Evaluation of microstructural uniformity and heat treatment guidance method for complex wall thickness single crystal superalloys

Abstract

The application discloses a kind of complex wall thickness single crystal superalloy structure uniformity evaluation and heat treatment guiding method, it is related to superalloy heat treatment technical field, comprising: according to the different wall thickness area of target component, constructs single crystal superalloy sample;Under different heat treatment parameter combinations, single crystal superalloy sample is heat treated;The organization size of strengthening phase in different wall thickness area of sample corresponding to heat treatment under different heat treatment parameter combinations is measured;Based on the organization size interval criterion of target component, the acceptable parameter interval of different wall thickness area is evaluated;Based on the organization size consistency criterion across wall thickness, the organization uniformity between different wall thickness area of sample is evaluated;The heat treatment parameter combination meeting the requirement of twice evaluation is used to guide the organization homogenization heat treatment of target component.The application solves the problem that the conventional single crystal superalloy heat treatment system determines heat treatment system according to single wall thickness area, and easily causes the whole organization mismatch of single crystal superalloy component.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy heat treatment technology, specifically to a method for evaluating the microstructure uniformity and providing guidance for heat treatment of complex-walled, thick-walled single-crystal high-temperature alloys. Background Technology

[0002] Single-crystal superalloys are widely used in hot-end components of aero-engines and gas turbines due to their excellent high-temperature strength, creep resistance, and microstructural stability. With the continuous increase in engine thrust-to-weight ratio and turbine inlet temperature, related components are gradually developing towards thinner walls, hollow structures, and complex cooling structures. A single component often contains extremely thin-walled regions, transitional wall thickness regions, and thick-walled load-bearing regions simultaneously, with significant local differences in wall thickness. For example, advanced hot-end components such as double-walled turbine blades and hollow blades with film cooling holes and internal cooling channels typically include outer walls, inner walls, baffles, rib structures, and locally thick-walled load-bearing regions. Their wall thickness spans are large, and their thermal response varies significantly. Traditional heat treatment regimes determined based on standard round bars or single-wall-thickness samples are insufficient to accurately represent the overall microstructural evolution of the component.

[0003] Traditional heat treatment regimes for single-crystal superalloys are typically established based on standard round bars, bulk specimens, or specimens with uniform wall thickness. Their fundamental assumption is that the material's microstructure response during heat treatment exhibits good consistency. However, for complex thick-walled components, the thermal responses of different wall thickness regions during heating, holding, cooling, and subsequent aging are not entirely consistent. Thin-walled regions, due to their small size and large surface area-to-volume ratio, are more sensitive to heat treatment temperature and time; thick-walled regions may exhibit delayed microstructure evolution or insufficient dimensional response.

[0004] Under the above conditions, if the heat treatment regime determined by a single thick-walled sample or a uniform sample is still used, it may result in the γ′ phase size in the thin-walled region being too small or too large, and the γ′ microstructure size in the thick-walled region being significantly inconsistent with that in the thin-walled region. This will cause the microstructure state within the same component to be inconsistent, affecting the overall mechanical properties and service reliability of the component. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, a method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys is provided. This method addresses the problem that traditional heat treatment regimes for single-crystal superalloys are determined based solely on a single wall thickness region, which can easily lead to overall microstructure mismatch in single-crystal superalloy components.

[0006] To achieve the above objectives, a method for evaluating the microstructure uniformity and providing heat treatment guidance for complex wall thickness single-crystal superalloys is provided, comprising the following steps: Based on the different wall thickness regions of the target component, a single-crystal high-temperature alloy sample is constructed such that the single-crystal high-temperature alloy sample has the different wall thickness regions. The single-crystal high-temperature alloy sample was heat-treated under different combinations of heat treatment parameters; The microstructure and size of the strengthening phase in different wall thickness regions of the single-crystal superalloy sample corresponding to heat treatment under different combinations of heat treatment parameters were measured. Based on the microstructure size range criterion of the target component, evaluate whether the microstructure size of different wall thickness regions of the single crystal high-temperature alloy sample is within the target size range; Based on the cross-wall thickness microstructure size consistency criterion, the microstructure uniformity between different wall thickness regions of the single-crystal superalloy sample is evaluated. The heat treatment parameters that meet the requirements of both evaluations are used to guide the homogenization heat treatment of the target component.

[0007] Furthermore, the reinforcing phase is a γ′ phase or a precipitated reinforcing phase dominated by the γ′ phase.

[0008] Furthermore, the target tissue size range criterion is that the average tissue size of the reinforcing phase is within a preset size range.

[0009] Furthermore, the cross-wall thickness tissue size consistency criterion is that the average tissue size difference of the reinforcing phase in the different wall thickness regions is less than a preset threshold.

[0010] Furthermore, the difference in the average tissue size of the reinforcing phase in different wall thickness regions is characterized by the ratio of the difference between the maximum and minimum tissue size of the reinforcing phase in different wall thickness regions to the average tissue size.

[0011] Furthermore, the combination of heat treatment parameters includes multiple parameters such as solution temperature, solution holding time, cooling rate, aging temperature, and aging time.

[0012] Furthermore, the wall thickness of the different wall thickness regions ranges from 0.3 mm to 10 mm.

[0013] Furthermore, the different wall thickness regions include at least a thin-walled region, a transitional wall thickness region, and a thick-walled region.

[0014] Furthermore, the single-crystal high-temperature alloy sample is a stepped or continuously variable wall thickness sample.

[0015] Furthermore, the target component is a Ni-based single-crystal superalloy, a Ni3Al-based single-crystal superalloy, or a γ′-strengthened single-crystal superalloy.

[0016] This invention provides a heat treatment method for homogenizing the microstructure of complex wall thickness single-crystal superalloy components. The method uses a method for evaluating the microstructure homogeneity of complex wall thickness single-crystal superalloys and guiding heat treatment to screen or adjust heat treatment parameters.

[0017] The beneficial effects of this invention are that the method for evaluating the uniformity of microstructure and guiding heat treatment of complex-walled thick single-crystal superalloys uses whether the average size of the strengthening phase is within the target size range and whether the size difference of the strengthening phase in different wall thickness regions is below a set threshold as the core microstructure criteria. It determines the acceptable heat treatment parameter range for each wall thickness region and determines the overall heat treatment process window by the intersection of the acceptable ranges for different wall thicknesses. This method avoids the size mismatch between thin-walled and thick-walled regions caused by traditional heat treatment processes that are based solely on uniform-thickness samples or standard round bars, thus achieving coordinated control of the strengthening microstructure size in different regions of complex-walled thick single-crystal superalloy components. Attached Figure Description

[0018] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a flowchart illustrating the method for evaluating the uniformity of microstructure and providing guidance on heat treatment of complex-walled, thick-walled single-crystal high-temperature alloys according to the present invention.

[0019] Figure 2 This is a schematic diagram of the gradient wall thickness single crystal sample of the present invention.

[0020] Figure 3 This is a schematic diagram of the tissue size response in different wall thickness regions according to the present invention.

[0021] Figure 4 This is a schematic diagram showing the intersection of acceptable heat treatment zones for different wall thicknesses in this invention.

[0022] Figure 5 Images of the thin-walled region, the transitional wall thickness region, and the thick-walled region under three heat treatment regimes in Embodiment 1 of the present invention.

[0023] Figure 6 This is a graph showing the verification results of the service life of different wall thickness regions under different heat treatment regimes in Embodiment 1 of the present invention. Detailed Implementation

[0024] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] This invention provides a method for evaluating the microstructure uniformity and providing heat treatment guidance for complex wall thickness single-crystal superalloys, comprising the following steps: S1. Construct single-crystal high-temperature alloy samples according to the different wall thickness regions of the target component, so that the single-crystal high-temperature alloy samples have different wall thickness regions.

[0027] Specifically, based on the actual wall thickness distribution of the target component (i.e., the complex wall thickness component to be evaluated), a single-crystal high-temperature alloy sample with multiple wall thickness regions is designed and prepared.

[0028] The target components are Ni-based single-crystal superalloys, Ni3Al-based single-crystal superalloys, or γ′-strengthened single-crystal superalloys.

[0029] In this embodiment, the wall thickness of different wall thickness regions of the target component ranges from 0.3 mm to 10 mm.

[0030] The target component has at least three wall thickness regions: a thin-walled region, a transitional wall thickness region, and a thick-walled region. The wall thickness increases sequentially from the thin-walled region to the transitional wall thickness region and the thick-walled region.

[0031] As a preferred embodiment, the single-crystal superalloy sample is a stepped or continuously variable wall thickness sample.

[0032] See Figure 2 As shown, the specimen is a single crystal sample with gradient wall thickness to illustrate the present invention, which uses the same sample to cover regions with different wall thicknesses to reduce interference caused by differences in composition, orientation and initial structure. Figure 2 The single crystal samples with medium gradient wall thickness were made with the same composition, orientation, and initial microstructure.

[0033] S2. Heat treatment of single-crystal high-temperature alloy samples under different combinations of heat treatment parameters.

[0034] Different combinations of heat treatment parameters include multiple parameters such as solution temperature, solution holding time, cooling rate, aging temperature, and aging time.

[0035] Specifically, the different combinations of heat treatment parameters are as follows: Θ={T s , t s v c T a , t a}(1) In this embodiment, the above formula (1) is used to illustrate that the heat treatment parameters are not a single temperature or a single time, but a set of process parameters that can jointly affect the size of the strengthening phase structure.

[0036] This set of process parameters includes the solution temperature T. s Solution treatment and heat preservation time t s Cooling rate vc Aging temperature T a and time limit t a wait.

[0037] Single-crystal superalloy samples were heat-treated with different heat treatment parameters, and the size of the strengthening phase structure of the single-crystal superalloy sample corresponding to each set of heat treatment parameters was obtained.

[0038] S3. Measure the microstructure and size of the strengthening phase in different wall thickness regions of single-crystal superalloy samples under different combinations of heat treatment parameters.

[0039] In a preferred embodiment, the reinforcing phase is the γ′ phase or a precipitated reinforcing phase dominated by the γ′ phase.

[0040] Specifically, in this embodiment, the strengthening phase is the γ′ phase. In this step, by statistically analyzing the γ′ microstructure size of different wall thickness regions of the single-crystal superalloy sample, the average size and distribution of the γ′ phase in each wall thickness region under different heat treatment regimes are obtained.

[0041] γ′ tissue size response relationship: d γ′ =f(h,Θ)(2); Where h represents regions with different wall thicknesses; Θ represents the combination of heat treatment parameters.

[0042] Equation (2) above is used to express that the average size of the γ′ phase is the result of the combined effect of wall thickness and heat treatment parameters.

[0043] The purpose of the above formula (2) is to clarify the technical concept of the present invention, so as to reflect that different wall thickness regions may have different microstructure size responses under the same heat treatment regime. Therefore, it is necessary to establish the correspondence between wall thickness, heat treatment parameters and microstructure size.

[0044] S4. Based on the microstructure size range criterion of the target component, evaluate or determine whether the microstructure size of different wall thickness regions of the single crystal high-temperature alloy sample is within the target size range.

[0045] Based on the average size and distribution of the γ′ phase in each wall thickness region under different heat treatment regimes, a mapping relationship between wall thickness, heat treatment parameters and γ′ microstructure size is established. Based on the target microstructure size range, it is determined whether the microstructure size of each wall thickness region of the single crystal high-temperature alloy sample is within the target size range.

[0046] In this embodiment, the target tissue size range criterion is that the average size of the reinforcing phase tissue is within a preset size range.

[0047] Specifically, the criteria for determining the target tissue size range are as follows: d min≤d γ′ (h) i ,Θ)≤d max (3); Where, d min d is the lower limit of the target size. max h is the upper limit of the target size. i Let Θ represent the i-th wall thickness region, and let Θ represent the combination of heat treatment parameters.

[0048] Equation (3) above is used to determine whether a certain wall thickness region meets the target microstructure size requirements under given heat treatment parameters.

[0049] If the average size of the γ′ phase in a certain wall thickness region is lower than the target lower limit, it indicates that the tissue size is too small; If the average size of the γ′ phase in a certain wall thickness region is higher than the target upper limit, it indicates that the tissue size is too large.

[0050] The heat treatment parameters can only be considered effective for the wall thickness region if the average size of the γ′ phase is within the target range.

[0051] This criterion addresses the question of whether a single wall thickness region is acceptable, and serves as the basis for subsequently determining the acceptable range.

[0052] Combination Figure 3 The figure shows the microstructure size response diagram of γ′ in different wall thickness regions, illustrating that different wall thickness regions exhibit different microstructure size responses under varying heat treatment parameters, and acceptable ranges can be selected from the target size range.

[0053] Among them, the blue line represents the γ′ microstructure size response of the 0.5 mm ultra-thin wall region, the orange line represents the γ′ microstructure size response of the 0.8 mm thin wall region, the green line represents the γ′ microstructure size response of the 1.2 mm transitional wall thickness region, the red line represents the γ′ microstructure size response of the 2 mm medium wall thickness region, and the purple line represents the γ′ microstructure size response of the 5 mm thick wall region. Figure 3 The target tissue size range is indicated by the horizontal blue rectangular area in the image.

[0054] The actual implementation process of this invention is as follows: setting several practically executable candidate heat treatment parameter combinations Θ j (Combinations 1-7 are schematic numbers for candidate parameter combinations, ordered according to parameter levels). Single-crystal samples with varying wall thicknesses were heat-treated, and then the average size of the γ′ phase in different wall thickness regions under each candidate regime was measured. The measured microstructure size was used as the basis for evaluating microstructure uniformity. Therefore, Figure 3The curves for different wall thickness regions are used to illustrate that "different wall thickness regions have different microstructure size response trends to changes in heat treatment parameters." Their purpose is to explain the technical principle of the present invention, rather than requiring the calculation of continuous response curves based on a specific mathematical model.

[0055] For the i-th wall thickness region, the candidate heat treatment parameter combinations that meet the target microstructure size requirements can be represented as its acceptable parameter set, i.e.: When d min ≤dγ′(h i Θ j )≤d max At that time, the candidate heat treatment parameter combination Θ j This can be considered effective for the i-th wall thickness region. Candidate heat treatment parameter combinations that satisfy the above dimensional conditions for all wall thickness regions and further satisfy the cross-wall thickness microstructure dimensional consistency criterion can be used as the recommended heat treatment parameters of this invention.

[0056] S5. Based on the cross-wall thickness microstructure size consistency criterion, evaluate the microstructure uniformity between different wall thickness regions of the single-crystal high-temperature alloy sample.

[0057] In this embodiment, the criterion for consistency of tissue size across wall thickness is that the average difference in tissue size of the reinforcing phase in different wall thickness regions is less than a preset threshold.

[0058] The difference in average tissue size of the reinforced phase in different wall thickness regions is characterized by the ratio of the difference between the maximum and minimum tissue size of the reinforced phase in different wall thickness regions to the average tissue size.

[0059] Criterion for consistency of wall thickness dimensions: (4); That is, the ratio of the difference between the maximum and minimum γ′ dimensions in regions with different wall thicknesses to the average γ′ dimension does not exceed a set threshold η.

[0060] Formula (4) is used to evaluate the dispersion of γ′ microstructure size in regions with different wall thicknesses under the same heat treatment regime. The basic idea is to divide the difference between the largest and smallest γ′ size in each wall thickness region by the average γ′ size of all wall thickness regions to obtain a dimensionless consistency index.

[0061] When this index is below the set threshold, it indicates that the γ′ size difference in different wall thickness regions is within an acceptable range; when this index is above the set threshold, it indicates that although the heat treatment process may allow some wall thickness regions to meet the size requirements, it cannot guarantee the overall dimensional consistency of complex components. This criterion is the key difference between this invention and traditional single-sample heat treatment optimization methods.

[0062] S6. The heat treatment parameters that meet the requirements of the two evaluations are combined to guide the heat treatment for homogenizing the microstructure of the target component.

[0063] In this embodiment, the recommended heat treatment parameter definitions are as follows: (5); In other words, the combination of heat treatment parameters that simultaneously satisfies both the size range criterion and the cross-wall thickness consistency criterion can serve as a recommended set of parameters for heat treatment to homogenize the microstructure of complex wall thickness single-crystal superalloys. This parameter set is not the optimal system for a single wall thickness region, but rather a range of parameters that satisfies the microstructure size requirements in thin-walled, transitional, and thick-walled regions, while controlling the microstructure differences across wall thicknesses. Ω represents the recommended heat treatment parameters from the recommended parameter set, Θ represents the combination of heat treatment parameters, and h... i For regions with different wall thicknesses.

[0064] Formula (5) is used to define the recommended heat treatment parameters for the recommended parameter set. That is, only when a combination of heat treatment parameters can make the average size of the γ′ phase in all wall thickness regions within the target range, and the difference in γ′ size between different wall thickness regions is lower than the set threshold, can the combination of parameters be used as the guiding parameters for tissue homogenization heat treatment.

[0065] Combination Figure 4 The diagram illustrates the selection of heat treatment parameters based on tissue homogenization evaluation criteria. It explains the acceptable parameter ranges and their intersections for different wall thickness regions, with the intersection serving as a guide parameter range for tissue homogenization heat treatment. Thin-walled, transitional-thickness, and thick-walled regions each have their own acceptable ranges (where 1 represents the acceptable range for thin-walled regions, 2 for transitional-thickness regions, and 3 for thick-walled regions). The overlapping area of ​​these three regions constitutes the recommended heat treatment parameter set Ω. Figure 4 Its purpose is to express the common constraint that regions with different wall thicknesses must meet organizational requirements, rather than requiring the calculation of continuous region boundaries through a pre-set mathematical model.

[0066] Therefore, the core of this invention is not to determine a specific heat treatment regime, but to establish an evaluation method for the microstructure uniformity of complex-walled, thick-walled single-crystal superalloys, and to screen and guide heat treatment parameters based on the evaluation results. The recommended parameter set can be represented as a two-dimensional or multi-dimensional parameter range composed of solution temperature, holding time, cooling rate, and aging parameters, used to guide the microstructure homogenization heat treatment of complex-walled, thick-walled single-crystal superalloy components.

[0067] The uniformity evaluation criteria described herein are used to guide the selection of heat treatment parameters and the control of component microstructure, and are not simply mathematical calculation methods. Recommended heat treatment parameters: For situations requiring further improvement in evaluation accuracy, a sensitivity criterion for the γ′ dimension as a function of wall thickness can be added to limit the slope of the γ′ dimension's response to changes in wall thickness.

[0068] This invention provides a method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys with recommended heat treatment parameters. It is applicable to the overall heat treatment of Ni-based, Ni3Al-based and other single-crystal superalloy system components with γ′ strengthening phase as the main component, especially suitable for single-crystal blades, guide vanes, hollow cooling structural components of aero-engines and other Ni-based and Ni3Al-based single-crystal superalloy components with significant wall thickness differences.

[0069] The core of the recommended heat treatment parameters for evaluating the microstructure uniformity of complex wall thickness single-crystal superalloys and providing heat treatment guidance in this invention lies in transforming the "heat treatment regime optimization problem" into a "parameter screening problem under the constraint of multi-wall thickness microstructure criteria." For the first time, it uses the microstructure synergy relationship between different regions of complex wall thickness components as the basis for evaluating the heat treatment regime, rather than focusing only on the optimal microstructure state of a single region.

[0070] The recommended heat treatment parameters of this invention provide a method for evaluating the uniformity of microstructure in complex wall thickness single-crystal superalloys and for guiding heat treatment. This method uses cross-wall thickness microstructure consistency criteria to incorporate the differences in microstructure response in different wall thickness regions into a unified evaluation framework for the first time. This achieves overall microstructure coordination control of complex components, avoids the microstructure mismatch problem between thin-walled and thick-walled regions caused by single wall thickness optimization, and improves the overall performance consistency and service reliability of components.

[0071] The present invention provides a method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys. It constructs a method for determining the heat treatment window based on multi-wall thickness constraints, transforming the traditional experience-based heat treatment regime design into a quantifiable and screenable parameter optimization problem.

[0072] The method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys of the present invention does not depend on a specific alloy system and can be extended to Ni-based, Ni3Al-based and other γ′-strengthened single-crystal superalloy systems, and has good versatility.

[0073] The present invention provides a method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys. By constructing gradient wall thickness single-crystal superalloy samples covering different wall thickness regions, and under the conditions of uniform alloy composition, crystal orientation and initial microstructure, the method systematically analyzes the size response of the strengthening phase microstructure in different wall thickness regions under multiple sets of heat treatment parameters, and establishes the correspondence between wall thickness, heat treatment parameters and microstructure size.

[0074] The present invention provides a method for evaluating the uniformity of microstructure and guiding heat treatment of complex-walled thick single-crystal superalloys. This method uses whether the average size of the strengthening phase is within the target size range and whether the size difference of the strengthening phase in different wall thickness regions is below a set threshold as core microstructure criteria. It determines the acceptable heat treatment parameter range for each wall thickness region and determines the overall heat treatment process window by the intersection of these acceptable ranges. This method avoids the size mismatch between thin-walled and thick-walled regions caused by traditional heat treatment processes based solely on uniform-thickness samples or standard round bars, thus achieving coordinated control of the strengthening microstructure size in different regions of complex-walled thick single-crystal superalloy components.

[0075] This invention provides a heat treatment method for homogenizing the microstructure of complex wall thickness single-crystal superalloy components. The method uses a method for evaluating the microstructure homogeneity of complex wall thickness single-crystal superalloys and guiding heat treatment to screen or adjust heat treatment parameters.

[0076] To further illustrate the implementation process of the method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal high-temperature alloys of the present invention, the following embodiments are provided for detailed explanation.

[0077] Example 1

[0078] See Figure 1 As shown, the target component in this embodiment is a Ni3Al-based single-crystal superalloy (specific composition is shown in Table 1 below). Different wall thickness regions of the target component are statistically analyzed. Based on the different wall thickness regions of the target component, gradient wall thickness single-crystal samples with multiple wall thickness regions are prepared. The number of these gradient wall thickness samples is multiple. The gradient wall thickness samples include a thin-walled region (0.2~0.5 mm), a transitional wall thickness region (0.7~1.5 mm), and a thick-walled region (2~4 mm).

[0079] Table 1. Nominal composition (wt.%) of Ni3Al-based single crystal superalloys

[0080] The sample was subjected to heat treatment using three different combinations of heat treatment parameters (i.e., heat treatment parameter matrices), denoted as heat treatment regimes Θ1, Θ2, and Θ3.

[0081] Heat treatment regime Θ1 includes: Solution treatment: 1290℃×2h+1295℃×2h+1300℃×2h+1305℃×2h+1310℃×2h+1315℃×2h+1320℃×4h (air cooling); Aging time: 1010℃×2h (air-cooled); Heat treatment regime Θ2 includes: Solution treatment: 1300℃×2h+1305℃×2h+1310℃×2h+1315℃×2h+1320℃×2h+1325℃×2h+1330℃×4h (air cooling); Aging time: 1020℃×2h (air-cooled); Heat treatment regime Θ3 includes: Solution treatment: 1310℃×2h+1315℃×2h+1320℃×2h+1325℃×2h+1330℃×2h+1335℃×2h+1340℃×4h (air cooling); Aging time: 1030℃×2h (air-cooled).

[0082] In this embodiment, Θ={T s , t s v c T a , t a The term Θ represents the set of heat treatment parameters that affect the microstructure size of γ′. It does not imply an exhaustive search within a continuous five-dimensional space consisting of solution temperature, holding time, cooling rate, aging temperature, and aging time. Instead, it treats each practically feasible heat treatment regime as a candidate parameter combination. j To conduct an evaluation.

[0083] This embodiment provides a specific method for constructing candidate parameter combinations. The solution treatment holding times, final holding times, and cooling methods for the three heat treatment regimes Θ1, Θ2, and Θ3 are kept consistent at each stage, with solution temperature and aging temperature as the main varying parameters, and increased progressively in increments of 10 °C. The highest solution temperature of Θ1 is 1320 ℃, and the aging temperature is 1010 ℃; The highest solution temperature of Θ2 is 1330 ℃, and the aging temperature is 1020 ℃; The highest solution temperature of Θ3 is 1340 ℃, and the aging temperature is 1030 ℃.

[0084] Meanwhile, the solution treatment temperatures at each step were increased uniformly in a 10 °C gradient, thus forming three candidate regimes with sequentially varying heat treatment parameters. By maintaining essentially consistent time and cooling conditions, the impact of temperature changes on the γ′ microstructure size in regions with different wall thicknesses can be evaluated.

[0085] Therefore, this embodiment adopts a candidate parameter combination construction method of "gradually varying one or more heat treatment parameters while maintaining basic consistency of some heat treatment parameters". For other single-crystal superalloys, since their applicable heat treatment regimes and the degree of influence of each heat treatment parameter on microstructure evolution may be different, different parameter combinations can be adopted accordingly, but they all fall within the range of heat treatment parameter combinations characterized by Θ. That is to say, the parameter values ​​of specific candidate regimes can vary with different alloy systems and heat treatment requirements, while the technical method for evaluating the microstructure uniformity of candidate regimes in this application remains consistent.

[0086] For each candidate parameter combination, it is not necessary to pre-determine whether it falls within the recommended range through theoretical calculations. Instead, after actual heat treatment, the γ′ microstructure dimensions of the thin-walled region, the transitional wall thickness region, and the thick-walled region are measured, and then the size range and cross-wall thickness consistency are determined separately. Thus, the heat treatment parameter matrix can be composed of several actual candidate heat treatment regimes, and the candidate parameter combinations can be further adjusted or supplemented based on the evaluation results.

[0087] It should be noted that this application does not aim to obtain all heat treatment parameter combinations that meet the conditions within a continuous multidimensional parameter space. Instead, it evaluates the microstructure uniformity of the actual candidate heat treatment parameter combinations and selects recommended parameters that meet the criteria. Therefore, the number of candidate parameter combinations does not necessarily need to cover the entire continuous parameter space. When a candidate system cannot simultaneously meet the size range criterion and the cross-wall thickness consistency criterion, one or more heat treatment parameters can be adjusted to form a new candidate combination for further evaluation. When a candidate system can ensure that different wall thickness regions meet the target size requirements and the microstructure size difference across wall thicknesses is below a set threshold, it can be used as a recommended heat treatment parameter.

[0088] Therefore, the core of this invention is not to specify a unique multidimensional parameter space sampling algorithm, nor to limit different single-crystal superalloys to using the same heat treatment parameter matrix, but to establish a method for evaluating the uniformity of microstructure across wall thickness applicable to different combinations of candidate heat treatment parameters, and to guide the screening and adjustment of heat treatment parameters based on the evaluation results.

[0089] See Figure 5 As shown, under each heat treatment regime, microstructure observations were conducted in the thin-walled region, the transitional wall thickness region, and the thick-walled region, and the average size of the γ′ phase was statistically analyzed. The γ′ phase size in each image was converted using a 5μm scale, and the side length of the γ′ phase square was taken as the microstructure size. The γ′ size was obtained through statistical analysis of no fewer than 50 microstructures. The statistical results were used to substitute into the size interval criterion and the cross-wall thickness size consistency criterion proposed in this invention to determine whether the heat treatment regime belongs to the recommended heat treatment parameters.

[0090] Specifically, determining whether a heat treatment regime falls under recommended heat treatment parameters includes the following steps: A. Statistical analysis of γ′ microstructure size under various heat treatment regimes.

[0091] To facilitate determination, the target size of the γ′ phase is set (d). γ′ The range is 0.40~0.75μm; the threshold for consistency of cross-wall thickness is set to 20%.

[0092] The target size range of γ′ phase (0.40–0.75 μm) and the consistency threshold η = 20% used in this embodiment are exemplary evaluation parameters set for the Ni3Al-based single-crystal superalloy used in the embodiment and its target high-temperature service conditions. They do not mean that different single-crystal superalloys should use the same microstructure size range and consistency threshold.

[0093] First, the optimal size of the γ′ phase is closely related to the specific alloy composition system, its operating temperature, stress level, and target performance. The volume fraction, composition, and high-temperature stability of the γ′ phase vary in different single-crystal superalloys, and the corresponding optimal or acceptable γ′ size range is not fixed.

[0094] For example, for single-crystal superalloys intended for operation in high-temperature environments above 1100 °C, determining the γ′ microstructure size requires careful consideration of high-temperature creep resistance and long-term microstructural stability. However, for single-crystal superalloys primarily operating in medium-temperature conditions below 1000 °C, the main performance requirements and γ′ strengthening states differ, thus the suitable γ′ microstructure size range may also vary. Even within the same type of single-crystal superalloy, the target γ′ size range needs to be adjusted accordingly due to differences in design service temperature, stress level, and performance indicators.

[0095] Therefore, d in this invention min and d max This method does not use fixed material constants, but rather pre-determined target microstructure requirements based on the alloy being evaluated and its specific service conditions. Therefore, before implementing this method, the target γ′ size range of the alloy is first determined based on its existing heat treatment microstructure requirements, design service temperature, and target performance, and its upper and lower limits are respectively used as d. min and d max The present invention subsequently addresses the issues of whether regions with different wall thicknesses can simultaneously meet the target under a given organizational objective, and whether cross-wall thickness structures are coordinated.

[0096] Secondly, the cross-wall thickness consistency threshold η characterizes the relative dispersion of the γ′ dimension between regions with different wall thicknesses under the same heat treatment regime. Its function is to prevent significant microstructural differences between thin-walled and thick-walled regions even if each local region meets the dimensional requirements. Therefore, η is not used to specify the absolute dimension of γ′, but rather to evaluate the degree of microstructural coordination between different regions of a complex thick-walled component.

[0097] In this embodiment, η was set to 20%, and the engineering rationality of this threshold was verified by subsequent durability tests. Under the Θ1 regime, the dimensions of γ′ in the thin-walled region, the transitional wall thickness region, and the thick-walled region are approximately 0.45 μm, 0.58 μm, and 0.72 μm, respectively. Although all are within the target size range of 0.40–0.75 μm, their cross-wall thickness consistency index C(Θ1) is approximately 46.3%, which is significantly higher than 20%. The corresponding durability of the three wall thickness regions are 48 h, 56 h, and 66 h, respectively, with a maximum durability difference of 18 h.

[0098] The consistency index of the Θ3 system is approximately 48.1%, which is also higher than 20%, and the maximum difference in service life between different wall thickness regions reaches 30 hours.

[0099] In contrast, under the Θ2 regime, the dimensions of the thin-walled region, the transitional wall thickness region, and the thick-walled region γ′ are approximately 0.46 μm, 0.50 μm, and 0.55 μm, respectively. All three wall thickness regions meet the target size range requirements, and their consistency index C(Θ2) is approximately 17.9%, which is lower than 20%. The corresponding durability lifetimes are 62 h, 65 h, and 68 h, respectively, with the maximum lifetime difference being only 6 h, which is the smallest among the three regimes.

[0100] The above results demonstrate that using 20% ​​as the evaluation threshold for cross-wall thickness microstructure consistency in the Ni3Al-based single-crystal superalloy used in this embodiment and under the verification conditions of 1150 ℃ / 137 MPa is reasonable. The Θ2 regime, which meets this threshold, exhibits a significantly smaller cross-wall thickness creep lifetime difference, while the Θ1 and Θ3 regimes, which significantly exceed this threshold, both exhibit larger cross-wall thickness performance differences. Therefore, the creep lifetime results of this embodiment provide microstructure-performance level verification support for the η=20% setting.

[0101] For single-crystal superalloy components with other composition systems, other design service temperatures, or other wall thickness spans, the corresponding consistency threshold can be determined based on the allowable differences in microstructure across wall thicknesses and performance requirements, rather than requiring a uniform 20%. This invention defines a technical method for evaluating the microstructure uniformity of complex wall thickness components through size range criteria and wall thickness consistency criteria, rather than limiting 0.40–0.75 μm or 20% to fixed values ​​applicable to all single-crystal superalloys.

[0102] according to Figure 5 (a) ~ Figure 5 The average size of the γ′ phase in each figure is estimated using a 5μm scale in (i), as shown in Table 2 below.

[0103] Table 2. Average γ′ phase size of samples under three heat treatment regimes

[0104] B. Verification of organizational size criteria.

[0105] According to formula (3): d min ≤d γ′ (h) i ,Θ)≤d max ; Where, d min d is the lower limit of the target size. max h is the upper limit of the target size. i Let Θ represent the i-th wall thickness region, and let Θ represent the combination of heat treatment parameters.

[0106] (1) Heat treatment regime Θ1.

[0107] Under the Θ1 regime, the dimensions of the thin-walled region, the transitional wall thickness region, and the thick-walled region γ′ are approximately 0.45 μm, 0.58 μm, and 0.72 μm, respectively, all within the target size range of 0.40–0.75 μm. Therefore, Θ1 satisfies the size interval criterion.

[0108] (2) Heat treatment regime Θ2.

[0109] Under the Θ2 regime, the dimensions of γ′ in the thin-walled region, the transitional wall thickness region, and the thick-walled region are approximately 0.46 μm, 0.50 μm, and 0.55 μm, respectively, all within the target size range of 0.40–0.75 μm. Therefore, Θ2 satisfies the size range criterion for all wall thickness regions.

[0110] (3) Heat treatment regime Θ3.

[0111] Under the Θ3 regime, the size of γ′ in the thick-walled region is approximately 0.55 μm, which is within the target size range; however, the size of γ′ in the thin-walled region is approximately 0.34 μm, which is below the target lower limit of 0.40 μm. Therefore, Θ3 does not satisfy the size range criterion for all wall thickness regions.

[0112] C. Verification of consistency criteria for cross-wall thickness dimensions.

[0113] According to formula (4), the consistency index of cross-wall thickness is defined as follows: ; When C(Θ)≤η, it indicates that the size difference of γ′ in regions with different wall thicknesses is within an acceptable range.

[0114] (1) Θ1 Institutional consistency determination.

[0115] .

[0116] therefore: ; Therefore, the Θ1 system does not meet the consistency criterion for cross-wall thickness dimensions.

[0117] (2) Θ2 Institutional Consistency Determination.

[0118] Under the Θ2 system: .

[0119] therefore: .

[0120] Therefore, the Θ2 system satisfies the consistency criterion for cross-wall thickness dimensions.

[0121] (3) Θ3 system consistency determination.

[0122] Under the Θ3 system: .

[0123] therefore: .

[0124] Therefore, the Θ3 system does not meet the consistency criterion for cross-wall thickness dimensions.

[0125] D. Heat treatment parameter guidance based on tissue homogeneity evaluation results.

[0126] According to formula (5): Ω={Θ|d min ≤d γ′ (h) i ,Θ)≤d max ,C(Θ)≤η,i=1,2,˙˙˙,n}; Where Ω represents the recommended heat treatment parameters, Θ represents the combination of heat treatment parameters, and h i For regions with different wall thicknesses.

[0127] Based on the above calculation results, the recommended heat treatment parameters are shown in Table 3 below.

[0128] Table 3. Results of Determining Recommended Heat Treatment Parameters for Three Heat Treatment Systems

[0129] Therefore, among the three heat treatment regimes, only Θ2 is the recommended heat treatment parameter combination selected by the microstructure uniformity evaluation criterion of this invention, and can be used as a guiding parameter for the heat treatment of microstructure uniformity of complex wall thickness components.

[0130] E. Durable life verification.

[0131] See Figure 6 To further verify the engineering applicability of the recommended heat treatment parameters determined in this invention, high-temperature creep life tests were conducted on samples with different wall thicknesses after different heat treatment regimes. The test conditions were 1150℃ / 137MPa. Creep life tests were conducted on samples from thin-walled, transition, and thick-walled regions under heat treatment regimes Θ1, Θ2, and Θ3, respectively. The test results are as follows: Figure 6 As shown.

[0132] Under the Θ1 regime, the lifespans of the thin-walled region, transition region, and thick-walled region were 48h, 56h, and 66h, respectively, with a difference of 18h between the highest and lowest lifespans. Under the Θ3 regime, the lifespans were 34h, 52h, and 64h, respectively, with a difference of 30h between the highest and lowest lifespans. These results indicate that the lifespan differences between different wall thickness regions are significant under the Θ1 and Θ3 regimes, making it difficult to ensure the overall performance coordination of complex wall thickness components.

[0133] In contrast, under the Θ2 regime, the lifespans of the thin-walled region, transition region, and thick-walled region are 62h, 65h, and 68h, respectively. The difference between the highest and lowest lifespans is only 6h, which is the smallest among the three heat treatment regimes, indicating that the lifespan distribution of different wall thicknesses is the most balanced under this regime.

[0134] Based on the aforementioned microstructure size criteria, the Θ2 regime simultaneously satisfies both the microstructure size range criterion and the cross-wall thickness size consistency criterion, thus falling under the recommended heat treatment parameters determined by this invention. The creep rupture life results further demonstrate that the recommended heat treatment parameters determined by this invention can reduce performance mismatch between different regions of complex wall thickness components, achieving synergistic optimization of cross-wall thickness microstructure and high-temperature creep rupture performance.

[0135] It should be noted that the durability test in this section is used to verify the engineering validity of the microstructure criterion of this invention, and is not a necessary limiting condition for determining the recommended heat treatment parameters. The recommended heat treatment parameters are still selected based on the microstructure size range criterion and the consistency criterion across wall thickness.

[0136] This embodiment shows that the overall heat treatment regime for complex wall thickness single crystal superalloy components cannot be determined solely based on the microstructure of a standard round bar, a single wall thickness specimen, or a certain local area. Instead, the differences in microstructure and dimensional response of the thin-walled region, transition region, and thick-walled region under the same heat treatment regime should be considered simultaneously.

[0137] Under the Θ1 regime, although the dimensions of γ′ in each wall thickness region are within the target size range, the dimensional differences between regions with different wall thicknesses are significant, resulting in insufficient consistency in microstructure across wall thicknesses. Therefore, it is not considered a recommended heat treatment parameter. Under the Θ3 regime, the dimensions of γ′ in the thick-walled region are within the target range, but the dimensions of γ′ in the thin-walled region are below the lower limit of the target, which also fails to meet the overall microstructure coordination requirements for complex wall thickness components. Therefore, neither Θ1 nor Θ3 meets the evaluation criteria for microstructure uniformity and can be used as guiding results for heat treatment parameters.

[0138] Under the Θ2 regime, the average γ′ size of the thin-walled region, the transition region, and the thick-walled region are all within the preset target size range, and the difference in γ′ size between different wall thickness regions is lower than the set threshold, which satisfies the tissue size interval criterion and the cross-wall thickness size consistency criterion. Therefore, Θ2 satisfies the tissue uniformity evaluation criterion and can be used as a guide result for heat treatment parameters.

[0139] Further durability testing showed that the difference in durability between different wall thickness regions was smallest and the durability distribution was most balanced under the Θ2 regime; while under the Θ1 and Θ3 regimes, the durability differences between different wall thickness regions were large, indicating significant performance mismatch across wall thicknesses. This result demonstrates that meeting the microstructure uniformity evaluation criterion of this invention not only enables coordinated control of the γ′ microstructure dimensions in different regions of complex wall thickness components, but also improves the high-temperature durability performance matching between different wall thickness regions.

[0140] This demonstrates that the microstructure size range criterion and cross-wall thickness microstructure consistency criterion proposed in this invention can quantitatively evaluate the degree of microstructure homogenization under different heat treatment regimes for complex wall thickness single-crystal superalloys. Based on the evaluation results, heat treatment parameter combinations that are conducive to cross-wall thickness microstructure synergy can be selected, providing a quantifiable and verifiable guiding method for the formulation of heat treatment regimes for complex wall thickness single-crystal superalloy components.

[0141] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by 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. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for evaluating the microstructure uniformity and providing guidance for heat treatment of complex wall thickness single-crystal superalloys, characterized in that, Includes the following steps: Based on the different wall thickness regions of the target component, a single-crystal high-temperature alloy sample is constructed such that the single-crystal high-temperature alloy sample has the different wall thickness regions. The single-crystal high-temperature alloy sample was heat-treated under different combinations of heat treatment parameters; The microstructure and size of the strengthening phase in different wall thickness regions of the single-crystal superalloy sample corresponding to heat treatment under different combinations of heat treatment parameters were measured. Based on the microstructure size range criterion of the target component, evaluate whether the microstructure size of different wall thickness regions of the single crystal high-temperature alloy sample is within the target size range; Based on the cross-wall thickness microstructure size consistency criterion, the microstructure uniformity between different wall thickness regions of the single-crystal superalloy sample is evaluated. The heat treatment parameters that meet the requirements of both evaluations are used as the heat treatment to guide the homogenization of the microstructure of the target component.

2. The method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys according to claim 1, characterized in that, The strengthening phase is the γ′ phase or a precipitated strengthening phase dominated by the γ′ phase.

3. The method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys according to claim 1, characterized in that, The target tissue size range criterion is that the average tissue size of the reinforcing phase is within a preset size range.

4. The method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys according to claim 1, characterized in that, The criterion for consistency of tissue size across wall thickness is that the average difference in tissue size of the reinforcing phase in different wall thickness regions is less than a preset threshold.

5. The method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys according to claim 4, characterized in that, The difference in the average tissue size of the reinforcing phase in different wall thickness regions is characterized by the ratio of the difference between the maximum and minimum tissue size of the reinforcing phase in different wall thickness regions to the average tissue size.

6. The method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys according to claim 1, characterized in that, The heat treatment parameter combination includes multiple parameters such as solution temperature, solution holding time, cooling rate, aging temperature, and aging time.

7. The method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys according to claim 1, characterized in that, The wall thickness of the different wall thickness regions ranges from 0.3 mm to 10 mm.

8. The method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys according to claim 7, characterized in that, The different wall thickness regions include at least a thin-walled region, a transitional wall thickness region, and a thick-walled region.

9. The method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys according to claim 8, characterized in that, The single-crystal high-temperature alloy sample is a stepped or continuously variable wall thickness sample.

10. The method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal superalloys according to claim 1, characterized in that, The target component is a Ni-based single-crystal superalloy, a Ni3Al-based single-crystal superalloy, or a γ′-strengthened single-crystal superalloy.

11. A heat treatment method for homogenizing the microstructure of a complex wall thickness single-crystal superalloy component, characterized in that, The heat treatment parameters can be screened or adjusted using the method for evaluating the uniformity of microstructure and guiding heat treatment of complex wall thickness single-crystal high-temperature alloys as described in any one of claims 1 to 10.

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