, and less than 0.315 wt% impurities.

[0009] Optionally, the alloy powder is irregularly shaped or spherical, with a particle size of less than 75 μm, and a loose packing density of 1-1.5 g / cm³. 3 The tap density is 1.7-1.9 g / cm³. 3 Specific surface area: 2.5-2.8 m² 2 / g.

[0010] Optionally, in the alloy powder, the impurities include Fe, Al, Cu, C and O, wherein the content of Fe is less than 0.02 wt%, the content of Al is less than 0.005 wt%, the content of Cu is less than 0.005 wt%, the content of C is less than 0.035 wt%, and the content of O is less than 0.25 wt%.

[0011] In a second aspect, the present invention provides a method for preparing the silicon-chromium-titanium-zirconium-hafnium alloy powder described in the first aspect, the method comprising the following steps:

[0012] S1: Weigh 50-74wt% silicon, 15-25wt% metallic chromium, 5-10wt% metallic titanium, 5-10wt% metallic zirconium and 1-5wt% metallic hafnium, add them to an induction melting crucible, and perform vacuum melting to obtain a liquid alloy.

[0013] S2: The liquid alloy is subjected to gas atomization to produce powder, or crushed and ball-milled after casting to produce powder, to obtain coarse alloy powder;

[0014] S3: The coarse alloy powder is sieved to obtain alloy powder with a particle size of less than 75μm.

[0015] Optionally, in step S1, the vacuum melting is carried out in an argon atmosphere, the melting temperature is 1700-2300℃, and the vacuum degree of the vacuum melting is not higher than 10. -2 Pa.

[0016] Optionally, in step S1, the purity of the silicon is not less than 5N, and the purity of the metallic chromium, metallic titanium, metallic zirconium, and metallic hafnium is not less than 3N.

[0017] Thirdly, the present invention proposes a silicon-chromium-titanium-zirconium-hafnium high-temperature anti-oxidation coating, wherein the coating is prepared on the surface of a niobium alloy by means of a slurry melting method using the silicon-chromium-titanium-zirconium-hafnium alloy powder described in the first aspect as raw material; the coating thickness is 60-100μm, and the coating provides effective protection for the niobium alloy material under heating conditions not exceeding 1700℃.

[0018] Fourthly, this invention proposes a method for preparing a silicon-chromium-titanium-zirconium-hafnium high-temperature antioxidant coating, the method comprising the following steps:

[0019] T1: Mix the silicon-chromium-titanium-zirconium-hafnium alloy powder described in the first aspect with a binder and a solvent in a mass ratio of 4-5:1:3-4 to prepare a slurry;

[0020] T2: The slurry is coated onto the surface of the niobium alloy, dried, and then sintered to form the high-temperature anti-oxidation coating.

[0021] Optionally, in step T1, the adhesive is varnish or polyethylene glycol; the solvent is ethyl acetate, acetone or ethanol.

[0022] Optionally, step T2 includes the following specific steps:

[0023] The slurry is sprayed onto the surface of the niobium alloy and then vacuum sintered. The sintering temperature is increased from room temperature to 1500-1650℃, and held at 1500-1650℃ for 30-60 minutes, with a vacuum degree of less than 5×10⁻⁶. -2 Pa.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] This invention provides a silicon-chromium-titanium-zirconium-hafnium alloy powder, its preparation method, and its application, resulting in a high-temperature anti-oxidation coating. Based on existing silicon-chromium-titanium alloy powders, metallic zirconium and metallic hafnium are added. Currently, most widely used niobium alloys, such as Nb521 (mainly composed of 5 wt% W, 2 wt% Mo, and 1 wt% Zr, with the balance being Nb) and C103 (10 wt% Hf, 1 wt% Ti, less than 0.7 wt% Zr, less than 0.5 wt% Ta, and less than 0.5 wt% W, with the balance being Nb), contain zirconium and hafnium. The silicon-chromium-titanium-zirconium-hafnium alloy powder can improve the adhesion between the coating and the niobium alloy substrate. Meanwhile, Zr and Hf are rare high-melting-point metals, and their oxides ZrO2 and HfO2 have excellent thermal stability and thermal barrier properties. They can form stable oxides (such as ZrO2 and HfO2) on the surface of niobium alloys. Since the melting points of ZrO2 and HfO2 are higher than those of TiO2, they further improve the performance of the original silicon-chromium-titanium alloy powder.

[0026] If a high-temperature anti-oxidation coating of silicon-chromium-titanium-zirconium-hafnium is prepared by mixing existing silicon-chromium-titanium alloy powder with a certain proportion of metallic zirconium powder and metallic hafnium powder, it will have a better protective effect than the coating prepared by existing silicon-chromium-titanium powder alone. However, there are problems such as uneven powder distribution and high oxygen content of impurities.

[0027] To further optimize the high-temperature oxidation resistance of coatings prepared from silicon-chromium-titanium-zirconium-hafnium alloy powder, this invention proposes a method for preparing uniformly composed silicon-chromium-titanium-zirconium-hafnium alloy powder through smelting. The pentaceous alloy system can generate a "high-entropy effect," enhancing solid solution strengthening. After smelting, a uniformly stable silicon-chromium-titanium-zirconium-hafnium alloy powder can be obtained, improving the material's overall mechanical properties and thermal stability. This alloy system possesses excellent high-temperature strength and oxidation resistance, making it suitable for protective coatings on high-temperature components such as rocket engine nozzles, aero-engines, and nuclear power equipment. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart illustrating the preparation method of silicon-chromium-titanium-zirconium-hafnium alloy powder provided in an embodiment of the present invention is shown.

[0030] Figure 2A flowchart illustrating the preparation method of the silicon-chromium-titanium-zirconium-hafnium high-temperature anti-oxidation coating provided in an embodiment of the present invention is shown.

[0031] Figure 3 The image shows a scanning electron microscope (SEM) image of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by crushing and ball milling according to an embodiment of the present invention.

[0032] Figure 4 The following are scanning electron microscope (SEM) images of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by crushing and ball milling according to an embodiment of the present invention at different magnifications.

[0033] Figure 5 This shows a scanning electron microscope image of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by gas atomization according to an embodiment of the present invention;

[0034] Figure 6 The following are scanning electron microscope (SEM) images of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by gas atomization according to an embodiment of the present invention at different magnifications.

[0035] Figure 7 The embodiment of the invention demonstrates the silicon-chromium-titanium-zirconium-hafnium high-temperature anti-oxidation coating. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0037] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0038] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0039] In the description of this invention, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0040] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] Before providing a detailed description of the silicon-chromium-titanium-zirconium-hafnium alloy powder, its preparation method, and its applications provided by this invention, it is necessary to explain the relevant technologies as follows:

[0042] Niobium has a melting point of 2468℃. Niobium alloys maintain good strength and stability at high temperatures, and can withstand the extremely high temperatures generated during rocket engine operation, ensuring that components do not deform, melt, or fail under extreme conditions. Niobium alloys are used as materials for rocket engine combustion chambers; however, niobium alloys are not resistant to high-temperature oxidation.

[0043] Niobium, upon oxidation, primarily forms niobium pentoxide (Nb₂O₅). The volume of this oxide is larger than that of metallic niobium, generating significant internal stress within the oxide film. This stress easily leads to oxide film rupture. The ruptured oxide film cannot completely cover the niobium alloy surface, failing to prevent oxygen from continuing to react with the internal metal, allowing oxidation to deepen. The oxidation reaction rate is rapid: niobium in niobium alloys exhibits high chemical reactivity at high temperatures, readily reacting with oxygen. When the temperature exceeds 600℃, the niobium alloy begins to oxidize rapidly. Crystal structure and electronic properties: From a crystal structure perspective, niobium's crystal structure allows oxygen atoms to easily diffuse into the interior through intercrystalline channels in a high-temperature, oxygen-rich environment, reacting with niobium atoms. Electronically, the outer electrons of niobium atoms readily interact with electrons of oxygen atoms at high temperatures, forming chemical bonds and initiating the oxidation reaction. Lack of self-healing ability: Unlike some metals with good oxidation resistance, such as aluminum and chromium, the oxide film formed after niobium alloy oxidation lacks self-healing capabilities. When the oxide film is damaged, it cannot repair itself quickly under the influence of the external environment like the oxide films of metals such as aluminum and chromium, and continue to provide protection for the substrate.

[0044] Existing high-temperature anti-oxidation coatings on niobium alloy surfaces are mainly silicide coatings. Under high-temperature conditions, silicides can form a dense and continuous low-oxygen-permeability oxide film, effectively preventing oxygen from contacting the niobium alloy substrate and providing excellent anti-oxidation properties. They possess high melting points, hardness, and chemical stability, maintaining structural stability at high temperatures, and also exhibit certain thermal shock resistance and corrosion resistance. Si-Cr-Ti or Si-Cr-Fe coatings prepared using the slurry melting method can generate multi-component silicide coatings (Nb, Ti, Cr)Si2 or (Nb, Cr, Fe)Si2, providing effective protection for niobium alloys below 1300℃.

[0045] In the 1970s, Sylavania developed two niobium alloy protective coatings: R512A, primarily composed of Si-20Cr-5Ti, and R512E, primarily composed of Si-20Cr-20Fe. The R512A coating achieved a protection life of 100 hours at 1371°C and 1-4 hours at 1649°C, and was successfully applied to the engines of the Apollo lunar module and service module. R512E withstood hundreds of thermal shocks in air or combustion atmospheres at 1400°C with excellent performance and was successfully applied to the niobium nozzle protective coating of the F100 rocket engine. However, there is still a need for improvements in high-temperature protective coatings for niobium alloys, requiring even higher protection temperatures and longer protection lifespans.

[0046] To enable those skilled in the art to better understand the present invention, the following embodiments are provided to illustrate in detail the silicon-chromium-titanium-zirconium-hafnium alloy powder, its preparation method, and its application.

[0047] In a first aspect, the present invention provides a silicon-chromium-titanium-zirconium-hafnium alloy powder, wherein, based on 100 wt% by weight, the alloy powder contains 50-73 wt% silicon, 15-25 wt% chromium, 5-10 wt% titanium, 5-10 wt% zirconium, 1-5 wt% hafnium, and less than 0.315 wt% impurities.

[0048] Using this technical solution, the pentagonal alloy system can generate a "high entropy effect," improving solid solution strengthening ability and enhancing the overall mechanical properties and thermal stability of the material. This alloy system possesses excellent high-temperature strength and oxidation resistance, making it suitable for protective coatings on high-temperature components such as those used in aero-engines and nuclear power equipment.

[0049] In some embodiments, the alloy powder is irregular or spherical in shape, with a particle size of less than 75 μm; the loose packing density of the alloy powder is 1-1.5 g / cm³. 3 The tap density is 1.7-1.9 g / cm³. 3 Specific surface area: 2.5-2.8 m² 2 / g.

[0050] Using this technical solution, fine powder is beneficial for slurry dispersion and spray uniformity, making it suitable for thermal spraying or vacuum sintering to form films. Spherical powder is more suitable for automated spraying and powder conveying; irregularly shaped powder has stronger adhesion, which is beneficial for coating bonding; moderate loose density and tapped density indicate that the powder has good filling properties, facilitating subsequent sintering and densification. Excessively high specific surface area may lead to agglomeration, while too low a specific surface area is detrimental to reactivity. This range balances powder flowability and sintering activity.

[0051] In some embodiments, in addition to impurities introduced from the raw materials, some impurities are also introduced during the preparation of the alloy powder. It is necessary to control the total content of the main impurities to be less than 0.315 wt%. The impurities include Fe, Al, Cu, C and O. The content of Fe is less than 0.02 wt%, the content of Al is less than 0.005 wt%, the content of Cu is less than 0.005 wt%, the content of C is less than 0.035 wt%, and the content of O is less than 0.25 wt%.

[0052] Using this technical solution, impurity elements such as Fe and Al may promote unintended phase transformations or the formation of brittle compounds, reducing material properties. C and O, on the other hand, easily form inclusions, affecting density and the quality of the anti-oxidation film. Low impurity levels contribute to a more uniform microstructure and prevent localized corrosion or oxidation failure.

[0053] Secondly, Figure 1 A flowchart of the method for preparing silicon-chromium-titanium-zirconium-hafnium alloy powder according to an embodiment of the present invention is shown, as follows: Figure 1 As shown, the present invention also proposes a method for preparing the silicon-chromium-titanium-zirconium-hafnium alloy powder described in the first aspect above, the method comprising the following steps:

[0054] S1: Weigh 50-74wt% silicon, 15-25wt% metallic chromium, 5-10wt% metallic titanium, 5-10wt% metallic zirconium and 1-5wt% metallic hafnium, add them to an induction melting crucible, and perform vacuum melting to obtain a liquid alloy.

[0055] S2: The liquid alloy is subjected to gas atomization to produce powder, or crushed and ball-milled after casting to produce powder, to obtain coarse alloy powder;

[0056] S3: The coarse alloy powder is sieved to obtain alloy powder with a particle size of less than 75μm.

[0057] This technical solution is highly efficient and controllable. Induction melting enables rapid heating in an inert atmosphere, preventing oxidation; gas atomization produces fine, uniform particles; and ball milling is suitable for crushing large ingots, flexibly adapting to different production scales. It maintains alloy composition consistency, and the entire process is conducted in a closed environment, reducing component segregation and contamination.

[0058] Figure 3-6 The following are scanning electron microscope (SEM) images of silicon-chromium-titanium-zirconium-hafnium alloy powders obtained by different powder preparation methods provided in the embodiments of the present invention at different magnifications. Figure 3 The image shows a scanning electron microscope (SEM) image of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by crushing and ball milling according to an embodiment of the present invention. Figure 4 This shows a scanning electron microscope image of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by crushing and ball milling according to an embodiment of the present invention at another magnification. Figure 5 This shows a scanning electron microscope image of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by gas atomization according to an embodiment of the present invention; Figure 6 This shows a scanning electron microscope (SEM) image of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by gas atomization according to an embodiment of the present invention at another magnification; as shown. Figure 3 and 4 As shown, the powder obtained by crushing and ball milling has irregular particle shapes, exhibiting a polygonal or blocky structure. The particle distribution is relatively uniform, with a size of less than 40 μm, and there is no obvious aggregation or separation phenomenon. Figure 5 and 6 As shown, the powder obtained by gas atomization exhibits a distinct spherical or near-spherical structure, with a smooth and uniform surface, relatively uniform particle distribution, a size of less than 70 μm, and no obvious aggregation or separation, demonstrating good dispersibility.

[0059] In some embodiments, in step S1, the vacuum melting is carried out in an argon atmosphere, the melting temperature is 1700-2300°C, and the vacuum degree of the vacuum melting is not higher than 10. -2 Pa.

[0060] Using this technical solution, during the smelting process, metals readily react with oxygen, water vapor, nitrogen, etc., forming undesirable products such as oxides and nitrides. Using argon inert protection and a high-vacuum environment can significantly reduce the partial pressure of reactive gases in the air; inhibit the oxidation, nitriding, and carburization of metal elements; reduce inclusion formation; and improve material purity. This results in a purer and more uniform alloy microstructure. High vacuum conditions (≤10) -2Argon helps lower the boiling point of substances, making it easier for some low-boiling-point impurities (such as Pb, Zn, Sn, Bi, etc.) to volatilize and be removed. This further purifies the material. As an inert gas, argon plays a certain role in stirring during the melting process, helping the melt to mix uniformly; at the same time, under vacuum conditions, dissolved gases (such as hydrogen and oxygen) in the melt can be effectively removed, preventing defects such as porosity and looseness in the casting. This improves the density and microstructure uniformity of the casting, enhancing its mechanical properties. Silicon (Si) has a melting point of 1414℃; chromium (Cr) has a melting point of 1907℃; titanium (Ti) has a melting point of 1668℃; zirconium (Zr) has a melting point of 1855℃; hafnium (Hf) has a melting point of 2233℃. Alloy systems can lower the melting point; a melting temperature of 1700-2300℃ is selected to ensure that the above alloy components can be fully melted.

[0061] In some embodiments, in S1, the purity of silicon is not less than 5N, and the purity of metallic chromium, metallic titanium, metallic zirconium, and metallic hafnium is not less than 3N.

[0062] Using this technical solution, high-purity raw materials are a prerequisite for obtaining high-performance alloy powder, ensuring that the total impurities in the finished product are below 0.315%.

[0063] In some embodiments, in step S2, the gas atomization powdering uses argon as the impinging fluid, with a gas pressure of 5-10 MPa. The specific pressure is adjusted according to the actual powder particle size, and the powder is cooled at a rate of 104-105 K / s to obtain coarse alloy powder.

[0064] This technical solution utilizes high-purity argon gas as the atomization medium, providing a low-oxygen, impurity-free environment throughout the process. This effectively prevents reactive metals (such as titanium, zirconium, and hafnium) from reacting with oxygen or other reactive gases in the air, reducing the presence of oxides and other impurities. Appropriate gas pressure and flow rate help form nearly spherical powder particles, generating fine powder particles with a narrow particle size distribution, improving powder flowability. Rapid cooling with argon gas promotes grain refinement and enhances the mechanical properties of the powder material.

[0065] In some embodiments, in S2, the crushing ball milling first uses a jaw crusher or hammer crusher to crush the molten alloy block into particles of 5-20mm, and then uses a planetary ball mill or vibrating ball mill to ball mill for 8-12 hours at a ball-to-material ratio of 5-10:1 and a rotation speed of 200-600rpm to obtain coarse alloy powder.

[0066] This technical solution utilizes jaw crushers or hammer crushers to quickly and effectively reduce raw material size, significantly shortening the time required for subsequent fine grinding. Ball milling can achieve an efficient fine grinding process in a shorter time. By employing a coarse crushing followed by fine grinding, the particle size distribution of the final powder can be better controlled. The primary crushing ensures the uniformity of material size, which helps to obtain more uniform powder particles during subsequent ball milling.

[0067] Thirdly, such as Figure 6 As shown, the present invention proposes a silicon-chromium-titanium-zirconium-hafnium high-temperature anti-oxidation coating. The coating is prepared on the surface of a niobium alloy by means of a slurry melting method using the silicon-chromium-titanium-zirconium-hafnium alloy powder described in the first aspect as raw material. The coating thickness is 60-100 μm, and the coating provides effective protection for the niobium alloy material under heating conditions not exceeding 1700℃.

[0068] This technical solution utilizes Si to form a dense SiO2 protective film at high temperatures, which is fluid enough to fill gaps in the coating. Cr forms a dense Cr2O3 protective film at high temperatures, enhancing oxidation resistance. Ti, Zr, and Hf, as high-melting-point metals, possess excellent thermal stability and can form stable oxides (such as TiO2, ZrO2, and HfO2) on their surfaces, exhibiting thermal barrier properties and further improving oxidation and corrosion resistance. The pentagonal alloy system generates a "high entropy effect," enhancing solid solution strengthening and improving the material's overall mechanical properties and thermal stability. This alloy system possesses good high-temperature strength and oxidation resistance, making it suitable for protective coatings on high-temperature components such as those used in aero-engines and nuclear power equipment. Existing niobium alloy high-temperature oxidation-resistant protective coatings primarily provide long-term protection at temperatures below 1400℃, while the high-temperature oxidation-resistant protective coating of this invention can provide extended protection at temperatures between 1400-1700℃.

[0069] Fourthly, this invention proposes a method for preparing a silicon-chromium-titanium-zirconium-hafnium high-temperature antioxidant coating, the method comprising the following steps:

[0070] T1: Mix the silicon-chromium-titanium-zirconium-hafnium alloy powder described in the first aspect with a binder and a solvent in a mass ratio of 4-5:1:3-4 to prepare a slurry;

[0071] T2: The slurry is coated onto the surface of the niobium alloy, dried, and then sintered to form the high-temperature anti-oxidation coating.

[0072] Using this technical solution, the prepared slurry exhibits good dispersibility and adhesion, with good compatibility between the binder and the alloy powder. The resulting slurry is uniform and stable, exhibiting strong adhesion after spraying, and sintering ensures sufficient densification and alloying. High-temperature treatment induces diffusion bonding between powder particles, forming a dense and continuous coating, thus improving the integrity of the anti-oxidation film. The niobium alloy maintains structural stability at high temperatures, and this process is well-matched to its coefficient of thermal expansion, preventing cracking or peeling.

[0073] In some embodiments, in step T1, the adhesive is a varnish or polyethylene glycol; the solvent is ethyl acetate, acetone or ethanol.

[0074] This technical solution is environmentally friendly and easy to implement. The selected solvents are all common organic solvents that evaporate quickly and have low toxicity, making them suitable for industrial applications. The binder is also reasonably selected and does not affect the subsequent sintering process.

[0075] In some implementations, step T2 includes the following specific steps:

[0076] The slurry is sprayed onto the surface of the niobium alloy and then vacuum sintered. The sintering temperature is increased from room temperature to 1500-1650℃, and held at 1500-1650℃ for 30-60 minutes, with a vacuum degree <5×10⁻⁶. -2 Pa.

[0077] This technical solution can effectively suppress secondary oxidation. Sintering in a vacuum environment can minimize the participation of oxygen and avoid the formation of pores or non-dense oxide layers inside the coating.

[0078] Example 1

[0079] Weigh out 62 wt% silicon, 20 wt% metallic chromium, 7.5 wt% metallic titanium, 7.5 wt% metallic zirconium, and 3 wt% metallic hafnium, and add them to an induction melting crucible. Melt at a temperature of 1950-2050℃ and a vacuum degree of 0.5 × 10⁻⁶. -2 Vacuum melting was carried out under the condition of Pa to obtain a liquid alloy. After casting the liquid alloy into ingots, the molten alloy blocks were crushed into particles of 5-20 mm using a jaw crusher, and then ball-milled for 10 hours using a planetary ball mill at a ball-to-material ratio of 7:1 and a rotation speed of 400 rpm to obtain coarse alloy powder. The coarse alloy powder was sieved to obtain alloy powder with a particle size of less than 75 μm. The silicon-chromium-titanium-zirconium-hafnium alloy powder was mixed with polyethylene glycol and ethyl acetate at a mass ratio of 4.5:1:3.5 to prepare a slurry. The slurry was coated on the surface of the niobium alloy, dried, and then heated from room temperature to 1500-1650℃ and held at 1500-1650℃ for 45 minutes under a vacuum degree of 1×10⁻⁶. -2 Pa forms the high-temperature antioxidant coating.

[0080] Figure 3 The image shows a scanning electron microscope (SEM) image of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by crushing and ball milling according to an embodiment of the present invention. Figure 4 The following are scanning electron microscope (SEM) images of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by crushing and ball milling according to an embodiment of the present invention at different magnifications; as shown. Figure 3 and 4 As shown, the powder obtained by crushing and ball milling has an irregular particle shape, exhibiting a polygonal or blocky structure. The particles are relatively uniformly distributed, with a size of less than 40 μm, and there is no obvious aggregation or separation phenomenon.

[0081] Example 2

[0082] Weigh out 62 wt% silicon, 20 wt% metallic chromium, 7.5 wt% metallic titanium, 7.5 wt% metallic zirconium, and 3 wt% metallic hafnium, and add them to an induction melting crucible. Melt at a temperature of 1950-2050℃ and a vacuum degree of 0.5 × 10⁻⁶. -2 Vacuum melting was performed under the condition of Pa to obtain a liquid alloy; the liquid alloy was then atomized into powder using argon gas as the impinging fluid at a pressure of 7 MPa, and the atomized particles were cooled at a rate of 10⁴-10⁵ K / s to obtain coarse alloy powder; the coarse alloy powder was sieved to obtain alloy powder with a particle size of less than 75 μm. The silicon-chromium-titanium-zirconium-hafnium alloy powder was mixed with polyethylene glycol and ethyl acetate at a mass ratio of 4.5:1:3.5 to prepare a slurry; the slurry was coated on the surface of a niobium alloy, dried, and then heated from room temperature to 1500-1650℃ and held at 1500-1650℃ for 45 min under a vacuum of 1×10⁻⁶. -2 Pa forms the high-temperature antioxidant coating.

[0083] Figure 5 This shows a scanning electron microscope image of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by gas atomization powder preparation according to an embodiment of the present invention; Figure 6 The following are scanning electron microscope (SEM) images of silicon-chromium-titanium-zirconium-hafnium alloy powder obtained by gas atomization powder preparation according to embodiments of the present invention at different magnifications; as shown Figure 5 and 6 As shown, the powder obtained by gas atomization exhibits a distinct spherical or near-spherical structure, with a smooth and uniform surface, relatively uniform particle distribution, a size of less than 70 μm, and no obvious aggregation or separation, demonstrating good dispersibility.

[0084] Example 3

[0085] Weigh out 55 wt% silicon, 25 wt% metallic chromium, 10 wt% metallic titanium, 6 wt% metallic zirconium, and 4 wt% metallic hafnium, and add them to an induction melting crucible. Melt the mixture at a temperature of 1950-2050℃ and a vacuum degree of 0.5 × 10⁻⁶.-2 Vacuum melting was carried out under the condition of Pa to obtain a liquid alloy. After the liquid alloy ingot was cast, the molten alloy block was crushed into particles of 5-20 mm using a jaw crusher, and then ball-milled for 10 hours in a planetary ball mill at a ball-to-material ratio of 7:1 and a rotation speed of 400 rpm to obtain coarse alloy powder. The coarse alloy powder was sieved to obtain alloy powder with a particle size of less than 75 μm. The silicon-chromium-titanium-zirconium-hafnium alloy powder was mixed with varnish and acetone at a mass ratio of 4.5:1:3.5 to prepare a slurry. The slurry was coated on the surface of the niobium alloy, dried, and then heated from room temperature to 1500-1650℃ and held at 1500-1650℃ for 100 min under a vacuum degree of 1×10⁻⁶. -2 Pa forms the high-temperature antioxidant coating.

[0086] Example 4

[0087] Weigh out 70 wt% silicon, 15 wt% metallic chromium, 6 wt% metallic titanium, 6 wt% metallic zirconium, and 3 wt% metallic hafnium, and add them to an induction melting crucible. Melt at a temperature of 1950-2050℃ and a vacuum degree of 0.5 × 10⁻⁶. -2 Vacuum melting was performed under the condition of Pa to obtain a liquid alloy; the liquid alloy was then atomized into powder using argon gas as the impinging fluid at a pressure of 7 MPa, and the atomized particles were cooled at a rate of 104-105 K / s to obtain coarse alloy powder; the coarse alloy powder was sieved to obtain alloy powder with a particle size of less than 75 μm. The silicon-chromium-titanium-zirconium-hafnium alloy powder was mixed with varnish and ethyl acetate at a mass ratio of 4.5:1:3.5 to prepare a slurry; the slurry was coated on the surface of a niobium alloy, dried, and then heated from room temperature to 1500-1650℃ and held at 1500-1650℃ for 120 min under a vacuum of 1×10⁻⁶. -2 Pa forms the high-temperature antioxidant coating.

[0088] To evaluate the stability and protective performance of the high-temperature anti-oxidation coating prepared by the silicon-chromium-titanium-zirconium-hafnium alloy powder described in this invention under extreme high-temperature conditions, the following test method was used to conduct a high-temperature oxidation test:

[0089] I. Test Conditions

[0090] Test temperature: 1700℃; Holding time: 10 hours; Atmosphere: Static air atmosphere (i.e., exposed to air at normal pressure, without airflow control); Heating method: Electric heating (clamping method at both ends); The sample is installed between graphite electrodes and heated directly by current; Heating rate: controlled at 5~10℃ / min to avoid thermal shock; Finally, the temperature is raised to 1700℃ and held for 10 hours; Temperature measurement method: Infrared thermometer (non-contact), temperature measurement range covering 0~2000℃, accuracy class not less than ±2℃; The installation position should avoid interference from reflections from the heating furnace cavity to ensure accurate measurement.

[0091] II. Sample Preparation:

[0092] Substrate material: Niobium alloy; Coating preparation: The high-temperature anti-oxidation coating preparation method provided in Example 2 is used. After spraying the coating slurry onto the substrate surface, a continuous coating is formed by vacuum sintering; Sample shape and size: Niobium alloy with a length of not less than 30 mm and a moderate width for easy clamping and temperature measurement; Before testing, the sample surface must be cleaned to remove oil and impurity particles to ensure test consistency.

[0093] III. Testing Apparatus:

[0094] The system uses a high-temperature electric heating furnace and is equipped with: graphite clamps for sample fixation; an infrared thermometer for real-time monitoring of the temperature in the middle area of ​​the sample; a temperature control system for precise heating and constant temperature control; and an observation window or camera system for in-situ observation of coating changes.

[0095] IV. Test Procedures

[0096] The sample coated with a high-temperature anti-oxidation coating is clamped at both ends on the heating device to ensure good electrical conductivity; the heating program is started and the temperature is raised to 1700℃ at the set rate; the temperature is kept constant at 1700℃ for 10 hours; the temperature of the sample is continuously monitored and recorded using an infrared thermometer during the experiment; the sample is allowed to cool to room temperature naturally after the experiment; the sample is visually inspected, with a focus on whether the coating shows signs of failure such as peeling, cracking, and blistering.

[0097] Whether the coating is completely adhered to the substrate surface without obvious peeling or cracking; whether the substrate has been oxidized by metallographic or compositional analysis.

[0098] A high-temperature antioxidant coating of 60-100 μm was prepared on the sample surface using the preparation methods of Examples 1-4 above. After heating at 1700℃ for 10 hours using the above test steps, the sample coating was still completely adhered to the sample surface, and no failure phenomena such as peeling, cracking and bubbling occurred.

[0099] in, Figure 7 The silicon-chromium-titanium-zirconium-hafnium high-temperature anti-oxidation coating provided in Example 2, after being electrically heated at 1700°C in air for 10 hours, shows the following coating characteristics: Figure 7 As shown, the sample coating did not exhibit any failure phenomena such as peeling or cracking, and no obvious oxidation traces were observed in the substrate material, indicating that the high-temperature anti-oxidation coating has excellent high-temperature stability and good interfacial bonding ability. In the description of this specification, the reference to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., means that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0100] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0101] The foregoing has provided a detailed description of the silicon-chromium-titanium-zirconium-hafnium alloy powder, its preparation method, and its applications. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A silicon-chromium-titanium-zirconium-hafnium alloy powder, characterized in that, Based on 100wt% of powder weight, the alloy powder contains 50-73wt% silicon, 15-25wt% chromium, 5-10wt% titanium, 5-10wt% zirconium, 1-5wt% hafnium, and less than 0.315wt% impurities.

2. The silicon-chromium-titanium-zirconium-hafnium alloy powder according to claim 1, characterized in that, The alloy powder is irregularly shaped or spherical, with a particle size of less than 75 μm, and a loose packing density of 1-1.5 g / cm³. 3 The tap density is 1.7-1.9 g / cm³. 3 Specific surface area: 2.5-2.8 m² 2 / g.

3. The silicon-chromium-titanium-zirconium-hafnium alloy powder according to claim 1, characterized in that, The impurities in the alloy powder include Fe, Al, Cu, C and O, wherein the content of Fe is less than 0.02 wt%, the content of Al is less than 0.005 wt%, the content of Cu is less than 0.005 wt%, the content of C is less than 0.035 wt%, and the content of O is less than 0.25 wt%.

4. A method for preparing the silicon-chromium-titanium-zirconium-hafnium alloy powder according to any one of claims 1-3, characterized in that, The method includes the following steps: S1: Weigh 50-74wt% silicon, 15-25wt% metallic chromium, 5-10wt% metallic titanium, 5-10wt% metallic zirconium and 1-5wt% metallic hafnium, add them to an induction melting crucible, and perform vacuum melting to obtain a liquid alloy. S2: The liquid alloy is subjected to gas atomization to produce powder, or crushed and ball-milled after casting to produce powder, to obtain coarse alloy powder; S3: The coarse alloy powder is sieved to obtain alloy powder with a particle size of less than 75μm.

5. The method for preparing silicon-chromium-titanium-zirconium-hafnium alloy powder according to claim 4, characterized in that, In step S1, the vacuum melting is carried out in an argon atmosphere, the melting temperature is 1700-2300℃, and the vacuum degree of the vacuum melting is not higher than 10. -2 Pa.

6. The method for preparing silicon-chromium-titanium-zirconium-hafnium alloy powder according to claim 4, characterized in that, In step S1, the purity of silicon is not less than 5N, and the purity of metallic chromium, metallic titanium, metallic zirconium and metallic hafnium is not less than 3N.

7. A silicon-chromium-titanium-zirconium-hafnium high-temperature anti-oxidation coating, characterized in that, The coating is prepared on the surface of a niobium alloy by means of a slurry melting method using silicon-chromium-titanium-zirconium-hafnium alloy powder as described in any one of claims 1-3; the coating thickness is 60-100 μm, and the coating provides effective protection for the niobium alloy material under heating conditions not exceeding 1700°C.

8. A method for preparing a silicon-chromium-titanium-zirconium-hafnium high-temperature antioxidant coating, characterized in that, The method includes the following steps: T1: Mix the silicon-chromium-titanium-zirconium-hafnium alloy powder according to any one of claims 1-3 with a binder and a solvent in a mass ratio of 4-5:1:3-4 to prepare a slurry; T2: The slurry is coated onto the surface of the niobium alloy, dried, and then sintered to form the high-temperature anti-oxidation coating.

9. The method for preparing silicon-chromium-titanium-zirconium-hafnium alloy powder according to claim 8, characterized in that, In step T1, the adhesive is varnish or polyethylene glycol; the solvent is ethyl acetate, acetone or ethanol.

10. The method for preparing silicon-chromium-titanium-zirconium-hafnium alloy powder according to claim 8, characterized in that, Step T2 includes the following specific steps: The slurry is sprayed onto the surface of the niobium alloy and then vacuum sintered. The sintering temperature is increased from room temperature to 1500-1650℃, and held at 1500-1650℃ for 30-60 minutes, with a vacuum degree <5×10⁻⁶. -2 Pa.

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