A method for designing a nickel-based directionally solidified superalloy composition and a nickel-based directionally solidified superalloy

Abstract

This invention relates to the field of nickel-based superalloy technology, and provides a method for designing the composition of a nickel-based directionally solidified superalloy and a nickel-based directionally solidified superalloy. The design method includes the following steps: S1, initially determining the element types and content ranges of the nickel-based directionally solidified superalloy; S2, based on the element types and content ranges, constructing an oxidation index model, a creep rupture performance model, and a casting performance model, using the content of key elements as variables; S3, using the oxidation index model, creep rupture performance model, and casting performance model to calculate the data of the key element content ranges, and by setting the boundary conditions of the above models, selecting the content ranges that meet the requirements, thus obtaining the composition range of the nickel-based directionally solidified superalloy. The nickel-based directionally solidified superalloy provided by this application has the advantages of both high-temperature creep rupture performance and low cost.

Description

Technical Field

[0001] This invention relates to the field of nickel-based superalloy technology, and in particular to a method for designing the composition of a nickel-based directionally solidified superalloy and a nickel-based directionally solidified superalloy. Background Technology

[0002] Nickel-based superalloys, with their excellent high-temperature strength, superior durability, and good oxidation and corrosion resistance, have become indispensable key structural materials in modern industry, especially in the manufacture of core components for extreme service environments such as aerospace and ground-based gas turbines. Among these, gas turbine blades, as the core power components of gas turbines, operate under harsh conditions of high temperature, high pressure, high speed, and complex media corrosion, placing extremely high demands on the high-temperature mechanical properties and structural stability of the materials.

[0003] Directional solidification technology, as a key preparation process for improving the performance of nickel-based superalloys, can transform the alloy microstructure from traditional equiaxed crystals to directional columnar or single-crystal structures arranged along the direction of stress. This effectively eliminates the adverse effects of grain boundaries on high-temperature performance, significantly improves the high-temperature creep strength, creep resistance, and thermal fatigue life of turbine blades, and provides an important guarantee for the efficient and stable operation of gas turbines.

[0004] As ground-based gas turbines evolve towards higher efficiency and longer lifespan, the market demand for high-performance nickel-based directionally solidified superalloys is becoming increasingly urgent, especially for alloy materials that combine excellent high-temperature mechanical properties with cost-effectiveness. Currently, commercial ground-based gas turbines primarily use first-generation directionally solidified superalloys, with typical examples including DZ38G, DSGTD-111, and DSMarM-247. To ensure good resistance to hot corrosion, these alloys are typically designed to contain a high content of Cr, with the total mass fraction of W and Mo generally controlled below 8%, while the total mass fraction of elements such as Al, Ti, Ta, Nb, and Hf is usually in the range of 11% to 13%. However, these traditional first-generation directionally solidified alloys generally suffer from the technical bottleneck of balancing high-temperature strength and cost.

[0005] Therefore, developing novel nickel-based directionally solidified superalloys that combine excellent high-temperature performance with cost advantages has become an important research direction and urgent need in this field. Summary of the Invention

[0006] The technical problem solved by this invention is to provide a method for designing the composition of nickel-based directionally solidified superalloys, which exhibit excellent high-temperature stability.

[0007] In view of this, this application provides a method for designing the composition of nickel-based directionally solidified superalloys, comprising the following steps:

[0008] S1. Preliminarily determine the types and content ranges of elements in nickel-based directionally solidified superalloys, and screen out the content of elements that form harmful phases through thermodynamic calculations;

[0009] S2. Based on the types and content ranges of the elements, and using the contents of Cr, Co, Mo, W, Al, Ti, Ta and Nb as variables, construct an oxidation index model, a creep rupture model and a casting performance model;

[0010] S3. Calculate the content ranges of Cr, Co, Mo, W, Al, Ti, Ta, and Nb using the oxidation index model, creep rupture model, and casting performance model. By setting the boundary conditions of the above models, select the content ranges that meet the requirements to obtain the composition range of the nickel-based directional solidification superalloy.

[0011] The expression for the oxidation index model is as follows:

[0012] M-oxidation=Σk i *W i ;

[0013] Where, k i A constant W is obtained by fitting the elements. i The mass fraction of each element;

[0014] The expression for the persistent performance model is as follows:

[0015] M-creep=a*(lg(Σx i / D i )) b +c*((W γ′ *(1-W γ′ )*( -1)) d ;

[0016] Among them, D i Let x be the diffusion coefficient of each element. i W represents the atomic fraction of each element within the γ phase. γ′ Let γ′ be the mass fraction, a = 48907, b = 0.008, c = -49789, d = -0.0003;

[0017] The expression for the casting performance model is as follows:

[0018] M-castability=(η*Δρ*ΔT) -1 ;

[0019] Where η is the liquid phase kinetic viscosity coefficient, Δρ is the characteristic height density difference of the paste region, and ΔT is the solid-liquid phase temperature difference.

[0020] In some specific embodiments, in step S1, the basis for initially determining the element types and content ranges of the nickel-based directionally solidified superalloy is: the strengthening mechanism of the nickel-based directionally solidified superalloy and the oxidation resistance and corrosion resistance characteristics that the nickel-based directionally solidified superalloy should possess.

[0021] In some specific embodiments, the element types in step S1 include: Cr, Co, Mo, W, Ta, Al, Ti, Nb, C, B, Zr, Hf, and Ni.

[0022] In some specific embodiments, in step S2, the K of element C in the oxidation index model i The K value of Cr is 0.375. i The K of Ni element is -0.100. i The K of Co is 0.075. i The K of element W is 0.149. i The K of the element Mo is 0.069. i The K of Al element is 0.140. i The K of the Ti element is -0.982. i The K of element Ta is 0.024. i The K value of Fe is -0.037. i The K value of element B is 0.637. i The K of the Hf element is -4.104. i The K of the Nb element is 0.235. i The K of the Zr element is -0.035. i It is -4.367.

[0023] In some specific embodiments, in step S3, the boundary condition is M-oxidation < 1 mg / cm³. 2 , M-creep>209MPa, M-castability>2.4.

[0024] This application also provides a nickel-based directionally solidified superalloy, the composition of which is designed by the design method described above; by mass percentage, it comprises:

[0025] Cr 12.0~13.0%, Co 3.0~8.0%, Mo 0.4~1.6%, W 6.2~8.0%, Ta 3.5~6.0%, Al 3.5~4.5%, Ti 1.5~2.7%, Nb 0~1.0%, C 0.03~0.3%, B 0.005~0.05%, Zr 0.001~0.05%, Hf≤0.02%, the remainder being Ni.

[0026] In some specific embodiments, the Cr content is 12.3~12.7%, and / or the Co content is 3.3~7.0%, and / or the Mo content is 0.8~1.0%, and / or the W content is 6.8~7.2%.

[0027] In some specific embodiments, the content of Ta is 3.9-5.0%, and / or the content of Al is 3.8-4.2%, and / or the content of Ti is 2.0-2.6%, and / or the content of Nb is 0.1-0.3%, and / or the content of C is 0.04-0.07%, and / or the content of B is 0.017-0.03%, and / or the content of Zr is 0.005-0.02%, and / or the content of Hf is 0.01%.

[0028] In some specific embodiments, the method for preparing the high-temperature alloy includes the following steps:

[0029] After the high-temperature alloy is batched according to the proportion, it is smelted and the resulting master alloy is directionally solidified and remelted to obtain a directionally solidified alloy.

[0030] The directional solidified alloy is subjected to hot isostatic pressing and then heat treatment.

[0031] In some specific embodiments, the directional solidification and remelting temperature is 1000~2000℃, and the pulling speed is 1~5mm / min; and / or, the hot isostatic pressing temperature is 1000~1500℃, the pressure is 1200~1800 atmospheres, and the time is 1~5h; and / or, the heat treatment specifically includes:

[0032] Under a vacuum atmosphere, the temperature is held at 1100~1300℃ for 1~3 hours and then quenched with argon gas. After that, the temperature is held at 950~1080℃ for 4~8 hours and then quenched with argon gas. Finally, the temperature is held at 850~900℃ for 7~10 hours and then quenched with argon gas.

[0033] This application provides a method for designing the composition of a nickel-based directionally solidified superalloy. First, the types and content ranges of elements in the nickel-based directionally solidified superalloy are preliminarily determined. Then, based on these element types and content ranges, the contents of Cr, Co, Mo, W, Al, Ti, Ta, and Nb, which have a significant impact on the performance of the nickel-based directionally solidified superalloy, are used as variables to construct an oxidation index model, a creep rupture performance model, and a casting performance model. Finally, the data corresponding to the models for the aforementioned alloying elements are calculated using these models. By setting the boundary conditions of the models, the required content range is selected, ultimately yielding the composition content of the nickel-based directionally solidified superalloy. Because the above design method introduces an oxidation index model and a strength creep rupture performance model that integrates solid solution strengthening and precipitation strengthening, the designed nickel-based directionally solidified superalloy exhibits excellent high-temperature creep rupture performance.

[0034] This application also provides a nickel-based directionally solidified superalloy, which, by designing the contents of Cr, Co, Mo, W, Al, Ti, Ta and Nb, exhibits excellent high-temperature creep resistance. Attached Figure Description

[0035] Figure 1 Comparison of data from the original creep strength model and the creep strength model of this application for nickel-based directionally solidified superalloys;

[0036] Figure 2 Microscopic images of the microstructure of the nickel-based directionally solidified superalloy prepared in Example 2 of this invention;

[0037] Figure 3 The Larson-Miller performance comparison chart of the nickel-based directionally solidified superalloy prepared in Example 2 of the present invention with nickel-based directionally solidified superalloys DZ38G, DS GTD111, and DS MarM247 is shown.

[0038] Figure 4 The equilibrium phase composition diagram is shown for the nickel-based directionally solidified superalloy prepared in Example 2 of this invention.

[0039] Figure 5 These are microstructure images of the nickel-based directional solidification superalloy prepared in Example 2 of this invention after being exposed to heat at 900°C for 10,000 hours, under different magnifications.

[0040] Figure 6 The images show the morphology and rate diagram of the nickel-based directional solidification superalloy and DZ38G alloy prepared in Example 2 of this invention during corrosion at 700℃ / 100h. Detailed Implementation

[0041] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0042] In view of the dual requirements of high-temperature creep performance and cost in existing nickel-based directionally solidified superalloys, this application provides a method for designing the composition of nickel-based directionally solidified superalloys. This method introduces a model with low prediction error, enabling accurate design of the superalloy composition. This allows the designed superalloy to simultaneously possess both high-temperature creep performance and cost advantages. Specifically, this invention discloses a method for designing the composition of a nickel-based directionally solidified superalloy, comprising the following steps:

[0043] S1. Preliminarily determine the types and content ranges of elements in nickel-based directionally solidified superalloys, and screen out the content of elements that form harmful phases through thermodynamic calculations;

[0044] S2. Based on the types and content ranges of the elements, and using the contents of Cr, Co, Mo, W, Al, Ti, Ta and Nb as variables, construct an oxidation index model, a creep rupture model and a casting performance model;

[0045] S3. Calculate the content ranges of Cr, Co, Mo, W, Al, Ti, Ta, and Nb using the oxidation index model, creep rupture model, and casting performance model. By setting the boundary conditions of the above models, select the content ranges that meet the requirements to obtain the composition range of the nickel-based directional solidification superalloy.

[0046] The expression for the oxidation index model is as follows:

[0047] M-oxidation=Σk i *W i ;

[0048] Where, k i A constant W is obtained by fitting the elements. i The mass fraction of each element;

[0049] The expression for the persistent performance model is as follows:

[0050] M-creep=a*(lg(Σx i / D i )) b +c*((W γ′ *(1-W γ′ )*( -1)) d ;

[0051] Among them, D iLet x be the diffusion coefficient of each element. i W represents the atomic fraction of each element within the γ phase. γ′ Let γ′ be the mass fraction, a = 48907, b = 0.008, c = -49789, d = -0.0003;

[0052] The expression for the casting performance model is as follows:

[0053] M-castability=(η*Δρ*ΔT) -1 ;

[0054] Where η is the liquid phase kinetic viscosity coefficient, Δρ is the characteristic height density difference of the paste region, and ΔT is the solid-liquid phase temperature difference.

[0055] In the design method of nickel-based directionally solidified superalloy composition, step S1 first preliminarily determines the types and content ranges of elements in the nickel-based directionally solidified superalloy. Specifically, this determination is based on the strengthening mechanism of the nickel-based directionally solidified superalloy and the target alloy's required oxidation and corrosion resistance. That is, in this step, the metal elements to be added to the nickel-based directionally solidified superalloy and their content ranges are preliminarily determined through the strengthening mechanism of the nickel-based directionally solidified superalloy and the final properties of the target alloy. Then, thermodynamic calculations are used to screen out elements that form harmful phases. For nickel-based directionally solidified superalloys, harmful phases include TCP and η phases, etc. The thermodynamic calculations are performed at 750~1050℃, specifically 780~1000℃. At this temperature, the stable phase composition and harmful phases of the nickel-based directionally solidified superalloy can be obtained.

[0056] In step S2, based on the elemental types and content ranges of the aforementioned nickel-based directionally solidified superalloys, and using the contents of key elements Cr, Co, Mo, W, Al, Ti, Ta, and Nb as variables, an oxidation index model M-oxidation, a creep rupture model M-creep, and a casting performance model M-castability are constructed. The parameters involved in the oxidation index model M-oxidation are obtained through linear regression fitting analysis of oxidation data from over 20 sets of actual superalloys. This model is used to evaluate the oxidation resistance of the designed alloy composition, and its specific expression is as follows:

[0057] M-oxidation=Σk i *W i

[0058] Where, k i Constants were obtained by fitting each element, and their specific values ​​are shown in Table 1. i The mass fraction of each element;

[0059] Table 1. k values ​​of each element in the M-oxidation model of oxidation index. i Data table

[0060]

[0061] The M-creep model, which describes the creep performance, was derived by analyzing creep test data from over 10 sets of actual directionally solidified superalloys. It comprehensively considers both solid solution strengthening and precipitation strengthening effects of elements, and the specific expression is as follows:

[0062] M-creep=a*(lg(Σx i / D i )) b +c*((W γ′ *(1-W γ′ )*( -1)) d ;

[0063] Among them, D i Let x be the interdiffusion coefficient between each element and nickel. i W represents the atomic fraction of each element within the γ phase. γ′ Let γ′ be the mass fraction, a = 48907, b = 0.008, c = -49789, and d = -0.0003. The constant term of this model is obtained through fitting. Compared with the traditional general-purpose persistence intensity prediction model, the calculation model provided in this application significantly improves the prediction accuracy, such as... Figure 1 As shown.

[0064] The casting performance model M-castability comprehensively considers the solid-liquid phase density difference, solid-liquid phase temperature difference, and liquid phase viscosity, which have a significant impact on the solidification process. The specific expression of the calculation model is as follows:

[0065] M-castability=(η*Δρ*ΔT) -1 ;

[0066] Where η is the liquid phase kinetic viscosity coefficient, Δρ is the characteristic height density difference of the paste region, and ΔT is the solid-liquid phase temperature difference; η, Δρ, and ΔT are characteristic parameters related to elements, which can be calculated by thermodynamic software after determining the combination of element types.

[0067] After constructing the above model, in step S3, the oxidation index model, creep rupture performance model, and casting performance model are used to calculate the content ranges of Cr, Co, Mo, W, Al, Ti, Ta, and Nb. By setting the boundary conditions of the above models, the required content ranges are selected to obtain the composition range of the nickel-based directionally solidified superalloy. In the above process, the calculations are performed according to calculation methods well known to those skilled in the art. In a specific embodiment, the calculations are performed using Thermal Calc software, and the boundary condition is M-oxidation < 1 mg / cm³. 2 M-creep > 209 MPa, M-castability > 2.4; the boundary conditions determined above are conducive to ensuring the excellent thermal stability of nickel-based directionally solidified superalloys.

[0068] Based on this, this application provides a nickel-based directionally solidified superalloy, the composition of which is designed by the above-mentioned design method, and comprises, by mass percentage:

[0069] Cr 12.0~13.0%, Co 3.0~8.0%, Mo 0.4~1.6%, W 6.2~8.0%, Ta 3.5~6.0%, Al 3.5~4.5%, Ti 1.5~2.7%, Nb 0~0.5%, C 0.03~0.013%, B 0.005~0.05%, Zr 0.001~0.05%, Hf≤0.02%, the remainder being Ni.

[0070] Specifically, a nickel-based directionally solidified superalloy was designed based on the above method, its composition was analyzed, and the performance of the nickel-based directionally solidified superalloy was described in detail based on actual testing:

[0071] The Cr content is 11.0~12.0 wt%, specifically 11.3~11.7 wt%, more specifically 11.4~11.6 wt%; for example, the Cr content in this application can also be 11.1 wt%, 11.2 wt%, 11.5 wt%, 11.8 wt%, or 11.9 wt%. Cr is an element that imparts corrosion resistance to nickel-based superalloys. The higher its content, the more significant the corrosion resistance effect. However, if the content exceeds 12.0 wt%, it will increase the tendency for TCP phase precipitation, affecting the long-term microstructural stability of nickel-based directionally solidified superalloys.

[0072] The Co content is 3.0~8.0 wt%, specifically 3.3~7.0 wt%, more specifically 3.7~6.5 wt%, more specifically 4.0~6.0 wt%, more specifically 4.8~5.7 wt%, and more specifically 5.0~5.5 wt%. Co can improve the resistance of nickel-based directionally solidified superalloys to intergranular corrosion and increase high-temperature strength. When the Co content exceeds 8.0 wt%, it causes a change in the equilibrium of nickel-based directionally solidified superalloys, thereby precipitating other TCP phases.

[0073] The Mo content is 0.4~1.6 wt%, specifically 0.6~1.3 wt%, more specifically 0.8~1.0 wt%. The W content is 6.2~8.0 wt%, specifically 6.5~7.8 wt%, more specifically 6.8~7.2 wt%, more specifically 6.9~7.0 wt%. Both Mo and W are very important solid solution strengthening elements, which can significantly improve the high-temperature strength of nickel-based superalloys. Excessive addition will increase the tendency of the alloy to form the TCP phase. At the same time, the addition of W and Mo can easily trigger acidic melting reactions in saline environments such as Na2SO4 and NaCl, especially in alloys with high Mo content.

[0074] The content of Ta is 3.5~6.0 wt%, specifically, the content of Ta is 3.9~5.0 wt%, more specifically, the content of Ta is 4.0~4.8 wt%, more specifically, the content of Ta is 4.2~4.6 wt%. The content of Al is 3.5~4.5 wt%, specifically, the content of Al is 3.8~4.2 wt%, more specifically, the content of Al is 3.9~4.0 wt%. The content of Ti is 1.5~2.7 wt%, specifically, the content of Ti is 2.0~2.6 wt%, more specifically, the content of Ti is 2.1~2.4 wt%. The content of Nb is 0~0.5 wt%, specifically, the content of Nb is 0.1~0.3 wt%. Ta, Al, Ti, and Nb are the main γ′ forming elements in nickel-based superalloys. Al is beneficial to improving the alloy's oxidation resistance, while Ti can improve the alloy's resistance to hot corrosion. Ta can also be used as a solid solution strengthening element, which can effectively improve the high-temperature strength of superalloys. However, excessive addition of Ta, Al, Ti, and Nb will lead to the formation of harmful phases. At the same time, Ta is relatively expensive, and the amount added will significantly affect the cost of the alloy.

[0075] The content of C is 0.03~0.30 wt%, specifically, the content of C is 0.04~0.22 wt%, more specifically, the content of C is 0.07~0.18 wt%, more specifically, the content of C is 0.10~0.15 wt%, more specifically, the content of C is 0.12~0.14 wt%. The content of B is 0.005~0.05 wt%, specifically, the content of B is 0.008~0.04 wt%, more specifically, the content of B is 0.012~0.035 wt%, more specifically, the content of B is 0.017~0.03 wt%, more specifically, the content of B is 0.02~0.026 wt%. In this application, the addition of appropriate amounts of C and B can form fine and dispersed carbides and borides at the grain boundaries of nickel-based directionally solidified superalloys, thereby strengthening the grain boundaries.

[0076] The Zr content is 0.001~0.05wt%, specifically 0.002~0.04wt%, more specifically 0.005~0.02wt%, more specifically 0.008~0.016wt%, and more specifically 0.012~0.014wt%. The addition of Zr can improve the γ / γ′ mismatch of the alloy, suppress grain boundary sliding at higher temperatures, thereby improving the high-temperature strength and creep life of the alloy. It also prevents the occurrence of grain boundary cracks by changing the morphology of grain boundary carbides, and can also improve the plasticity of the alloy. Excessive addition of C, B, and Zr elements will degrade the properties.

[0077] The Hf content is ≤0.02wt%, specifically 0.01wt%. The addition of Hf can improve the high-temperature performance of nickel-based directionally solidified superalloys, but Hf is expensive.

[0078] In this application, the method for preparing the nickel-based directionally solidified superalloy includes the following steps:

[0079] After the high-temperature alloy is batched according to the proportion, it is smelted and the resulting master alloy is directionally solidified and remelted to obtain a directionally solidified alloy.

[0080] The directional solidified alloy is subjected to hot isostatic pressing and then heat treatment.

[0081] In the above preparation method, the raw materials for the high-temperature alloy are preferably Co, Cr, Ni, Mo, W, Al, Ti, Nb, Ta, Hf, C, and B with a purity of 5N or higher. The smelting is preferably carried out in a vacuum melting furnace. The directional solidification remelting is performed according to a smelting method well known to those skilled in the art, with a directional solidification remelting temperature of 1000~2000℃ and a pulling speed of 1~5 mm / min; specifically, the directional solidification remelting temperature is 1300~1700℃ and the pulling speed is 2~4 mm / min; more specifically, the directional solidification remelting temperature is 1550~1650℃ and the pulling speed is 2~3 mm / min.

[0082] After obtaining the directionally solidified alloy, it is subjected to hot isostatic pressing (HIP) under argon protection. The HIP temperature is 1000-1500℃, the pressure is 1200-1800 atmospheres, and the time is 1-5 hours. Specifically, the HIP temperature is 1100-1400℃, the pressure is 1300-1700 atmospheres, and the time is 1.5-4 hours. More specifically, the HIP temperature is 1170-1210℃, the pressure is 1400-1600 atmospheres, and the time is 1.5-2.5 hours.

[0083] According to the present invention, after hot isostatic pressing, the obtained sample is subjected to heat treatment, which is carried out under a vacuum atmosphere, and the heat treatment specifically includes:

[0084] Under a vacuum atmosphere, the temperature is held at 1100~1300℃ for 1~3 hours and then quenched with argon gas. After that, the temperature is held at 950~1080℃ for 4~8 hours and then quenched with argon gas. Finally, the temperature is held at 850~900℃ for 7~10 hours and then quenched with argon gas.

[0085] More specifically, the heat treatment is as follows: under a vacuum atmosphere, the temperature is held at 1230~1260℃ for 1.5~2.5h and then quenched with Ar gas; then under a vacuum atmosphere, the temperature is held at 1030~1060℃ for 4.5~6.5h and then quenched with Ar gas; then under a vacuum atmosphere, the temperature is held at 860~890℃ for 7.5~8.5h and then quenched with Ar gas.

[0086] This application provides a method for designing the composition of a nickel-based directionally solidified superalloy. This method utilizes three models to design the composition of the superalloy, achieving a good balance of Cr, W, Mo, Al, Ti, and Ta elements. This results in the alloy of this invention exhibiting superior high-temperature creep resistance compared to existing nickel-based superalloys. Compared to the typical high-strength nickel-based directionally solidified superalloy DS MarM247 used in gas turbines, the nickel-based directionally solidified superalloy provided by this invention achieves comparable high-temperature creep resistance while having lower raw material costs, resulting in significant economic benefits. Furthermore, the nickel-based directionally solidified superalloy provided by this invention exhibits good long-term microstructural stability at 850–900°C. The models introduced in the design method provided by this invention, especially the creep resistance model, have a prediction error of only 2.9%, compared to other models with prediction errors exceeding 20%.

[0087] To further understand the present invention, the design method for the composition of nickel-based directionally solidified superalloys and the nickel-based directionally solidified superalloys provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0088] Example 1

[0089] The composition design first determined the composition range shown in Table 2 based on the characteristics of the composition range of directionally solidified superalloys, and set the step size for each range to obtain 1,693,440 components. Thermodynamic calculations were then performed to determine the stable phase composition at 900℃ and 780℃, and components containing harmful phases such as TCP and η phases were removed. Next, the aforementioned M-oxidation, M-creep, and M-castability were calculated, and the boundary condition was set as M-oxidation < 1 mg / cm³. 2 With M-creep > 209 MPa and M-castability > 2.4, the components in Table 3 were obtained through screening. Further, the components obtained from Table 3 were subjected to more detailed calculations, and the iterative calculations shown in Table 4 were established.

[0090] Table 2. Calculation space of components in Example 1 (wt%)

[0091]

[0092] Table 3. Component ranges obtained from screening (wt%)

[0093]

[0094] Table 4. Detailed calculation of component space (wt%)

[0095]

[0096] Examples 2-4

[0097] The compositions of the nickel-based directionally solidified superalloys provided in Examples 2-4 are detailed in Table 5, and the chemical compositions of commercial alloys DZ38G, DSGTD111, and DS MarM247 are also listed. The specific preparation method of the nickel-based directionally solidified superalloys is as follows:

[0098] The master alloy was prepared by vacuum melting according to the composition ratio in Table 5, and then remelted in a directional solidification device. The mold heating temperature was 1600℃ and the pulling speed was 2mm / min to obtain a directional solidified columnar crystal sample. The prepared directional solidified columnar crystal sample was then subjected to hot isostatic pressing under argon atmosphere at a temperature of 1180℃ and a pressure of 1500 atmospheres for 2 hours. Subsequently, it was quenched under Ar gas in a vacuum atmosphere at a temperature of 1240℃ for 2 hours. Then, it was quenched under Ar gas in a vacuum atmosphere at a temperature of 1050℃ for 5 hours. Finally, it was quenched under Ar gas in a vacuum atmosphere at a temperature of 870℃ for 8 hours. After the above heat treatment, a nickel-based directional solidified high-temperature alloy was obtained.

[0099] Table 5. Composition (wt%) of the alloy of the present invention and the alloys DZ38G, DS GTD111, and DS MarM247.

[0100]

[0101] Microstructure photographs of the nickel-based directionally solidified superalloy prepared in Example 2 are shown below. Figure 2 As shown.

[0102] The Larson-Miller curves of the nickel-based directionally solidified superalloy prepared in Example 2 are compared with those of typical nickel-based directionally solidified superalloys DZ38G, DSGTD111, and DS MarM247. Figure 3 As shown, by Figure 3 It can be seen that the high-temperature creep performance of the nickel-based superalloy prepared in Example 2 exceeds that of DZ38G and DS GTD111, and is comparable to that of DS MarM247. However, the higher Hf content of the DS MarM247 alloy results in a higher alloy cost than the nickel-based directional solidification superalloy.

[0103] The equilibrium phase composition of the nickel-based directionally solidified superalloy prepared in Example 2 is as follows: Figure 4 As shown, by Figure 4 It is known that nickel-based directionally solidified superalloys do not form harmful phases above 800℃.

[0104] The nickel-based directionally solidified superalloy of Example 2 was subjected to long-term heat exposure at 900°C for 10,000 hours. The microstructure after heat exposure is as follows: Figure 5 As shown, by Figure 5It can be seen that nickel-based directionally solidified superalloys can maintain good microstructure stability and no harmful phase precipitation during long-term heat exposure.

[0105] The hot corrosion resistance of the alloy in Example 2 was tested using the crucible test method. The sample size was machined to 10mm × 10mm × 3mm. The sample was first polished with sandpaper, its actual dimensions were measured, and then it was cleaned with alcohol and acetone, dried, and weighed. To better understand the hot corrosion resistance of the alloy in Example 2, the DZ38G alloy, known for its excellent hot corrosion resistance, was used as a control. The test temperature was set at 700℃, the corrosion time at 100h, and a mixed salt of 25% NaCl + 75% Na2SO4 (NaCl:Na2SO4 = 1:3) was used. During the test, the sample was in line contact with the crucible. After the hot corrosion test, the corrosion products on the sample surface were removed, and the net weight of the remaining sample was weighed. The corrosion rate was calculated using the weight loss method: Hot corrosion rate = (original sample weight - net sample weight) / total sample surface area. The corrosion rate of each alloy was the arithmetic mean of the hot corrosion rates of its three samples. The morphology of the corroded samples and the measured data are shown below. Figure 6 As shown, by Figure 6 It can be seen that when the alloy of Example 2 is corroded at 700℃ for 100 hours using a mixed salt of 25% NaCl and 75% Na2SO4, it exhibits hot corrosion resistance that is close to that of the currently recognized DZ38G alloy with excellent hot corrosion resistance.

[0106] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0107] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for designing the composition of a nickel-based directionally solidified superalloy, comprising the following steps: S1. Preliminarily determine the types and content ranges of elements in nickel-based directionally solidified superalloys, and screen out the content of elements that form harmful phases through thermodynamic calculations; S2. Based on the types and content ranges of the elements, and using the contents of Cr, Co, Mo, W, Al, Ti, Ta and Nb as variables, construct an oxidation index model, a creep rupture model and a casting performance model; S3. Calculate the content ranges of Cr, Co, Mo, W, Al, Ti, Ta, and Nb using the oxidation index model, creep rupture model, and casting performance model. By setting the boundary conditions of the above models, select the content ranges that meet the requirements to obtain the composition range of the nickel-based directional solidification superalloy. The expression for the oxidation index model is as follows: M-oxidation=Σk i *W i ; Where, k i A constant W is obtained by fitting the elements. i The mass fraction of each element; The expression for the persistent performance model is as follows: M-creep=a*(lg(Σx i / D i )) b +c*((W γ′ *(1-W γ′ )*( -1)) d ; Among them, D i Let x be the diffusion coefficient of each element. i W represents the atomic fraction of each element within the γ phase. γ′ Let γ′ be the mass fraction, a = 48907, b = 0.008, c = -49789, d = -0.0003; The expression for the casting performance model is as follows: M-castability=(η*Δρ*ΔT) -1 ; Where η is the liquid phase kinetic viscosity coefficient, Δρ is the characteristic height density difference of the paste region, and ΔT is the solid-liquid phase temperature difference.

2. The design method according to claim 1, characterized in that, In step S1, the basis for initially determining the element types and content ranges of the nickel-based directionally solidified superalloy is: the strengthening mechanism of the nickel-based directionally solidified superalloy and the oxidation resistance and corrosion resistance characteristics that the nickel-based directionally solidified superalloy should possess.

3. The design method according to claim 1 or 2, characterized in that, In step S1, the types of elements include: Cr, Co, Mo, W, Ta, Al, Ti, Nb, C, B, Zr, Hf, and Ni.

4. The design method according to claim 1, characterized in that, In step S2, the K of element C in the oxidation index model i The K value of Cr is 0.

375. i The K of Ni element is -0.

100. i The K of Co is 0.

075. i The K of element W is 0.

149. i The K of the element Mo is 0.

069. i The K of Al element is 0.

140. i The K of the Ti element is -0.

982. i The K of element Ta is 0.

024. i The K value of Fe is -0.

037. i The K value of element B is 0.

637. i The K of the Hf element is -4.

104. i The K of the Nb element is 0.

235. i The K of the Zr element is -0.

035. i It is -4.

367.

5. The design method according to claim 4, characterized in that, In step S3, the boundary condition is M-oxidation < 1 mg / cm³. 2 , M-creep>209MPa, M-castability>2.

4.

6. A nickel-based directionally solidified superalloy, the composition of which is designed by the design method according to any one of claims 1 to 5; comprising, by mass percentage: Cr 12.0~13.0%, Co 3.0~8.0%, Mo 0.4~1.6%, W 6.2~8.0%, Ta 3.5~6.0%, Al 3.5~4.5%, Ti 1.5~2.7%, Nb 0~1.0%, C 0.03~0.3%, B 0.005~0.05%, Zr 0.001~0.05%, Hf≤0.02%, the remainder being Ni.

7. The nickel-based directionally solidified superalloy according to claim 6, characterized in that, The Cr content is 12.3-12.7%, and / or the Co content is 3.3-7.0%, and / or the Mo content is 0.8-1.0%, and / or the W content is 6.8-7.2%.

8. The nickel-based directionally solidified superalloy according to claim 6 or 7, characterized in that, The content of Ta is 3.9-5.0%, and / or the content of Al is 3.8-4.2%, and / or the content of Ti is 2.0-2.6%, and / or the content of Nb is 0.1-0.3%, and / or the content of C is 0.04-0.07%, and / or the content of B is 0.017-0.03%, and / or the content of Zr is 0.005-0.02%, and / or the content of Hf is 0.01%.

9. The nickel-based directionally solidified superalloy according to claim 6, characterized in that, The method for preparing the high-temperature alloy includes the following steps: After the high-temperature alloy is batched according to the proportion, it is smelted and the resulting master alloy is directionally solidified and remelted to obtain a directionally solidified alloy. The directional solidified alloy is subjected to hot isostatic pressing and then heat treatment.

10. The nickel-based directionally solidified superalloy according to claim 9, characterized in that, The directional solidification and remelting temperature is 1000~2000℃, and the pulling speed is 1~5mm / min; and / or, the hot isostatic pressing temperature is 1000~1500℃, the pressure is 1200~1800 atmospheres, and the time is 1~5h. And / or, the heat treatment specifically includes: Under a vacuum atmosphere, the temperature is held at 1100~1300℃ for 1~3 hours and then quenched with argon gas. After that, the temperature is held at 950~1080℃ for 4~8 hours and then quenched with argon gas. Finally, the temperature is held at 850~900℃ for 7~10 hours and then quenched with argon gas.

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