A non-destructive testing method for ceramic cores of directional solidification high-temperature alloy hollow blades
By using real-time backgroundless projection of the ceramic core formed by neutron beam incident and combining it with neutron beam intensity analysis, the problem of real-time non-destructive testing of deformation and fracture of ceramic core during the casting process of high-temperature alloy blades was solved, and the precision casting quality control of high-temperature alloy blades was realized.
Patent Information
- Application Number
- CN202610291057.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-11
- Publication Date
- 2026-07-10
AI Technical Summary
In the casting process of directional solidification high-temperature alloy hollow blades, the deformation and fracture of the ceramic core are difficult to detect in real time without damage. Existing technologies cannot achieve real-time observation and analysis of the ceramic core during the casting process.
A real-time background-free projection of a ceramic core is formed by incident neutron beams. By combining the neutron beam intensity and the transmitted neutron beam intensity, the changes in the ceramic core are observed and analyzed in real time through an imaging system. The thickness change of the ceramic core is calculated using the neutron linear attenuation coefficient, thus achieving non-destructive testing.
Real-time non-destructive testing of ceramic cores during the directional solidification casting process of high-temperature alloy blades has been achieved, which can accurately characterize the change process and characteristics of ceramic cores, and improve the accuracy and real-time performance of the testing.
Smart Images
Figure CN122361475A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of high-temperature alloy blade casting and testing technology, specifically a non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades. Background Technology
[0002] With the continuous increase in the inlet air temperature of aero-engines and gas turbines, the structure of the internal cooling channels of high-temperature alloy hollow turbine blades is becoming increasingly complex, which places more stringent demands on the precision casting and testing technologies of the blades. As a key component in forming the complex internal cavity structure of hollow blades, the ceramic core must withstand various complex and harsh environments during the precision investment casting process of high-temperature alloy blades. For example, during the casting of high-temperature alloy blades, the ceramic core must withstand the thermal and mechanical shocks of the molten metal. Under directional solidification process conditions, the working conditions of the ceramic core are even more demanding. At molten metal pouring temperatures exceeding 1500℃ and during solidification processes lasting several hours, the ceramic core is highly susceptible to high-temperature creep deformation, leading to issues such as core misalignment or even fracture. The degree of high-temperature deformation of the ceramic core directly affects parameters such as the wall thickness accuracy, internal cavity structural integrity, and blade casting yield of the blade casting.
[0003] However, in directional solidification casting, the observation and characterization of the deformation and fracture processes of the ceramic core are severely limited because the ceramic core is located within the mold shell and is encased in metal or molten metal. It is impossible to clearly understand when the ceramic core deforms and fractures during casting, or what forms of deformation and fracture occur. Currently, the only methods available are destructive cutting of the blades after casting for observation, or detection using wall thickness or deep hole measuring instruments after removing the core, to perform post-cast analysis or deduction of the deformation and fracture processes of the ceramic core. The limitation of these methods is that they cannot achieve non-destructive testing of the blades or real-time in-situ characterization of the complex deformation and fracture processes and characteristics of the ceramic core during casting. Summary of the Invention
[0004] The purpose of this invention is to provide a non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades. This method utilizes the incident neutron beam to form a real-time background-free projection of the ceramic core for defect observation and analysis. Simultaneously, it can obtain the real-time changes in parameters such as the ceramic core thickness based on the intensity of the incident neutron beam and the intensity of the transmitted neutron beam. This allows for real-time characterization of the ceramic core's change process and characteristics during the directional solidification casting of high-temperature alloy blades, thus achieving the goal of real-time non-destructive testing of the ceramic core.
[0005] The objective of this invention is achieved through the following technical solution: A non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades includes the following steps: Step 1: Incorporate strong neutron absorbers into the ceramic core slurry and prepare the ceramic core; Step 2: Prepare the outer shell of the ceramic core; Step 3: The detector in the imaging system is activated and probes the interior of the insulated chamber of the directional solidification device to obtain the dark field under natural conditions; Step 4: The neutron beam enters the insulation chamber through the incident window on one side of the directional solidification device, and exits through the exit window on the other side of the directional solidification device and enters the detector, thereby enabling the imaging system to obtain a blank original background. Step 5: Place the shell with ceramic core obtained in Step 2 into the insulation chamber of the directional solidification device; Step 6: The directional solidification device begins the casting process. At the same time, the neutron beam is injected into the insulation chamber through the entrance window on one side of the directional solidification device and exited into the detector through the exit window on the other side of the directional solidification device. The imaging system obtains the original projection including the ceramic core. Step 7: The imaging system processes the dark field obtained in Step 3, the original background obtained in Step 4, and the original projection obtained in Step 6 in real time to obtain the real-time background-free projection of the ceramic core. At the same time, the thickness change of the ceramic core is obtained according to the following formula (1): I=I0·e -μ·t (1); In the above formula (1), I0 is the intensity of the incident neutron beam input through the incident window, I is the intensity of the transmitted neutron beam output through the exit window, μ is the neutron linear attenuation coefficient of the ceramic core material, e is the natural exponent, and t is the thickness of the ceramic core.
[0006] In step one, the neutron-absorbing strong absorber Gd2O3 powder is processed and then incorporated into the ceramic core slurry according to a set ratio to prepare the ceramic core.
[0007] In step two, the preparation process of the shell is as follows: Step 2.1: Precisely position the ceramic core prepared in Step 1 into the wax mold, and inject molten wax. After cooling, a wax mold with an internal ceramic core is obtained. Step 2.2: Dip the wax model into the corresponding slurry and dry it to form a surface layer. Repeat this process a set number of times to form a shell with a multi-layered structure. Step 2.3: Dewaxing the wax model to obtain a shell with an internal ceramic core.
[0008] In step four, the imaging system continuously acquires a set number of original background images. In step six, the imaging system continuously acquires a set number of original projection images.
[0009] In step seven, the imaging system processes the dark field, raw background, and raw projection as follows: Step 7.1: Perform median filtering on the original background to obtain the filtered background, and perform median filtering on the original projection to obtain the filtered projection; Step 7.2: Use dark field to process the filtered background to obtain a dark-field removed background, and use dark field to process the filtered projection to obtain a dark-field removed projection. Step 7.3: Use the dark field background removal process to perform background removal processing on the dark field projection to obtain the background removal projection of the ceramic core.
[0010] In step 7.1, the median filtering process of the original background is as follows: based on the multiple original backgrounds obtained in step four, the pixel values at the same position are sorted, the median value is selected, and then the median values are recombined in sequence to form the filtered background. The median filtering process for the original projection is as follows: based on the multiple original projections obtained in step six, the pixel values at the same position are sorted, the median value is selected, and then the median values are recombined sequentially to form the filtered projection.
[0011] In step 7.2, the dark field removal process specifically involves subtracting the dark field from the filtered background and the filtered projection at the corresponding pixel points.
[0012] In step 7.3, the background removal process specifically involves dividing the corresponding pixel values of the background removal and dark projection removal processes, which means removing the dark projection from the background removal process.
[0013] In step seven, the neutron linear attenuation coefficient μ is obtained through prior sample imaging detection. Specifically, a sample with the same material as the ceramic core is made with consistent thickness on the top and bottom. The incident neutron beam intensity I0 is obtained based on the original background of the sample. The transmitted neutron beam intensity I through the sample is obtained based on the original projection of the sample including the sample. Then, the neutron linear attenuation coefficient μ of the ceramic core material is obtained by back-calculation according to the above formula (1).
[0014] The incident window material and the exit window material of the directional solidification device are preferably aluminum alloys, and the insulation layer material of the heat-insulating furnace is preferably graphite carbon felt.
[0015] The advantages and positive effects of this invention are as follows: 1. In the directional solidification casting process of high-temperature alloy hollow blades, this invention utilizes the incident neutron beam to form a real-time background-free projection of the ceramic core, thereby enabling real-time defect observation and analysis of the ceramic core. Simultaneously, it can obtain real-time changes in parameters such as the ceramic core thickness based on the intensity of the incident and transmitted neutron beams. This allows for real-time characterization of the ceramic core's change process and characteristics during the directional solidification casting of high-temperature alloy blades, achieving the goal of real-time non-destructive testing of the ceramic core.
[0016] 2. This invention incorporates a strong neutron-absorbing substance into the ceramic core slurry to prepare the ceramic core. This can greatly increase the attenuation of the transmitted neutron beam output from the emission window of the directional solidification device, thereby ensuring that a sufficiently clear original image of the ceramic core is obtained, making it possible to observe and detect the ceramic core in real time during the directional solidification casting process of the blade.
[0017] 3. In order to ensure that the final background-removed projection meets the requirements for defect observation and analysis of ceramic cores, this invention first obtains the dark field under natural conditions inside the insulation chamber of the directional solidification device, then obtains the blank original background inside the insulation chamber under neutron beam input conditions, and finally uses an imaging system to process the obtained original projection including the ceramic core in combination with the dark field and the original background. This ensures the imaging clarity of the final background-removed projection and meets the real-time observation requirements of the ceramic cores.
[0018] 4. This invention utilizes Beer's Law (also known as the neutron decay law), which is adapted to the characteristics of neutron beams, to perform back-calculation based on the intensity of the incident neutron beam and the intensity of the transmitted neutron beam. This allows for real-time changes in the thickness of the ceramic core during the casting process, making the method of this invention more comprehensive and accurate in characterizing the process and characteristics of ceramic core changes. Furthermore, for ceramic cores doped with neutron-absorbing materials, this invention can conduct experimental testing on samples beforehand to obtain the accurate neutron linear decay coefficient μ of the ceramic core material, thereby ensuring the accuracy of the aforementioned ceramic core thickness calculation. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the process of the method of the present invention. Figure 2 This is a schematic diagram of the neutron beam path in the method of the present invention. Figure 3 for Figure 2 A cross-sectional view of the structure of a directional solidification device. Figure 4 for Figure 3 AA view of the directional solidification device. Figure 5 This is a schematic diagram of a ceramic core structure for which the method of the present invention is applied. Figure 6 This is a schematic diagram of the image data processing flow of the imaging system of the present invention. Figure 7 for Figure 6 The original backbed in Figure 8 for Figure 6 The filtered backplane in the middle, Figure 9 for Figure 6 The dark background in the middle, Figure 10 for Figure 6 The original projection in Figure 11 for Figure 6 Filtered projection in Figure 12 for Figure 6 Dark field projection in Figure 13 for Figure 6 Background removal projection in the middle, Figure 14 for Figure 6 A schematic diagram of the original grayscale distribution of the original projection. Figure 15 for Figure 6 A schematic diagram of the filtered grayscale distribution of the projection after filtering.
[0020] In this diagram, 1 is the neutron source, 2 is the pinhole selector, 3 is the flight tube, 4 is the directional solidification device, 401 is the furnace crucible, 402 is the insulation chamber, 403 is the heater, 404 is window A, 405 is window B, 406 is the core stretching mechanism, 407 is the incident window, 408 is the exit window, 5 is the detector, 6 is the imaging data processing module, 7 is the shell, 8 is the original background, 9 is the original grayscale distribution diagram, 10 is the original projection, 11 is the filtered background, 12 is the dark field, 13 is the filtered projection, 14 is the background without dark field, 15 is the projection without dark field, 16 is the grayscale distribution diagram after filtering, 17 is the projection without background, and 18 is the defect diagram. Detailed Implementation
[0021] The invention will now be described in further detail with reference to the accompanying drawings.
[0022] like Figure 1 As shown, the method of the present invention includes the following steps: Step 1: Incorporate the neutron-absorbing material into the ceramic core slurry and prepare the ceramic core.
[0023] In this embodiment, the neutron-absorbing material Gd2O3 powder is ball-milled and then incorporated into the ceramic core slurry at a ratio of 0.5% to 5.0% wt. After being pressed into a green body, the ceramic core of the blade is prepared by high-temperature sintering and curing.
[0024] The ceramic core structure formed in this embodiment is as follows: Figure 5 As shown.
[0025] Step 2: Prepare the outer shell 7 of the ceramic core.
[0026] The specific process for preparing shell 7 in this embodiment is as follows: Step 2.1: Precisely position the ceramic core prepared in Step 1 into the wax mold, inject molten wax, and after cooling, obtain a wax mold with an internal ceramic core.
[0027] Step 2.2: Dip the wax mold into fine ceramic powder slurry (i.e., surface coating) and sprinkle fine sand on it, then dry it to form a smooth, high-form-resistance surface layer. This process is repeated several times to form a shell 7 with sufficient strength and a multi-layered structure.
[0028] In this step, the slurry used for subsequent wax film impregnations can be a slurry with a larger particle size (such as alumina powder) as needed to ensure the strength of the shell 7.
[0029] Step 2.3: Dewaxing the wax model to obtain a shell 7 with an internal ceramic core.
[0030] In this embodiment, the shell 7 is sent into a high-pressure, high-temperature dewaxing kettle, so that the wax material forming the wax mold melts into a liquid and flows out, leaving only the shell 7 with the ceramic core inside in the kettle, thus preparing for subsequent directional casting.
[0031] Step 3: As Figures 2-4 As shown, the detector 5 in the imaging system is activated and probes the interior of the chamber 402 of the directional solidification device 4 to obtain the dark field 12 under natural conditions.
[0032] The dark field refers to a situation where the mold shell 7 with the ceramic core obtained in step two is not placed inside the insulation chamber 402, and the insulation chamber 402 is not irradiated by a neutron beam. In this case, the detector 5 detects the pixel values inside the insulation chamber 402 under its natural state. Figure 6 As shown, in subsequent steps of the present invention, the influence of natural pixels on imaging is reduced by subtracting the original background 8 and the original projection 10 from the dark field 12 by pixels.
[0033] like Figure 2 As shown, in this embodiment, the imaging system, in addition to the detector 5, also includes an imaging data processing module 6. Both the detector 5 and the imaging data processing module 6 are technologies known in the art and are commercially available products. Figure 6 As shown, the imaging data processing module 6 is mainly responsible for processing the acquired dark field 12, original background 8 and original projection 10 to obtain the final background-removed projection 17.
[0034] Step Four: As Figure 2 and Figure 4 As shown, the neutron beam is injected into the insulation chamber 402 through the incident window 407 on one side of the directional solidification device 4, and is output through the exit window 408 on the other side of the directional solidification device 4 and injected into the detector 5, thereby enabling the imaging system to obtain a blank original background 8.
[0035] In this step, the imaging system needs to continuously acquire a set number of original background images to meet the needs of subsequent median filtering and other processing.
[0036] Other examples Figure 4 As shown, in the directional solidification device 4 used in this invention, the materials of the incident window 407, the exit window 408, and the insulation layer material of the insulation chamber 402 are all selected from materials with high neutron penetration, good mechanical properties, and excellent radiation stability. In this embodiment, the materials of the incident window 407 and the exit window 408 can be aluminum alloys, and the insulation layer material of the insulation furnace can be graphite carbon felt.
[0037] like Figure 2 As shown, in this embodiment, the system for generating the neutron beam includes a neutron source 1, a pinhole selector 2, and a flight tube 3. All of the above devices are technologies known in the art.
[0038] Step 5: As Figure 3 As shown, the shell 7 with ceramic core obtained in step two is placed in the insulation chamber 402 of the directional solidification device 4.
[0039] Step 6: The directional solidification device 4 begins the casting process. At the same time, the neutron beam is injected into the insulation chamber 402 through the incident window 407 on one side of the directional solidification device 4, and is output into the detector 5 through the exit window 408 on the other side of the directional solidification device 4. The imaging system obtains the original projection 10 including the ceramic core.
[0040] In this step, the imaging system also needs to continuously acquire a set number of original projections 10 to meet the needs of subsequent median filtering and other processes.
[0041] In addition, the ceramic core with strong neutron-absorbing material prepared in step one of this invention can greatly increase the attenuation of the transmitted neutron beam output from the exit window 408, thereby ensuring that a sufficiently clear original image of the ceramic core is obtained.
[0042] The directional solidification device 4 is a technology known in the art, such as Figures 3-4 As shown, in the directional solidification device 4 used in this embodiment, a furnace crucible 401 is provided above the insulation chamber 402 for inputting high-temperature alloy molten metal into the shell 7 inside the insulation chamber 402. A heater 403 (a carbon-carbon heater in this embodiment) is provided inside the insulation chamber 402 to ensure the temperature inside the insulation chamber 402. A core stretching mechanism 406 is provided on the lower side of the insulation chamber 402 to realize directional solidification stretching.
[0043] Step 7: The imaging system processes the dark field 12 obtained in Step 3, the original background 8 obtained in Step 4, and the original projection 10 obtained in Step 6 in real time to obtain the real-time background-free projection 17 of the ceramic core for defect observation and analysis. At the same time, the thickness variation of the ceramic core is obtained according to the following formula (1): I=I0·e -μ·t (1); like Figure 4 As shown, in the above formula (1), I0 is the intensity of the incident neutron beam input by the incident window 407, I is the intensity of the transmitted neutron beam output by the exit window 408, μ is the neutron linear decay coefficient of the material, which is determined by the capture and absorption of neutrons and atomic nuclei and elastic / inelastic scattering, e is the natural exponent, and t is the thickness of the ceramic core.
[0044] Equation (1) above is Beer's Law (also known as the neutron decay law) adapted to the characteristics of neutron beams. That is, when a parallel monochromatic neutron beam penetrates a uniform sample, the decay law of the neutron intensity follows an exponential decay relationship. However, in addition to utilizing... Figure 6 In addition to observing and analyzing the final formed ceramic core with the background removed projection 17, the thickness t of each part of the ceramic core can be quantitatively inverted by measuring the incident neutron beam intensity I0 and the transmitted neutron beam intensity I and combining them with the known neutron linear attenuation coefficient μ. Then, as needed, the density distribution or composition of each part of the ceramic core can be further quantitatively inverted by combining parameters such as the density of the ceramic core material.
[0045] In this embodiment, the neutron linear attenuation coefficient μ can be obtained through prior sample imaging detection. For example, a sample with the same material as the ceramic core and the same thickness at the top and bottom can be made. The sample thickness t is 10 mm. According to the original background of the sample, the average value of the incident neutron beam intensity I0 is 30000. According to the original projection of the sample including the sample, the average value of the transmitted neutron beam intensity I through the sample is 13000. Then, the neutron linear attenuation coefficient μ = 0.09 of the ceramic core material can be obtained by back-calculation according to the above formula (1). During the normal real-time imaging process of the ceramic core, μ = 0.09 will be substituted into the above formula (1) and combined with the real-time obtained I0 and I values to obtain the real-time change of the thickness t of the ceramic core during the directional solidification casting process of the blade. Wherein I0 can be obtained through Figure 2 The neutron beam is obtained in real time by a neutron source 1, a pinhole selector 2, a flight tube 3, etc., and I can be obtained in real time by detector 5. The acquisition of I0 and I is a well-known technology in this field.
[0046] In this step, the imaging system processes the dark field 12, the original background 8, and the original projection 10 as follows: Step 7.1: As Figure 6 As shown, the original background 8 is subjected to median filtering to obtain the filtered background 11, and the original projection 10 is subjected to median filtering to obtain the filtered projection 13.
[0047] The median filtering process specifically involves: continuously acquiring multiple images of the same image (i.e., obtaining multiple original background images 8 in step four and multiple original projection images 10 in step six), sorting the pixel values at the same position in the multiple repeated images, selecting the median value, and then recombining the median values into a new image. Since the median value has the lowest probability of being a noise point, this method can reduce a large amount of noise and improve image quality.
[0048] In this embodiment, Figure 6 The original back bottom 8 can be seen in Figure 7 As shown, Figure 6 The filtered background 11 after median filtering can be seen in [reference 11]. Figure 8 As shown.
[0049] In this embodiment, Figure 6 The original projection 10 can be seen in Figure 10 As shown, and the original grayscale distribution diagram 9 generated by the imaging system via the original projection 10 can be seen in [reference 9]. Figure 14 As shown, the horizontal axis represents the area distance (in inches), and the vertical axis represents the grayscale value. Figure 6 The filtered projection 13 can be found in [reference 13]. Figure 12 As shown, and the filtered grayscale distribution diagram 16 generated by the imaging system after the filtered projection 13 can be seen in [reference 16]. Figure 15 As shown. By Figure 14 and Figure 15 It can be seen that median filtering can reduce a lot of noise.
[0050] Step 7.2: As Figure 6 As shown, the background 11 after filtering is processed by dark field 12 to obtain dark field removed background 14, and the projection 13 after filtering is processed by dark field 12 to obtain dark field removed projection 15.
[0051] Dark field removal involves subtracting from the corresponding pixels. Since dark field 12 is the pixel value detected by the detector in the natural state of the incubation chamber 402 when it is not irradiated by neutrons in step three, the influence of the natural pixel value on the imaging can be reduced by subtracting the dark field from the background image and the projection image according to the corresponding pixels.
[0052] In this embodiment, Figure 6 See section 14 for dark field background removal. Figure 9 As shown, Figure 6 For dark field projection in section 15, please refer to [link / reference]. Figure 12 As shown.
[0053] Step 7.3: Use the de-dark-field background removal 14 to perform background removal processing on the de-dark-field projection 15 to obtain the background removal projection 17 of the ceramic core.
[0054] Background removal is a process of dividing the corresponding pixel values between background removal 14 and dark field projection removal 15. In other words, background removal removes dark field projection, and the final value of each pixel can represent the transmittance of neutrons.
[0055] In this embodiment, Figure 6 See also the backgroundless projection 17 in the middle. Figure 13 As shown, and Figure 13 The location indicated by point B is... Figure 6 The defect is illustrated in Figure 18.
[0056] In this embodiment, the above image processing can be implemented using ImageJ software, and subsequent defect segmentation is performed on the background-removed projection 17 to obtain... Figure 6 The defect shown in Figure 18 can be addressed using the threshold segmentation method, which can be implemented in software such as MatLab or Avizo.
[0057] Other examples Figure 4 As shown, the present invention can provide windows on all four sides of the insulation chamber 402 of the directional solidification device 4 as needed, such as... Figure 4 The windows A404 and B405 in the middle allow the neutron beam to flexibly select the incident angle according to actual needs, thereby achieving the purpose of multi-angle and all-round imaging of the ceramic core. In addition to achieving real-time imaging of the ceramic core, each angle can obtain the change of the ceramic core thickness t in real time according to the above formula (1), so that the change process and change characteristics of the ceramic core can be more comprehensively characterized in real time during the directional solidification casting process of the blade.
Claims
1. A non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades, characterized in that: Includes the following steps: Step 1: Incorporate strong neutron absorbers into the ceramic core slurry and prepare the ceramic core; Step 2: Prepare the outer shell of the ceramic core; Step 3: The detector in the imaging system is activated and probes the interior of the insulated chamber of the directional solidification device to obtain a dark-field image under natural conditions; Step 4: The neutron beam enters the insulation chamber through the incident window on one side of the directional solidification device, and exits through the exit window on the other side of the directional solidification device and enters the detector, thereby enabling the imaging system to obtain a blank original background image. Step 5: Place the shell with ceramic core obtained in Step 2 into the insulation chamber of the directional solidification device; Step 6: The directional solidification device begins the casting process. At the same time, the neutron beam is injected into the insulation chamber through the entrance window on one side of the directional solidification device and exited into the detector through the exit window on the other side of the directional solidification device. The imaging system obtains the original projection image including the ceramic core. Step 7: The imaging system processes the dark field image obtained in Step 3, the original background image obtained in Step 4, and the original projection image obtained in Step 6 in real time to obtain the real-time background-free projection image of the ceramic core. At the same time, the thickness variation of the ceramic core is obtained according to the following formula (1): I=I0·e -μ·t (1); In the above formula (1), I0 is the intensity of the incident neutron beam input through the incident window, I is the intensity of the transmitted neutron beam output through the exit window, μ is the neutron linear attenuation coefficient of the ceramic core material, e is the natural exponent, and t is the thickness of the ceramic core.
2. The non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades according to claim 1, characterized in that: In step one, the neutron-absorbing strong absorber Gd2O3 powder is processed and then incorporated into the ceramic core slurry according to a set ratio to prepare the ceramic core.
3. The non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades according to claim 1, characterized in that: In step two, the specific process of preparing the shell is as follows: Step 2.1: Precisely position the ceramic core prepared in Step 1 into the wax mold, and inject molten wax. After cooling, a wax mold with an internal ceramic core is obtained. Step 2.2: Dip the wax model into the corresponding slurry and dry it to form a surface layer. Repeat this process a set number of times to form a shell with a multi-layered structure. Step 2.3: Dewax the wax model to obtain a shell with an internal ceramic core.
4. The non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades according to claim 1, characterized in that: In step four, the imaging system continuously acquires a set number of original background images. In step six, the imaging system continuously acquires a set number of original projection images.
5. The non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades according to claim 4, characterized in that: In step seven, the imaging system processes the dark field image, the original background image, and the original projection image as follows: Step 7.1: Perform median filtering on the original background image to obtain the filtered background image, and perform median filtering on the original projection image to obtain the filtered projection image; Step 7.2: Use the dark field image to perform dark field removal processing on the filtered background image to obtain the dark field removed background image, and use the dark field image to perform dark field removal processing on the filtered projection image to obtain the dark field removed projection image; Step 7.3: Use the dark field background removal image to perform background removal processing on the dark field projection image to obtain the background removal projection image of the ceramic core.
6. The non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades according to claim 5, characterized in that: In step 7.1, the median filtering process of the original background image is as follows: based on the multiple original background images obtained in step four, the pixel values at the same position are sorted, the median value is selected, and then the median values are recombined in sequence to form the filtered background image. The median filtering process for the original projection image is as follows: based on the multiple original projection images obtained in step six, the pixel values at the same position are sorted, the median value is selected, and then the median values are recombined sequentially to form the filtered projection image.
7. The non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades according to claim 5, characterized in that: In step 7.2, the dark field removal process specifically involves subtracting the filtered background image and the filtered projection image from the dark field image according to their respective pixel values.
8. The non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades according to claim 5, characterized in that: In step 7.3, the background removal process specifically involves dividing the corresponding pixel values of the background removal image and the projection image, that is, removing the projection image from the background removal image.
9. The non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades according to claim 1, characterized in that: In step seven, the neutron linear attenuation coefficient μ is obtained through prior sample imaging detection. Specifically, a sample with the same material as the ceramic core is made with consistent thickness on both the top and bottom. The incident neutron beam intensity I0 is obtained based on the original background image of the sample. The transmitted neutron beam intensity I through the sample is obtained based on the original projection image of the sample including the sample. Then, the neutron linear attenuation coefficient μ of the ceramic core material is obtained by back-calculation according to the above formula (1).
10. The non-destructive testing method for ceramic cores used in directional solidification high-temperature alloy hollow blades according to claim 1, characterized in that: The incident window material and the exit window material of the directional solidification device are preferably aluminum alloys, and the insulation layer material of the heat-insulating furnace is preferably graphite carbon felt.