A nickel-based single crystal superalloy casting property evaluation mold and method

Abstract

The present application relates to a kind of nickel-based single crystal superalloy casting performance evaluation mould, including sprue cup, gate and selector, also include pagoda-shaped cavity, the pagoda-shaped cavity is located below gate, and is connected with the spiral selector below, for obtaining casting performance evaluation sample;The pagoda-shaped cavity is a body of revolution, including multiple different diameter but uniform height disc platform and uniform size cylinder, disc diameter gradually increases from bottom to top.The present application utilizes the designed pagoda-shaped casting performance evaluation sample can converge to the side of disc-shaped platform at last solidification, promote hot crack formation, combine the carrier of different diameter disc-shaped platform simultaneously qualitatively, quantitatively evaluate the single crystal integrity and shrinkage characteristics of nickel-based single crystal superalloy.In the evaluation alloy shrinkage characteristics, consider the solidification characteristics of pagoda-shaped casting, deduct the area occupied by mixed crystal, can make the evaluation result more accurate.

Description

Technical Field

[0001] This invention belongs to the field of single-crystal blade casting and forming, and specifically relates to a mold and method for evaluating the casting performance of nickel-based single-crystal high-temperature alloys. Background Technology

[0002] Single-crystal blades are key components of aero-engines, primarily formed by investment casting of nickel-based single-crystal superalloys. With the development of modern aviation and national defense, the content of refractory elements in nickel-based single-crystal superalloys has increased, leading to increasingly complex blade structures. This pursuit of improved performance has resulted in a growing trend of solidification defects during blade forming, such as impurities, small-angle grain boundaries, freckles, striations, and shrinkage porosity, significantly reducing the yield of single-crystal blades.

[0003] The casting properties of alloys are one of the key factors to consider in casting, directly affecting the yield of cast products. To improve the yield of single-crystal blades, it is necessary to fully understand the casting properties of nickel-based single-crystal superalloys. Based on the forming characteristics of single-crystal blades and common solidification defect types, researchers have found that the single-crystal integrity and shrinkage characteristics of nickel-based single-crystal superalloys are key casting performance indicators affecting the yield of single-crystal blades.

[0004] Currently, the single-crystal integrity of nickel-based single-crystal superalloys is a widely concerned casting performance indicator. Zhang Xiaoli et al., in patent CN102706920A, disclosed a method for designing two molds by adjusting the length and height of a square platform. They quantitatively averaged the single-crystal integrity of the alloy by analyzing the platform length and height of impurity crystal formation in castings formed using the two molds. Li Jiarong et al., in patent CN115586317A, disclosed a method for evaluating the tendency of nickel-based single-crystal superalloys to form freckle defects using stepped samples. These patented methods can only evaluate the single-crystal integrity of nickel-based single-crystal superalloys and cannot be used to evaluate the alloy's shrinkage characteristics. Zeng Long et al., in patent CN115047160A, disclosed an apparatus and method for evaluating the casting performance of single-crystal superalloys, capable of evaluating both the single-crystal integrity and shrinkage characteristics of nickel-based single-crystal superalloys, but this requires the use of different molds. Literature such as "Influence of Crystal Orientation on As-cast Microstructure and Segregation of Nickel-based Single-crystal Superalloys" indicates that crystal orientation has a significant impact on the solidification behavior and casting performance of nickel-based single-crystal superalloys, but this issue has not been considered in current casting performance evaluations. Summary of the Invention

[0005] The purpose of this invention is to address the problems of existing evaluation methods, such as the inability to use a single mold to comprehensively evaluate the casting performance of nickel-based single-crystal superalloys and the failure to consider the influence of single-crystal orientation on the casting performance of the alloy. This invention proposes a mold for evaluating the casting performance of nickel-based single-crystal superalloys, enabling a comprehensive evaluation of casting performance using a single mold, namely, the evaluation of the single-crystal integrity and shrinkage characteristics of nickel-based single-crystal superalloys.

[0006] Another objective of this invention is to propose a method for evaluating the casting performance of nickel-based single-crystal superalloys. This method uses a pagoda-shaped sample to evaluate the single-crystal integrity and shrinkage characteristics of nickel-based single-crystal superalloys.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A mold for evaluating the casting performance of a nickel-based single-crystal superalloy includes a pouring cup, a runner, and a crystal selector, as well as a pagoda-shaped cavity. The pagoda-shaped cavity is located below the runner and is connected to the spiral crystal selector below it, used to obtain casting performance evaluation samples. The pagoda-shaped cavity is a body of revolution, including multiple circular platforms of different diameters but uniform height and cylinders of uniform size, with the diameter of the circular platforms gradually increasing from bottom to top.

[0009] Preferably, the diameter of the disc ranges from 25mm to 85mm, and the height ranges from 2.5mm to 7mm; the diameter of the cylinder ranges from 10mm to 20mm, and the height ranges from 15mm to 25mm.

[0010] Preferably, the casting performance evaluation mold includes four independent pagoda-shaped cavities that surround the central axis of the casting performance evaluation device at equal angles and intervals.

[0011] Preferably, the pouring cup is used to constrain the flow direction of the poured alloy; the gating system is located below the pouring cup and is used to fill the molten alloy into the pagoda-shaped cavity and provide filling pressure; the crystal selector is a spiral crystal selector, divided into a spiral selection section and a cylindrical crystal initiation section, which are used to prepare evaluation samples. <001> An oriented seed crystal is placed in the starting section of a spiral crystal selector to achieve seed crystal selection preparation, used to guide the crystal entering the pagoda-shaped cavity... <001> Oriented single crystal, the <001> Orientation refers to the orientation of a single crystal. <001> The orientation is parallel to the axis of the pagoda-shaped casting. The seed crystal selection method refers to a method used in the preparation of single-crystal superalloys by placing a seed crystal within the initiation section of a spiral crystal selection process to prepare a single crystal with an orientation consistent with the seed crystal.

[0012] A method for evaluating the casting performance of nickel-based single-crystal superalloys, using any of the molds described above, mainly includes the following steps:

[0013] 1) Prepare evaluation samples according to the casting performance evaluation mold and the seed crystal selection method;

[0014] 2) Evaluation of single crystal integrity of nickel-based single crystal superalloys: The single crystal integrity of nickel-based single crystal superalloys is graded according to the number of disk platforms. From bottom to top, the single crystal integrity is rated according to the number of disk platforms on which the impurity defects first appear.

[0015] 3) Evaluation of the shrinkage characteristics of nickel-based single-crystal superalloys: The shrinkage characteristics of nickel-based single-crystal superalloys are graded according to the number of disk platforms. From bottom to top, the shrinkage characteristics are rated according to the number of disk platforms on which hot cracks first appear.

[0016] Preferably, in step 2), the higher the level, the better the single crystal integrity, thus achieving qualitative evaluation; within the same level, the smaller the ratio of impurity crystals to the area of ​​the disk platform, the better the single crystal integrity, thus achieving quantitative evaluation.

[0017] Preferably, in step 3), the higher the grade, the better the shrinkage performance, achieving qualitative evaluation; within the same grade, the smaller the hot cracking coefficient K, the better the shrinkage performance, achieving quantitative evaluation; wherein, the hot cracking coefficient K is equal to the product of the hot crack length l and the maximum width H divided by the single crystal growth area S in the plane, and the single crystal growth area S in the plane = the total area S0 of the plane - the area S occupied by the impurity crystals in the plane. A .

[0018] Preferably, step 1) includes the following steps:

[0019] The first step is to prepare the mold shell according to the casting performance evaluation mold: the mold shell is made using the standard investment casting process, including making the investment model, coating with refractory ceramics, dewaxing, firing and curing the mold shell, washing, drying and other steps.

[0020] The second step involves obtaining casting performance evaluation samples using a high-pulling-rate method: <001> The seed crystal is placed into the starting section of the spiral crystal selector of the mold shell. The mold shell and the seed crystal are placed together into the directional solidification furnace, and a vacuum is drawn. Then the mold shell is heated and held at the temperature. After that, the molten master alloy is poured into the mold shell. After standing, the mold shell is pulled from the hot zone to the cold zone of the directional solidification furnace at a certain pulling rate to obtain a casting performance evaluation sample, which is then etched using a macro-etching agent.

[0021] Preferably, in the first step, the parameters including mold shell heating, heat preservation, molten master alloy pouring temperature, and settling time are set to commonly used parameters for industrial production of single crystal blades. The mold shell heating and heat preservation temperature is 1450℃~1600℃, the heat preservation time is 3min~15min, the master alloy pouring temperature is 1480℃~1550℃, and the settling time is 3min~15min.

[0022] Preferably, in the second step, the pulling speed is set to 1.2 to 2 times the commonly used parameters for single-crystal blades in industrial production, with a pulling rate range of 60 μm / s to 200 μm / s.

[0023] Compared with the prior art, the present invention has the following advantages

[0024] 1. This invention provides a method for evaluating the casting performance of nickel-based single-crystal superalloys. A designed pagoda-shaped casting performance evaluation specimen can simultaneously evaluate the single-crystal integrity and shrinkage characteristics of nickel-based single-crystal superalloys. The casting performance evaluation specimen is obtained using a high-pulling rate method. On the one hand, this promotes a more convex solid / liquid interface on the entire casting during directional solidification, thus facilitating the formation of impurity defects on the side of the disc-shaped platform facing the mold's central axis. On the other hand, it facilitates the final solidification of the disc-shaped platform facing the directional solidification furnace wall, allowing the overall shrinkage of the disc-shaped platform to accumulate at the final solidification point, promoting hot crack formation. By using disc-shaped platforms of different diameters as a carrier, qualitative and quantitative evaluation of alloys with different casting properties can be rapidly achieved.

[0025] 2. When quantitatively evaluating the shrinkage characteristics of alloys, this invention deducts the area occupied by impurities based on the solidification characteristics of pagoda-shaped castings, which makes the evaluation results more accurate.

[0026] 3. This invention employs a seed crystal selection method to ensure that the crystal orientation of the samples entering the casting performance evaluation specimen is... <001> This avoids the influence of crystal orientation on the alloy solidification process and improves the accuracy of casting performance evaluation results.

[0027] 4. This invention can be used to compare the casting performance of different grades of nickel-based single crystal high-temperature alloys. It is simple and quick to operate, and can save time and costs. Attached Figure Description

[0028] Figure 1 A schematic diagram of the mold structure for evaluating casting performance.

[0029] Figure 2 This is a schematic diagram of a pagoda-shaped sample.

[0030] Figure 3 The pagoda-shaped casting performance evaluation sample obtained in Example 1.

[0031] Among them, 1. pouring cup; 2. runner; 3. pagoda-shaped cavity; 4. crystal selector; 5. disc-shaped platform; 6. cylinder. Detailed Implementation

[0032] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0033] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0034] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0035] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0036] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0037] The present invention will be further described in conjunction with the following examples, but this does not limit the scope of protection of the present invention.

[0038] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0039] Based on the mechanism of impurity crystal formation caused by supercooling nucleation at the corners of abrupt cross-sections during the directional solidification of nickel-based single-crystal superalloys, and the formation of hot cracks due to casting shrinkage, this application designs a casting performance evaluation specimen with a pagoda-shaped structure. The single-crystal integrity and shrinkage characteristics of the nickel-based single-crystal superalloy are evaluated by assessing the location of impurities and hot cracks on the pagoda-shaped specimen after directional solidification, the area occupied by the impurities, or the hot cracking coefficient. Specifically, this invention discloses a method for evaluating the casting performance of nickel-based single-crystal superalloys.

[0040] Example 1

[0041] This embodiment designs a mold for evaluating the casting performance of nickel-based single-crystal high-temperature alloys, including: a pouring cup, a runner, a pagoda-shaped cavity, and a crystal selector.

[0042] The pouring cup primarily serves to constrain the flow direction of the poured alloy. The gating system, located below the pouring cup, facilitates the filling of the molten alloy into the pagoda-shaped cavity and provides filling pressure. The pagoda-shaped cavity, situated below the gating system, is primarily used to obtain samples for evaluating casting performance. The crystal selector is a spiral crystal selector commonly used in industrial production, its main purpose being to ensure that the crystals entering the pagoda-shaped cavity are... <001> Oriented single crystal.

[0043] In this embodiment, the pagoda-shaped cavity is a rotating body, composed of five circular platforms of different diameters but uniform heights and cylinders of uniform size. The diameters of the disks gradually increase from bottom to top. The diameters of the disks are 35mm, 45mm, 55mm, 65mm, and 75mm, respectively. All disks have a height of 5mm. The cylinder has a diameter of 15mm and a height of 20mm.

[0044] In this embodiment, the casting performance evaluation mold includes four independent pagoda-shaped cavities that surround the central axis of the casting performance evaluation device at equal angles and intervals.

[0045] A method for evaluating the casting performance of nickel-based single-crystal superalloys, using the aforementioned mold to evaluate the casting performance of nickel-based single-crystal superalloy DD6, mainly includes the following steps:

[0046] The first step is to prepare the mold shell according to the casting performance evaluation mold. The mold shell is made using a standard investment casting process, including making the investment model, coating with refractory ceramic, dewaxing, firing and curing the mold shell, washing, and drying.

[0047] The second step involves obtaining casting performance evaluation samples using a high pulling rate method. <001> The seed crystal is placed into the starting section of the spiral crystal selector of the mold shell. The mold shell and the seed crystal are placed together into the directional solidification furnace, and a vacuum is drawn. Then the mold shell is heated and held at the temperature. After that, the molten master alloy is poured into the mold shell. After standing, the mold shell is pulled from the hot zone to the cold zone of the directional solidification furnace at a certain pulling rate to obtain a casting performance evaluation sample, which is then etched using a macro-etching agent.

[0048] In this embodiment, the heating and holding temperatures of the mold shell, the pouring temperature of the molten master alloy, and the settling time are set as commonly used parameters for the industrial production of single-crystal blades. The heating and holding temperature of the mold shell is 1520℃, the holding time is 5min, the pouring temperature of the master alloy is 1520℃, and the settling time is 5min.

[0049] In this embodiment, the pulling speed is set to 125 μm / s, which is within 1.2 to 2 times the commonly used parameters for industrial production of single-crystal blades.

[0050] In this embodiment, the macroscopic etchant used is a mixture of H2O2 and HCl in a 1:1 volume ratio.

[0051] The third step is to evaluate the single-crystal integrity of the nickel-based single-crystal superalloy. The single-crystal integrity of the nickel-based single-crystal superalloy is graded according to the number of disk platforms. From bottom to top, the single-crystal integrity is rated according to the first disk platform where the impurity defect appears. The higher the grade, the better the single-crystal integrity, achieving a qualitative evaluation. Within the same grade, the smaller the proportion of impurity area on that disk platform, the better the single-crystal integrity, achieving a quantitative evaluation.

[0052] In this embodiment, impurities first appear on the second disk-shaped platform, and the area of ​​impurities accounts for 0.23. Therefore, the single-crystal integrity of the DD6 alloy is rated as level 2, 23%.

[0053] The fourth step is to evaluate the shrinkage characteristics of nickel-based single-crystal superalloys. The shrinkage characteristics are graded based on the number of disk platforms, from bottom to top. The platform on which hot cracks first appear is assigned a corresponding grade. A higher grade indicates better shrinkage performance, achieving a qualitative evaluation. Within the same grade, a smaller hot cracking coefficient K (equal to the product of the hot crack length l and the maximum width H divided by the single-crystal growth area S in that plane) indicates better shrinkage performance, achieving a quantitative evaluation.

[0054] In this embodiment, hot cracking first appears on the third disk-shaped platform, and the hot cracking coefficient K is 0.0453. Therefore, the shrinkage characteristics of the DD6 alloy are rated as level 3, 0.0453.

[0055] Example 2

[0056] This embodiment designs a mold for evaluating the casting performance of nickel-based single-crystal high-temperature alloys, including: a pouring cup, a runner, a pagoda-shaped cavity, and a crystal selector.

[0057] The pouring cup primarily serves to constrain the flow direction of the poured alloy. The gating system, located below the pouring cup, facilitates the filling of the molten alloy into the pagoda-shaped cavity and provides filling pressure. The pagoda-shaped cavity, situated below the gating system, is primarily used to obtain samples for evaluating casting performance. The crystal selector is a spiral crystal selector commonly used in industrial production, its main purpose being to ensure that the crystals entering the pagoda-shaped cavity are... <001> Oriented single crystal.

[0058] In this embodiment, the pagoda-shaped cavity is a rotating body, composed of seven circular platforms of different diameters but uniform heights and cylinders of uniform size. The diameters of the circular platforms gradually increase from bottom to top. The diameters of the circular platforms are 25mm, 35mm, 45mm, 55mm, 65mm, 75mm, and 85mm, respectively. All platforms have a height of 10mm. The cylinders have a diameter of 20mm and a height of 25mm.

[0059] In this embodiment, the casting performance evaluation mold includes four independent pagoda-shaped cavities that surround the central axis of the casting performance evaluation device at equal angles and intervals.

[0060] A method for evaluating the casting performance of nickel-based single-crystal superalloys, using the aforementioned mold to evaluate the casting performance of nickel-based single-crystal superalloy DD3, mainly includes the following steps:

[0061] The first step is to prepare the mold shell according to the casting performance evaluation mold. The mold shell is made using a standard investment casting process, including making the investment model, coating with refractory ceramic, dewaxing, firing and curing the mold shell, washing, and drying.

[0062] The second step involves obtaining casting performance evaluation samples using a high pulling rate method. <001> The seed crystal is placed into the starting section of the spiral crystal selector of the mold shell. The mold shell and the seed crystal are placed together into the directional solidification furnace, and a vacuum is drawn. Then the mold shell is heated and held at the temperature. After that, the molten master alloy is poured into the mold shell. After standing, the mold shell is pulled from the hot zone to the cold zone of the directional solidification furnace at a certain pulling rate to obtain a casting performance evaluation sample, which is then etched using a macro-etching agent.

[0063] In this embodiment, the heating and holding temperatures of the mold shell, the pouring temperature of the molten master alloy, and the settling time are set as commonly used parameters for the industrial production of single-crystal blades. The heating and holding temperature of the mold shell is 1550℃, the holding time is 10min, the pouring temperature of the master alloy is 1520℃, and the settling time is 3min.

[0064] In this embodiment, the pulling speed is set to 150 μm / s, which is within 1.2 to 2 times the commonly used parameters for industrial production of single-crystal blades.

[0065] In this embodiment, the macroscopic etchant used is a mixture of H2O2 and HCl in a 1:1 volume ratio.

[0066] The third step is to evaluate the single-crystal integrity of the nickel-based single-crystal superalloy. The single-crystal integrity of the nickel-based single-crystal superalloy is graded according to the number of disk platforms. From bottom to top, the single-crystal integrity is rated according to the first disk platform where the impurity defect appears. The higher the grade, the better the single-crystal integrity, achieving a qualitative evaluation. Within the same grade, the smaller the proportion of impurity area on that disk platform, the better the single-crystal integrity, achieving a quantitative evaluation.

[0067] In this embodiment, the impurity crystals first appear on the fourth disk-shaped platform, and the area ratio of the impurity crystals is 0.41. Therefore, the single crystal integrity of the DD6 alloy is rated as level 4, 0.41.

[0068] The fourth step is to evaluate the shrinkage characteristics of nickel-based single-crystal superalloys. The shrinkage characteristics are graded based on the number of disk platforms, from bottom to top. The platform on which hot cracks first appear is assigned a corresponding grade. A higher grade indicates better shrinkage performance, achieving a qualitative evaluation. Within the same grade, a smaller hot cracking coefficient K (equal to the product of the hot crack length l and the maximum width H divided by the single-crystal growth area S in that plane) indicates better shrinkage performance, achieving a quantitative evaluation.

[0069] In this embodiment, hot cracks first appear on the 6th disk-shaped platform, and the hot cracking coefficient K is 0.0361. Therefore, the shrinkage characteristics of the DD6 alloy are rated as level 3, 0.0361.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A nickel-based single crystal superalloy casting property evaluation mold comprising a sprue cup, a gate, and a selector, characterized in that, Also included is a pagoda-shaped cavity, which is located below the sprue and connected with the spiral selector below, used to obtain casting performance evaluation samples by combining seed crystal selection method; the pagoda-shaped cavity is a rotary body, including multiple disc platforms with different diameters but uniform height and a uniform size cylinder, and the disc diameter gradually increases from bottom to top; The casting performance evaluation sample is used to evaluate the single crystal integrity of the nickel-based single crystal superalloy: the single crystal integrity of the nickel-based single crystal superalloy is graded according to the number of disc platforms, and from bottom to top, the first disc platform where the heterogeneous crystal defect appears is graded as the corresponding series, and the single crystal integrity is evaluated. The casting performance evaluation sample is used to evaluate the shrinkage characteristics of the nickel-based single crystal superalloy: the shrinkage characteristics of the nickel-based single crystal superalloy are graded according to the number of disc platforms, and from bottom to top, the first disc platform where the hot crack appears is graded as the corresponding series, and the shrinkage characteristics are evaluated.

2. A nickel-based single crystal superalloy cast property evaluation die according to claim 1, wherein, The disc diameter ranges from 25mm to 85mm, and the height ranges from 2.5mm to 7mm; the cylinder diameter ranges from 10mm to 20mm, and the height ranges from 15mm to 25mm.

3. A nickel-based single crystal superalloy cast property evaluation die according to claim 2, wherein, The casting performance evaluation mold includes four independent pagoda-shaped cavities, which are equally angular and equally spaced around the central axis of the casting performance evaluation mold.

4. A nickel-based single crystal superalloy cast property evaluation die according to claim 3, wherein, The sprue cup is used to constrain the flow of the pouring alloy; the sprue is located below the sprue cup and is used to fill the molten alloy into the pagoda-shaped cavity and provide filling pressure; the selector is a spiral selector, which is divided into a spiral selector section and a cylindrical nucleation section, and when preparing the evaluation sample, the <001> oriented seed crystal is placed in the nucleation section of the spiral selector to realize the seed crystal selection method for preparing the evaluation sample, so that the crystal entering the pagoda-shaped cavity is a <001> oriented single crystal.

5. A method of evaluating the castability of a nickel-based single crystal superalloy, characterized by, The mold of any one of claims 1 to 4 is used for evaluation, and the main process includes the following steps: 1) preparing the evaluation sample according to the casting performance evaluation mold combined with the seed crystal selection method; 2) evaluating the single crystal integrity of the nickel-based single crystal superalloy: grading the single crystal integrity of the nickel-based single crystal superalloy according to the number of disc platforms, and from bottom to top, the first disc platform where the heterogeneous crystal defect appears is graded as the corresponding series, and the single crystal integrity is evaluated; 3) evaluating the shrinkage characteristics of the nickel-based single crystal superalloy: grading the shrinkage characteristics of the nickel-based single crystal superalloy according to the number of disc platforms, and from bottom to top, the first disc platform where the hot crack appears is graded as the corresponding series, and the shrinkage characteristics are evaluated.

6. A method of evaluating the castability of a nickel-based single crystal superalloy according to claim 5, characterized in that, The higher the series in step 2), the better the single crystal integrity, and a qualitative evaluation is realized; within the same level, the smaller the area ratio of heterogeneous crystals on the disc platform, the better the single crystal integrity, and a quantitative evaluation is realized.

7. The method of evaluating the castability of a nickel-base single crystal superalloy according to claim 5, wherein The higher the series in step 3) is, the better the shrinkage performance is, and a qualitative evaluation is realized; within the same level, the smaller the thermal cracking coefficient K is, the better the shrinkage performance is, and a quantitative evaluation is realized; wherein the thermal cracking coefficient K is equal to the product of the thermal cracking length l and the maximum width H divided by the single crystal growth area S in the plane, and the single crystal growth area S in the plane = the total area S0 of the plane - the area S of the miscellaneous crystal in the plane A .

8. The method of evaluating the castability of a nickel-base single crystal superalloy according to claim 5, wherein Step 1) includes the following steps: First, prepare the mold shell according to the casting performance evaluation mold: use standard investment casting process to make the mold shell, including making the investment model, coating refractory ceramic, dewaxing, baking and curing the mold shell, water washing, and drying steps; In the second step, the casting performance evaluation sample is obtained by using a high pulling speed mode: a <001> orientation seed crystal is placed in a seed selection section of a mold shell spiral seed selector, the mold shell and the seed crystal are placed in a directional solidification furnace, vacuum is drawn, then the mold shell is heated and kept warm, then the molten mother alloy is poured into the mold shell, after standing for a period of time, the mold shell is pulled from the hot zone to the cold zone of the directional solidification furnace at a certain pulling speed, and the casting performance evaluation sample is obtained, and macro-etching agent is used for etching.

9. The method of evaluating the castability of a nickel-base single crystal superalloy according to claim 8, wherein In the first step, the parameters of the mold shell heating, holding, the molten mother alloy pouring temperature and the standing time are set as the commonly used parameters for industrial production of single crystal blades, the mold shell heating and holding temperature is 1450-1600 DEG C, the holding time is 3-15 min, the mother alloy pouring temperature is 1480-1550 DEG C, and the standing time is 3-15 min.

10. The method of evaluating the castability of a nickel-base single crystal superalloy according to claim 8, wherein In the second step, the pulling speed is set to 1.2-2 times of the commonly used parameters for industrial production of single crystal blades, and the pulling speed range is 60-200 μm / s.

Images