Optimization methods for hot working processes of nickel-based hard-to-deform superalloys resistant to molten salt corrosion

Abstract

This application relates to the field of high-temperature alloy rolling and hot working technology, and discloses an optimization method for the hot working process of nickel-based difficult-to-deform high-temperature alloys resistant to molten salt corrosion, which can improve the production efficiency of alloy processing. The method includes: obtaining alloy ingots through alloy smelting and casting and performing homogenization heat treatment; obtaining samples by cutting; performing isothermal hot compression on the samples and collecting true stress-strain data; performing friction correction and adiabatic correction on the collected true stress-strain data; constructing the constitutive equation of the alloy based on the corrected rheological stress data and drawing a hot working diagram of the alloy; determining the optimal hot deformation region, safe region, and unstable region of hot working based on the dissipation values ​​of plastic deformation and microstructure evolution in the hot working diagram, and thereby determining the optimal range of hot working process parameters for the alloy.

Description

Technical Field

[0001] This application relates to the field of high-temperature alloy rolling and hot working technology, and in particular to the hot working process of nickel-deformed high-temperature alloys resistant to molten salt corrosion. Background Technology

[0002] Since the beginning of this century, the global energy crisis and environmental problems have become increasingly serious. To ensure my country's long-term sustainable development and achieve its dual-carbon strategic goals, developing low-carbon and clean energy is the only option for my country's energy development strategy. With my country's growing demand for clean nuclear power, molten salt reactors, as one of the key fourth-generation advanced nuclear reactors being developed in my country, have received widespread attention. A molten salt reactor is a liquid-fuel fission reactor that typically uses high-temperature molten fluoride or chloride salts as the primary coolant or even nuclear fuel, enabling waterless operation and high thermal efficiency. However, the main container, loop piping, and other core structural components of the molten salt energy system are subjected to a complex environment of interaction between high-temperature molten salt and neutron radiation for extended periods. This harsh service load condition places higher demands on the comprehensive performance of materials. Simultaneously, to achieve higher thermal energy conversion efficiency, the temperature of the molten salt reactor system needs to be increased to above 800℃. Currently, mature alloys with allowable temperatures above 800℃ in international ASME standards (Haynes 230, Inconel 617, etc.) cannot meet the requirements for resistance to high-temperature molten salt corrosion. Among the existing high-temperature molten salt corrosion resistant structural materials internationally, Hastelloy N alloy is the only molten salt reactor structural alloy that has been successfully used, possessing excellent comprehensive performance. However, its maximum allowable temperature is 704℃. Therefore, China faces a dilemma of having no suitable materials for high-temperature molten salt environments above 800℃, urgently requiring solutions to import substitution and the independent development of a high-temperature structural material that meets the corrosion resistance requirements of molten salt reactors above 800℃. Considering the high-temperature mechanical properties and molten salt corrosion resistance of alloys in higher-temperature molten salt environments, the Institute of Metal Research, Chinese Academy of Sciences, and the Shanghai Institute of Applied Physics, Chinese Academy of Sciences, have further collaborated to initially develop a GH3539 alloy (Ni-(26-28W)-6Cr alloy) for molten salt environments above 800℃, based on Hastelloy N alloy.

[0003] The thermal processing of structural materials in molten salt energy systems is complex and involves a large amount of engineering applications. The materials used for core components such as heat collection tubes must not only have excellent mechanical properties in the high-temperature molten salt environment, but also good thermal processing performance.

[0004] However, although GH3539 alloy has excellent high-temperature mechanical properties and resistance to molten salt corrosion, the addition of a large number of refractory metal elements inevitably leads to difficulties in hot working, which seriously reduces process stability and yield, and significantly increases research and development costs. Summary of the Invention

[0005] The purpose of this application is to provide an optimized method for the hot working process of nickel-based hard-to-deform high-temperature alloys resistant to molten salt corrosion, thereby improving the rationality of process design and increasing production efficiency.

[0006] This application discloses an optimized method for the hot working process of nickel-based hard-to-deform superalloys resistant to molten salt corrosion, comprising the following steps:

[0007] Alloy ingots are obtained by alloy smelting and casting.

[0008] The alloy ingot is subjected to homogenization heat treatment;

[0009] A sample is obtained by cutting at a designated location on the alloy ingot;

[0010] The sample is heated to a specified temperature range at a specified heating rate and held at that temperature for a specified duration. Then, it is subjected to isothermal hot compression at a specified deformation rate. When the engineering strain reaches a specified threshold, it is immediately water-quenched to preserve the high-temperature deformation structure under different conditions. True stress-strain data are collected during this process.

[0011] Frictional and adiabatic corrections were performed on the collected true stress-strain data to correct for the effects of interfacial friction and adiabatic temperature rise and obtain accurate rheological stress data.

[0012] The constitutive equation of the alloy is constructed based on the corrected rheological stress data, and the hot working diagram of the alloy is drawn. The optimal hot deformation region, safe region and unstable region of hot working are determined according to the dissipation values ​​of plastic deformation and microstructure evolution in the hot working diagram.

[0013] The optimal range of hot working parameters for the alloy is determined based on the optimal hot deformation region, the safe region, and the instability region.

[0014] In the embodiments of this application, constitutive equations are constructed based on true stress-strain data corrected for material friction and temperature through thermal simulation compression experiments, the optimal hot working process window is determined, and the influence of different deformation parameters on the evolution of alloy microstructure is combined to optimize the hot working process parameters, thereby improving the rationality of process formulation and significantly improving production efficiency.

[0015] The embodiments of this application perform friction and temperature correction on the true stress-strain data obtained by hot compression, eliminating the problem that the data obtained cannot truly reflect the deformation behavior of the alloy due to uneven deformation and deformation heat caused by the interface friction between the specimen and the compression bar during uniaxial hot compression testing.

[0016] Based on traditional industrial processing equipment and methods, and according to the thermophysical properties of the alloy, the evolution of recrystallization structure, and the grain growth kinetics model, a dynamic material model is used to construct hot working diagrams of the alloy under different deformation conditions based on the corrected rheological stress data. This can quickly and effectively identify and avoid the unstable zones (wedge crack propagation zone, grain boundary crack zone, adiabatic shear band formation zone, and local processing danger zones that are prone to forming coarse grain and mixed grain defect structures) of the alloy during high-temperature deformation.

[0017] This application combines simulation results with physical experimental results for verification. It analyzes the influence of parameters such as deformation temperature, strain rate, and friction factor on the evolution of the alloy microstructure, optimizes the hot working process parameters of the alloy, and conducts hot compression deformation tests on the alloy using the determined optimal hot working process parameters. Ultimately, a deformed microstructure with uniformity, fine texture, and good strength is obtained. This provides theoretical guidance for the forging process of actual workpieces under different conditions, significantly improving production efficiency and saving time and costs.

[0018] The various technical features disclosed in the above-described invention, the various technical features disclosed in the following embodiments and examples, and the various technical features disclosed in the accompanying drawings can be freely combined to form various new technical solutions (all of which should be considered as having been recorded in this specification), unless such a combination of technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed. Features C and D are equivalent technical means that serve the same function, and technically only one needs to be used; it is impossible to use both simultaneously. Feature E can be technically combined with feature C. Therefore, the solution A+B+C+D should not be considered as having been recorded because it is technically infeasible, while the solution A+B+C+E should be considered as having been recorded. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the initial as-cast microstructure of the nickel-based wrought superalloy resistant to molten salt corrosion of Example 1 of this application;

[0020] Figure 2 This is a schematic diagram showing the sampling location and microstructure of the nickel-based deformable superalloy resistant to molten salt corrosion in Example 1 of this application.

[0021] Figure 3 The true stress-strain curve after thermal simulation of Example 1 of this application;

[0022] Figure 4 The image shows the hot working of the alloy in Example 1 at a true strain of 0.693.

[0023] Figures 5-9This is a schematic diagram of the deformed microstructure of the alloy in Example 1 at different temperatures and strain rates. Figure 5 1150℃ / 0.1s -1 ; Figure 6 1100℃ / 1s -1 ; Figure 7 1120℃ / 0.001s -1 ; Figure 8-9 1200℃ / 0.5s -1 ;

[0024] Figure 10 This is a schematic flowchart of an optimized method for hot working of nickel-based hard-to-deform high-temperature alloys resistant to molten salt corrosion, according to an embodiment of this application. Detailed Implementation

[0025] In the following description, many technical details are presented to help the reader better understand this application. However, those skilled in the art will understand that the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0026] This application relates to an optimized method for the hot working process of nickel-based, difficult-to-deform superalloys resistant to molten salt corrosion, such as... Figure 10 As shown, it includes the following steps:

[0027] In step 101, an alloy ingot is obtained by alloy smelting and casting.

[0028] In step 102, the alloy ingot is subjected to homogenization heat treatment.

[0029] In step 103, a sample is obtained by cutting at a designated location on the alloy ingot.

[0030] In step 104, the sample is heated to a specified temperature range at a specified heating rate and held at that temperature for a specified duration. Then, it is subjected to isothermal hot compression at a specified deformation rate. When the engineering strain reaches a specified threshold, it is immediately water-quenched to preserve the high-temperature deformation structure under different conditions. During this process, true stress-strain data are collected.

[0031] In step 105, the collected true stress-strain data are subjected to friction correction and adiabatic correction to correct the effects of interfacial friction and adiabatic temperature rise to obtain accurate rheological stress data.

[0032] In step 106, the constitutive equation of the alloy is constructed based on the corrected rheological stress data and the hot working diagram of the alloy is drawn. The optimal hot deformation region, safe region and unstable region of hot working are determined according to the dissipation values ​​of plastic deformation and microstructure evolution in the hot working diagram.

[0033] In step 107, the optimal range of hot working parameters for the alloy is determined based on the optimal hot deformation region, the safe region, and the instability region.

[0034] Optionally, in one embodiment, step 101 may further include: smelting the raw material alloy by sequentially employing vacuum induction melting and vacuum consumable remelting to obtain an alloy ingot of 200 kg.

[0035] Optionally, in one embodiment, the chemical composition of the raw material alloy, by weight percentage, may be: 5.0-8.0% Cr, 26.0-28.0% W, 0.5-0.8% Mn, 0.1-0.5% Si, 0.02-0.06% C, 0-1.0% Mo, 0-0.2% Ti, 0.03-0.1% Zr, and the balance Ni. The optimization method of this application can also be applied to other alloys.

[0036] Optionally, in one embodiment, step 102 may further include: loading the alloy ingot into a heating furnace with a furnace temperature ≤300℃ and heating it at a gradient rate of 30℃ / h to 1200℃-1300℃, and then holding it at that temperature for 15-25 hours.

[0037] Optionally, in one embodiment, step 103 may further include: cutting a cylindrical sample with dimensions of Φ8mm×12mm at half the radius of the alloy ingot, and polishing the surface of the sample.

[0038] Optionally, in one embodiment, step 104 may further include: heating the sample to 1050℃-1200℃ at a heating rate of 10℃ / s, holding it at that temperature for 10 minutes, and then heating it at a rate of 0.001-10s. -1 The deformation rate was subjected to isothermal hot compression, and water quenching was performed immediately after the strain reached 50% to preserve the high-temperature deformation microstructure under different conditions. The deformation temperatures could be selected as 1050℃, 1080℃, 1110℃, 1140℃, 1170℃, and 1200℃, and the deformation rate could be selected as 0.001s. -1 0.01s -1 0.1s -1 1s -1 Of course, you can also choose other values ​​within a specified range.

[0039] Optionally, in one embodiment, friction correction is achieved in the following manner:

[0040]

[0041] Where, σ f This is the true stress value after friction correction.

[0042] σ and ε are the actual measured true stress and true strain, respectively.

[0043] r0 and h0 are the initial radius and height of the sample before compression, respectively.

[0044] exp is an exponential function.

[0045] f is the friction correction factor, which is calculated as follows:

[0046]

[0047] Where h is the height of the sample after hot compression, Δh is the height difference of the sample before and after hot compression, and Δr is the difference between the maximum and minimum radii of the sample after hot compression.

[0048] Optionally, in one embodiment, the adiabatic correction is achieved in the following manner:

[0049] The temperature increment caused by the adiabatic temperature rise effect can be expressed as:

[0050]

[0051] In the formula, ΔT is the change in temperature.

[0052] ρ and C p These are the density and specific heat capacity of the alloy.

[0053] σ f This is the true stress value after friction correction.

[0054] B is the adiabatic correction factor;

[0055] Based on the above formula, the temperature increment at each deformation temperature during deformation at different strain rates of the alloy is calculated. This temperature increment ΔT is then compared with the true stress value σ obtained above after friction correction. f By integrating the data, we obtain the peak stress value at the actual deformation temperature T after friction and temperature correction.

[0056]

[0057] The constitutive equations for the alloy, based on the corrected rheological stress data, are as follows:

[0058]

[0059] in, Where is the strain rate, T is the deformation temperature, and R is the molar gas constant.

[0060] Optionally, in one embodiment, for the Ni-(26-28W)-6Cr alloy (with a chemical composition of 5.0-8.0% Cr, 26.0-28.0% W, 0.5-0.8% Mn, 0.1-0.5% Si, 0.02-0.06% C, 0-1.0% Mo, 0-0.2% Ti, 0.03-0.1% Zr, and the balance Ni), the optimal hot working parameters are: a deformation temperature of 1180℃-1200℃ and a strain rate of 0.5s when the engineering strain is 50%. -1 -1s -1 .

[0061] This invention employs a thermal simulation compression method to rapidly and effectively determine the optimal hot working process for difficult-to-deform high-tungsten superalloys. Based on the alloy's thermophysical properties, recrystallization, and grain growth kinetics models, it identifies the influence of deformation parameters on the hot working process, thereby optimizing the hot working parameters. This improves process stability and economy, avoids defects such as mixed grains, coarse grains, and cracks in the deformed microstructure, increases the yield of the final forging, and reduces production costs.

[0062] To better understand the technical solution of this application, the technical principles of this application are explained below.

[0063] This application constructs a hot working diagram of an alloy (e.g., Ni-(26-28W)-6Cr) to reflect the dynamic recrystallization mechanism of the alloy during deformation under various deformation parameters, so as to optimize its hot deformation process parameters and control its microstructure during hot deformation.

[0064] The energy consumed by a material during high-temperature deformation can be divided into two parts: one part is the energy dissipated by plastic deformation (G); the other part is the energy dissipated by microstructure evolution (J), such as phase transformation, dynamic recovery (DRV), dynamic recrystallization (DRX), as well as rheological instability and superplastic deformation. The relationship between them can be expressed as:

[0065]

[0066] Assuming the strain and deformation temperature are constant, the stress With strain rate The following relationship must be satisfied:

[0067]

[0068] Where K is the intrinsic parameter of the alloy, and m is the strain rate sensitivity index. The strain rate sensitivity index m is used to represent the ratio between the dissipated energy in the two components G and J, and can represent the thermal deformation mechanism under certain strain and deformation temperature conditions, that is:

[0069]

[0070] The relationship between dissipated energy J and the strain rate sensitivity index m under corresponding deformation conditions can be expressed as:

[0071]

[0072] For nonlinear dissipation processes, after normalizing the dissipated energy J, the dissipation efficiency (η), which characterizes the energy consumed by tissue changes, can be expressed as:

[0073]

[0074] Under a given strain, the change of η value with deformation temperature and strain rate constitutes a power dissipation diagram. The higher the value, the more fully the dynamic recrystallization of the corresponding deformed structure is achieved, which is more conducive to obtaining a uniform and refined recrystallized structure after hot deformation.

[0075] However, power dissipation diagrams alone cannot effectively determine the safe processing range and deformation instability range of an alloy under given deformation conditions. Therefore, the instability factor can be calculated. To determine the flow stability of an alloy, and to use this as a criterion for alloy processing instability, the expression is:

[0076]

[0077] Similar to the power dissipation diagram, The value can be calculated based on the functional relationship of changes in hot working process parameters, and a processing instability diagram under specific strain variables can be constructed based on this. Negative instability factor. This indicates that the material is in the rheological instability region, and a positive instability factor... This indicates that the process is within a safe processing range. Finally, by overlaying the power dissipation diagram and the processing instability diagram, the hot working diagram of the alloy is formed.

[0078] Nickel-based high-temperature alloys resistant to molten salt corrosion (Ni-(26-28W)-6Cr) exhibit greater deformation resistance compared to other deformable high-temperature alloys, necessitating research into the interaction mechanism and modeling of deformation parameters and microstructure during forging. Since hot working diagram theory reflects, to a certain extent, the mutual influence between microstructure evolution and deformation behavior, optimizing forging processes and parameters using this theory can effectively improve the rationality and reliability of process design. Furthermore, it provides a foundation for optimizing complex and costly hot forging processes.

[0079] To better understand the technical solution of this application, a specific example is provided below. The details listed in this example are mainly for ease of understanding and are not intended to limit the scope of protection of this application.

[0080] In step (1), the alloy is smelted and cast into alloy ingots. The raw materials can be batched according to the following composition, with the chemical composition by mass percentage as follows: Cr: 5.0-8.0%, W: 26.0-28.0%, Mn: 0.5-0.8%, Si: 0.1-0.5%, C: 0.02-0.06%, Mo: 0-1.0%, Ti: 0-0.2%, Zr: 0.03-0.1%, and the balance Ni. Vacuum induction melting and vacuum consumable remelting are used to produce 200kg ingots;

[0081] Then proceed to step (2), where the alloy ingot obtained by casting is placed in a heating furnace with a furnace temperature ≤300℃ and heated at a gradient rate of 30℃ / h to 1200℃-1300℃ and held for 15-25 hours.

[0082] Afterwards, proceed to step (3). After heat preservation, the alloy ingot is removed from the furnace and processed by wire EDM for sampling. A cylindrical sample with a size of Φ8mm×12mm can be cut from half the radius of the homogeneous ingot. The sample surface is polished and heated to the preset deformation temperature at a heating rate of 10℃ / s. After holding at the temperature for 10min, a hot compression deformation test is performed at the strain rate preset by the system. Six temperature values ​​are selected in the temperature range of 1050-1200℃, namely 1050℃, 1080℃, 1110℃, 1140℃, 1170℃, and 1200℃; the strain rates are selected as follows: 0.001s. -1 0.01s -1 0.1s -1 1s -1 Throughout the experiment, the deformation temperature was kept constant, and the true stress-strain data were automatically collected and recorded by computer. When the deformation reached 50%, the material was immediately water-quenched to preserve the deformed structure.

[0083] Then proceed to step (4), where a thermal simulation compression experiment is conducted under the selected temperature and strain rate constraints. The system automatically collects stress-strain data and performs temperature and friction corrections based on the collected stress-strain data to correct for the effects of interfacial friction and adiabatic temperature rise, thereby obtaining accurate rheological stress. This prepares for subsequent calculation of the alloy's hot deformation activation energy through constitutive equations and the construction of a hot working diagram to obtain the alloy's optimal deformation range. The correction process can be divided into friction correction and adiabatic temperature correction, with friction correction being the first step.

[0084] The friction effect can be expressed by the following formula:

[0085]

[0086] In the formula, σ f This is the true stress value after friction correction.

[0087] σ and ε are the actual measured true stress and true strain, respectively.

[0088] r0 and h0 are the initial radius and height of the sample before compression, respectively.

[0089] f is the friction correction factor, which can be calculated by measuring the dimensions of the hot-compressed sample after deformation. The calculation method is as follows:

[0090]

[0091] In the formula, h is the height of the sample after hot compression, Δh is the height difference of the sample before and after hot compression, and Δr is the difference between the maximum and minimum radii of the sample after hot compression.

[0092] The true stress value σ after friction correction during the hot compression of the alloy can be obtained from the above formula. f It is worth noting that, compared with the actual measured true stress value σ of the alloy, this value shows that, under all deformation conditions, σ f All are below σ. This deviation will increase continuously as the strain increases and the friction surface between the mold and the sample becomes larger.

[0093] Subsequently, the alloy rheological stress data were adiabatic corrected, and the temperature increment caused by the adiabatic temperature rise effect can be expressed as:

[0094]

[0095] In the formula, ΔT is the change in temperature.

[0096] ρ and C p These are the density and specific heat capacity of the alloy.

[0097] σ f It is the rheological stress after friction correction.

[0098] B is the adiabatic correction factor;

[0099] According to Formula 11, the alloy's performance at 0.001s was calculated. -1 0.01s -1 0.1s -1 1s -1 The temperature increment ΔT at each deformation temperature during strain rate deformation is then compared with the true stress value σ obtained above after friction correction. f The data is integrated; therefore, the peak stress value after friction and temperature correction is obtained at the actual deformation temperature T. This value will serve as the basis for providing experimental data for the subsequent construction of constitutive equations and thermal processing diagrams. It can be expressed by the following formula, namely:

[0100]

[0101] Subsequently, based on the corrected peak stress The constitutive equation for the Ni-(26-28W)-6Cr alloy is established, and its hyperbolic sinusoidal Arrhenius constitutive equation is expressed as follows:

[0102]

[0103] In the formula, Z is the Zener-Holloman parameter, which can represent the strain rate. and deformation temperature (T) on peak stress The impact;

[0104] Q is the activation energy (kJ·mol⁻¹) -1 ),

[0105] T is the deformation temperature (K).

[0106] This is the corrected peak stress (MPa).

[0107] R is the molar gas constant, with a value of 8.314 J / mol / K;

[0108] The constitutive equation for this alloy is obtained as follows:

[0109]

[0110] According to the equation, its deformation activation energy Q is 322.769 kJ·mol⁻¹. -1 The activation energy of hot deformation is closely related to the alloy composition, reflecting the ease or difficulty of hot working of the alloy, and providing a reference for selecting the optimal hot working range of the alloy through the hot working diagram.

[0111] Then proceed to step (5), where the corrected flow stress data under different deformation conditions are obtained through the above formula derivation, consisting of deformation temperature T and strain rate. The region formed is called a rheological instability diagram. The values ​​can be calculated based on the functional relationship of changes in hot working process parameters, and a processing instability diagram under specific strain can be constructed. Overlaying the power dissipation diagram with the processing instability diagram creates the hot working diagram of the alloy (e.g., ...). Figure 4 As shown in the figure, the shaded area represents the unstable region of the alloy under this deformation condition, which is not easily processed and deformed, and this serves as the basis for initially selecting hot working process parameters; generally, the main deformation mechanism of a specific region in the hot working diagram can be inferred from the microstructure evolution during the hot deformation process. Figures 5-9 As shown, the deformation temperatures are 1050℃-1200℃, and the strain rate is 0.001s. -1 -1s -1 Microstructure diagram under deformation conditions. Alloy at 1150℃ / 0.1s.-1 Under these conditions, deformation occurs within a hazardous zone of hot working. Within this zone, recrystallized grain sizes are uneven, such as… Figure 5 As shown. This is because, under the current deformation conditions, the stress state varies in different regions of the alloy during hot compression. In the later stages of deformation, the deformation compatibility of the DRX microstructure with larger grain size is poor. As the strain increases, cracks will eventually form in the stress concentration area and propagate rapidly under stress, causing the sample to crack. However, when the alloy is at 1100℃ / 1s... -1 and 1120℃ / 0.001s -1 Under these conditions, deformation occurs within the rheological instability region of the alloy, where the η value is relatively low. The deformed microstructure under these conditions exhibits a typical "necklace structure," and the DRX fraction is relatively low. This makes the alloy prone to instability mechanisms such as adiabatic shear banding, wedge cracking, and localized plastic deformation during hot deformation. Therefore, the hot working parameters of the alloy should avoid this region. When the temperature reaches 1200℃, the strain rate increases to 0.1 s⁻¹. -1 At this time, fully dynamic recrystallization occurs, such as Figure 9 As shown, in this region, the η value is higher than 40% (m value is approximately 0.29). Furthermore, the η value increases with increasing strain rate, representing the optimal hot deformation region for this alloy, yielding a fully recrystallized microstructure with uniform size.

[0112] It should be noted that, in this application, "designation" can be pre-defined or presumed based on known rules; the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, if it refers to performing an action based on a certain element, it means performing the action at least based on that element, including two cases: performing the action only based on that element, and performing the action based on that element and other elements. Expressions such as multiple, numerous, and various include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0113] This specification includes combinations of various embodiments described herein. Individual references to embodiments (e.g., “one embodiment”, “some embodiments”, or “preferred embodiments”) do not necessarily refer to the same embodiment; however, these embodiments are not mutually exclusive unless indicated to be mutually exclusive or are readily apparent to those skilled in the art. It should be noted that the word “or” is used in a non-exclusive sense throughout this specification unless the context explicitly indicates or requires it.

[0114] All references to this application are considered to be incorporated in their entirety into the disclosure of this application so that they can serve as a basis for modifications if necessary. Furthermore, it should be understood that after reading the contents of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. An optimized method for hot working of nickel-based hard-to-deform superalloys resistant to molten salt corrosion, characterized in that, Includes the following steps: Alloy ingots are obtained by alloy smelting and casting. The alloy ingot is subjected to homogenization heat treatment; A sample is obtained by cutting at a designated location on the alloy ingot; The sample is heated to a specified temperature range at a specified heating rate and held at that temperature for a specified duration. Then, it is subjected to isothermal hot compression at a specified deformation rate. When the engineering strain reaches a specified threshold, it is immediately water-quenched to preserve the high-temperature deformation structure under different conditions. True stress-strain data are collected during this process. Frictional and adiabatic corrections were performed on the collected true stress-strain data to correct for the effects of interfacial friction and adiabatic temperature rise and obtain accurate rheological stress data. The constitutive equation of the alloy is constructed based on the corrected rheological stress data, and the hot working diagram of the alloy is drawn. The optimal hot deformation region, safe region and unstable region of hot working are determined according to the dissipation values ​​of plastic deformation and microstructure evolution in the hot working diagram. The optimal range of hot working process parameters for the alloy is determined based on the optimal hot deformation region, the safe region, and the instability region. The friction correction is achieved in the following way: Where, σ f This is the true stress value after friction correction. σ and ε are the actual measured true stress and true strain, respectively. r0 and h0 are the initial radius and height of the sample before compression, respectively. exp is an exponential function. f is the friction correction factor, which is calculated as follows: Where h is the height of the sample after hot compression, Δh is the height difference of the sample before and after hot compression, and Δr is the difference between the maximum and minimum radii of the sample after hot compression.

2. The optimized method for hot working of nickel-based hard-to-deform superalloys resistant to molten salt corrosion as described in claim 1, characterized in that, The process of obtaining alloy ingots through alloy smelting and casting further includes: sequentially smelting the raw material alloy using vacuum induction melting and vacuum consumable remelting to obtain 200 kg of alloy ingots.

3. The optimized method for hot working of nickel-based hard-to-deform superalloys resistant to molten salt corrosion as described in claim 2, characterized in that, The chemical composition of the raw material alloy, by weight percentage, is: 5.0-8.0% Cr, 26.0-28.0% W, 0.5-0.8% Mn, 0.1-0.5% Si, 0.02-0.06% C, 0-1.0% Mo, 0-0.2% Ti, 0.03-0.1% Zr, and the balance Ni.

4. The optimized method for hot working of nickel-based hard-to-deform superalloys resistant to molten salt corrosion as described in claim 1, characterized in that, The adiabatic correction is achieved in the following way: The temperature increment caused by the adiabatic temperature rise effect can be expressed as: In the formula, ΔT is the change in temperature. ρ and C p These are the density and specific heat capacity of the alloy. σ f This is the true stress value after friction correction. B is the adiabatic correction factor; Based on the above formula, the temperature increment at each deformation temperature during deformation at different strain rates of the alloy is calculated. This temperature increment ΔT is then compared with the true stress value σ obtained above after friction correction. f By integrating the data, we obtain the peak stress value at the actual deformation temperature T after friction and temperature correction. The constitutive equation for the alloy is constructed based on the corrected rheological stress data as follows: in, Where is the strain rate, T is the deformation temperature, and R is the molar gas constant.

5. The optimized method for hot working of nickel-based hard-to-deform superalloys resistant to molten salt corrosion as described in claim 4, characterized in that, The process of homogenizing the alloy ingot through heat treatment further includes: The alloy ingot is placed in a heating furnace with a furnace temperature ≤300℃ and heated at a gradient rate of 30℃ / h to 1200℃-1300℃, and then held at that temperature for 15-25 hours.

6. The optimized method for hot working of nickel-based hard-to-deform superalloys resistant to molten salt corrosion as described in claim 1, characterized in that, The step of obtaining a sample by cutting at a designated location on the alloy ingot further includes: A cylindrical sample with dimensions of Φ8mm×12mm was cut from half the radius of the alloy ingot, and the surface of the sample was polished.

7. The optimized method for hot working of nickel-based hard-to-deform superalloys resistant to molten salt corrosion as described in claim 5, characterized in that, The process of heating the sample to a specified temperature range at a specified heating rate and holding it at that temperature for a specified duration, followed by isothermal hot compression at a specified deformation rate, and then immediately water quenching it after the engineering strain reaches a specified threshold to preserve the high-temperature deformed microstructure under different conditions, further includes: The sample was heated to 1050℃-1200℃ at a heating rate of 10℃ / s, held at that temperature for 10 minutes, and then heated at a rate of 0.001-10s. -1 The deformation rate was subjected to constant temperature hot compression, and when the strain reached 50%, it was immediately water quenched to retain the high-temperature deformed structure under different conditions.

8. The optimized method for hot working of nickel-based hard-to-deform superalloys resistant to molten salt corrosion as described in claim 7, characterized in that, The sample was heated to a deformation temperature of 1050℃-1200℃ at a heating rate of 10℃ / s, held for 10 minutes, and then heated at a rate of 0.001-10s. -1 During isothermal hot compression, the deformation rate is adjusted. The deformation temperatures are selected as 1050℃, 1080℃, 1110℃, 1140℃, 1170℃, and 1200℃. The deformation rate was selected as 0.001s. -1 0.01s -1 0.1s -1 1s -1 .

9. The optimized method for hot working of nickel-based hard-to-deform superalloys resistant to molten salt corrosion as described in any one of claims 1-8, characterized in that, For alloys with a chemical composition of 5.0-8.0% Cr, 26.0-28.0% W, 0.5-0.8% Mn, 0.1-0.5% Si, 0.02-0.06% C, 0-1.0% Mo, 0-0.2% Ti, 0.03-0.1% Zr, and the balance Ni, the optimal range of hot working parameters is as follows: When the strain is 50%, the deformation temperature is 1180℃-1200℃ and the strain rate is 0.5s. -1 -1s -1 .

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