A method for manufacturing an adaptive structure single crystal blade and an adaptive structure single crystal blade

Abstract

The application discloses a preparation method of a self-adaptive structure single crystal blade, and comprises the following steps: fast cooling homogenization treatment, treating at a temperature above a large-size gamma prime phase dissolving line for 4-30 hours, sufficiently dissolving a cast structure, and then cooling to room temperature at a speed of greater than 1000 DEG C / s to precipitate a large amount of small-size gamma prime phase; self-adaptive structure treatment, treating in an actual service environment of the blade for 2-8 hours, and then air cooling to room temperature to obtain a target structure; and structure stabilization treatment, treating at a temperature below a small-size gamma prime phase dissolving line for 12-48 hours, and then air cooling to room temperature to solidify the target structure obtained by the self-adaptive structure treatment. The application further discloses a self-adaptive structure single crystal blade. The application changes a traditional single crystal alloy heat treatment and structure regulation idea, forms a non-uniform gamma prime phase distribution in the single crystal blade through heat treatment process design, and the gamma prime phase distribution characteristics of different regions depend on the service environment of the regions, so that the strength of each region is improved, and a self-adaptive strengthening effect is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-temperature structural components of combustion engines, and particularly relates to a preparation method of a self-adaptive structural single-crystal blade and a self-adaptive structural single-crystal blade prepared by the method. BACKGROUND

[0002] Based on the working principle and design of modern combustion engines, increasing the turbine inlet temperature is one of the main technical means to improve the engine efficiency and thrust ratio. Increasing the turbine inlet temperature requires the turbine first-stage high-pressure rotor / stator blades at the end of the inlet and the material itself to have higher temperature resistance. Currently, the turbine first-stage high-pressure rotor / stator blades of advanced aero-engines mainly use nickel-based single-crystal high-temperature alloys, which are composed of disordered face-centered austenite γ phase and ordered L12 structure A3B intermetallic compound γ' phase, and the two phases form a basic coherent interface.

[0003] In actual service, the turbine blades bear extremely uneven force and thermal conditions under the coupling of temperature, aerodynamic load and centrifugal force. The advanced aero-engine first-stage high-pressure rotor blade tip bears a stress of about 140 MPa at a high temperature of 1150°C, the blade root bears an average stress of more than 700 MPa at a temperature of 650-850°C, and the blade body bears a stress of 280-650 MPa at a temperature of 850-1000°C. The high-temperature performance is directly related to the temperature resistance of the material and the inlet temperature of the engine, and is the focus of alloy design in the past. Based on alloying strategies such as γ phase solid solution strengthening, γ' phase precipitation strengthening and γ / γ' phase interface strengthening, or using solid solution and aging heat treatment to control and optimize the structure, the high-temperature performance of advanced single-crystal alloys has made great progress. In comparison, the medium-temperature and low-temperature performance of the alloy has improved less. Since the third generation of single-crystal alloys, the medium-temperature and low-temperature performance of the alloy has generally been lower than the high-temperature performance, so that the low-temperature region of the blade becomes a weak point during service, affecting the overall reliability of the blade.

[0004] The above problems are caused by the following two factors. First, for high-temperature performance, the focus of the total composition design is to improve the high-temperature stability of the structure, and for this purpose, a large amount of refractory elements such as rhenium (Re), tungsten (W) and molybdenum (Mo) are added to the advanced single-crystal alloy to increase the solid-liquid transition temperature and the γ' phase solvus. In a low-temperature environment, the structural stability is not the key to the performance of the alloy, so the composition design for high-temperature performance in the past has limited improvement in low-temperature performance. Second, the deformation behavior of the microstructure of the single-crystal alloy under different temperatures and stresses is different, the deformation under low temperature / high stress comes from the <112> type dislocation shearing γ, γ' phase and the formation of dislocation slip bands, while the dislocation movement under high temperature / low stress is mainly limited in the γ phase. The difference in deformation mechanism determines the different focus of the structure design for high-temperature and low-temperature performance. The γ' phase morphology, content and distribution are beneficial to the high-temperature performance, but may not be suitable for the low-temperature performance.

[0005] In summary, for turbine blades operating in complex temperature and stress environments, a uniform material structure makes it difficult to simultaneously ensure the performance of different parts of the blade. To address this, some patents disclose blade local treatment strategies (US20100043929A1, CN 114718655B), which adjust the local microstructure to meet the performance requirements of different regions under their respective service environments. This improves the overall performance of the blade to some extent, but the following problems still exist:

[0006] Firstly, published patents divide blades into sections from top to bottom—tip, blade body, and root—based on their approximate service temperature and stress distribution characteristics, corresponding to three service ranges: high temperature and low stress, medium temperature and medium stress, and low temperature and high stress, respectively. However, the actual service environment of blades is far more complex, with varying temperature and stress conditions in any given region. While published patents achieve localized structural control by employing different heat treatment regimes for the tip, blade body, and root, thus improving the strength of these sections under high temperature and low stress, medium temperature and medium stress, and low temperature and high stress conditions, they still cannot meet the performance requirements of blades in complex service environments, making it difficult to achieve the overall performance design of the blade.

[0007] Secondly, the localized processing strategy adopted in the published patents requires regional and multi-step heat treatment of small, complex structural components (turbine blades), demanding special heat insulation and cooling designs for the heat treatment equipment, resulting in high process complexity and difficulty. Furthermore, the localized processing generates a high temperature gradient within the material, leading to significant thermal stress, which can easily cause recrystallization in subsequent processing, severely damaging the blade's service performance and reliability. Summary of the Invention

[0008] Given the current mismatch between high and low temperatures in nickel-based single-crystal superalloys, the performance of single-crystal blades under complex temperature and stress environments is not fully realized. This invention proposes a method for preparing an adaptive single-crystal blade through material structure design and heat treatment, and the resulting adaptive single-crystal blade. This blade exhibits a naturally formed non-uniform structure within a complex temperature field, where the microstructure in any region is the optimal microstructure that exists and functions best at the corresponding service temperature, possessing an adaptive combination of microstructures. Compared to traditional uniform structure blades or locally treated structure blades, the adaptive single-crystal blade proposed in this invention achieves optimal strength and lifespan in any region, improving the overall performance of single-crystal blades in complex temperature fields.

[0009] The technical solution adopted by this invention to solve its technical problem is: a method for preparing an adaptive structure single-crystal blade, comprising the following steps:

[0010] Rapid cooling homogenization treatment: The temperature is treated for 4-30 hours above the dissolution line of the large-size γ′ phase to fully dissolve the as-cast structure. Then, it is cooled to room temperature at a rate of more than 1000℃ / s to precipitate a large amount of small-size γ′ phase.

[0011] Adaptive structural treatment involves treating the blade in its actual service environment for 2-8 hours, followed by air cooling to room temperature to obtain the target microstructure.

[0012] The tissue stabilization treatment involves treating at temperatures below the small-size γ′ phase dissolution line for 12-48°C, followed by air cooling to room temperature to solidify the target tissue structure obtained by the adaptive structure treatment.

[0013] Furthermore, the actual service environment of the blade is the actual working environment of the first-stage high-pressure turbine blade of the engine.

[0014] Furthermore, in the rapid cooling homogenization process, the processing temperature is 1250-1380℃, and after the process is completed, liquid nitrogen quenching and supersaturated brine quenching are used for cooling.

[0015] Furthermore, in the adaptive structure processing step, the blade is placed on the first-stage high-pressure turbine blade of the engine and processed in a coupled field of temperature, aerodynamic load, and centrifugal force, with the temperature field being 650-1200℃.

[0016] Furthermore, in the tissue stabilization treatment step, the treatment temperature is 780-850℃.

[0017] This invention also discloses an adaptive single-crystal blade with a non-uniform microstructure.

[0018] It operates in the low-temperature service range of 650-850℃ and exhibits a dual-mode γ′ phase distribution;

[0019] It operates in the intermediate temperature range of 850-1000℃ and has a single-mode γ′ phase distribution;

[0020] It operates in a high-temperature service area of ​​1000℃-1200℃ and has a raft-type γ′ phase distribution;

[0021] This allows the blades to adapt to the complex operating temperature field during service.

[0022] It has an adaptive combination of tissue structures and a non-uniform tissue structure. Its formation includes at least a process of treatment in a complex service temperature field within the actual service environment of the blade. The γ′ phase distribution characteristics of the blade are different in different service temperature regions. The γ′ phase distribution characteristics are the tissue structures that can exist and play the best role in the corresponding service temperature of the region, so that the overall strength and life of the blade in each part of the complex service temperature field are optimal.

[0023] Furthermore, the γ′ phase is composed of an A3B type intermetallic compound with an ordered L12 structure, accounting for 50-70% of the total integral, and is distributed in a disordered face-centered austenitic γ phase matrix;

[0024] The single-mode γ′ phase distribution consists only of large-sized cubic γ′ phases with side lengths of 200-600 nm.

[0025] The dual-mode γ′ phase distribution contains a large-sized cubic γ′ phase and a small-sized spherical γ′ phase, with the small-sized γ′ phase having a diameter of 1-50 nm.

[0026] The raft γ′ phase distribution is a continuous structure formed by the growth of large-sized γ′ phases, which is thin and lamellar with a long side ≥1200nm.

[0027] The single-crystal blades of this invention are mainly obtained through precision casting and heat treatment. Conventional heat treatment consists of three steps: high-temperature solution treatment, medium-temperature aging treatment, and low-temperature aging treatment, all followed by air cooling. Solution treatment is primarily used to dissolve the primary γ′ phase and eutectic phase in the cast alloy, achieving homogenization through high-temperature diffusion. During air cooling after solution treatment, the γ′ phase re-precipitates and grows during the subsequent medium-temperature aging treatment, increasing in size and volume fraction. Low-temperature aging does not affect the morphology, size, or content of the γ′ phase, but it helps to balance the distribution of alloying elements between the γ and γ′ phases, improving phase interface stability. After solution treatment, medium-temperature aging, and low-temperature aging, the γ′ phase fully precipitates and grows to a relatively large size (200-600 nm), exhibiting a cubic morphology and uniformly distributed within the γ phase, displaying a single-mode distribution characteristic. Under this structure, the single-crystal blade exhibits the highest strength in the service temperature range above 850℃. However, γ-phase solid solutions are relatively soft, allowing dislocations to move and multiply rapidly, resulting in plastic deformation. Therefore, the strengthening effect of this single-mode structure may not be optimal for service temperatures below 850°C.

[0028] In addition to the primary γ′ phase, the material also contains smaller secondary and tertiary γ′ phases, ranging in size from 1 to 50 nm. After traditional medium- and low-temperature failure treatments, the growth of the primary γ′ phase consumes a large amount of γ′ phase-forming elements, resulting in little or no precipitation of secondary or tertiary γ′ phases. By sacrificing a small amount of the primary γ′ phase and allowing it to recrystallize as secondary or tertiary γ′ phases, the resistance to dislocation movement within the γ phase can be increased, effectively improving the material's low-temperature performance. However, the small-sized γ′ phase exhibits poor stability at high temperatures, and the reduced content of the primary γ′ phase decreases the material's deformation resistance at high temperatures, inevitably leading to a decline in the alloy's high-temperature performance and negatively impacting its overall properties.

[0029] This invention changes the traditional approach to heat treatment and microstructure control of single-crystal alloys. Through heat treatment process design, it induces a non-uniform γ′ phase distribution within the single-crystal blade. The γ′ phase distribution characteristics in different regions depend on the service environment of that region, thereby improving the strength of each region and achieving an adaptive strengthening effect. The main process steps and design concepts are as follows:

[0030] 1) Rapid cooling homogenization treatment: After solution treatment, liquid nitrogen quenching or supersaturated brine quenching is used to achieve an extremely high cooling rate (~1000℃ / s). At this cooling rate, the nucleation driving force of the γ′ phase is extremely high, but due to the low diffusion kinetics, it cannot grow to a large size. The distribution characteristics of the γ′ phase obtained after rapid cooling homogenization treatment are: the γ′ phase with extremely high nucleation density but extremely small size (≤50nm) is uniformly distributed in the γ phase, and the supersaturation degree in the γ phase is high.

[0031] 2) Adaptive structural treatment: Unlike traditional intermediate-temperature aging which is carried out in a constant-temperature environment, this treatment is performed under a coupled field of temperature, aerodynamic load, and centrifugal force. In this environment, in the region below the dissolution line temperature of the small-sized γ′ phase, the small-sized γ′ phase grows slowly, some of which grows to a larger size, while others retain their small size morphology; in the region above the dissolution line temperature of the small-sized γ′ phase, a large amount of the small-sized γ′ phase dissolves and grows into a large-sized γ′ phase under the influence of temperature; in the region with even higher temperatures, the large-sized γ′ phase further grows under the influence of high temperature and stress, forming a continuous lamellar raft structure. The γ′ phase distribution characteristics obtained after adaptive structural processing are as follows: in the region with an service temperature between 650-850℃, there is a dual-mode γ′ phase distribution composed of large cubic γ′ phases (200-600nm) and small spherical γ′ phases (1-50nm); in the region with an service temperature between 850-1000℃, there is a single-mode γ′ phase distribution composed only of large cubic γ′ phases; and in the region with an service temperature between 1000℃-1150℃, there is a rafted γ′ phase distribution.

[0032] 3) Tissue stabilization treatment: Treating at temperatures below the dissolution line of the small-sized γ′ phase for a longer period of time allows the distribution characteristics of the γ′ phase in each region to reach equilibrium, thereby improving tissue stability.

[0033] Compared to single-crystal blades obtained through traditional solution treatment, medium-temperature aging, and low-temperature aging, the advantages of the adaptive structure are as follows: In the low service temperature region, the small-sized γ′ phase exhibits high stability and can provide additional precipitation strengthening on top of the large-sized γ′ phase. This dual-mode distribution has higher deformation resistance than the single-mode distribution, resulting in optimal low-temperature performance in this region. In the medium service temperature region, it exhibits single-mode distribution characteristics and has superior deformation resistance compared to the dual-mode distribution, resulting in optimal medium-temperature performance in this region. In the high service temperature region, the large-sized γ′ phase transforms into a raft distribution in a short time. This process is accompanied by the release of interfacial mismatch stress and the formation of a dislocation network, resulting in stronger dislocation movement resistance and deformation resistance, thus achieving optimal high-temperature performance in this region. Based on this adaptive structural design, the structure of the single-crystal blade is optimally designed in the high-temperature, medium-temperature, and low-temperature service regions, effectively improving the overall performance of the blade under complex temperature and stress conditions.

[0034] This invention improves the overall performance of single-crystal blades without altering the composition of existing alloys, solely through heat treatment process design, resulting in significant economic benefits and promising application prospects. Attached Figure Description

[0035] Figure 1 This is a scanning electron microscope image showing the γ′ phase distribution characteristics of the adaptive structure single-crystal blades in an embodiment of the present invention.

[0036] Figure 2 This is a scanning electron microscope image of the γ′ phase distribution characteristics of a conventional uniform single-crystal blade, as shown in Comparative Example 1 of this invention.

[0037] Figure 3 This is a scanning electron microscope image showing the distribution characteristics of the γ′ phase after rapid cooling homogenization treatment in an embodiment of the present invention.

[0038] Figure 4 This is a scanning electron microscope image of the γ′ phase distribution characteristics of a single crystal blade without rapid cooling homogenization treatment in Comparative Example 2 of this invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0040] The comparative examples and embodiments of this invention use a known nickel-based single-crystal high-temperature alloy, the chemical composition of which is shown in Table 1.

[0041] Table 1. Chemical composition (wt.%) of single-crystal superalloys of the embodiments and comparative examples of the present invention

[0042] Element Chromium Cobalt Tungsten Molybdenum Rhenium Tantalum Aluminum Ruthenium Niobium Cerium Carbon Yttrium wt.% 2.8 6.6 5.5 3.2 4.8 6.2 6.0 2.1 0.1 0.05 0.02 0.005

[0043] The embodiments of this invention employ a three-step process: rapid cooling homogenization, adaptive structure processing, and microstructure stabilization, as detailed below:

[0044] 1) Rapid cooling homogenization treatment: Treat at a temperature above the dissolution line of the large-size γ′ phase for 4-30 hours to fully dissolve the as-cast structure, and then cool to room temperature at a rate greater than 1000℃ / s to precipitate a large amount of small-size γ′ phase;

[0045] Specifically, the cast single-crystal blades are held at 1300-1350℃ for 20 hours, then quenched with liquid nitrogen and cooled to room temperature at a rate of over 1000℃ / s.

[0046] 2) Adaptive structural treatment: The blade is treated in its actual service environment for 2-8 hours, and then air-cooled to room temperature to obtain the target microstructure; the actual service environment of this blade can be the actual working environment of the first-stage high-pressure turbine blade of an engine.

[0047] Specifically, the blades are placed in the high-pressure turbine of the first stage of the engine. The engine is run to treat the blades under a coupled field of temperature, aerodynamic load and centrifugal force. The temperature field where the blades are located is non-uniform, ranging from 650 to 1200°C. The treatment time is 4 hours, and then the blades are air-cooled to room temperature.

[0048] 3) Tissue stabilization treatment: Treat at a temperature 12-48°C below the small-size γ′ phase dissolution line, then air-cool to room temperature to solidify the target tissue structure obtained by the adaptive structure treatment;

[0049] Specifically, the leaves were kept at 830℃ for 24 hours and then air-cooled to room temperature.

[0050] Comparative Example 1 of the present invention removes the rapid cooling homogenization treatment from the previous example and directly performs adaptive structural treatment and microstructure stabilization treatment on the cast single crystal blade.

[0051] Comparative Example 2 of this invention employs a traditional three-step process: high-temperature solution treatment, medium-temperature aging, and low-temperature aging, as detailed below:

[0052] 1) High-temperature solution treatment: The cast single-crystal turbine blades are kept at 1300-1350℃ for 20 hours, and then air-cooled to room temperature;

[0053] 2) Medium-temperature aging: The leaves were kept at 1100℃ for 4 hours, and then air-cooled to room temperature;

[0054] 3) Low temperature aging: The leaves were kept at 870℃ for 24 hours, and then air-cooled to room temperature.

[0055] Figure 1 , Figure 2 Scanning electron microscope (SEM) images of the γ′ phase distribution characteristics of the single-crystal blades in Examples 1 and 1 (Comparative Example 1) are provided. In Examples 1, a non-uniform γ′ phase distribution was formed through a three-step process of rapid cooling homogenization, adaptive structure processing, and microstructure stabilization as described in this invention: the region with an service temperature between 650-850℃ exhibits a bimodal γ′ phase distribution composed of large cubic γ′ phases (200-600 nm) and small spherical γ′ phases (1-50 nm); the region with an service temperature between 850-1000℃ exhibits a monomodal γ′ phase distribution consisting only of large cubic γ′ phases; and the region with an service temperature between 1000℃-1150℃ exhibits a raft-like γ′ phase distribution. In 1 (Comparative Example 1), a uniform γ′ phase distribution, a monomodal γ′ phase distribution, was achieved through a traditional three-step process of high-temperature solution treatment, medium-temperature aging, and low-temperature aging.

[0056] Figure 3 This is a scanning electron microscope (SEM) image of the cast single-crystal blade after rapid cooling and homogenization treatment, as shown in the embodiment. It reveals the formation of a high-density, small-sized spherical γ′ phase within the rapidly cooled and homogenized material, uniformly and consistently distributed within the γ′ phase, with γ′ phase dendrites ≤50nm. This γ′ phase lays the foundation for the formation of an adaptive structure for the blade in actual service environments.

[0057] Figure 4 This is a scanning electron microscope (SEM) image of the γ′ phase distribution characteristics of the single-crystal blade in Comparative Example 2. Due to the lack of rapid cooling homogenization treatment, there are very few small-sized γ′ phases inside the material, and the required bimodal γ′ phase distribution is not formed in the service temperature range of 650-850℃. In addition, due to the lack of high-temperature treatment, the coarse primary γ′ phase and eutectic structure in the cast alloy are not sufficiently eliminated, resulting in a large amount of eutectic remaining in the service temperature ranges of 650-850℃ and 800-1000℃ after treatment, while the coarsening is even higher in the 1000℃-1150℃ region, leading to poor overall microstructure stability of the blade.

[0058] The tensile properties of different regions of the single-crystal blade in the comparative examples and Comparative Example 1 were compared. Samples were taken at the corresponding positions along the

[001] direction, including the bottom of the blade with an service temperature between 650-800℃, the middle of the blade with an service temperature between 800-1000℃, and the top of the blade with an service temperature between 1000-1150℃. The test conditions were 700, 900, and 1100℃, respectively. The yield strength and tensile strength were measured as shown in Table 2.

[0059] Table 2 Tensile properties of corresponding regions in the examples and comparative examples.

[0060]

[0061] The above results demonstrate that the adaptive single-crystal blade obtained in this patent embodiment exhibits dual-mode γ′ phase distribution, single-mode γ′ phase distribution, and rafted γ′ phase distribution in the low-temperature, medium-temperature, and high-temperature service regions, respectively. This non-uniform γ′ phase distribution characteristic results in the embodiment demonstrating superior strength compared to the comparative example under corresponding location and temperature conditions. Therefore, the adaptive single-crystal blade obtained in this patent exhibits higher overall performance under complex temperature fields.

[0062] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method of manufacturing an adaptive structure single crystal blade, characterized by, The method comprises the following steps: a fast cooling homogenization treatment, treating at a temperature above the solvus of large size γ' phase for 4-30 hours, fully dissolving the as-cast structure, then cooling to room temperature at a speed of more than 1000 ℃ / s to precipitate a large amount of small size γ' phase; the large size γ' phase has a side length of 200-600 nm, and the small size γ' phase has a diameter of 1-50 nm; an adaptive structure treatment, treating in the actual service environment of the blade for 2-8 hours, then air cooling to room temperature to obtain a target structure; a structure stabilization treatment, treating at a temperature below the solvus of small size γ' phase for 12-48 hours, then air cooling to room temperature to solidify the target structure obtained by the adaptive structure treatment.

2. The method of claim 1, wherein: The actual service environment of the blade is the actual working environment of a first-stage high-pressure turbine blade of an engine.

3. The method of claim 1, wherein: In the fast cooling homogenization treatment step, the treatment temperature is 1250-1380 ℃, and after the treatment, liquid nitrogen quenching or supersaturated salt water quenching is used for cooling.

4. The method of claim 1, wherein: In the adaptive structure treatment step, the blade is placed in the position of a first-stage high-pressure turbine blade of an engine, and is treated in a temperature field, a pneumatic load field and a centrifugal force coupling field, and the temperature of the temperature field is 650-1200 ℃.

5. The method of claim 1, wherein: In the structure stabilization treatment step, the treatment temperature is 780-850 ℃.

6. An adaptive structure single crystal blade characterized by: obtained by the preparation method in any one of claims 1-5, having a non-uniform structure, in a low-temperature service region of 650-850 ℃, having a bimodal γ' phase distribution; in a medium-temperature service region of 850-1000 ℃, having a unimodal γ' phase distribution; in a high-temperature service region of 1000-1200 ℃, having a raft γ' phase distribution; so that the blade as a whole adapts to the working environment of a complex service temperature field; the γ' phase is a A3B type intermetallic compound with an ordered L12 structure, accounting for 50-70% of the total volume fraction, and is distributed in an unordered face-centered structure austenite γ phase matrix; the unimodal γ' phase distribution only has large size cubic γ' phase with a side length of 200-600 nm; the bimodal γ' phase distribution contains large size cubic γ' phase and small size spherical γ' phase, and the small size γ' phase has a diameter of 1-50 nm; the raft γ' phase distribution has a continuous structure formed by growth of large size γ' phase, and the structure is flaky with a long side of more than or equal to 1200 nm.

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