A medium-entropy high-temperature alloy with excellent oxidation resistance and its preparation method and application

Abstract

The present invention discloses a medium-entropy high-temperature alloy with excellent oxidation resistance, a preparation method and application thereof, and specifically relates to the field of metallurgical technology. The alloy comprises Co: 30.6-34.5%, Ni: 30.0-34.5%, Cr: 26.6-30.6%, Al: 0.4-3.4%, Ti: 1.6-4.6%, W: 0.5-3.5%, Mo: 0.01-2.5%, Ta: 0.01-2.7%, and C: 0.001-0.085%. The alloy of the present invention has excellent oxidation resistance at high temperatures, and has the characteristics of low density, excellent high-temperature strength and long-lasting life, and is easy to process and shape, and can meet the use requirements of hot end components of aircraft engines and gas turbines.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a medium-entropy high-temperature alloy with excellent oxidation resistance, and a preparation method and application thereof. Background Art

[0002] High entropy alloy is a new type of alloy material developed in recent years that is different from traditional alloys. It is composed of 5 to 13 main elements, and the constituent elements have equal or approximately equal atomic ratios. After solidification, multi-principal high entropy alloys will not form complex intermetallic compounds, but will form simple FCC or BCC solid solutions. High entropy alloys have high entropy effects in thermodynamics, lattice distortion effects in structure, hysteresis diffusion effects in kinetics, and cocktail effects in performance. By utilizing these effects and rationally designing the composition of the alloy, good comprehensive properties such as high strength, good wear resistance, and corrosion resistance can be obtained.

[0003] Although high entropy alloys have excellent performance, they generally have poor strength-toughness matching. For example, the tensile plasticity of FeCoNiCrMn high entropy alloy can reach 60%, but its tensile strength is less than 500MPa; while AlCoCrFeNiTi 0.5 The compressive strength of high entropy alloys is as high as 3200MPa, but there is almost no tensile plasticity. The trace addition of Ti and Al elements can promote the precipitation of the second phase, thereby enhancing the performance of high entropy alloys, but it is not possible to improve the strength-toughness matching of all high entropy alloys. For example, for AlFeCrCoCu alloys, the addition of Ti elements can significantly increase the hardness of the alloy, but there is almost no tensile plasticity. Although the existing AlCrFeNiV system high entropy alloys have a certain strength-toughness matching effect, it is not enough for practical applications. It is precisely because of these reasons that the development and engineering application of high entropy alloys are limited.

[0004] Chinese patent CN202111423519.7, a nickel-based alloy and its preparation method and application, by adding 21.5-25.5% Cr to generate a Cr2O3 oxide film on the alloy surface, thereby improving oxidation resistance and corrosion resistance; in addition, the Co element has better oxidation resistance than Ni and Fe itself, so the addition of 24.5-27.5% Co element further improves the oxidation resistance of the alloy; however, after subsequent research, the simple use of Co element antioxidant can not meet the subsequent application requirements, which limits the subsequent application of medium-entropy alloys.

[0005] At present, more and more research in the field of high entropy alloys has shifted to medium entropy alloys. CrCoNi medium entropy alloy is a single face-centered cubic structure (FCC) solid solution with better strength and plasticity than FeCoNiCrMn high entropy alloy. However, the strength of the medium entropy alloy is still relatively low, and the oxidation resistance needs to be further optimized. The alloy components are commonly used elements in high-temperature alloys such as Cr, Co and Ni, and can be used as the matrix of high-temperature alloys. On this basis, by adding other alloying elements and controlling the preparation process, whether a new oxidation-resistant alloy with the characteristics of both high-temperature alloys and medium entropy alloys can be developed, and promoting its application in engineering is a problem that needs to be solved urgently. Summary of the invention

[0006] To this end, the present invention provides a medium-entropy high-temperature alloy with excellent oxidation resistance and a preparation method and application thereof, so as to solve the problems such as the lack of oxidation resistance of existing medium-entropy alloys.

[0007] Medium-entropy high-temperature alloy refers to an alloy composed of three main elements with equal or approximately equal atomic ratios, and has high strength, good durability and corrosion resistance above 600°C. Although the room temperature performance of existing medium-entropy high-temperature alloys is better, as various industries have increasingly higher requirements for the high-temperature resistance of high-temperature resistant alloys, the medium-entropy high-temperature alloys in the existing technology cannot meet the use requirements, and it is necessary to prepare medium-entropy high-temperature alloys with excellent oxidation resistance at higher temperatures to meet the use requirements. To this end, the present invention provides a medium-entropy high-temperature alloy with excellent oxidation resistance and a preparation method and application thereof, which solve the technical problems faced by existing medium-entropy alloys, such as insufficient resistance to high-temperature oxidation and corrosion, and low high-temperature strength.

[0008] 1. In the embodiment of the present invention, Cr, Co and Ni are added in equal molar atomic percentages, maintaining a relatively high entropy value, and playing a strong solid solution strengthening and high temperature oxidation resistance effect; at the same time, W, Mo and Ta elements are further added for solid solution strengthening to improve the high temperature strength of the alloy. In addition, by adding two γ' phase-forming elements, Al and Ti, the alloy has a stable nano-scale γ' phase at 800-900°C to play a precipitation strengthening role. By reasonably matching grain boundary strengthening elements such as C, the high temperature strength and durability of the alloy are significantly improved.

[0009] 2. In the embodiment of the present invention, the medium-entropy high-temperature alloy has a wide hot working window of 900℃~1200℃, and has few surface cracks, good plasticity and high yield rate during alloy forging. By controlling the content of elements such as Al and Ti, the alloy has good processing properties while fully playing the aging strengthening effect, and controls the γ' phase to be dispersed in nanoparticles.

[0010] 3. In the embodiments of the present invention, the medium-entropy high-temperature alloy reaches a complete oxidation resistance level through the antioxidant effect of elements such as Cr and Al in the oxidation resistance evaluation at 1000°C, meeting the requirements for the design and use of hot end components of advanced aircraft engines and gas turbines.

[0011] 4. In the embodiment of the present invention, the medium-entropy high-temperature alloy has a tensile strength of 209-344 MPa at 1000°C and a density of ≤8.12 g / cm2 through the solid solution strengthening effect of elements such as Cr, Co, W, Mo, and Ta, and the aging strengthening effect of elements such as Al and Ti. 3 , meeting the requirements for the design and use of hot end components of advanced aircraft engines and gas turbines.

[0012] In order to achieve the above object, the present invention provides the following technical solutions:

[0013] According to the first aspect of the present invention, a medium-entropy high-temperature alloy with excellent oxidation resistance is provided. The medium-entropy high-temperature alloy with excellent oxidation resistance comprises, by weight percentage: Co: 30.6-34.5%, Ni: 30.0-34.5%, Cr: 26.6-30.6%, Al: 0.4-3.4%, Ti: 1.6-4.6%, W: 0.5-3.5%, Mo: 0.01-2.5%, Ta: 0.01-2.7%, and C: 0.001-0.085%.

[0014] In some embodiments, the medium-entropy high-temperature alloy with excellent oxidation resistance is composed of the following components, in weight percentage: Co: 30.6~34.5%, Ni: 30.0~34.5%, Cr: 26.6~30.6%, Al: 0.6~3.0%, Ti: 1.8~3.8%, W: 0.5~3.5%, Mo: 0.01~2.5%, Ta: 0.01~2.7%, C: 0.001~0.085%.

[0015] Furthermore, in the medium-entropy high-temperature alloy with excellent oxidation resistance, the atomic percentage of Cr:Co:Ni is 1:1:1.

[0016] Furthermore, in the medium-entropy high-temperature alloy with excellent oxidation resistance, the atomic percentages of Al, W, Mo and Ta satisfy the relationship 0.7≤3(W+Mo+Ta) / Al≤1.3.

[0017] The alloy of the present invention adds W and Mo solid solution strengthening elements, which can be dissolved in the alloy matrix and in the γ' strengthening phase, and can improve the interatomic bonding force, the diffusion activation energy and the recrystallization temperature, thereby effectively improving the high temperature strength. However, when the W and Mo content is too high, long-term high temperature use is easy to generate brittle phases and reduce the toughness of the alloy. Al and Ta are the main elements for forming the γ' strengthening phase, which can greatly improve the precipitation strengthening effect of the alloy, significantly improve the complete dissolution temperature, volume fraction and stability of the γ' phase, and enhance the high temperature mechanical properties of the alloy. However, too high Ta will precipitate the η phase, which is not conducive to the stability of the organization. In addition, Ta will significantly reduce the solidus temperature, reduce the hot working window, and is not conducive to the hot working performance of the alloy. Moreover, the density of Ta is very high, and excessive addition will cause the alloy density to increase significantly. Therefore, in order to maximize the synergistic effect of Al, W, Mo and Ta, the atomic percentage content of Al, W, Mo and Ta is further optimized to satisfy the relationship 0.7≤3(W+Mo+Ta) / Al≤1.3.

[0018] Furthermore, in the medium-entropy high-temperature alloy with excellent oxidation resistance, the weight percentage of Al, Ti and Ta satisfies the relationship 3.0%≤Al+Ti+2Ta≤7.8%. Preferably, the weight percentage of Al, Ti and Ta satisfies the relationship 4.0%≤Al+Ti+2Ta≤6.5%. The synergistic effect of Al, Ti and Ta can be maximized, and the obtained medium-entropy high-temperature alloy has more excellent comprehensive performance and can meet the requirements of the design and use of advanced aircraft engines and gas turbines.

[0019] According to a second aspect of the present invention, a method for preparing a medium-entropy high-temperature alloy with excellent oxidation resistance is provided, comprising:

[0020] Step 1: Mix and heat Co, Ni, Cr, W, Mo, Ta and part of C raw materials to discharge the gas attached to the raw materials;

[0021] Step 2, heating the raw material of the exhaust gas to a molten state, then raising the temperature, performing high-temperature refining, and then stopping the heating to allow the molten raw material to form a film;

[0022] Step 3, raising the temperature of the film raw material to break the film of the molten raw material, adding Al, Ti and the remaining C raw material, and mixing them evenly; the mixed raw material is subjected to high-temperature refining;

[0023] Step 4, controlling the temperature of the refined raw material for pouring to obtain a slab;

[0024] Step 5, finishing, hot rolling, annealing and softening the slab, finishing again, cold rolling, intermediate heat treatment and trimming to obtain an alloy strip;

[0025] Step six, heat treating the alloy strip to form a medium-entropy high-temperature alloy with excellent oxidation resistance.

[0026] Furthermore, in the step 1, the mixing and heating is performed in an environment with a vacuum degree of ≤1Pa.

[0027] Furthermore, in the step 2, the heating and melting is carried out in an environment with a vacuum degree of ≤0.5Pa; and / or, the temperature of the high-temperature refining is 1530-1680°C.

[0028] Furthermore, in the step three, the temperature of the high temperature refining is 1580-1620°C; and / or, in the step four, the pouring temperature is 1400-1500°C.

[0029] Furthermore, in step six, the heat treatment condition is 700-900° C. for 5-20 hours.

[0030] According to the third aspect of the present invention, a high-strength and high-toughness, low-density, medium-entropy high-temperature alloy is used in aircraft engines and gas turbines.

[0031] The medium-entropy high-temperature alloy with excellent oxidation resistance in the embodiment of the present invention meets the requirements of advanced aircraft engine design and use, and can be used in the hot end components of advanced aircraft engines. The medium-entropy high-temperature alloy with excellent oxidation resistance in the embodiment of the present invention meets the requirements of advanced gas turbine design and use, and can be used in the hot end components of advanced gas turbines.

[0032] The present invention has the following advantages:

[0033] In the medium-entropy high-temperature alloy with excellent oxidation resistance of the present invention, Cr, Co and Ni are added in equal molar atomic percentages, maintaining a high entropy value, playing a strong solid solution strengthening and high temperature oxidation resistance effect; at the same time, W, Mo and Ta elements are further added for solid solution strengthening to improve the high temperature strength of the alloy. In addition, by adding two γ' phase forming elements Al and Ti, the alloy has a stable nano-scale γ' phase at 800-900°C to play a precipitation strengthening role, and then by reasonably matching grain boundary strengthening elements such as C, the high temperature strength and durability of the alloy are significantly improved. The medium-entropy high-temperature alloy with excellent oxidation resistance of the present invention has a wide hot working window of 900°C to 1200°C, few surface cracks during alloy forging, good plasticity and high yield rate. By controlling the content of elements such as Al and Ti, while fully playing the aging strengthening effect, it is ensured that the alloy has good processing performance and the γ' phase is controlled to be dispersed in nanoparticles. The medium-entropy high-temperature alloy with excellent oxidation resistance of the present invention has achieved a complete oxidation resistance level in the oxidation resistance performance evaluation at 1000°C through the oxidation resistance of elements such as Cr and Al, meeting the requirements for the design and use of hot end components of advanced aircraft engines and gas turbines. The medium-entropy high-temperature alloy with excellent oxidation resistance of the present invention has achieved a yield strength of 209-344MPa at 1000°C and a density of ≤8.12g / cm through the solid solution strengthening effect of elements such as Cr, Co, W, Mo, Ta, and the aging strengthening effect of elements such as Al and Ti. 3 , meeting the requirements for the design and use of hot end components of advanced aircraft engines and gas turbines.

[0034] The medium-entropy high-temperature alloy of the present invention has excellent oxidation resistance, high-temperature tensile performance, long-lasting life and low density. It meets the requirements of advanced aircraft engine and gas turbine design and use by not forming cracks during forging, hot rolling and cold rolling. The alloy not only has good high-temperature oxidation resistance, but also has good plasticity at high temperature and room temperature, good processing performance, simple preparation process, reduced energy consumption, shortened production cycle, improved production efficiency, and is suitable for promotion and application in industrial production. DETAILED DESCRIPTION

[0035] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The alloy of the present invention comprehensively considers the influence of alloy elements on the high temperature mechanical properties, hot working properties and oxidation resistance of the alloy when designing the composition. The specific considerations are as follows:

[0037] Cr: It mainly enters the γ matrix and plays a role in solid solution strengthening. It can also strengthen the grain boundary by precipitating granular M23C6 carbides on the grain boundary. Another important function of Cr is to protect the alloy surface from oxidation and thermal corrosion caused by O, S, and salt. At present, alloys with good corrosion resistance generally have a higher Cr content. However, Cr is an element that promotes the formation of brittle σ harmful phase. Too high Cr content will deteriorate the structural stability of the alloy. Therefore, the Cr content is 26.6-30.6%.

[0038] Co: Mainly dissolved in the γ matrix, it plays a role in solid solution strengthening, reduces the stacking fault energy of the matrix, reduces the solubility of Al and Ti in the matrix, thereby increasing the amount of γ' phase and the dissolution temperature of the γ' phase, thus significantly improving the creep resistance of the alloy. Therefore, the Co content is 30.6-34.5%.

[0039] Ni: γ' phase forming element, significantly expands the γ / γ' two-phase region, improves the stability of the alloy structure, and to a certain extent increases the temperature at which the γ' phase completely dissolves. However, if the Ni content is too high, the chemical composition of the γ' phase will be closer to Ni3Al, and its coarsening rate will increase. Therefore, the Ni content is Ni: 30.0-34.5%.

[0040] Al, Ti: Al, Ti and Ta are the main elements that form the γ' phase, which can greatly improve the precipitation strengthening effect of the alloy. At the same time, the addition of Al will form an Al2O3 protective film on the surface of the alloy, which is beneficial to improve the oxidation resistance of the alloy, Ti is beneficial to improve the corrosion resistance, and Ta significantly increases the complete dissolution temperature, volume fraction and stability of the γ' phase, and enhances the high-temperature mechanical properties of the alloy. However, excessive Al and Ti will precipitate harmful β phases, which is not conducive to organizational stability. In addition, Ti and Ta will significantly reduce the solidus temperature, narrow the hot working window, and are not conducive to the hot working performance of the alloy. The density of Ta is very high, and excessive addition will lead to a significant increase in the density of the alloy. Therefore, Al is 0.4-3.4%, Ti is 1.6-4.6%, and Ta is 0.01-2.7%.

[0041] C: Grain boundary strengthening element, also a strong deoxidizer, is beneficial to deoxidation during alloy smelting, improves the purity of the alloy, and improves the processing performance of the alloy. At the same time, C can form carbides with some refractory elements, reduce the supersaturation of the matrix, and is beneficial to the stability of the organization. However, if the C content is too high, continuous and network-distributed carbides will be formed on the grain boundaries, which is not conducive to the mechanical properties of the alloy. Therefore, the C content is 0.001-0.085%.

[0042] Al+Ti+Ta: Al, Ti and Ta are all γ' phase forming elements, and their content directly affects the volume fraction of γ' phase and the complete dissolution temperature, and determines the high temperature mechanical properties of the alloy. However, too high Al, Ti and Ta content is not conducive to the processing performance of the alloy, so it is controlled to be 3.0%≤Al+Ti+2Ta≤7.8%.

[0043] In the embodiment of the present invention, Cr, Co and Ni are added in equal molar atomic percentages, maintaining a high entropy value, playing a strong solid solution strengthening and high temperature oxidation resistance effect; at the same time, W, Mo and Ta elements are further added for solid solution strengthening to improve the high temperature strength of the alloy. In addition, by adding two γ' phase forming elements Al and Ti, the alloy has a stable nano-scale γ' phase at 800-900°C to play a precipitation strengthening role, and then by reasonably matching grain boundary strengthening elements such as C, the high temperature strength and durability of the alloy are significantly improved. In the embodiment of the present invention, the medium entropy high temperature alloy has a wide hot working window of 900°C to 1200°C, and the surface cracks are few during the alloy forging process, the plasticity is good, and the yield rate is high. By controlling the content of elements such as Al and Ti, while fully playing the aging strengthening effect, it is ensured that the alloy has good processing performance and the γ' phase is controlled to be dispersed in nanoparticles. In the embodiment of the present invention, the medium-entropy high-temperature alloy has achieved a complete anti-oxidation level at 1000°C through the anti-oxidation effect of elements such as Cr and Al, meeting the requirements for the design and use of hot end components of advanced aircraft engines and gas turbines. In the embodiment of the present invention, the medium-entropy high-temperature alloy has achieved a yield strength of 209-344MPa at 1000°C and a density of ≤8.12g / cm through the solid solution strengthening effect of elements such as Cr, Co, W, Mo, Ta, and the aging strengthening effect of elements such as Al and Ti. 3 , meeting the requirements for the design and use of hot end components of advanced aircraft engines and gas turbines.

[0044] A medium-entropy high-temperature alloy with excellent oxidation resistance according to an embodiment of the present invention comprises the following components by weight percentage: Co: 30.6-34.5%, Ni: 30.0-34.5%, Cr: 26.6-30.6%, Al: 0.4-3.4%, Ti: 1.6-4.6%, W: 0.5-3.5%, Mo: 0.01-2.5%, Ta: 0.01-2.7%, and C: 0.001-0.085%.

[0045] In some embodiments, preferably, the atomic percentage of Cr:Co:Ni of the medium-entropy high-temperature alloy with excellent oxidation resistance is 1:1:1.

[0046] In some embodiments, preferably, the atomic percentages of Al, W, Mo and Ta in the medium-entropy high-temperature alloy with excellent oxidation resistance satisfy the relationship 0.7≤3(W+Mo+Ta) / Al≤1.3.

[0047] In the embodiment of the present invention, W and Mo solid solution strengthening elements are added, which can be dissolved in the alloy matrix and in the γ' strengthening phase, and can improve the interatomic bonding force, the diffusion activation energy and the recrystallization temperature, thereby effectively improving the high temperature strength. However, when the W and Mo content is too high, long-term high temperature use is easy to generate brittle phases and reduce the toughness of the alloy. Al and Ta are the main elements for forming the γ' strengthening phase, which can greatly improve the precipitation strengthening effect of the alloy, significantly improve the complete dissolution temperature, volume fraction and stability of the γ' phase, and enhance the high temperature mechanical properties of the alloy. However, too high Ta will precipitate the η phase, which is not conducive to the stability of the organization. In addition, Ta will significantly reduce the solidus temperature, reduce the hot working window, and is not conducive to the hot working performance of the alloy. Moreover, the density of Ta is very high, and excessive addition will cause the alloy density to increase significantly. Therefore, in order to maximize the synergistic effect of Al, W, Mo and Ta, the atomic percentage content of Al, W, Mo and Ta is further optimized to satisfy the relationship 0.7≤3(W+Mo+Ta) / Al≤1.3.

[0048] In some embodiments, preferably, the weight percentages of Al, Ti and Ta in the medium-entropy high-temperature alloy with excellent oxidation resistance satisfy the relationship 3.0%≤Al+Ti+2Ta≤7.8%. Further preferably, the weight percentages of Al, Ti and Ta satisfy the relationship 4.0%≤Al+Ti+2Ta≤6.5%.

[0049] In the embodiment of the present invention, the mass percentages of Al, Ti and Ta are further optimized to satisfy the relationship 3.0%≤Al+Ti+2Ta≤7.8%, which can maximize the synergistic effect of Al, Ti and Ta. The obtained medium-entropy high-temperature alloy has more excellent comprehensive performance and can meet the requirements of the design and use of advanced aircraft engines and gas turbines.

[0050] In an embodiment of the present invention, preferably, the medium-entropy high-temperature alloy with excellent oxidation resistance is composed of the following components, in weight percentage: Co: 30.6-34.5%, Ni: 30.0-34.5%, Cr: 26.6-30.6%, Al: 0.6-3.0%, Ti: 1.8-3.8%, W: 0.5-3.5%, Mo: 0.01-2.5%, Ta: 0.01-2.7%, and C: 0.001-0.085%.

[0051] The embodiment of the present invention also provides the application of the medium-entropy high-temperature alloy with excellent oxidation resistance in an aero-engine. The medium-entropy high-temperature alloy with excellent oxidation resistance in the embodiment of the present invention meets the requirements of advanced aero-engine design and use, and can be applied to the hot end components of advanced aero-engines.

[0052] The embodiment of the present invention also provides the application of the medium-entropy high-temperature alloy with excellent oxidation resistance in a gas turbine. The medium-entropy high-temperature alloy with excellent oxidation resistance in the embodiment of the present invention meets the requirements of advanced gas turbine design and use, and can be used in the hot end components of advanced gas turbines.

[0053] The present invention also provides a method for preparing a medium-entropy high-temperature alloy with excellent oxidation resistance, comprising the following steps:

[0054] (1) Co, Ni, Cr, W, Mo, Ta and part of C raw materials are placed in an environment with a vacuum degree of ≤1 Pa and mixed and heated to discharge the gas attached to the raw materials;

[0055] (2) in a vacuum environment of ≤0.8 Pa, heating the raw material to a molten state, then raising the temperature to 1530-1680° C. for high-temperature refining, and then stopping the heating to allow the molten raw material to form a film;

[0056] (3) raising the temperature to break the film of the molten raw material, adding Al, Ti and the remaining C raw material, and mixing them uniformly;

[0057] (4) refining the mixed raw material to which Al, Ti and the remaining C raw material are added at 1580-1620° C.;

[0058] (5) Casting the refined raw material at 1400-1500° C. to obtain a slab;

[0059] (6) finishing, hot rolling, annealing and softening treatment, re-finishing, cold rolling, intermediate heat treatment and trimming the slab to obtain an alloy strip;

[0060] (7) The alloy strip is subjected to heat treatment at 700-900° C. for 5-20 hours to form the medium-entropy high-temperature alloy with excellent oxidation resistance.

[0061] The method for preparing a medium-entropy high-temperature alloy in an embodiment of the present invention has excellent oxidation resistance, high-temperature tensile performance, long-lasting life and low-density performance, and no forging, hot rolling and cold rolling crack formation, which meets the requirements of the design and use of advanced aircraft engines and gas turbines. The alloy not only has good high-temperature oxidation resistance, but also has good plasticity at high temperature and room temperature, good processing performance, simple preparation process, reduced energy consumption, shortened production cycle, and improved production efficiency, and is suitable for promotion and application in industrial production.

[0062] The present invention is described in detail below with reference to embodiments.

[0063] Example 1

[0064] This embodiment provides a method for preparing a medium-entropy high-temperature alloy with excellent oxidation resistance:

[0065] (1) Co, Ni, Cr, W, Mo, Ta and part of C raw materials are placed in a vacuum environment of 0.9 Pa and mixed and heated to discharge the gas attached to the raw materials;

[0066] (2) in a vacuum environment of 0.7 Pa, heating the raw material to a molten state, then raising the temperature to 1630° C., and performing high-temperature refining for 14 min, and then stopping the heating to allow the molten raw material to form a film;

[0067] (3) raising the temperature to break the film of the molten raw material, adding Al, Ti and the remaining C raw material, and mixing them uniformly;

[0068] (4) refining the mixed raw material to which Al, Ti and the remaining C raw material are added at 1600° C.;

[0069] (5) Casting the refined raw material at 1480° C. to obtain a slab;

[0070] (6) finishing, hot rolling, annealing and softening treatment, re-finishing, cold rolling, intermediate heat treatment and trimming the slab to obtain an alloy strip;

[0071] (7) The alloy strip is subjected to heat treatment at 800° C. for 10 hours to form the low-density medium-entropy high-temperature alloy.

[0072] The composition of the alloy prepared in Example 1 is shown in Table 1, and the properties are shown in Table 2.

[0073] The preparation methods of Examples 2-8 are the same as those of Example 1, except that the alloy compositions are different. The alloy compositions of Examples 2-8 are shown in Table 1, and the properties are shown in Table 2.

[0074] Example 9

[0075] The preparation method of Example 9 is the same as that of Example 1, but the alloy composition is different, wherein the atomic percentage of Cr:Co:Ni is 1:1:1. The alloy composition prepared in Example 9 is shown in Table 1, and the properties are shown in Table 2.

[0076] Comparative Example 1

[0077] The preparation method of Comparative Example 1 is the same as that of Example 1, except that the alloy composition does not contain W and Mo elements. The alloy composition prepared in Comparative Example 1 is shown in Table 1, and the properties are shown in Table 2.

[0078] Comparative Example 2

[0079] The preparation method of Comparative Example 2 is the same as that of Example 1, except that the alloy composition contains 32.4% of element Cr by mass, and 3(W+Mo+Ta) / Al is 2.1. The alloy composition prepared in Comparative Example 2 is shown in Table 1, and the properties are shown in Table 2.

[0080] Comparative Example 3

[0081] The preparation method of Comparative Example 3 is the same as that of Example 1, except that the alloy composition contains 0.3% by mass of element Ti, and Al+Ti+2Ta is 2.4%. The alloy composition prepared in Comparative Example 3 is shown in Table 1, and the properties are shown in Table 2.

[0082] Comparative Example 4

[0083] The preparation method of Comparative Example 4 is the same as that of Example 1, except that the alloy composition contains 4.4% by mass of element Ta. The alloy composition prepared in Comparative Example 4 is shown in Table 1, and the properties are shown in Table 2.

[0084] Table 1 shows the alloy compositions of Examples 1-9 and Comparative Examples 1-4.

[0085] Table 2 shows the alloy compositions of Examples 1-9 and the properties of the alloys of Comparative Examples 1-4.

[0086] Table 1

[0087]

[0088] Table 2

[0089]

[0090] It can be seen from the data in Table 1 and Table 2 that the average oxidation rate of the medium-entropy high-temperature alloy prepared by controlling the content of each element in the embodiment of the present invention at 1000°C is less than 0.1 g / m 2 h, all reached the complete oxidation resistance level; the density of the alloys in Examples 1 to 9 was less than 8.12 g / cm 3 The alloy has good plasticity and high tensile strength at room temperature, and the room temperature tensile strength exceeds 1100MPa. In terms of high-temperature mechanical properties, the alloy's 800℃ high-temperature tensile yield strength is much higher than 600MPa, and the 1000℃ yield strength is also higher than 200MPa. It also has good processing performance, and no cracks are generated after forging, hot rolling and cold rolling.

[0091] The alloy of comparative example 1 does not contain W and Mo elements. Since W and Mo elements have a solid solution strengthening effect, the room temperature and high temperature strengths of the alloy of comparative example 1 are low and cannot meet the use requirements.

[0092] The alloy composition of Comparative Example 2 contains 32.4% of element Cr by mass, and 3(W+Mo+Ta) / Al is 2.1. The excessive Cr content causes a decrease in mechanical strength. In addition, the (W+Mo+Ta) / Al ratio exceeds 1.3. Excessive W, Ta and other elements cause the alloy density to increase significantly, which cannot meet the structural weight reduction effect in application.

[0093] In the alloy composition of Comparative Example 3, the Ti content is too low, only 0.3%, and the Al+Ti+2Ta content is 2.4%. Al and Ti are the main γ' phase-forming elements, which make the alloy have a stable nano-scale γ' phase at 800-900°C to play a precipitation strengthening role. In addition, the Ta element as a strengthening element can also improve the strength of the alloy. In Comparative Example 3, since the Ti element is far less than 1.6%, and the Al+Ti+2Ta content is far less than 3.0%, the strengthening effect is severely weakened, and a sufficiently stable strengthening phase cannot be formed at a high temperature above 800°C, which causes the yield strength at 900°C to be significantly reduced to below 100MPa. In addition, due to the inability to exert the synergistic effect of Al, Ti and Ta, its high-temperature oxidation resistance is also affected. The average oxidation rate of the alloy at 1000°C exceeds 0.10g / m 2 ·h, the antioxidant capacity decreased.

[0094] In Comparative Example 4, the Ta element in the alloy composition is excessive, reaching 4.4%. Although Ta can greatly improve the precipitation strengthening effect of the alloy, significantly increase the complete dissolution temperature, volume fraction and stability of the γ' phase, and enhance the high-temperature mechanical properties of the alloy. However, too much Ta will precipitate the η phase, which is not conducive to organizational stability. Therefore, the high-temperature strength of the alloy decreases significantly, and the yield strength at 1000℃ is less than 100MPa. In addition, the density of Ta is very high, and excessive addition will cause the alloy density to increase significantly, reaching 8.37g / cm 3 , cannot meet the usage needs.

[0095] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A medium-entropy high-temperature alloy with excellent oxidation resistance, characterized in that: The medium-entropy high-temperature alloy with excellent oxidation resistance comprises, by weight percentage: Co: 30.6-34.5%, Ni: 30.0-34.5%, Cr: 26.6-30.6%, Al: 0.4-3.4%, Ti: 1.6-4.6%, W: 0.5-3.5%, Mo: 0.01-2.5%, Ta: 0.01-2.7%, C: 0.001-0.085%; In the medium-entropy high-temperature alloy with excellent oxidation resistance, the atomic percentages of Al, W, Mo and Ta satisfy the relationship of 0.7≤3(W+Mo+Ta) / Al≤1.3; the weight percentages of Al, Ti and Ta satisfy the relationship of 3.0%≤Al+Ti+2Ta≤7.8%.

2. A medium-entropy high-temperature alloy with excellent oxidation resistance according to claim 1, characterized in that: In the medium-entropy high-temperature alloy with excellent oxidation resistance, the atomic percentage of Cr:Co:Ni is 1:1:

1.

3. A method for preparing the medium-entropy high-temperature alloy with excellent oxidation resistance according to claim 1, characterized in that: include: Step 1: Mix and heat Co, Ni, Cr, W, Mo, Ta and part of C raw materials to discharge the gas attached to the raw materials; Step 2, heating the raw material of the exhaust gas to a molten state, then raising the temperature, performing high-temperature refining, and then stopping the heating to allow the molten raw material to form a film; Step 3, raising the temperature of the film raw material to break the film of the molten raw material, adding Al, Ti and the remaining C raw material, and mixing them evenly; the mixed raw material is subjected to high-temperature refining; Step 4, controlling the temperature of the refined raw material for pouring to obtain a slab; Step 5, finishing, hot rolling, annealing and softening the slab, finishing again, cold rolling, intermediate heat treatment and trimming to obtain an alloy strip; Step six, heat treating the alloy strip to form a medium-entropy high-temperature alloy with excellent oxidation resistance.

4. The method for preparing a medium-entropy high-temperature alloy with excellent oxidation resistance according to claim 3, characterized in that: In the step 1, the mixing and heating is carried out in an environment with a vacuum degree of ≤1Pa.

5. The preparation method according to claim 3, characterized in that: In the step 2, the heating and melting is carried out in a vacuum environment of ≤0.5Pa; and / or the temperature of high-temperature refining is 1530-1680°C.

6. The preparation method according to claim 3, characterized in that: In the step three, the temperature of the high temperature refining is 1580-1620°C; and / or, in the step four, the pouring temperature is 1400-1500°C.

7. The preparation method according to claim 3, characterized in that: In step six, the heat treatment condition is 700-900° C. for 5-20 hours.

8. Use of the medium-entropy high-temperature alloy with excellent oxidation resistance as claimed in claim 1 in aircraft engines and gas turbines.

Images