Coordinated control method for residual stress and microstructure of high-temperature alloy forgings based on heat treatment

Abstract

This invention provides a method for synergistically controlling residual stress and microstructure of high-temperature alloy forgings based on heat treatment, belonging to the field of high-temperature alloy heat treatment. The method involves solution treatment of the forged high-temperature alloy at a temperature in the γ′ / γ dual-phase region; rapid transfer of the solution-treated high-temperature alloy to a low-temperature heat treatment furnace, followed by low-temperature heat treatment in the converter, and then air cooling to room temperature; controlling the temperature difference between the high-temperature and low-temperature furnaces to effectively reduce residual stress while keeping the γ′ phase size within a small range; and aging treatment of the cooled high-temperature alloy at a temperature lower than the standard aging temperature for 14-20 hours to precipitate more and finer-sized tertiary γ′ phases with better strengthening effects. This invention achieves synergistic control of residual stress and microstructure in high-temperature alloys, reducing residual stress while improving the mechanical properties of the alloy.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy heat treatment, specifically relating to a method for synergistic control of residual stress and microstructure of high-temperature alloy forgings based on heat treatment. Background Technology

[0002] High-temperature alloys are a class of metallic materials based on iron, nickel, and cobalt, capable of long-term operation at temperatures above 600℃ and under certain stress. They possess excellent high-temperature strength, good resistance to oxidation and hot corrosion, good fatigue performance, fracture toughness, and other comprehensive properties. They also exhibit good machinability and stable microstructure and properties, making them suitable for manufacturing large-sized forgings such as turbine disks and guide vane inner rings. Examples include iron-based precipitation-hardening high-temperature alloys like K401 and nickel-based wrought high-temperature alloys like GH4169. Turbine disks and guide vane inner rings are core components of aero-engines and gas turbines, and the workpiece's geometry and material properties directly determine the efficiency and reliability of power output. Material properties are closely related to residual stress and microstructure in the alloy, requiring heat treatment and other processes to eliminate the influence of residual stress on material properties. The most significant process affecting residual stress in high-temperature alloy forgings is the quenching process after solution treatment. Studies have shown that the residual stress of GH4169 alloy disks after water quenching is 340.62 MPa, the maximum residual stress of GH4096 disks after salt bath quenching is 430 MPa, the maximum residual stress of FGH95 turbine disks after quenching is 530 MPa, and the maximum residual stress of GH4738 disks after water quenching can reach 600 MPa.

[0003] The engineering impacts of residual stress from quenching are mainly twofold. First, during the machining process, the residual stress remaining in the disc forging is released as part of the material is removed. As a self-balancing internal stress, this residual stress redistributes after machining to achieve rebalancing, simultaneously causing deformation of the disc in its free state after machining, thus significantly affecting the shape and dimensional accuracy of the part. Second, during subsequent service, the residual stress remaining in the part will superimpose with the service load, altering the actual stress state of the disc, thereby affecting its dimensional stability and fatigue performance during service, and consequently having a significant impact on the overall performance, lifespan, and reliability of the engine.

[0004] Besides residual stress, the microstructure of high-temperature alloy forgings is another key factor determining their service performance. Taking the nickel-based wrought high-temperature alloy GH4169 as an example, its strengthening phases are mainly γ″ (Ni3Nb) and γ′ (Ni3(Al,Ti)), supplemented by the δ phase (Ni3Nb) to control grain size; the iron-based high-temperature alloy K4169 (K401) relies on the precipitation strengthening of the γ′ phase. During heat treatment, the solution temperature determines the degree of δ phase re-dissolution and grain growth behavior, the cooling rate determines the nucleation density and size distribution of the γ′ / γ″ phase, and the aging regime determines the final morphology and volume fraction of the strengthening phase. The microstructure (grain size, strengthening phase size / distribution, grain boundary carbide morphology, etc.) directly determines the tensile strength, creep rupture, low-cycle fatigue, and other key performance indicators of the forgings. Therefore, slow cooling processes aimed solely at "reducing residual stress" will sacrifice microstructure properties, while rapid cooling processes aimed solely at "refining the strengthening phase" will worsen the residual stress level. Traditional single-target control methods are difficult to balance residual stress control and microstructure properties.

[0005] In existing technologies, heat treatment, aging treatment, and cryogenic treatment are generally used to reduce the impact of residual stress on material properties. For example, the residual stress of GH4169 after water quenching can be reduced from 340.62 MPa to 177.97 MPa through aging treatment, and the residual stress of steel after quenching can be reduced by 57-63% through cryogenic treatment. However, the above-mentioned aging methods can only reduce the stress by 47.75%. Although cryogenic treatment can reduce the stress by more than 50%, studies have shown that cryogenic treatment will affect the microstructure of high-temperature alloys, such as the precipitation of large amounts of carbides. The stress-relief annealing of GH4169 alloy proposed in Chinese patent CN110551955A is only up to 580℃, which is even far lower than its standard aging process temperature, and the effect of reducing residual stress is weaker. Chinese patent CN111705277A uses solution treatment followed by cold drawing deformation to eliminate more than 70% of the residual stress after quenching, but this method is limited to plates and wires. Chinese patent CN116005088A describes a method for reducing residual stress during quenching by using gas cooling at different flow rates in different thickness regions of disc forgings. However, the interaction between gases at different speeds inevitably leads to the formation of vortex mixing zones, making practical implementation difficult. Therefore, the aforementioned methods for controlling residual stress have limited effectiveness and introduce corresponding side effects. Consequently, a synergistic control method that can balance residual stress levels and microstructure is urgently needed. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for synergistically controlling residual stress and microstructure of high-temperature alloy forgings based on heat treatment. By controlling the solution treatment temperature, combined with the converter process to control the temperature difference between the high-temperature furnace and the low-temperature furnace, as well as the aging temperature, synergistic control of residual stress and microstructure of high-temperature alloy forgings is achieved, thereby reducing residual stress while improving the mechanical properties of the alloy.

[0007] To achieve the above objectives, the technical solutions adopted in the embodiments of the present invention are as follows:

[0008] This invention provides a method for synergistic control of residual stress and microstructure in high-temperature alloy forgings based on heat treatment, the method comprising the following steps:

[0009] Step S1: The forged high-temperature alloy is solution treated at the γ′ / γ dual-phase temperature.

[0010] Step S2: The high-temperature alloy after solution treatment is quickly transferred to a low-temperature heat treatment furnace. After low-temperature heat treatment in the converter, it is taken out and air-cooled to room temperature. The temperature difference between the high-temperature furnace and the low-temperature furnace is controlled so that the cooling rate can effectively reduce residual stress while controlling the size of the γ′ phase within a preset small size range.

[0011] Step S3: The cooled high-temperature alloy is subjected to aging treatment at a temperature lower than the standard aging temperature.

[0012] In a preferred embodiment of the present invention, the forged high-temperature alloy includes GH4738, GH4169, GH4169D, GH2909, GH4151, GH4720Li, FGH96 or FGH97.

[0013] In a preferred embodiment of the present invention, the forged high-temperature alloy is GH4738; the solution temperature in step S1 is 1020±10℃, and the solution holding time is 4±0.5h.

[0014] In a preferred embodiment of the present invention, during the solution treatment in step S1, the high-temperature alloy is heated to 800°C at a rate of 100~150°C / h, held at 800°C for 1±0.5h, and then heated to the solution temperature at a rate of 50~80°C / h.

[0015] In a preferred embodiment of the present invention, the temperature of the low-temperature heat treatment furnace is 150~250℃.

[0016] As a preferred embodiment of the present invention, the low-temperature heat treatment after the converter includes: the alloy is transferred into a low-temperature heat treatment furnace and allowed to cool to the set temperature of the low-temperature heat treatment furnace, and held for 20 to 30 minutes.

[0017] As a preferred embodiment of the present invention, the residual stress after quenching following solution treatment in a high-temperature furnace to a low-temperature furnace is reduced by 75% to 80%.

[0018] In a preferred embodiment of the present invention, the average size of the γ′ phase obtained in step S2 is 36~38nm; the aging treatment in step S3 precipitates more and finer tertiary γ′ phases with better strengthening effect, and the overall average size of the γ′ phase is 34~36nm.

[0019] In a preferred embodiment of the present invention, the forged high-temperature alloy is GH4738; during the aging treatment in step S3, the GH4738 alloy is heated in the furnace at a rate of 100~150℃ / h to 600℃, held at 600℃ for 1±0.5h, and then heated to the aging temperature at a rate of 50~80℃ / h.

[0020] In a preferred embodiment of the present invention, the aging temperature is set to 760±10℃ and the aging time is 14~20h.

[0021] The solutions of the embodiments of the present invention have the following beneficial effects:

[0022] The method for synergistic control of residual stress and microstructure of high-temperature alloy forgings based on heat treatment provided in this invention sets the solution temperature within the γ′ / γ dual-phase region temperature. During the solution treatment process, some large-sized primary γ′ phases are retained at the grain boundaries, effectively preventing rapid grain coarsening at high temperatures and improving the alloy's strength and toughness. The converter quenching from a high-temperature furnace to a low-temperature furnace mitigates the residual stress caused by the thermal expansion difference between different regions of the sample. Higher temperatures result in faster stress release. Simultaneously, controlling the temperature difference between the high-temperature and low-temperature furnaces strictly controls the cooling rate within a suitable range, ensuring that the γ′ phase does not undergo severe coarsening during slow cooling. An aging process adapted to converter quenching is set up, employing an aging process below the standard aging temperature. This avoids excessive coarsening of the precipitated γ′ phase size and, on top of that, precipitates more and finer-sized tertiary γ′ phases with better strengthening effects. This effectively reduces the significant coarsening of the γ′ phase precipitated during converter quenching at standard high-temperature aging such as 845℃, thus preventing a weakening of the strengthening effect. This invention achieves synergistic control of residual stress and microstructure in high-temperature alloys, reducing residual stress while improving the mechanical properties of the alloys.

[0023] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a residual stress distribution cloud map of Embodiment 1 of the present invention;

[0026] Figure 2 This is a grain structure diagram of Embodiment 1 of the present invention;

[0027] Figure 3 This is a distribution diagram of the γ′ phase in Embodiment 1 of the present invention;

[0028] Figure 4 This is a residual stress distribution cloud map of Embodiment 2 of the present invention;

[0029] Figure 5 This is a grain structure diagram of Embodiment 2 of the present invention;

[0030] Figure 6 This is a distribution diagram of the γ′ phase in Embodiment 2 of the present invention;

[0031] Figure 7 This is a residual stress distribution cloud map of Comparative Example 1 of the present invention;

[0032] Figure 8 This is a grain structure diagram of Comparative Example 1 of the present invention;

[0033] Figure 9 This is a distribution diagram of the γ′ phase in Comparative Example 1 of the present invention. Detailed Implementation

[0034] After discovering the aforementioned problems, the inventors of this application conducted a detailed study on existing methods for synergistically controlling residual stress and microstructure in high-temperature alloy forgings through heat treatment processes. The study found that residual stress originates from uneven plastic deformation within the material during manufacturing, essentially representing lattice distortion remaining within the material. For high-temperature alloy forgings, hot forging near the recrystallization temperature makes it difficult to form significant residual stress due to recrystallization. Quenching stress is primarily caused by differences in volume expansion between different regions of the forging, including thermal expansion differences due to temperature variations caused by different cooling rates, and volume changes caused by phase transformations. Asynchronous and uneven plastic deformation within the forging will result in residual stress after complete isothermal cooling; external pressure and internal tension are the basic characteristics of residual stress distribution in quenched disc forgings. A certain level of residual stress formed during low-temperature forging or post-forging cooling can usually be fully released during subsequent high-temperature solution heat treatment, as high temperatures can give the atoms or molecules of the material greater thermal kinetic energy, reducing the yield strength and allowing the residual stress to be released through plastic deformation. However, different heat treatment processes, such as heating or cooling rates, treatment temperatures, and holding times, will have varying effects on the treatment outcome; furthermore, the changes in microstructure brought about by the heat treatment process will affect the material properties. For high-temperature alloy forgings, how to select a suitable heat treatment process to synergistically control residual stress and microstructure remains unclear.

[0035] It should be noted that the defects in the above-mentioned prior art solutions are all the result of the inventors' practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the embodiments of the present invention in the following text should be the inventors' contributions to the present invention.

[0036] The technical solutions of 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can also be combined with each other.

[0037] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of the embodiments of the present invention, the terms "first," "second," "third," "fourth," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, sometimes a subscript such as W1 may be written in a non-subscript form such as W1, and their meanings are consistent unless the distinction is emphasized.

[0038] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0039] Following the above in-depth analysis, this invention provides a method for synergistic control of residual stress and microstructure in high-temperature alloy forgings based on heat treatment. The method includes solution treatment and heat preservation of the alloy forging; then, rapid transfer of the alloy forging to a low-temperature heat treatment furnace for cooling to reduce the generation of quenching residual stress; followed by a low-temperature aging treatment, and air cooling to obtain an alloy forging with improved tensile and creep properties. This invention reduces the generation of quenching residual stress by 75%–85% by controlling the cooling rate of the workpiece after solution treatment, and controls the cooling stage to ensure the precipitated strengthening phases are small in size. By matching this with the aging regime, the size of the secondary strengthening phases in the alloy is refined, resulting in improved overall mechanical properties. This method is simple and easy to operate, effectively reducing residual stress and improving the overall mechanical properties of alloy forgings. It is environmentally friendly, low-cost, has a short process, and is highly efficient.

[0040] The method for synergistic control of residual stress and microstructure of high-temperature alloy forgings based on heat treatment includes the following steps:

[0041] Step S1: The forged high-temperature alloy is solution treated at the γ′ / γ dual-phase temperature.

[0042] In this step, when performing solution treatment on the forged high-temperature alloy, a segmented heating method can be adopted, such as a two-stage heating method. In the first stage, the temperature is raised at a higher rate to the first stage temperature, and then raised at a lower rate to the solution temperature. The first stage temperature is 200~250℃ lower than the solution temperature.

[0043] The solution temperature is selected as the temperature of the γ′ / γ dual-phase region of the high-temperature alloy. At the solution temperature, a large-sized primary γ′ phase remains inside the high-temperature alloy matrix, which can effectively prevent the grains from coarsening rapidly at high temperatures, and has a positive impact on the strength and toughness of the high-temperature alloy.

[0044] The forged superalloys include GH4738, GH4169, GH4169D, GH2909, GH4151, GH4720Li, FGH96, FGH97, etc. Each superalloy has its own γ′ / γ two-phase region temperature, and generally, different superalloys have different γ′ / γ two-phase region temperatures.

[0045] Taking GH4738 high-temperature alloy as an example, during the solution treatment process, the high-temperature alloy is first heated in the furnace at a rate of 100~150℃ / h to 800℃, and held at 800℃ for 1±0.5h. Then, the temperature is increased to the solution temperature at a rate of 50~80℃ / h, which is 1020±10℃, and the solution holding time is 4±0.5h.

[0046] Step S2: The high-temperature alloy after solution treatment is quickly transferred to a low-temperature heat treatment furnace, and after low-temperature heat treatment in the converter, it is taken out and air-cooled to room temperature.

[0047] In this step, the high-temperature alloy after solution treatment and heat preservation is quickly transferred to a low-temperature heat treatment furnace at a preset temperature. The preset temperature difference between the high-temperature furnace and the low-temperature furnace is maintained. By controlling the temperature difference between the high-temperature furnace and the low-temperature furnace, the cooling rate can effectively reduce residual stress while controlling the size of the γ′ phase within a preset small size range. The average size of the γ′ phase is 36~38nm.

[0048] Taking GH4738 alloy as an example, after solution treatment and heat treatment, it is quickly transferred to a low-temperature heat treatment furnace at 150~250℃. The workpiece is then allowed to cool statically in the furnace to the set temperature for 20~30 minutes, and then removed and air-cooled to room temperature. The residual stress after solution treatment and quenching is reduced by 75%~80% compared to water cooling.

[0049] This step involves transferring the sample from a high-temperature furnace to a low-temperature furnace for quenching. This controls the cooling rate within the range between furnace cooling and air cooling, avoiding the large residual stresses that occur after traditional quenching methods like oil cooling, water cooling, and air cooling, and preventing the significant reduction in subsequent mechanical properties that can result from furnace cooling. Specifically, after placing the sample in the low-temperature heat treatment furnace, heat transfer occurs through three methods: conduction, convection, and radiation. The sample's heat is gradually transferred to the furnace chamber, and the temperature difference between the two controls the cooling rate. The reduced cooling rate further mitigates the residual stress caused by the thermal expansion differences between different regions of the sample, with higher temperatures resulting in faster stress release. While considering the benefits of a reduced cooling rate in controlling residual stress, the precipitation of the strengthening γ′ phase in the high-temperature alloy during cooling is also taken into account. To prevent severe coarsening of the γ′ phase during slower cooling, the cooling rate is strictly controlled within a suitable range by adjusting the temperature difference between the high-temperature and low-temperature furnaces. Taking GH4738 alloy as an example, after multiple experimental studies and demonstrations, the temperature of the low-temperature heat treatment furnace is set to 150~250℃. Within this temperature range, residual stress can be effectively reduced while the average size of the γ′ phase can be controlled at 36~38nm.

[0050] Step S3: The cooled high-temperature alloy is subjected to aging treatment at a temperature lower than the standard aging temperature.

[0051] In this step, during the aging treatment, the GH4738 alloy is heated in the furnace at a rate of 100~150℃ / h to 600℃, held at 600℃ for 1±0.5h, and then heated at a rate of 50~80℃ / h to the aging temperature, which is set to 760±10℃. The aging holding time is 14~20h, and then the alloy is taken out and air-cooled to room temperature.

[0052] The aging treatment described differs from the standard aging process for GH4738 (845℃×4h / AC+760℃×16h / AC) to match the converter quenching process from a high-temperature furnace to a low-temperature furnace. This step omits the 845℃×4h / AC high-temperature aging process and directly adopts a 760℃×14~20h / AC aging process. This avoids excessive coarsening of the already precipitated γ′ phase size and, on top of that, supplements the precipitation of more and finer-sized tertiary γ′ phases with better strengthening effects. This effectively reduces the significant coarsening of the γ′ phase precipitated during converter quenching and cooling at 845℃, thus preventing a weakening of the strengthening effect. At this point, the overall average size of the γ′ phase is 34~36nm. This aging treatment is crucial for improving the mechanical properties of the GH4738 alloy and shortens the process flow, achieving cost reduction and efficiency improvement.

[0053] Through the above heat treatment process, the high-temperature alloy ensures the stability of its structure and even further refines and strengthens the phase size, improving the strengthening effect. Its tensile properties and creep properties are higher than those of the standard heat treatment process.

[0054] The present invention will be further described in detail below through specific embodiments.

[0055] Example 1

[0056] This embodiment provides a method for synergistic control of residual stress and microstructure in high-temperature alloy forgings based on heat treatment, including:

[0057] Step S1: The forged GH4738 alloy is heated to 800℃ at 120℃ / h, held at 800℃ for 1h, and then heated to the solution temperature of 1020℃ at 60℃ / h, and held at the solution temperature for 4h.

[0058] Step S2: Quickly transfer the GH4738 alloy after solution treatment and heat preservation to a low-temperature heat treatment furnace, where the low-temperature heat treatment temperature is set to 200℃. After the workpiece is allowed to cool in the furnace to the temperature of the low-temperature heat treatment furnace, wait for 25 minutes, and then take it out and air-cool it to room temperature.

[0059] At this point, the contour method is used to determine the residual stress of the workpiece after quenching. This method is suitable for determining the stress distribution across the entire cross-section of large workpieces. The testing principle is as follows: the component is cut along the plane to be measured. The release of residual stress causes deformation of the cut surface contour. If an external force is applied to restore this deformed surface to its original ideal planar state, then the stress required to restore the plane is equivalent to the residual stress that originally existed on that plane. The residual stress test results are as follows: Figure 1 As shown, the maximum residual force at this time is 103 MPa.

[0060] Step S3: The workpiece is heated in the furnace at a rate of 120℃ / h to 600℃, held at 600℃ for 1 hour, then heated at a rate of 60℃ / h to aging temperature of 760℃, and held for aging for 16 hours. After that, it is taken out and air-cooled to room temperature.

[0061] Characterization of workpiece grain structure, such as Figure 2 The grain size grade is 6.23, and the internal microstructure of the alloy is as follows: Figure 3 As shown, the average size of the secondary γ′ phase is 36 nm. The results of the tensile and creep rupture tests on the workpiece are recorded in Table 1.

[0062] Example 2

[0063] This embodiment provides a method for synergistic control of residual stress and microstructure in high-temperature alloy forgings based on heat treatment, including:

[0064] Step S1: The forged GH4738 alloy is heated to 800℃ at a rate of 100℃ / h, held at 800℃ for 1h, and then heated to the solution temperature of 1020℃ at a rate of 50℃ / h, and held at the solution temperature for 4h.

[0065] Step S2: Quickly transfer the GH4738 alloy after solution treatment and heat preservation to a low-temperature heat treatment furnace, where the low-temperature heat treatment temperature is set to 150°C. After the workpiece is allowed to cool in the furnace to the temperature of the low-temperature heat treatment furnace, wait for 20 minutes, and then take it out and air-cool it to room temperature.

[0066] At this point, the residual stress of the workpiece from step two is measured using the contour method. The results of the residual stress test are as follows: Figure 4 As shown, the maximum residual force at this time is 130 MPa;

[0067] Step S3: The workpiece is heated in the furnace at a rate of 100℃ / h to 600℃, held at 600℃ for 1 hour, and then heated at a rate of 50℃ / h to aging temperature of 760℃. The aging holding time is 20 hours, and then the workpiece is taken out and air-cooled to room temperature.

[0068] Characterization of workpiece grain structure, such as Figure 5 The grain size grade is 6.25, and the internal microstructure of the alloy is as follows: Figure 6 As shown, the average size of the secondary γ′ phase is 34 nm. The results of the tensile and creep rupture tests on the workpiece are recorded in Table 1.

[0069] Example 3

[0070] This embodiment provides a method for synergistic control of residual stress and microstructure in high-temperature alloy forgings based on heat treatment, including:

[0071] Step S1: The forged GH4738 alloy is heated to 800℃ at a rate of 150℃ / h, held at 800℃ for 1h, and then heated to the solution temperature of 1020℃ at a rate of 80℃ / h, and held at the solution temperature for 4h.

[0072] Step S2: Quickly transfer the GH4738 alloy after solution treatment and heat preservation to a low-temperature heat treatment furnace, where the low-temperature heat treatment temperature is set to 250°C. Allow the workpiece to cool to the temperature of the low-temperature heat treatment furnace in the furnace, wait for 30 minutes, and then take it out and air-cool it to room temperature.

[0073] Step S3: The workpiece is heated in the furnace at a rate of 150℃ / h to 600℃, held at 600℃ for 1 hour, and then heated at a rate of 80℃ / h to the aging temperature of 760℃. The aging holding time is 14 hours, and then the workpiece is taken out and air-cooled to room temperature.

[0074] Fill in Table 1 with the test results of the tensile properties and creep properties of the workpiece.

[0075] Although the above embodiments all use forged GH4738 alloy, the method is applicable to a variety of high-temperature alloys such as GH4738, GH4169, GH4169D, GH2909, GH4151, GH4720Li, FGH96 or FGH97.

[0076] Comparative Example 1

[0077] This comparative example provides a heat treatment process similar to Examples 1-3. For comparison, the same high-temperature alloy is used to compare the different abilities to control residual stress and microstructure, including:

[0078] Step S1: Heat the forged GH4738 alloy to 800℃ at 120℃ / h, hold at 800℃ for 1h, then heat to the solution temperature of 1020℃ at 60℃ / h, and hold at the solution temperature for 4h.

[0079] Step S2: Quickly place the GH4738 alloy after solution treatment and heat preservation into 25°C water to cool to room temperature, and continuously shake the workpiece during the process to accelerate cooling.

[0080] At this point, the residual stress of the workpiece from step two is measured using the contour method. The results of the residual stress test are as follows: Figure 7 As shown, the maximum residual force at this time is 522 MPa;

[0081] Step S3: The workpiece is heated in the furnace at a rate of 120℃ / h to 600℃, held at 600℃ for 1 hour, then heated at 60℃ / h to the aging temperature of 845℃, and held for aging for 4 hours. It is then removed and air-cooled to room temperature. The temperature is then increased again at 120℃ / h to 600℃, held at 600℃ for 1 hour, then heated at 60℃ / h to the aging temperature of 760℃, and held for aging for 16 hours. It is then removed and air-cooled to room temperature.

[0082] Characterization of workpiece grain structure, such as Figure 8 The grain size grade is 6.26, and the internal microstructure of the alloy is as follows: Figure 9 As shown, the average size of the secondary γ′ phase is 39 nm. The tensile and creep rupture properties of the workpiece are recorded in Table 1.

[0083] Table 1

[0084]

[0085] contrast Figure 1 , Figure 2 , Figure 7 According to Examples 1 and 2 of the present invention, compared with the conventional heat treatment process for GH4738, the quenching residual stress of Comparative Example 1 was reduced from 522 MPa to 103 and 130 MPa, respectively, effectively reducing the generation of residual stress by 75% to 80%. Figure 2 , Figure 5 , Figure 8 The grain size of Examples 1 and 2, performed according to the present invention, is not significantly different from that of Comparative Example 1, which uses the conventional heat treatment process for GH4738. (Comparison) Figure 3 , Figure 6 , Figure 9 In Examples 1 and 2 of the present invention, the average size of the secondary γ′ phase was refined from 39 nm to 34-36 nm compared to Comparative Example 1, which uses the traditional heat treatment process for GH4738. Table 1 shows the tensile and creep rupture test results of each example and comparative example. The room temperature and high temperature yield strengths of the examples according to the present invention are improved compared to Comparative Example 1, which uses the traditional heat treatment process for GH4738, with room temperature yield strength increased by 44-50 MPa and high temperature yield strength increased by 42-48 MPa. The creep rupture life of the examples according to the present invention is improved by 5-9 hours compared to Comparative Example 1, which uses the traditional heat treatment process for GH4738. Therefore, the present invention significantly reduces the generation of residual stress during quenching while also ensuring improved mechanical properties of the alloy. Of course, the present invention is applicable not only to GH4738 alloy, but also to other precipitation-type high-temperature alloys, such as GH4169, GH4169D, GH2909, GH4151, GH4720Li, FGH96, and FGH97.

[0086] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0087] The above description is merely a preferred embodiment of the present invention and an explanation of the technical principles employed, and is not intended to limit the scope of the claimed invention, but merely to illustrate preferred embodiments of the invention. Those skilled in the art should understand that the scope of the invention is not limited to the specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for synergistic control of residual stress and microstructure in high-temperature alloy forgings based on heat treatment, characterized in that, The method includes the following steps: Step S1: The forged high-temperature alloy is solution treated at the γ′ / γ dual-phase temperature. Step S2: The high-temperature alloy after solution treatment is quickly transferred to a low-temperature heat treatment furnace. After low-temperature heat treatment in the converter, it is taken out and air-cooled to room temperature. The temperature difference between the high-temperature furnace and the low-temperature furnace is controlled so that the cooling rate can effectively reduce residual stress while controlling the size of the γ′ phase within a preset small size range. Step S3: The cooled high-temperature alloy is subjected to aging treatment at a temperature lower than the standard aging temperature.

2. The method according to claim 1, characterized in that, The forged high-temperature alloys include GH4738, GH4169, GH4169D, GH2909, GH4151, GH4720Li, FGH96, or FGH97.

3. The method according to claim 1, characterized in that, The forged high-temperature alloy is GH4738; the solution temperature in step S1 is 1020±10℃, and the solution holding time is 4±0.5h.

4. The method according to claim 3, characterized in that, In step S1, during the solution treatment process, the high-temperature alloy is heated to 800℃ in the furnace at a rate of 100~150℃ / h, held at 800℃ for 1±0.5h, and then heated to the solution temperature at a rate of 50~80℃ / h.

5. The method according to claim 3, characterized in that, The temperature of the low-temperature heat treatment furnace is 150~250℃.

6. The method according to claim 1, characterized in that, The low-temperature heat treatment after the converter includes: the alloy is transferred into a low-temperature heat treatment furnace and allowed to cool to the set temperature of the low-temperature heat treatment furnace, and held for 20~30 minutes.

7. The method according to claim 1, characterized in that, After solution treatment in a high-temperature furnace and then transferred to a low-temperature furnace, the residual stress after quenching is reduced by 75% to 80%.

8. The method according to claim 1, characterized in that, The average size of the γ′ phase obtained in step S2 is 36~38nm; the aging treatment in step S3 precipitates more and finer tertiary γ′ phases with better strengthening effect, and the overall average size of the γ′ phase is 34~36nm.

9. The method according to claim 1, characterized in that, The forged high-temperature alloy is GH4738; during the aging treatment in step S3, the GH4738 alloy is heated in the furnace at a rate of 100~150℃ / h to 600℃, held at 600℃ for 1±0.5h, and then heated to the aging temperature at a rate of 50~80℃ / h.

10. The method according to claim 9, characterized in that, The aging temperature is set to 760±10℃, and the aging time is 14~20h.

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