Nickel-based single-crystal high-temperature alloy as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high-temperature alloys, in particular to a nickel-based single-crystal high-temperature alloy and a preparation method and application thereof. The nickel-based single-crystal high-temperature alloy comprises the following chemical components in percentage by mass: 3%-4% of Cr, 0.5%-0.8% of Mo, 5%-6.5% of W, 5%-6% of Al, 0.7%-1% of Ti, 4%-5% of Re, 9%-11% of Co, 7.5%-9% of Ta, 0.078%-0.15% of Hf and the balance of Ni. According to the nickel-based single-crystal high-temperature alloy, through coordination and cooperation of all the components, the nickel-based single-crystal high-temperature alloy has excellent high temperature bearing capacity, the cost of the alloy can be remarkably reduced, meanwhile, the long-term structure stability of the alloy is improved, and the TCP precipitation tendency is low.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy technology, and more specifically, to a nickel-based single-crystal high-temperature alloy, its preparation method, and its application. Background Technology

[0002] With the development and innovation of alloy manufacturing processes, cast superalloys have evolved from equiaxed crystals and oriented columnar crystals to single crystals. By gradually eliminating weak points—grain boundaries—the heat resistance of cast superalloys has been gradually improved. As a major material for aero-engine blades, the development of cast superalloys has also promoted the continuous improvement of the thrust-to-weight ratio of aero-engines. Nickel-based single-crystal superalloys are irreplaceable key materials for the preparation of aero-engine turbine blades, and their microstructure stability under service conditions determines the engine's service safety. Under service conditions, engine turbine blades are mainly subjected to the combined effects of high temperature and centrifugal loads. Creep damage is the main failure mechanism of the alloy, and creep performance has become an important performance indicator for evaluating engine reliability.

[0003] To improve the creep performance of nickel-based single-crystal superalloys, a large amount of refractory elements are added to the alloy to reduce the diffusion rate and improve the stability of the microstructure. Currently, the amount of refractory element Re has become a key indicator for distinguishing the first three generations of alloys. Previous experience in developing traditional single-crystal alloys suggests that first-generation single-crystal superalloys contain no Re, second-generation single-crystals contain about 3% Re, and third-generation single-crystal superalloys contain about 6% Re. The temperature resistance of these alloys is generally considered to be 1050℃ for first-generation single-crystals and 1100℃ for third-generation single-crystals. Third-generation single-crystal alloys such as CMSX-10 and ReneN6 also have Re content controlled at around 6%. However, research has found that with increasing Re content, not only does the alloy cost increase significantly, but it also causes the easy precipitation of topologically dense (TCP) harmful phases. When the Re content exceeds 5%, the tendency for this unstable phase to precipitate increases sharply, easily initiating cracks near the TCP phase, leading to a sharp decrease in the alloy's creep performance, poor long-term microstructure stability, and high alloy density.

[0004] Therefore, it is crucial to balance excellent high-temperature performance with the suppression of TCP phase precipitation to improve the microstructure stability of single-crystal alloys.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One objective of this invention is to provide a nickel-based single-crystal superalloy with excellent high-temperature performance, which can reduce alloy costs and improve the long-term structural stability of the alloy.

[0007] Another object of the present invention is to provide a method for preparing nickel-based single-crystal superalloys.

[0008] Another object of the present invention is to provide an application of the nickel-based single-crystal superalloy described above in spacecraft.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A nickel-based single-crystal superalloy comprising the following chemical composition by weight percentage: Cr 3%~4%, Mo 0.5%~0.8%, W 5%~6.5%, Al 5%~6%, Ti 0.7%~1%, Re 4%~5%, Co 9%~11%, Ta 7.5%~9%, Hf 0.078%~0.15%, balance Ni.

[0010] In some embodiments, the nickel-based single-crystal superalloy comprises the following chemical composition by weight percentage: Cr 3.2%~3.9%, Mo 0.5%~0.7%, W 5.3%~6.5%, Al 5.6%~5.8%, Ti 0.75%~0.9%, Re 4.3%~4.9%, Co 9.4%~10.5%, Ta 7.8%~8.5%, Hf 0.08%~0.15%, balance Ni.

[0011] In some implementations, the total mass percentage X1 of Mo, W and Re satisfies: 9.5% ≤ X1 ≤ 11.8%.

[0012] In some implementations, the total mass percentage of Al, Ti, and Ta multiplied by 2 satisfies: 13.5%. <X2<15.5%。

[0013] In some embodiments, the mass ratio R1 of Cr and Co satisfies: 0.3 ≤ R1 ≤ 0.4.

[0014] In some implementations, the mass ratio R2 of Ta and Re satisfies: 1.5 <R2<1.8。

[0015] In some embodiments, the nickel-based single-crystal superalloy further contains impurity elements, including O, N, and S, with a total mass content of ≤15ppm; wherein O≤6ppm, N≤6ppm, and S≤4ppm.

[0016] In some embodiments, the γ' phase size of the nickel-based single-crystal superalloy is 0.35~0.6μm.

[0017] In some embodiments, the volume fraction of the γ' phase in the nickel-based single-crystal superalloy is 65% to 72%.

[0018] In some embodiments, the tensile properties of the nickel-based single-crystal superalloy at 1120°C satisfy the following:σ b ≥463MPa σ 0.2 ≥415MPa.

[0019] In some embodiments, the nickel-based single-crystal superalloy has a creep life of >100h under conditions of 1150°C and 110MPa.

[0020] The preparation method of the nickel-based single-crystal superalloy as described above includes the following steps: (a) According to the stoichiometric ratio of the chemical composition of the nickel-based single crystal superalloy, Ni is added to the crucible in the vacuum induction device to cover the inner bottom surface of the crucible, then a desulfurizing agent is added, and then Cr, Mo, W, Re, Co and Ta are added; (b) Vacuum the vacuum induction device, then perform preliminary melting on the raw materials in step (a) until all the materials are melted; after heating, perform refining to obtain a refined system; (c) Cool the refining system, then add Al, Ti, deoxidized carbon and Hf and stir to obtain an alloy liquid; (d) The alloy liquid is cooled and then prepared into master alloy rods.

[0021] (e) The master alloy rod is prepared into a single crystal test rod with a crystal orientation of

[001] by means of a spiral crystal selection method; (f) The single crystal test rod is subjected to multi-stage heat treatment to obtain a nickel-based single crystal high-temperature alloy.

[0022] In some embodiments, the desulfurizing agent is used to control the sulfur content of the master alloy bar to be no more than 4 ppm; the desulfurizing agent includes CaO and CaF, and the mass ratio of CaO to CaF is 1:(0.3~0.5); the mass of the desulfurizing agent is 0.1%~0.3% of the mass of the master alloy.

[0023] In some embodiments, the vacuuming process is performed to a vacuum level ≤ 5 Pa.

[0024] In some embodiments, the temperature of the initial melting treatment is 1420~1480°C.

[0025] In some embodiments, the refining temperature is 1500~1560℃, and the refining time is 40~70min.

[0026] In some implementations, in step (c), the cooling is reduced to the conjunctival state at a temperature of 1440~1500°C.

[0027] In some embodiments, the mass percentage of the deoxidized carbon in the alloy is 0.01% to 0.04%.

[0028] In some embodiments, the stirring process takes 8 to 15 minutes.

[0029] In some implementations, in step (d), the temperature is cooled to 1420~1480°C.

[0030] In some embodiments, in step (e), the pouring temperature of the single crystal test rod preparation process is 1520~1560℃, the mold temperature is 1520~1560℃, and the single crystal pulling rate is 2~4mm / min.

[0031] In some embodiments, the spacing between the primary dendrite arms of the single crystal test rod is controlled to be no greater than 400 μm.

[0032] In some embodiments, the axial deviation of the single crystal test rod from the

[001] direction is no more than 10°.

[0033] In some embodiments, the multi-stage heat treatment includes a first heat treatment, a second heat treatment, and a third heat treatment performed sequentially; the first heat treatment includes five stages of isothermal treatment with progressively increasing temperatures; wherein, the first isothermal treatment is at a temperature of 1300℃~1305℃, held for 3~4 hours, and then air-cooled to room temperature; the second isothermal treatment is at a temperature of 1310℃~1313℃, held for 2~3 hours, and then air-cooled to room temperature; the third isothermal treatment is at a temperature of 1315℃~1318℃, held for 2~3 hours, and then air-cooled to room temperature; and the fourth isothermal treatment is at a temperature of 1322℃~1325℃. The heat treatment process involves holding the material at 1330℃~1335℃ for 5~7 hours, followed by air cooling to room temperature. The fifth constant temperature treatment involves holding the material at 1330℃~1335℃ for 6~8 hours, followed by air cooling to room temperature. The second heat treatment includes a sixth and a seventh constant temperature treatment with decreasing temperatures. The sixth constant temperature treatment involves holding the material at 1322℃~1325℃ for 5~7 hours, followed by air cooling to room temperature. The seventh constant temperature treatment involves holding the material at 1160℃~1165℃ for 6~8 hours, followed by air cooling to room temperature. The third heat treatment involves holding the material at 870℃~900℃ for 20~24 hours, followed by air cooling to room temperature.

[0034] The applications of nickel-based single-crystal superalloys as described above in aviation and spacecraft.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the nickel-based single-crystal high-temperature alloy of the present invention, the appropriate proportions of elements W, Mo and Re can better strengthen the γ matrix, enhance the solid solution strengthening effect, and reduce the cost at the same time; Al, Ti and Ta mainly form the precipitation strengthening phase γ', and the appropriate proportions of Al, Ti and Ta can improve the high-temperature performance of the alloy and form a suitable volume fraction of γ'; the appropriate proportions of element Cr can improve the corrosion resistance of the alloy; the appropriate proportions of Co can stabilize the matrix of the alloy and improve the stability of the alloy structure; the appropriate proportions of Hf are beneficial to improving the casting performance of the alloy; through the coordinated combination of the above components, it has excellent high temperature resistance, good high-temperature creep performance, can significantly reduce the cost of the alloy, and at the same time improve the long-term structural stability of the alloy, with a low tendency for TCP precipitation.

[0036] (2) The present invention ensures uniform composition and reduces impurities by mixing and melting the above alloying elements according to the stoichiometric ratio of the alloy. Single crystal alloy is generated by spiral crystallization method, and further subjected to multi-stage heat treatment to ensure reduced element segregation, elimination of harmful eutectic phase in the alloy, and ensure that the alloy strengthening phase γ' has a regular square structure and appropriate size. Through the coordination of each step, the obtained nickel-based single crystal high temperature alloy has good high temperature performance and long-term stability. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 The as-cast microstructure of the nickel-based single-crystal superalloy of Example 2; Figure 2 The low-magnification microstructure of the nickel-based single-crystal superalloy in Example 2 after heat treatment; Figure 3 This is a magnified 1000x microstructure image of the nickel-based single-crystal superalloy after heat treatment in Example 2. Figure 4 This is a 5000x magnified microstructure of the nickel-based single-crystal superalloy after heat treatment in Example 2. Figure 5 The image shows the microstructure of the nickel-based single-crystal superalloy of Example 2 after being subjected to a long-term high-temperature load of 3000 hours at 913°C and 248 MPa, magnified 2000 times. Figure 6 The image shows the microstructure of the nickel-based single-crystal superalloy of Example 2 after being subjected to a long-term high-temperature load of 913°C and 248MPa for 3000 hours, magnified 10000 times. Detailed Implementation

[0039] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0040] According to one aspect of the present invention, the present invention relates to a nickel-based single-crystal superalloy comprising the following chemical composition by mass percentage: Cr 3%~4%, Mo 0.5%~0.8%, W 5%~6.5%, Al 5%~6%, Ti 0.7%~1%, Re 4%~5%, Co 9%~11%, Ta 7.5%~9%, Hf 0.078%~0.15%, balance Ni.

[0041] In the nickel-based single-crystal superalloy of the present invention, appropriate proportions of elements W, Mo, and Re can better strengthen the γ matrix, enhance solid solution strengthening, and reduce costs; Al, Ti, and Ta mainly form the precipitation strengthening phase γ', and appropriate proportions of Al, Ti, and Ta can improve the high-temperature performance of the alloy and form a suitable volume fraction of γ'; appropriate proportions of element Cr can improve the corrosion resistance of the alloy; appropriate proportions of Co can stabilize the alloy matrix and improve the stability of the alloy structure; appropriate proportions of Hf are beneficial to improving the casting performance of the alloy; through the coordinated combination of the above components, it has excellent high-temperature resistance, good high-temperature creep performance, can significantly reduce the cost of the alloy, improve the long-term structural stability of the alloy, and has a low tendency for TCP precipitation.

[0042] In some embodiments, Cr is 3%, 3.2%, 3.3%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or 4%, or any value within a range of both. Cr is a key element for improving the corrosion resistance of the alloy, and the alloy of the present invention must contain the above-mentioned appropriate amount of Cr. Adding a large amount of Cr will affect the microstructure stability of the alloy.

[0043] In some embodiments, Mo is 0.5%, 0.53%, 0.55%, 0.58%, 0.6%, 0.65%, 0.7%, 0.72%, 0.75%, 0.78%, 0.8%, or any value within a range of both. Mo is a solid solution strengthening element and can increase the mismatch degree of γ / γ', making the mismatched dislocation network denser, which can effectively hinder dislocation movement and improve alloy properties; however, excessive Mo has an adverse effect on the hot corrosion resistance of the alloy and should not be added in excess.

[0044] In some implementations, W is 5% to 6.5%, such as 5%, 5.2%, 5.5%, 5.7%, 5.9%, 6%, 6.2%, 6.3%, 6.5%, or any value in any range between the two. W is a solid solution strengthening element that can strengthen the γ matrix, but excessive addition of W can lead to γ ​​supersaturation, affecting the stability of the microstructure, easily causing the precipitation of TCP embrittlement phase, and reducing alloy properties.

[0045] In some implementations, Re is 4%, 4.2%, 4.3%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, or any value within a range of both. Re is an important strengthening element in nickel-based superalloys. It can reduce the bulk diffusion coefficient, slow down the diffusion-controlled process, and thus reduce the growth rate of the γ' strengthening phase and slow down the diffusion rate controlling the creep mechanism. Re agglomerates in the γ matrix, forming atomic clusters that hinder dislocation movement, resulting in a more significant diffusion effect than the traditional solid solution effect. However, the addition of a large amount of Re can exacerbate element agglomeration and may lead to the formation of the unstable TCP phase. Adding an appropriate amount of Re to single-crystal superalloys is necessary and can significantly improve the high-temperature performance of the alloy. However, considering that Re is a scarce and expensive element, and that a large increase in Re can easily lead to the precipitation of the TCP phase, if the Re content in the alloy is greater than 5%, the tendency for the formation of the second reaction zone (SRZ) in the alloy will increase significantly.

[0046] In some implementations, Al content is 5% to 6%, such as 5%, 5.2%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, or 6%, or any value in between. Al is mainly the element that forms the strengthening phase γ' (Ni3Al), and its content plays an important role in the high-temperature performance of the alloy. At the same time, Al content is also crucial to the oxidation resistance of the alloy. Appropriate amounts of aluminum can enhance the oxidation resistance and high-temperature performance of the alloy.

[0047] In some embodiments, Ti is 0.7% to 1%, such as 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, or 1%, or any value in between. Suitable amounts of Ti can form a suitable precipitation strengthening phase γ', improving the alloy's corrosion resistance and high-temperature performance.

[0048] In some embodiments, Co is 9%, 9.2%, 9.5%, 9.6%, 9.8%, 10%, 10.5%, 10.8%, 11%, or any value in any range between the two. Co can stabilize the alloy matrix. Adding an appropriate proportion of Co to the alloy can improve the stability of the alloy structure while obtaining a uniform structure at a relatively low solid solution temperature, so as to give full play to the strengthening effect of other elements.

[0049] In some embodiments, Ta is 7.5%, 7.8%, 7.9%, 8%, 8.2%, 8.5%, 8.8%, 9%, etc., or a range value between any two of them. Ta can not only strengthen the γ matrix but also enter γ' to play a precipitation strengthening role. Appropriate Ta can improve the high-temperature performance of the alloy and effectively promote the oxidation and corrosion resistance of the alloy.

[0050] In some embodiments, Hf is 0.078% - 0.15%, such as 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, etc., or a range value between any two of them. Appropriate Hf can improve the casting performance of the alloy and enhance the subsequent compatibility with the coating.

[0051] In some embodiments, the total mass percentage X1 of Mo, W, and Re satisfies: 9.5% ≤ X1 ≤ 11.8%. For example, the total mass percentage X1 of Mo, W, and Re is 10%, 10.1%, 10.2%, 10.3%, 10.5%, 10.6%, 10.8%, 10.9%, 11% or 11.2%, 11.3%, 11.5%, etc. The coordinated cooperation of W, Mo, and Re can better strengthen the γ matrix, greatly reduce the cost of the alloy, and improve the long-term stability of the alloy.

[0052] In some embodiments, the total mass percentage X2 of Al, Ti, and Ta satisfies: 13.5% < X2 < 15.5%. For example, the total mass percentage X2 of Al, Ti, and Ta is 13.5%, 13.7%, 14%, 14.2%, 14.3%, 14.5%, 14.6%, 14.7%, 14.8%, 15%, 15.2%, 15.3%, 15.5%, etc. In the alloy, Al, Ti, and Ta mainly form the precipitation strengthening phase γ'. The volume fraction of γ' should be maintained at 65% - 72%. Controlling the total mass percentage of Al, Ti, and Ta to meet the above range can better improve the excellent high-temperature performance of the alloy and enhance its long-term stability.

[0053] In some embodiments, the mass ratio R1 of Cr and Co satisfies: 0.3 ≤ R1 ≤ 0.4. For example, the mass ratio R1 of Cr and Co (Cr / Co) is 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, or 0.4, etc. When the mass ratio R1 of Cr and Co satisfies the above range, it is more conducive to synergistically optimizing the oxidation resistance and phase stability of the alloy.

[0054] In some embodiments, the nickel-based single crystal superalloy comprises chemical components with the following mass percentages: Cr 3.2% - 3.9%, Mo 0.5% - 0.7%, W 5.3% - 6.5%, Al 5.6% - 5.8%, Ti 0.75% - 0.9%, Re 4.3% - 4.9%, Co 9.4% - 10.5%, Ta 7.8% - 8.5%, Hf 0.08% - 0.15%, and the balance is Ni. By further optimizing the ratios of the components of the nickel-based single crystal superalloy, the functions can be better coordinated to improve the high-temperature performance of the alloy.

[0055] In some embodiments, the mass ratio R2 of the Ta and the Re satisfies: 1.5 < R2 < 1.8, and R2 is, for example, 1.5, 1.6, 1.7, 1.8, etc. Using an appropriate mass ratio R2 of Ta and Re can better optimize the high-temperature performance and tissue stability of the superalloy and help improve the casting performance of the alloy.

[0056] In some embodiments, the nickel-based single crystal superalloy further contains impurity elements, and the impurity elements include O, N, and S. The total mass content of the impurity elements is ≤ 15 ppm, such as 1 ppm, 2 ppm, 3 ppm, 4 ppm, 5 ppm, 6 ppm, 7 ppm, 8 ppm, 10 ppm, 12 ppm, 15 ppm, etc. Among them, O ≤ 6 ppm (0.2 ppm, 0.5 ppm, 1 ppm, 5 ppm, etc.), N ≤ 6 ppm (for example, 0.5 ppm, 1 ppm, 2 ppm, 3 ppm, 4 ppm, 6 ppm), and S ≤ 4 ppm (for example, 0.5 ppm, 1 ppm, 2 ppm, 3 ppm, 4 ppm, etc.). The content of impurity elements in the nickel-based single crystal superalloy of the present invention is relatively low, which is beneficial to ensuring the excellent high-temperature performance of the alloy.

[0057] In some embodiments, the size of the γ' phase of the nickel-based single crystal superalloy is 0.35 - 0.6 μm, such as 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, or 0.6 μm, etc. By controlling the size range of the γ' phase of the nickel-based single crystal superalloy, the high-temperature performance of the alloy is ensured, and the performance potential of the alloy is maximally explored.

[0058] In some embodiments, the volume fraction of the γ' phase of the nickel-based single crystal superalloy is 65% - 72%, such as 65%, 67%, 70%, 71%, 72%, etc. The nickel-based single crystal superalloy having an appropriate volume fraction of the γ' phase is beneficial to improving its high-temperature mechanical properties and stability.

[0059] In some embodiments, the tensile properties of the nickel-based single crystal superalloy under the condition of 1120 °C satisfy: σ b≥463MPa (e.g., 463MPa, 470MPa, 500MPa, 550MPa, etc.). σ 0.2 ≥415MPa (e.g., 415MPa, 430MPa, 450MPa, 460MPa, etc.).

[0060] In some embodiments, the nickel-based single-crystal superalloy has a creep life of >100h under conditions of 1150℃ and 110MPa, such as 101h, 105h, 150h, 160h, 200h, 225h, 250h, etc.

[0061] In some embodiments, the nickel-based single-crystal superalloy has a creep life of >90h (e.g., 150h, 180h, 200h, etc.) under conditions of 1200°C and 80MPa.

[0062] According to another aspect of the present invention, the present invention also relates to a method for preparing the nickel-based single-crystal superalloy as described above, comprising the following steps: (a) According to the stoichiometric ratio of the chemical composition of the nickel-based single crystal superalloy, Ni is added to the crucible in the vacuum induction device to cover the inner bottom surface of the crucible, then a desulfurizing agent is added, and then Cr, Mo, W, Re, Co and Ta are added; (b) Vacuum the vacuum induction device, and then perform preliminary melting on the raw materials in step (a) until all the materials are melted; after heating, perform refining to obtain a refined system; (c) Cool the refining system, then add Al, Ti, deoxidized carbon and Hf and stir to obtain an alloy liquid; (d) The alloy liquid is cooled and then prepared into master alloy rods.

[0063] (e) The master alloy rod is prepared into a single crystal test rod with a crystal orientation of

[001] by means of a spiral crystal selection method; (f) The single crystal test rod is subjected to multi-stage heat treatment to obtain a nickel-based single crystal high-temperature alloy.

[0064] The method for preparing the nickel-based single-crystal superalloy of the present invention, through the above-mentioned appropriate feeding sequence, involves mixing and melting alloying elements according to the stoichiometric ratio of the alloy to ensure uniform composition and reduce impurities. The single-crystal alloy is generated by a spiral crystallization method, and further subjected to multi-stage heat treatment to ensure reduced elemental segregation, elimination of harmful eutectic phases in the alloy, and to ensure that the strengthening phase γ' of the alloy exhibits a regularly arranged square structure and appropriate size. Through the coordination of each step, the resulting nickel-based single-crystal superalloy possesses excellent high-temperature performance and long-term stability.

[0065] In some implementations, the raw material Ni is Ni plate or Ni bead.

[0066] In some embodiments, the desulfurizing agent is used to control the sulfur content of the master alloy bar to be no more than 4 ppm; the desulfurizing agent comprises CaO and CaF, wherein the mass ratio of CaO to CaF is 1:(0.3~0.5), for example, 1:0.3, 1:0.4, or 1:0.5. The mass of the desulfurizing agent is 0.1%~0.3% of the mass of the master alloy, for example, 0.1%, 0.15%, 0.2%, 0.3%, etc. By using a suitable proportion of desulfurizing agent, the sulfide content can be better reduced, and the high-temperature performance of the alloy can be improved.

[0067] In some embodiments, the vacuuming process is performed to a vacuum level ≤5Pa, such as 1Pa, 2Pa, 3Pa, 4Pa, or 5Pa.

[0068] In some embodiments, the temperature of the preliminary melting treatment is 1420~1480°C, for example 1420°C, 1430°C, 1450°C, 1460°C, or 1480°C. The material is completely melted by applying electricity.

[0069] In some embodiments, the refining temperature is 1500~1560℃, such as 1500℃, 1520℃, 1550℃, 1560℃, etc. The refining time is 40~70min, such as 40min, 50min, 60min, or 70min, etc. Suitable refining conditions can ensure the refining effect.

[0070] In some embodiments, the cooling is reduced to a film-forming state, with the temperature reduced to 1440~1500℃, for example, 1440℃, 1450℃, 1460℃, 1470℃, or 1500℃. By appropriately cooling the temperature and then adding other raw materials, the deoxidation effect of the deoxidized carbon is ensured, thereby improving the alloy's performance.

[0071] In some embodiments, the deoxidized carbon accounts for 0.01% to 0.04% of the mass of the master alloy, for example, 0.01%, 0.02%, 0.03%, 0.04%, etc. An appropriate proportion of deoxidized carbon is beneficial for improving the treatment effect and enhancing the alloy's properties. In some embodiments, the stirring time is 8 to 15 minutes, such as 8 minutes, 9 minutes, 10 minutes, 12 minutes, or 15 minutes. Appropriate stirring ensures that all materials are thoroughly mixed.

[0072] In some implementations, in step (c), Al, Ti, deoxidized carbon, and Hf are added sequentially.

[0073] In some embodiments, in step (d), the temperature is cooled to 1420~1480°C, for example, 1420°C, 1450°C, 1455°C, 1460°C, 1480°C, etc. After the cooling treatment, the material is placed into a steel ingot mold to obtain a master alloy bar.

[0074] In some embodiments, the preparation of the single crystal test rod specifically includes: loading the master alloy rod into the crucible of the directional solidification furnace, and simultaneously loading the single crystal test rod mold shell into the heating induction coil of the directional solidification furnace mold shell, and preparing the single crystal test rod with crystal orientation

[001] by the spiral crystal selection method.

[0075] In some embodiments, in step (e), the pouring temperature of the single crystal test rod preparation process is 1520~1560℃, for example 1520℃, 1530℃, 1540℃, 1550℃, 1560℃, etc., the mold temperature is 1520~1560℃, for example 1520℃, 1530℃, 1540℃, 1550℃, 1560℃, etc., and the single crystal pulling rate is 2~4mm / min, for example 2mm / min, 2.5mm / min, 3mm / min or 4mm / min, etc.

[0076] In some embodiments, the spacing of the primary dendrite arms of the single-crystal alloy matrix is ​​controlled to be no greater than 400 μm, for example, 250 μm, 300 μm, 300 μm, 390 μm, etc. By controlling the appropriate spacing of the primary dendrite arms of the single-crystal alloy matrix, microsegregation is reduced and the heat treatment effect is improved.

[0077] In some embodiments, the axial deviation of the single-crystal test bar from the

[001] direction is no more than 10°. This range is beneficial for ensuring the excellent mechanical properties of the single-crystal alloy.

[0078] In some embodiments, the multi-stage heat treatment includes a first heat treatment, a second heat treatment, and a third heat treatment performed sequentially; the first heat treatment includes five stages of isothermal treatment with progressively increasing temperatures; wherein, the first isothermal treatment is performed at a temperature of 1300℃~1305℃ for 3~4 hours, followed by air cooling to room temperature; the second isothermal treatment is performed at a temperature of 1310℃~1313℃ for 2~3 hours, followed by air cooling to room temperature; the third isothermal treatment is performed at a temperature of 1315℃~1318℃ for 2~3 hours, followed by air cooling to room temperature; the fourth isothermal treatment is performed at a temperature of 1322℃~1325℃ for 5~7 hours, followed by air cooling to room temperature; and the fifth isothermal treatment is performed at a temperature of 1330℃~1335℃ for 6~8 hours, followed by air cooling to room temperature. The second heat treatment includes a sixth and a seventh isothermal treatment with decreasing temperatures. The sixth isothermal treatment is performed at 1322℃~1325℃ for 5~7 hours, followed by air cooling to room temperature. The seventh isothermal treatment is performed at 1160℃~1165℃ for 6~8 hours, followed by air cooling to room temperature. The third heat treatment is performed at 870℃~900℃ (e.g., 870℃, 880℃, 890℃, 900℃, etc.), for 20~24 hours (e.g., 20 hours, 21 hours, 22 hours, or 24 hours, etc.), followed by air cooling to room temperature. This invention, through the above-mentioned suitable multi-stage heat treatment, achieves the dissolution, precipitation, and size optimization of the γ' phase, thereby improving the high-temperature performance and microstructure durability of the alloy.

[0079] In some embodiments, the nickel-based single-crystal superalloy of the present invention exhibits a creep rupture life greater than 200 hours at 1100℃ / 137MPa, greater than 140 hours at 1120℃ / 135MPa, and greater than 150 hours at 1150℃ / 110MPa. It possesses excellent long-term microstructural stability, with a TCP precipitation tendency far lower than that of the third-generation single-crystal superalloy CMSX-10, and even lower than that of the second-generation single-crystal superalloy CMSX-4. No TCP phase precipitation was observed after 3000 hours of long-term operation at 913℃ / 248MPa.

[0080] According to another aspect of the present invention, the present invention relates to the application of nickel-based single-crystal superalloys as described above in spacecraft.

[0081] The nickel-based single-crystal superalloy of the present invention has a temperature resistance of up to 1120℃ and can be applied in aviation and spacecraft, such as engine turbine blades, which can effectively improve their operating temperature and meet the requirements of high-performance engine development. At the same time, the alloy has the characteristics of low cost and high stability, which can increase the feasibility of the alloy in practical applications.

[0082] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.

[0083] Example 1 A nickel-based single-crystal superalloy comprising the following chemical composition by weight percentage: Cr 3.2%, Mo 0.5%, W 5.3%, Al 5.6%, Ti 0.75%, Re 4.3%, Co 9.4%, Ta 7.8%, Hf 0.08%, balance Ni.

[0084] A method for preparing nickel-based single-crystal superalloys includes the following steps: (1) First, the raw materials of different elements are weighed according to the chemical composition stoichiometry of nickel-based single crystal high-temperature alloy. Then, a Ni plate is laid at the bottom of the crucible in the vacuum induction furnace to cover the inner bottom of the crucible. A desulfurizing agent, consisting of CaO and CaF2 in a mass ratio of 1:0.4, is added, with the amount of desulfurizing agent being 0.2% of the weight of the master alloy. Raw materials Cr, Mo, W, Re, Co, and Ta are then added. The furnace is evacuated to a vacuum degree of 4.5 Pa, and electroplating of steel begins (initial melting at 1465℃). After all the steel has melted, the temperature is raised to 1545℃ for refining for 55 minutes. After refining, the temperature is lowered to a film-forming state (1480℃), and Al, Ti, deoxidized carbon, and Hf are added and stirred. The mass percentage of deoxidized carbon in the master alloy is 0.02%, and the stirring time is 10 minutes to obtain an alloy liquid. Finally, the alloy liquid is cooled to 1465℃ and poured into a steel ingot mold to obtain a single-crystal high-temperature alloy master alloy rod. The S content of the master alloy rod is no more than 4 ppm.

[0085] (2) The above-mentioned master alloy rod is placed into the crucible of the directional solidification furnace, and the single crystal test rod mold is placed into the heating induction coil of the directional solidification furnace mold. The single crystal test rod with crystal orientation

[001] is prepared by spiral crystal selection method. The pouring temperature of the single crystal test rod preparation process is 1548℃, the mold temperature is 1548℃, and the single crystal pulling rate is 3mm / min. The spacing of the primary dendrite arms of the single crystal alloy matrix is ​​controlled to be 250~400μm, and the axial deviation of the single crystal test rod from the

[001] direction is not greater than 5°.

[0086] (3) The single crystal alloy matrix is ​​subjected to heat treatment, which includes: first isothermal treatment: temperature is 1301℃, holding time is 3.5h, and air cooling to room temperature; second isothermal treatment: temperature is 1312℃, holding time is 2.5h, and air cooling to room temperature; third isothermal treatment: temperature is 1316℃, holding time is 2.5h, and air cooling to room temperature; fourth heat treatment: temperature is 1324℃, holding time is 6h, and air cooling to room temperature; fifth isothermal treatment: temperature is 1332℃, holding time is 6h, and air cooling to room temperature; sixth isothermal treatment: temperature is 1323℃, holding time is 6h, and air cooling to room temperature; seventh isothermal treatment: temperature is 1163℃, holding time is 7h, and air cooling to room temperature; eighth isothermal treatment: temperature is 870℃, holding time is 22h, and air cooling to room temperature.

[0087] Example 2 A nickel-based single-crystal superalloy comprising the following chemical composition by weight percentage: Cr 3.57%, Mo 0.62%, W 6.07%, Al 5.75%, Ti 0.87%, Re 4.71%, Co 9.95%, Ta 7.93%, Hf 0.11%, balance Ni.

[0088] The preparation method of the nickel-based single-crystal superalloy in this embodiment is the same as that in Example 1, except that each element adopts the stoichiometric ratio described in this embodiment.

[0089] Example 3 A nickel-based single-crystal superalloy comprising the following chemical composition by weight percentage: Cr 3.55%, Mo 0.6%, W 5.5%, Al 5.75%, Ti 0.87%, Re 4.6%, Co 9.6%, Ta 8.15%, Hf 0.11%, balance Ni.

[0090] The preparation method of the nickel-based single-crystal superalloy in this embodiment is the same as that in Example 1, except that each element adopts the stoichiometric ratio described in this embodiment.

[0091] Example 4 A nickel-based single-crystal superalloy comprising the following chemical composition by weight percentage: Cr 3.9%, Mo 0.7%, W 6.5%, Al 5.8%, Ti 0.9%, Re 4.6%, Co 10.5%, Ta 8.5%, Hf 0.15%, balance Ni.

[0092] The preparation method of the nickel-based single-crystal superalloy in this embodiment is the same as that in Example 1, except that each element adopts the stoichiometric ratio described in this embodiment.

[0093] Example 5 A nickel-based single-crystal superalloy comprising the following chemical composition by weight percentage: Cr 3%, Mo 0.8%, W 6.5%, Al 5.8%, Ti 0.9%, Re 5%, Co 11%, Ta 7.5%, Hf 0.15%, balance Ni.

[0094] The preparation method of the nickel-based single-crystal superalloy in this embodiment is the same as that in Example 2, except that each element adopts the stoichiometric ratio described in this embodiment.

[0095] Example 6 The preparation method of the nickel-based single-crystal superalloy in this embodiment differs from that in Example 2 in that: The first constant temperature treatment was conducted at 1305℃ for 3 hours, followed by air cooling to room temperature. The second constant temperature treatment was conducted at 1313℃ for 2 hours, followed by air cooling to room temperature. The third constant temperature treatment was conducted at 1318℃ for 2 hours, followed by air cooling to room temperature. The fourth constant temperature treatment was conducted at 1325℃ for 5 hours, followed by air cooling to room temperature. The fifth constant temperature treatment was conducted at 1335℃ for 5 hours, followed by air cooling to room temperature. The sixth constant temperature treatment was conducted at 1325℃ for 5 hours, followed by air cooling to room temperature. The seventh constant temperature treatment was conducted at 1165℃ for 6 hours, followed by air cooling to room temperature. The eighth constant temperature treatment was conducted at 900℃ for 20 hours, followed by air cooling to room temperature.

[0096] Comparative Example 1 The third-generation single-crystal alloy CMSX-10 has the following chemical composition by mass percentage: Cr 2%, Mo 0.4%, W 5%, Al 5.75%, Ti 0.2%, Re 6%, Co 3%, Ta 8%, Hf 0.03%, Nb 0.1%, balance Ni.

[0097] Comparative Example 2 A nickel-based single-crystal superalloy, differing from Example 2 in that: Cr 2.8%, Mo 0.85%, W 7%, Al 5.75%, Ti 0.87%, Re 5.5%, Co 11.5%, Ta 7%, Hf 0.18%, balance Ni.

[0098] The preparation method of the nickel-based single-crystal superalloy in this embodiment is the same as that in Example 1, except that each element adopts the stoichiometric ratio described in this embodiment.

[0099] Comparative Example 3 The preparation method of the nickel-based single-crystal superalloy in this comparative example differs from that in Example 2 in that: The heat treatment includes a primary heat treatment and a secondary heat treatment. The primary heat treatment is performed at 1320℃ for 30 hours, followed by air cooling to room temperature. The secondary heat treatment is performed at 860℃ for 25 hours.

[0100] Experimental Example 1. Volume and size of the γ' phase in nickel-based single-crystal superalloys The volume and size of the γ' phase in the nickel-based single-crystal superalloys of each embodiment and comparative example were tested using metallographic quantitative analysis. The test results are shown in Table 1.

[0101] Table 1. Volume and size of the γ' phase in nickel-based single-crystal superalloys

[0102] 2. Tensile property test The nickel-based single-crystal superalloy of Example 2 was subjected to tensile property tests at different temperatures. The test methods were GB / T228.1 and GB / T228.2. The test results are shown in Table 1. The as-cast microstructure of the nickel-based single-crystal superalloy of Example 2 is as follows: Figure 1 As shown; the low-magnification microstructure of the nickel-based single-crystal superalloy after heat treatment in Example 2 is shown below. Figure 2 As shown; the microstructure of the nickel-based single-crystal superalloy of Example 2 after heat treatment, magnified 1000 times, is shown below. Figure 3 As shown; the microstructure of the nickel-based single-crystal superalloy of Example 2 after heat treatment, magnified 5000 times, is shown below. Figure 4 As shown; the microstructure of the nickel-based single-crystal superalloy of Example 2 after being subjected to a long-term high-temperature load of 3000 hours at 913℃ and 248MPa is magnified 2000 times as follows. Figure 5 As shown; the microstructure of the nickel-based single-crystal superalloy of Example 2 after being subjected to a long-term high-temperature load of 3000 hours at 913℃ and 248MPa is magnified 10000 times. Figure 6 As shown.

[0103] Table 1. Tensile properties of the nickel-based single-crystal superalloy of Example 2 at different temperatures.

[0104] The tensile properties of alloys from other embodiments and comparative examples were tested at 1120°C, and the test results are shown in Figure 2.

[0105] Table 2 shows the tensile properties of the alloys in the examples and comparative examples at 1120°C.

[0106] 3. Durability Testing The nickel-based single-crystal superalloy of Example 2 was subjected to a durability test using the GB / T2039 standard. The test results are shown in Table 3.

[0107] Table 3. Durability test results of the nickel-based single-crystal superalloy in Example 2

[0108] The alloys of other embodiments and comparative examples were subjected to durability tests at 1150°C and 110MPa, and the test results are shown in Table 4.

[0109] Table 4. Durability of alloys from various examples and comparative examples at 1150°C and 110 MPa.

[0110] As can be seen from the above, the nickel-based superalloys obtained by the methods in the various embodiments of the present invention have excellent high-temperature tensile properties and creep resistance.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A nickel-based single crystal superalloy, characterized in that, Chemical composition comprising the following mass percentages: Cr 3%~4%, Mo 0.5%~0.8%, W 5%~6.5%, Al 5%~6%, Ti 0.7%~1%, Re 4%~5%, Co 9%~11%, Ta 7.5%~9%, Hf 0.078%~0.15%, balance Ni.

2. The nickel-based single crystal superalloy of claim 1, wherein, Chemical composition comprising the following mass percentages: Cr 3.2%~3.9%, Mo 0.5%~0.7%, W 5.3%~6.5%, Al 5.6%~5.8%, Ti 0.75%~0.9%, Re 4.3%~4.9%, Co 9.4%~10.5%, Ta 7.8%~8.5%, Hf 0.08%~0.15%, balance Ni.

3. The nickel-base, single-crystal superalloy of claim 1, wherein, At least one of the following features (1) to (4) is included: (1) the total mass percentage X1 of Mo, W and Re satisfies: 9.5%≤X1≤11.8%; (2) the total mass percentage X2 of Al, Ti and Ta satisfies: 13.5%<X2<15.5%; (3) the mass ratio R1 of Cr and Co satisfies: 0.3≤R1≤0.4; (4) the mass ratio R2 of Ta and Re satisfies: 1.5<R2<1.

8.

4. The nickel-based single crystal superalloy of claim 1, wherein, The nickel-based single crystal superalloy further comprises impurity elements, the impurity elements comprise O, N and S, and the total mass content of the impurity elements is ≤15ppm; wherein, O≤6ppm, N≤6ppm, and S≤4ppm.

5. The nickel-based single crystal superalloy of claim 1, wherein: At least one of the following features (1) to (2) is included: (1) the γ' phase size of the nickel-based single crystal superalloy is 0.35~0.6μm; (2) the γ' phase volume fraction of the nickel-based single crystal superalloy is 65%~72%.

6. The nickel-based single crystal superalloy of claim 1, wherein, At least one of the following features (1) to (2) is included: (1) the tensile properties of the nickel-based single crystal superalloy at 1120°C satisfy: σ b ≥ 463 MPa, σ 0.2 ≥ 415 MPa; (2) the nickel-based single crystal superalloy has a stress-rupture life >100h at 1150℃, 110MPa.

7. The method of producing a nickel-based single crystal superalloy according to any one of claims 1 to 6, wherein The method comprises the following steps: (a) according to the chemical composition of the nickel-based single crystal superalloy, Ni is added to the crucible in the vacuum induction device to cover the inner bottom surface of the crucible, then a desulfurizing agent is added, and then Cr, Mo, W, Re, Co and Ta are added; (b) the vacuum induction device is subjected to vacuumizing treatment, and the raw materials in step (a) are subjected to preliminary melting treatment until the materials are completely melted; after warming, refining treatment is performed to obtain a refining system; (c) the refining system is subjected to cooling, Al, Ti, deoxidized carbon and Hf are added and subjected to stirring treatment to obtain an alloy liquid; (d) the alloy liquid is subjected to cooling treatment, and then a master alloy rod is prepared; (e) the master alloy rod is prepared into a single crystal test rod with a crystal orientation of [001] by a spiral crystal selection method; (f) the single crystal test rod is subjected to multi-stage heat treatment to obtain a nickel-based single crystal superalloy.

8. The method of producing a nickel-based single crystal superalloy according to claim 7, characterized in that, At least one of the following features (1) to (11) is included: (1) the desulfurizer is used to control the S content of the master alloy rod to be not more than 4 ppm; the desulfurizer comprises CaO and CaF, and the mass ratio of the CaO and CaF is 1:(0.3-0.5); the mass of the desulfurizer is 0.1%-0.3% of the mass of the master alloy; (2) the vacuum treatment is performed until the vacuum degree is less than or equal to 5 Pa; (3) the temperature of the preliminary melting treatment is 1420-1480℃; (4) the temperature of the refining is 1500-1560℃, and the time of the refining is 40-70 min; (5) in step (c), the temperature is decreased to the temperature of the solidification, which is 1440-1500℃; (6) the mass of the deoxidized carbon accounts for 0.01-0.04% of the mass of the master alloy; (7) the time of the stirring treatment is 8-15 min; (8) in step (d), the temperature is decreased to 1420-1480℃; (9) in step (e), the pouring temperature of the single crystal test rod preparation process is 1520-1560℃, the mold temperature is 1520-1560℃, and the single crystal pulling rate is 2-4 mm / min; (10) the primary dendrite arm spacing of the single crystal test rod is controlled to be not more than 400 μm; (11) the axial deviation of the single crystal test rod from the [001] direction is not more than 10°.

9. The method of producing a nickel-based single crystal superalloy according to claim 7, wherein The multi-stage heat treatment comprises a first heat treatment, a second heat treatment and a third heat treatment performed in sequence; The first heat treatment comprises five constant temperature treatments with the temperature increasing in sequence; the temperature of the first constant temperature treatment is 1300-1305℃, the holding time is 3-4 h, and the temperature is air-cooled to room temperature; the temperature of the second constant temperature treatment is 1310-1313℃, the holding time is 2-3 h, and the temperature is air-cooled to room temperature; the temperature of the third constant temperature treatment is 1315-1318℃, the holding time is 2-3 h, and the temperature is air-cooled to room temperature; the temperature of the fourth constant temperature treatment is 1322-1325℃, the holding time is 5-7 h, and the temperature is air-cooled to room temperature; the temperature of the fifth constant temperature treatment is 1330-1335℃, the holding time is 6-8 h, and the temperature is air-cooled to room temperature; The second heat treatment comprises a sixth constant temperature treatment and a seventh constant temperature treatment with the temperature decreasing in sequence; the temperature of the sixth constant temperature treatment is 1322-1325℃, the holding time is 5-7 h, and the temperature is air-cooled to room temperature; the temperature of the seventh constant temperature treatment is 1160-1165℃, the holding time is 6-8 h, and the temperature is air-cooled to room temperature; The temperature of the third heat treatment is 870-900℃, the holding time is 20-24 h, and the temperature is air-cooled to room temperature.

10. Use of the nickel-based single crystal superalloy according to any one of claims 1-6 in an aircraft or spacecraft.

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