Defect decoupling nondestructive evaluation method for thermal barrier coating system based on electromagnetic-thermal decision-level fusion

Abstract

The present invention belongs to the technical field of non-destructive testing of blade thermal barrier coating systems, and relates to a method for non-destructive evaluation of thermal barrier coating system defects decoupling by electromagnetic-thermal decision-level fusion, comprising: 1: building an experimental device; 2: using the experimental device to perform electromagnetic excitation on the blade to be tested, generating an electromagnetic field and a temperature field in the tested area of ​​the blade; 3: collecting temperature field signals on the surface of the blade to be tested, to achieve rapid detection of defects; 4: scanning and collecting electromagnetic field signals on the defect target range quantified from the temperature field signal, to achieve defect classification and decoupling quantification of substrate cracks through the electromagnetic field signal; 5: combining substrate crack information and temperature field signals to achieve quantitative evaluation of interface debonding; the present invention realizes non-destructive decoupling quantitative evaluation of various types of typical defects in the blade thermal barrier coating system by performing decision-level fusion of temperature field signals and electromagnetic field signals, and has the advantages of fast detection speed, system integration and the ability to simultaneously detect multiple types of defects.

Description

Technical Field

[0001] The present invention belongs to the technical field of nondestructive testing of blade thermal barrier coating systems, and relates to a nondestructive evaluation method for thermal barrier coating system defects decoupling by electromagnetic-thermal decision-level fusion. Background Art

[0002] A gas turbine is a rotary power machine that uses a continuously flowing gas as a working fluid and converts the heat energy generated by fuel combustion into mechanical energy. Gas turbines are widely used in a variety of industries. Thermal barrier coating systems are key components that protect gas turbine blades from high temperatures, foreign particle impact, and chemical corrosion. They typically consist of a multi-layer structure consisting of a top coating, a bond coat, and a superalloy substrate. During the manufacturing and use of gas turbines, defects such as interface debonding and substrate cracks are inevitable due to factors such as thermal expansion mismatch and fatigue loads. These defects can significantly reduce the performance, safety, and service life of the gas turbine. Currently, non-destructive evaluation methods used for defect detection in thermal barrier coating systems include infrared testing, terahertz testing, eddy current testing, and ultrasonic testing.

[0003] However, existing defect detection methods for gas turbine thermal barrier coating systems have limitations in detecting multiple defects. Terahertz detection methods have limited resolution and slow detection speeds. Infrared thermal imaging, while sensitive to interfacial debonding, struggles to detect substrate cracks. Eddy current testing is effective for detecting substrate cracks but insensitive to non-conductive interfacial debonding.

[0004] Therefore, a nondestructive evaluation method that can quickly detect complex defects, accurately identify defect types, and quantify coexisting multiple defects is needed to ensure the safe operation of gas turbine blades. Summary of the Invention

[0005] The technical solution adopted by the present invention to solve the technical problem is: a nondestructive evaluation method for thermal barrier coating system defects decoupling by electromagnetic thermal decision-making level fusion, comprising the following steps:

[0006] Step 1: Build an experimental device that can generate an eddy current field and a Joule heat source in the blade being tested, and can also collect electromagnetic field signals and temperature field signals of the tested area of ​​the blade being tested;

[0007] Step 2: Use the experimental device to electromagnetically excite the blade to be tested, generating an eddy current field and a temperature field in the tested area of ​​the blade;

[0008] Step 3: Collect the temperature field signal on the surface of the blade to be inspected to achieve rapid defect detection;

[0009] Step 4: Scan the target defect range quantified from the temperature field signal and collect electromagnetic field signals, and achieve defect classification and decoupling quantification of matrix cracks through electromagnetic field signals;

[0010] Step 5: Combine the information of substrate cracks and temperature field signals to achieve quantitative evaluation of interface debonding; finally, by performing decision-level fusion of the temperature field signal and electromagnetic field signal detected on the blade surface, a non-destructive decoupling quantitative evaluation of various typical defects in the blade thermal barrier coating system is achieved.

[0011] Preferably, in step 1, the experimental device includes: a control system, an induction heater, an excitation coil, a magnetic yoke, a cooling device, a detection coil, a scanning platform, an electromagnetic signal acquisition device and an infrared thermal imager;

[0012] The control system is used to trigger the induction heater, the scanning stage, the electromagnetic signal acquisition device and the infrared camera. The control system is also used to store and process the electromagnetic field signals collected by the electromagnetic signal acquisition device and the temperature field signals collected by the infrared camera;

[0013] The induction heater is used to apply pulsed high-frequency current excitation to the excitation coil after receiving the trigger signal;

[0014] The magnetic yoke is used to guide the primary magnetic field generated by the excitation coil to the blade under test;

[0015] The cooling device is used to cool the induction heater and the excitation coil;

[0016] The detection coil is used to scan the target detection area under the control of the scanning stage;

[0017] The electromagnetic signal acquisition device is used to acquire the electromagnetic field signal of the detection coil;

[0018] The infrared thermal imager is used to collect the temperature field signal on the surface of the blade thermal barrier coating system after receiving the trigger signal from the control system;

[0019] The connection method of the experimental device is: the control system is electrically connected to the electromagnetic signal acquisition device and the scanning platform in sequence; the control system is electrically connected to the induction heater and the cooling device in sequence; the induction heater is electrically connected to the excitation coil, and the detection coil is electrically connected to the scanning platform.

[0020] More preferably, the step 2 specifically includes the following steps:

[0021] First, pass the yoke beam through the excitation coil and keep the excitation coil in the middle position of the yoke beam; then place the blade inspection area between the two pole legs of the yoke to ensure that the primary magnetic field generated by the excitation coil can be accurately guided to the inspection area, generating relatively uniform electromagnetic and temperature fields in the inspection area; then perform temperature calibration on the infrared camera and focus after calibration to ensure a clear image of the thermal barrier coating system in the infrared imager; set the excitation parameters of the induction heater in the control system; and then set the acquisition parameters of the infrared camera.

[0022] More preferably, the excitation parameters include: current amplitude, excitation frequency and excitation time; the acquisition parameters of the infrared camera include: sampling frequency and acquisition time.

[0023] More preferably, the specific steps in step 3 include:

[0024] The control system simultaneously gives a trigger signal to the induction heater and the infrared camera. After receiving the trigger signal, the induction heater applies a pulse excitation current to the excitation coil. Under the action of the pulse excitation current, the excitation coil will generate a primary magnetic field. The primary magnetic field is guided into the metal matrix of the blade through the magnetic yoke and induces eddy currents. The Joule heat generated by the eddy current is heat-conducted within the blade thermal barrier coating system, and the temperature field signal on the blade surface is collected by the infrared camera to realize defect detection.

[0025] More preferably, the specific steps in step 4 include:

[0026] The position, shape and size of defects in the temperature signal are quantified through the image instance segmentation algorithm. The excitation coil is re-energized by the control system. Then, the detection coil fixed to the scanning table is used to scan the target defect range quantified from the temperature field signal and collect electromagnetic field signals. The electromagnetic field signal is used to achieve defect classification and decoupled quantification of matrix cracks.

[0027] More preferably, the specific steps in step 5 include:

[0028] Step 5-1: For a single type of interface debonding defect, first perform rapid defect detection using temperature field signals, then determine the defect as interface debonding using electromagnetic field signals, and finally complete the quantitative determination of interface debonding using temperature field signals.

[0029] Step 5-2: For single-type defects such as matrix cracks, first perform rapid defect detection using temperature field signals, then determine the defect as a matrix crack using electromagnetic field signals, and finally complete the quantitative determination of the matrix crack using electromagnetic field signals;

[0030] Step 5-3: For the coexistence of interface debonding and matrix cracks, first perform rapid defect detection through temperature field signals, then identify the type of matrix cracks and decouple them quantitatively through electromagnetic field signals, and finally combine the matrix crack information and achieve quantitative interface debonding through temperature field signals.

[0031] More preferably, the detection method adopts pulsed high-frequency current as the excitation signal for eddy current detection.

[0032] The beneficial effects of the present invention are:

[0033] 1. Compared with traditional thermal barrier coating detection methods, the present invention has the advantages of fast detection speed, system integration and the ability to detect multiple types of defects simultaneously.

[0034] 2. The present invention not only collects temperature field signals, but also uses pulsed high-frequency current as the excitation signal for eddy current detection, and simultaneously scans and collects electromagnetic field signals.

[0035] 3. The excitation signal used in the present invention is a pulsed high-frequency current, and its detection range (i.e., the potential defect area) can be quickly narrowed and located in advance through the distortion of the temperature field signal. There is no need to perform electromagnetic detection and scanning on the entire area of ​​the object to be tested, thereby greatly improving the efficiency of eddy current testing.

[0036] 4. The present invention has strong interpretability and scalability, and can realize rapid detection, type identification and decoupling quantitative evaluation of typical defects (including substrate cracks and interface debonding) in thermal barrier coating systems without human intervention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of a temperature field signal and electromagnetic field signal decision-level fusion method and a flow chart of a thermal barrier coating system defect decoupling nondestructive evaluation method of the present invention;

[0038] Figure 2 It is a schematic diagram of the connection of the components of the nondestructive evaluation system of the present invention;

[0039] Figure 3 It is a schematic diagram of the influence of interface debonding and matrix cracks on temperature field signals and electromagnetic field signals of the present invention.

[0040] Among them, 1. control system; 2. induction heater; 3. excitation coil; 4. magnetic yoke; 5. cooling device; 6. detection coil; 7. scanning platform; 8. electromagnetic signal acquisition device; 9. infrared thermal imager; 10. blade. DETAILED DESCRIPTION

[0041] The following will provide a clear and complete description of the relevant technologies in the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] refer to Figures 1 to 3 In this embodiment, the experimental device consists of a control system 1, an induction heater 2, an excitation coil 3, a magnetic yoke 4, a cooling device 5, a detection coil 6, a scanning platform 7, an electromagnetic signal acquisition device 8 and an infrared thermal imager 9. When implementing this embodiment, according to Figure 2The induction heater 2 is first triggered by the control system 1. After receiving the trigger signal, the induction heater 2 applies a pulsed high-frequency current to the excitation coil 3. The cooling device 5 cools the induction heater 2 and the excitation coil 3 at the same time. The alternating magnetic field generated by the excitation coil 3 can induce eddy currents and Joule heat in the metal matrix of the thermal barrier coating system through the guidance of the magnetic yoke 4. The Joule heat will diffuse to the surface of the blade 10 through heat conduction. The electromagnetic field signal generated by the eddy current field and the temperature field signal on the surface of the blade 10 can be collected respectively by the detection coil 6 and the infrared camera. Figure 3 As shown in FIG, substrate cracks in thermal barrier coatings not only affect the distribution of eddy currents, that is, the Joule heat source, but also affect the heat conduction process, while interface debonding only affects the heat conduction process. Therefore, this embodiment adopts Figure 1 The decision-level electromagnetic thermal signal fusion method shown in the figure first realizes rapid defect detection from the temperature field signal, then identifies the defect type through the electromagnetic field signal and realizes the decoupling quantification of the matrix crack, and finally combines the matrix crack information and realizes the quantification of the interface debonding through the temperature field signal. The non-destructive evaluation process is as follows: Figure 1 The following further describes this embodiment in detail with reference to specific examples.

[0043] The nondestructive evaluation method for thermal barrier coating system defects decoupling based on electromagnetic-thermal decision-level fusion includes the following steps:

[0044] Step 1: Build the experimental device, which consists of a control system 1, an induction heater 2, an excitation coil 3, a magnetic yoke 4, a cooling device 5, a detection coil 6, a scanning platform 7, an electromagnetic signal acquisition device 8, and an infrared thermal imager 9. The control system 1 is responsible for triggering the induction heater 2, the scanning platform 7, the electromagnetic signal acquisition device 8, and the infrared camera, and for storing and processing the electromagnetic field signals collected by the electromagnetic signal acquisition device 8 and the temperature field signals collected by the infrared camera. After receiving the trigger signal, the induction heater 2 applies a pulsed high-frequency current to the excitation coil 3, and the magnetic yoke 4 guides the primary magnetic field generated by the excitation coil 3 to the blade 10 under test. The cooling device 5 is responsible for cooling the induction heater 2 and the excitation coil 3. During the excitation phase, the detection coil 6 scans the target detection area under the control of the scanning platform 7, and the electromagnetic signal acquisition device 8 is responsible for collecting the electromagnetic field signals of the detection coil 6. After receiving the trigger signal from the control system 1, the infrared thermal imager 9 is responsible for collecting the temperature field signals of the thermal barrier coating system surface of the blade 10. Finally, the electromagnetic field signals and temperature field signals are transmitted to the control system 1 for storage and processing.

[0045] Step 2: First, pass the crossbeam of the magnetic yoke 4 through the excitation coil 3, and keep the excitation coil 3 in the middle position of the crossbeam of the magnetic yoke 4; then place the inspection area of ​​the blade 10 between the two pole legs of the magnetic yoke 4, ensuring that the primary magnetic field generated by the excitation coil 3 can be accurately guided to the inspection area, generating a relatively uniform electromagnetic field and temperature field in the inspection area; then perform temperature calibration on the infrared camera, and after calibration, perform focusing operation to ensure that the image of the thermal barrier coating system in the infrared thermal imager 9 is clear; set the excitation parameters of the induction heater 2 in the control system 1, including: current amplitude, excitation frequency and excitation time; then set the acquisition parameters of the infrared camera, including: sampling frequency and acquisition time;

[0046] Step 3: Use the control system 1 to simultaneously give a trigger signal to the induction heater 2 and the infrared camera. After receiving the trigger signal, the induction heater 2 applies a pulse excitation current to the excitation coil 3. The excitation waveform can be expressed as:

[0047] (1)

[0048] Where: express The excitation current value at the moment, represents the amplitude of the pulse excitation current, is the excitation frequency of the pulse excitation current.

[0049] According to Maxwell's equations, the excitation coil 3 generates a primary magnetic field under the action of the pulsed excitation current. The primary magnetic field is guided into the metal matrix of the blade 10 through the magnetic yoke 4, thereby inducing eddy currents in the metal material. According to Joule's law, the eddy currents are converted from electrical energy to thermal energy inside the material, and the generated Joule heat Proportional to the square of the eddy current density:

[0050] (2)

[0051] in, represents the electrical conductivity of the metal matrix of the blade 10; represents the eddy current density.

[0052] According to Fourier's heat transfer law, the Joule heat generated by the eddy current will be transferred within the thermal barrier coating system of the blade 10:

[0053] (3)

[0054] in, Indicates density; represents specific heat capacity; represents thermal conductivity; Indicates temperature.

[0055] Cracks in the substrate of a thermal barrier coating system not only disrupt the distribution of the eddy current field but also the heat conduction process. However, interfacial debonding defects only affect the heat conduction process. The disturbances in the eddy current and temperature fields caused by defects ultimately lead to an uneven distribution of the temperature field on the blade 10 surface. Rapid detection of defects is possible by capturing the temperature field signal on the blade surface with an infrared camera.

[0056] Step 4: The temperature field signal captured by the infrared camera is an image sequence. The image instance segmentation algorithm can be used to quantify the position, shape, and size of defects in the temperature signal. However, since both matrix cracks and interface debonding affect the temperature field signal, defect classification cannot be performed directly from the defect quantification results of the temperature field signal. At this point, the excitation coil 3 is re-energized by the control system 1, and then the detection coil 6, fixed to the scanning stage 7, is used to scan the target defect range (i.e., the potential defect area) quantified from the temperature field signal and collect electromagnetic field signals. Since interface debonding does not affect the distribution of the eddy current field, the electromagnetic field signal can be used to achieve classification and decoupled quantification of matrix cracks.

[0057] Step 5: By performing a decision-level fusion of the temperature field signal and the electromagnetic field signal, a non-destructive decoupling quantitative evaluation of various typical defects of the thermal barrier coating system of blade 10 can be achieved, specifically including: (1) For the single-type defect of interface debonding, the defect is firstly detected quickly by the temperature field signal, and then the defect is judged to be interface debonding by the electromagnetic field signal, and finally the interface debonding is quantified by the temperature field signal; (2) For the single-type defect of substrate crack, the defect is firstly detected quickly by the temperature field signal, and then the defect is judged to be substrate crack by the electromagnetic field signal, and finally the substrate crack is quantified by the electromagnetic field signal; (3) For the coexistence of interface debonding and substrate crack, the defect is firstly detected quickly by the temperature field signal, and then the type of substrate crack is identified and decoupled quantitatively by the electromagnetic field signal, and finally the interface debonding is quantified by the temperature field signal in combination with the substrate crack information. Therefore, by performing a decision-level fusion of the temperature field signal and the electromagnetic field signal, a decoupling quantitative evaluation of various types of defects of the thermal barrier coating system can be achieved.

[0058] In summary, the present invention first achieves rapid defect detection from temperature field signals, then uses electromagnetic field signals to identify defect types and achieve decoupled quantification of substrate cracks. Finally, combining substrate crack information with temperature field signals, the present invention achieves quantification of interfacial debonding. Compared to traditional nondestructive testing methods, this method enables rapid detection, type identification, and decoupled quantitative evaluation of multiple defects in thermal barrier coating systems, offering broad application prospects.

[0059] It should be emphasized that the above are only preferred embodiments of the present invention and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A nondestructive evaluation method for thermal barrier coating system defects decoupling based on electromagnetic-thermal decision-level fusion, characterized by: The following steps are involved: Step 1: Build an experimental device that can generate an eddy current field and a Joule heat source in the blade being tested, and can also collect electromagnetic field signals and temperature field signals of the tested area of ​​the blade being tested; Step 2: Using the experimental device to electromagnetically excite the blade to be tested, generating an eddy current field and a temperature field in the tested area of ​​the blade to be tested; Step 3: Collect the temperature field signal on the surface of the blade to be inspected to achieve rapid defect detection; Step 4: Scan the target defect range quantified from the temperature field signal and collect electromagnetic field signals, and achieve defect classification and decoupling quantification of matrix cracks through electromagnetic field signals; Step 5: Combine substrate crack information and temperature field signals to achieve quantitative assessment of interface debonding. Finally, by integrating the temperature field signal and electromagnetic field signal detected on the blade surface at the decision-making level, a non-destructive decoupled quantitative assessment of various typical defects in the blade thermal barrier coating system is achieved. The specific steps in step 5 include: Step 5-1: For a single type of interface debonding defect, first perform rapid defect detection using temperature field signals, then determine the defect as interface debonding using electromagnetic field signals, and finally complete the quantitative determination of interface debonding using temperature field signals. Step 5-2: For single-type defects such as matrix cracks, first perform rapid defect detection using temperature field signals, then determine the defect as a matrix crack using electromagnetic field signals, and finally complete the quantitative determination of the matrix crack using electromagnetic field signals; Step 5-3: For the coexistence of interface debonding and matrix cracks, first perform rapid defect detection through temperature field signals, then identify the type of matrix cracks and decouple them quantitatively through electromagnetic field signals, and finally combine the matrix crack information and achieve quantitative interface debonding through temperature field signals.

2. The nondestructive evaluation method for thermal barrier coating system defects decoupling based on electromagnetic-thermal decision-level fusion according to claim 1 is characterized in that: In step 1, the experimental device includes: a control system, an induction heater, an excitation coil, a magnetic yoke, a cooling device, a detection coil, a scanning platform, an electromagnetic signal acquisition device and an infrared thermal imager; The control system is used to trigger the induction heater, the scanning stage, the electromagnetic signal acquisition device and the infrared camera, and the control system is also used to store and process the electromagnetic field signals acquired by the electromagnetic signal acquisition device and the temperature field signals acquired by the infrared camera; The induction heater is used to apply pulsed high-frequency current excitation to the excitation coil after receiving a trigger signal; The magnetic yoke is used to guide the primary magnetic field generated by the excitation coil to the blade to be measured; The cooling device is used to cool the induction heater and the excitation coil; The detection coil is used to scan the target detection area under the control of the scanning platform; The electromagnetic signal acquisition device is used to acquire the electromagnetic field signal of the detection coil; The infrared thermal imager is used to collect the temperature field signal of the surface of the blade thermal barrier coating system after receiving the trigger signal from the control system; The connection method of the experimental device is: the control system is electrically connected to the electromagnetic signal acquisition device and the scanning platform in sequence; the control system is electrically connected to the induction heater and the cooling device in sequence; the induction heater is electrically connected to the excitation coil, and the detection coil is electrically connected to the scanning platform.

3. The nondestructive evaluation method for thermal barrier coating system defects decoupling based on electromagnetic-thermal decision-level fusion according to claim 2 is characterized in that: The step 2 specifically includes the following steps: First, pass the yoke beam through the excitation coil and keep the excitation coil in the middle position of the yoke beam; then place the blade inspection area between the two pole legs of the yoke to ensure that the primary magnetic field generated by the excitation coil can be accurately guided to the inspection area, generating relatively uniform electromagnetic and temperature fields in the inspection area; then perform temperature calibration on the infrared camera and focus after calibration to ensure a clear image of the thermal barrier coating system in the infrared imager; set the excitation parameters of the induction heater in the control system; and then set the acquisition parameters of the infrared camera.

4. The nondestructive evaluation method for thermal barrier coating system defects decoupling based on electromagnetic-thermal decision-level fusion according to claim 3 is characterized in that: The excitation parameters include: current amplitude, excitation frequency and excitation time; the acquisition parameters of the infrared camera include: sampling frequency and acquisition time.

5. The nondestructive evaluation method for thermal barrier coating system defects decoupling based on electromagnetic-thermal decision-level fusion according to claim 2 is characterized in that: The specific steps in step 3 include: The control system simultaneously gives a trigger signal to the induction heater and the infrared camera. After receiving the trigger signal, the induction heater applies a pulse excitation current to the excitation coil. Under the action of the pulse excitation current, the excitation coil will generate a primary magnetic field. The primary magnetic field is guided into the metal matrix of the blade through the magnetic yoke and induces eddy currents. The Joule heat generated by the eddy current is heat-conducted within the blade thermal barrier coating system, and the temperature field signal on the blade surface is collected by the infrared camera to realize defect detection.

6. The nondestructive evaluation method for thermal barrier coating system defects decoupling based on electromagnetic-thermal decision-level fusion according to claim 5 is characterized in that: The specific steps in step 4 include: The position, shape and size of defects in the temperature signal are quantified through the image instance segmentation algorithm. The excitation coil is re-energized by the control system. Then, the detection coil fixed to the scanning table is used to scan the target defect range quantified from the temperature field signal and collect electromagnetic field signals. The electromagnetic field signal is used to achieve defect classification and decoupled quantification of matrix cracks.

7. The nondestructive evaluation method for thermal barrier coating system defects decoupling based on electromagnetic-thermal decision-level fusion according to claim 2 is characterized in that: By using pulsed high-frequency current as the excitation signal for eddy current detection.

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