A method for improving high temperature oxidation resistance of refractory high entropy alloy, high performance refractory high entropy alloy and preparation and application thereof

Abstract

A method for improving the high-temperature oxidation resistance of a refractory high-entropy alloy, a high-performance refractory high-entropy alloy, and its preparation and application. The present invention belongs to the field of high-temperature alloy materials. The purpose of the present invention is to solve the technical problem that the existing refractory high-entropy alloys have poor inherent oxidation resistance under high-temperature conditions. The method of the present invention is to perform surface remelting and in-situ surface deposition of a pure aluminum layer on a cast refractory high-entropy alloy through electron beam surface treatment, so that the alloy surface treatment layer is metallurgically combined with the substrate, and a high-quality surface treatment layer and a bonding interface are obtained by regulating process parameters such as electron beam current density and wire feeding speed, thereby improving the high-temperature environmental stability of the refractory high-entropy alloy. The product and technology can be expanded to the surface treatment of other high-melting-point high-temperature alloys, applied to different types of high-temperature materials and meet high-temperature service requirements.

Description

Technical Field

[0001] The present invention belongs to the field of high-temperature alloy materials, and specifically relates to a method for improving the high-temperature oxidation resistance of a refractory high-entropy alloy, a high-performance refractory high-entropy alloy, and a preparation and application thereof. Background Art

[0002] With the development of weapons and aerospace technology, high-temperature structures such as hot-end components of aircraft engine turbine guide vanes have higher and higher requirements for the use temperature and performance of high-temperature resistant materials. The use temperature of traditional high-temperature alloys can no longer meet the service requirements of the new generation of hot-end components, and it is urgent to develop / seek high-temperature structural materials with higher temperature resistance and good comprehensive performance.

[0003] At present, although refractory high entropy alloys have extremely high high-temperature performance, due to the high content of refractory elements added, they show poor high-temperature oxidation resistance under high-temperature conditions, which will restrict their practical application. At present, the way to improve the high-temperature oxidation resistance of refractory high-entropy alloys is to add alloying elements or oxidation coatings. However, considering the high-temperature mechanical strength and plasticity synergy, alloying elements such as Al, Cr, and Si are mostly limited to trace / small amounts, which makes it difficult to form a single and continuous selective oxidation layer such as Al2O3, Cr2O3 and SiO2; although the application of anti-oxidation coatings, such as Mo-Si-B coatings, can improve the oxidation resistance of alloys to a certain extent, the heterogeneous combination between the coating and the base alloy may cause the coating to fail if it works for a long time under high load. Once the coating fails, it will cause catastrophic oxidation of the base alloy. Therefore, it is still necessary to develop a method to effectively improve the inherent oxidation resistance of the base alloy, deeply optimize the comprehensive performance of refractory high entropy alloys, and promote their application and development in high-temperature environments. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problem that the existing refractory high entropy alloys have poor inherent oxidation resistance under high temperature conditions, and to provide a method for improving the high temperature oxidation resistance of refractory high entropy alloys, high performance refractory high entropy alloys and their preparation and application.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] One of the purposes of the present invention is to provide a method for improving the high-temperature oxidation resistance of a refractory high-entropy alloy, the method comprising electron beam surface remelting the refractory high-entropy alloy and in-situ depositing a pure aluminum layer on the surface of an electron beam fuse under vacuum conditions, and then performing stress relief annealing after cooling.

[0007] Further definition, the electron beam surface remelting parameters: beam current density I b 20-30mA, scanning speed (electron beam running speed) V printThe scanning speed is 500-700mm / min, the scanning interval is 1.5-2.0mm, the scanning number is 1 time, and the scanning path is unidirectional.

[0008] Further definition, the parameters of the in-situ deposition of pure aluminum layer on the surface of the electron beam fuse are: beam density I b 30-40mA, scanning speed (electron beam running speed) V print 500-700mm / min, scanning interval is 2.0-3.0mm, wire feeding speed V feed The scanning speed is 1.5-2.0m / min, the scanning path is unidirectional, and the dwell time between paths is 15-25s.

[0009] It is further defined that the annealing temperature is 350-450°C and the time is 2-4h.

[0010] It is further defined that the refractory high entropy alloy includes but is not limited to TiNbMoAlSi alloy.

[0011] The second object of the present invention is to provide a method for preparing a high-performance refractory high-entropy alloy, the preparation method being carried out according to the following steps:

[0012] S1: Press TiNbMo 0.5 Al 0.225 Si x , x≤0.6 atomic stoichiometric ratio material, adopt non-consumable vacuum arc melting to prepare alloy ingot, then obtain flat surface by wire cutting, and then obtain pre-treated sample by grinding, polishing and cleaning;

[0013] S2: Fix the substrate and the sample on a workbench, evacuate the sample after sealing, and then treat the surface of the sample according to the above method to obtain a high-performance TiNbMoAlSi refractory high-entropy alloy.

[0014] Further, S2 was evacuated to 7×10 -2 Pa.

[0015] The third object of the present invention is to provide a high-performance TiNbMoAlSi refractory high-entropy alloy prepared by the above method, in which the pure aluminum layer is metallurgically combined with the substrate.

[0016] It is further defined that the alloy structure includes BCC solid solution, β-(Nb,Ti)5Si3, γ-(Nb,Ti)5Si3, Al5Mo and Al3Ti.

[0017] A fourth object of the present invention is to provide a high-performance TiNbMoAlSi refractory high-entropy alloy prepared by the above method for use in hot end components in the aerospace field.

[0018] Compared with the prior art, the present invention has the following significant effects:

[0019] The present invention utilizes electron beam surface treatment technology to metallurgically combine the alloy surface treatment layer with the substrate, and obtains a high-quality surface treatment layer and a bonding interface by regulating process parameters such as electron beam current density and wire feeding speed, thereby improving the high-temperature environment stability of the refractory high-entropy alloy. The products and technologies can be extended to the surface treatment of other high-melting-point high-temperature alloys, applied to different types of high-temperature materials and meet high-temperature service requirements. At the same time, due to the limited plasticity of the refractory high-entropy alloy itself, the present invention adopts a stress relief annealing process to effectively inhibit the generation of cracks and ensure the acquisition of high-quality surface-treated alloys. The specific advantages are as follows:

[0020] (1) The alloy mother ingot preparation process of the present invention is simple, that is, ingots of different compositions are obtained by non-consumable arc melting technology.

[0021] (2) The present invention can achieve rapid remelting and rapid deposition on the surface of refractory high entropy alloys. By adjusting the process parameters, a well-formed and densely organized surface treatment layer structure can be obtained, which effectively inhibits the generation of microcracks during the rapid solidification process.

[0022] (3) The present invention significantly improves the oxidation resistance of refractory high entropy alloys while taking into account mechanical properties. Compared with the cast state, the oxidation weight gain of the samples treated by surface remelting and surface deposition of pure aluminum layer technology after cyclic high-temperature oxidation at 1000℃ for 36 hours was reduced by 15.64% and 20.19%, respectively.

[0023] (4) The preparation method provided by the present invention is extensible and can be applied to the rapid surface treatment of other high-temperature alloys and the in-situ, large-scale surface fuse deposition of complex components, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a macroscopic morphology of the TiNbMoAlSi alloy after surface remelting and surface deposition in an embodiment of the present invention;

[0025] Figure 2 The surface macroscopic images of the TiNbMoAlSi alloy samples before and after surface remelting treatment and after in-situ deposition of a pure aluminum layer on the surface after cyclic high-temperature oxidation according to the embodiment of the present invention are shown;

[0026] Figure 3 The XRD diagram of the TiNbMoAlSi alloy after the surface is remelted and after the pure aluminum layer is in-situ deposited on the surface in the embodiment of the present invention;

[0027] Figure 4The oxidation kinetic curve of the sample after cyclic high-temperature oxidation of the TiNbMoAlSi alloy surface after remelting treatment and in-situ deposition of a pure aluminum layer on the surface in the embodiment of the present invention;

[0028] Figure 5 This is the microstructure diagram of the TiNbMoAlSi alloy after surface remelting treatment in this embodiment;

[0029] Figure 6 The oxidized cross-sectional microstructure diagram of the sample of the TiNbMoAlSi alloy before and after surface remelting treatment and after cyclic high-temperature oxidation in this embodiment, wherein (a) is before remelting treatment, and (b) is after remelting treatment;

[0030] Figure 7 This is a microstructure diagram of the TiNbMoAlSi alloy in this embodiment after a pure aluminum layer is deposited on the surface;

[0031] Figure 8 The oxidized cross-sectional microstructure diagram of the sample of the TiNbMoAlSi alloy before and after the surface deposition of a pure aluminum layer in this embodiment after cyclic high-temperature oxidation, where (a) is before surface deposition and (b) is after surface deposition. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0034] The terms "comprising," "including," "having," "containing," or any other variations thereof, as used in the following examples, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus comprising the listed elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0035] When equivalent, concentration or other value or parameter is represented by the range limited by range, preferred range or a series of upper preferred value and lower preferred value, this should be understood as specifically disclosing all ranges formed by any pairing of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the scope is disclosed separately. For example, when disclosing range "1 to 5", described range should be interpreted as including range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When numerical range is described in this article, unless otherwise stated, the scope is intended to include its end value and all integers and fractions within the scope. In the present application specification and claims, range limitation can be combined and / or interchanged, if these ranges are not otherwise stated, include all sub-ranges contained therein.

[0036] The indefinite articles "a" and "an" before the elements or components of the present invention have no limitation on the quantity requirements (i.e. the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the elements or components in the singular form also include the plural form, unless the quantity obviously refers to the singular form only.

[0037] Example:

[0038] The preparation method of the high-performance TiNbMoAlSi refractory high-entropy alloy of this embodiment is carried out according to the following steps:

[0039] (1) According to TiNbMo 0.5 Al 0.225 Si 0.25 The raw materials are weighed according to the atomic stoichiometric ratio, placed in a vacuum arc furnace, evacuated and filled with inert gas, and under inert gas conditions, non-consumable vacuum arc melting technology is used to melt to obtain TiNbMoAlSi refractory high entropy alloy ingots. Then, wire cutting is used to obtain a flat ingot surface, and the sample surface is ground and polished. After ultrasonic cleaning, the sample is dried in a drying oven at 60°C for 1 hour to remove residual moisture on the surface.

[0040] (2) A cast iron substrate with a size of 150 mm × 100 mm × 20 mm was sanded until the surface was smooth and clean, and then the surface of the substrate was wiped with acetone to remove oil and impurities on the surface, and then placed in a drying oven at 60°C for 1 hour for drying to remove residual moisture on the surface.

[0041] (3) The cast iron substrate treated in step (2) is clamped on a motion system in a vacuum chamber of an electron beam device, and the TiNbMoAlSi refractory high entropy alloy sample in step (1) is fixed on the substrate.

[0042] (4) Close the hatch, operate the equipment, and wait until the vacuum degree of the equipment vacuum chamber reaches the use requirements (7×10 -2 Pa), the electron beam scans the surface of the TiNbMoAlSi refractory high entropy alloy sample according to the preset process parameters and scanning path, causing the sample surface to melt and solidify, forming a fine and uniform remelting layer. The specific remelting process parameters and scanning path are as follows: beam current density I b is 25mA, scanning speed (electron beam running speed) V print The scanning speed is 600mm / min, the scanning interval is 1.8mm, the number of scans is 1, and the scanning path is unidirectional. The actual picture after surface remelting is as shown in the attached figure. Figure 1 As shown, it can be seen that its surface is dense, crack-free and has good formability.

[0043] (5) The electron beam performs fuse deposition on the surface of the TiNbMoAlSi refractory high entropy alloy sample according to the pre-set process parameters and scanning path, causing the pure aluminum wire to melt and evenly deposit on the surface of the sample to form a metallurgical bond. The specific deposition process parameters and scanning path are as follows: beam current density I b is 35mA, scanning speed (electron beam running speed) V print is 600mm / min, the scanning interval is 2.5mm, and the wire feeding speed V feed The scanning speed is 1.8m / min, the scanning path is unidirectional, and the interval between passes is 20s. The actual picture after the pure aluminum layer is deposited in situ on the surface is shown in the attached figure. Figure 1 As shown, it can be seen that its surface is dense, crack-free and has good formability.

[0044] (6) After the sample is cooled to room temperature, it is taken out. The whole process is carried out in a vacuum environment. After being taken out, it is cut by wire to obtain a sample that meets the size of a quartz sealing tube. The cut sample is placed in a quartz tube for sealing treatment. The sealed tube is placed in a heat treatment furnace and kept at a constant temperature of 400°C for 3 h to complete stress relief annealing, thereby obtaining a high-performance TiNbMoAlSi refractory high-entropy alloy.

[0045] Detection test

[0046] The samples before and after the surface remelting treatment and before and after the in-situ deposition of the pure aluminum layer on the surface were cut into 6mm×6mm×3mm, sanded to 1500# to ensure that the surface was smooth and flat, ultrasonically cleaned and dried, and placed in a separate corundum crucible (to eliminate the influence of the crucible's own weight change on the experiment during the oxidation experiment, the crucible was pre-calcined at 1200℃ for 6h), and then placed in a high-temperature muffle furnace for 1000℃ cyclic high-temperature oxidation, with a heating rate of 10℃ / min. After keeping at 1000℃ for 6 hours, the power was cut off, the furnace door was opened, and the samples were taken out. Repeat the above operation after the furnace is completely cooled. After each operation, the weight of all samples was measured using an electronic scale and the data was recorded. After the cyclic high-temperature oxidation test, the cross-section of the oxidation layer after oxidation was observed using a scanning electron microscope, and the difference in high-temperature oxidation resistance between the samples without surface remelting treatment and those with surface remelting treatment was compared.

[0047] Figure 2 The macroscopic images of the samples before and after surface remelting treatment and after in-situ deposition of pure aluminum layer on the surface after constant temperature oxidation at 1000℃ for 6h show that the treated oxide scale is grayish white, while the untreated oxide scale is yellow. This indicates that the TiNb2O7 and Nb2O5 oxide layers formed early in the original alloy are suppressed. Excessive volume expansion of such oxides will cause premature cracking of the oxide layer, so the surface treatment effectively improves the adhesion between the oxide layer and the substrate. At the same time, due to the metallurgical bonding of the deposition process, the alloy surface presents different oxidation rates, and oxidation in different areas is restricted, thereby effectively improving the oxidation resistance.

[0048] Figure 3 Figure 2 shows the XRD diagram of TiNbMoAlSi alloy after surface remelting treatment and in-situ deposition of pure aluminum layer on the surface. The results show that after surface remelting treatment, the alloy is mainly composed of BCC solid solution and γ-(Nb,Ti)5Si3 phases. After surface deposition treatment, the alloy is mainly composed of BCC solid solution and β-(Nb,Ti)5Si3, γ-(Nb,Ti)5Si3, Al5Mo and Al3Ti phases.

[0049] Figure 4 Curve b in the figure is the oxidation kinetic curve of the refractory high entropy alloy obtained in this embodiment after surface remelting treatment and cyclic high temperature oxidation at 1000°C for 36 hours, and curve a is the original (untreated) oxidation weight gain curve. By comparison, it can be seen that the weight gain of the alloy after surface remelting treatment in this embodiment is significantly reduced, and the oxidation weight gain is reduced by 4.59% after 6 hours, and the oxidation weight gain is reduced by 15.64% after 36 hours, and the oxidation weight gain of 36 hours oxidation does not exceed 46.04 mg / cm 2 . Figure 4Curve c in FIG. 1 is an oxidation kinetic curve of the refractory high entropy alloy obtained in this embodiment after surface deposition treatment and cyclic high temperature oxidation at 1000°C for 36 hours. By comparison, it can be seen that the weight gain of the alloy after surface deposition treatment in this embodiment is significantly reduced, and the oxidation weight gain is reduced by 71.33% after 6 hours and by 20.19% after 36 hours. The oxidation weight gain of 36 hours oxidation does not exceed 43.56 mg / cm 2 .

[0050] Figure 5 This is the microstructure diagram of the TiNbMoAlSi alloy after surface remelting treatment in this embodiment. It can be seen that the sample structure after electron beam surface remelting treatment is obviously fine and uniform.

[0051] Figure 6 The oxidation cross-sectional microstructure of the TiNbMoAlSi alloy in this embodiment after 6 hours of cyclic high-temperature oxidation before and after surface remelting treatment is shown in Figure 1. The thickness of the oxide layer is reduced from the original 88 μm to 63 μm. Based on the above analysis, the electron beam surface remelting treatment significantly improves the high-temperature oxidation resistance of the base alloy.

[0052] Figure 7 The microstructure of the TiNbMoAlSi alloy after the surface deposition of pure aluminum layer in this embodiment shows that the sample after the electron beam surface deposition treatment has fine and uniform structure and no microcracks. At the same time, due to the stirring effect of the molten pool, the pure aluminum layer and the matrix alloy undergo metallurgical reaction, and there are a large number of equiaxed crystals in the molten pool formed by local quenching.

[0053] Figure 8 The oxidation cross-sectional microstructure of the TiNbMoAlSi alloy in this embodiment after cyclic high temperature oxidation for 6 hours before and after the surface deposition of pure aluminum layer, the thickness of the oxide layer is reduced from the original 88μm to 35μm, and the thickness of the oxide layer is significantly reduced by 60.23%. Based on the above analysis, the electron beam surface deposition of pure aluminum layer treatment significantly improves the high temperature oxidation resistance of the base alloy.

[0054] In summary, the electron beam surface treatment method provided by the present invention can effectively improve the high temperature oxidation resistance of TiNbMoAlSi refractory high entropy alloy. At the same time, the provided method can be applied to the surface treatment of samples of different sizes, better meet the actual workpiece morphology and size requirements, and the performance after surface treatment can meet different occasions of practical application. In addition, the alloy density involved is as low as 6g / cm 3 , low density matched with effective means to improve oxidation resistance can better serve the aerospace field.

[0055] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for improving the high temperature oxidation resistance of a refractory high entropy alloy, characterized in that: The refractory high entropy alloy is TiNbMo 0.5 Al 0.225 Si x , x≤0.6, the method comprises performing electron beam surface remelting on the refractory high entropy alloy and in-situ deposition of a pure aluminum layer on the surface of the electron beam fuse under vacuum conditions, and then performing stress relief annealing after cooling.

2. The method according to claim 1, characterized in that Electron beam surface remelting parameters: I b 20-30mA, V print The scanning speed is 500-700mm / min, the scanning interval is 1.5-2.0mm, the scanning number is 1 time, and the scanning path is unidirectional.

3. The method according to claim 1, characterized in that: Parameters of in-situ deposition of pure aluminum layer on the surface of electron beam fuse: I b 30-40mA, V print 500-700mm / min, scanning interval is 2.0-3.0mm, wire feeding speed V feed The scanning speed is 1.5-2.0m / min, the scanning path is unidirectional, and the dwell time between paths is 15-25s.

4. The method according to claim 1, characterized in that: The annealing temperature is 350-450°C and the time is 2-4h.

5. A method for preparing a high-performance refractory high-entropy alloy, characterized in that: Follow these steps: S1: Press TiNbMo 0.5 Al 0.225 Si x , x≤0.6 atomic stoichiometric ratio material, adopt non-consumable vacuum arc melting to prepare alloy ingot, then obtain flat surface by wire cutting, and then obtain pre-treated sample by grinding, polishing and cleaning; S2: Fix the substrate and the sample on a workbench, evacuate the sample after sealing, and then treat the surface of the sample according to the method described in any one of claims 1 to 4 to obtain a high-performance TiNbMoAlSi refractory high-entropy alloy.

6. The method according to claim 5, characterized in that S2 is evacuated to 7×10 -2 Pa.

7. The high performance TiNbMoAlSi refractory high entropy alloy prepared by the method according to claim 5 or 6, characterized in that: The pure aluminum layer in the alloy is metallurgically bonded to the substrate.

8. The high performance TiNbMoAlSi refractory high entropy alloy according to claim 7, characterized in that: The alloy structure includes BCC solid solution, β-(Nb,Ti)5Si3, γ-(Nb,Ti)5Si3, Al5Mo and Al3Ti.

9. Application of the high-performance TiNbMoAlSi refractory high-entropy alloy prepared by the method according to claim 5 or 6 in hot end components in the aerospace field.

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