A high-frequency resonance-based method for measuring the thickness of a ceramic layer of a thermal barrier coating

Abstract

This invention discloses an eddy current measurement method for the thickness of thermal barrier coating ceramic layers based on high-frequency resonance, belonging to the field of eddy current nondestructive testing. By utilizing high-frequency excitation to decouple the ceramic layer thickness characteristics, the influence of the substrate and binder layer on the ceramic thickness measurement is suppressed, resulting in a more accurate acquisition of the ceramic layer thickness in the thermal barrier coating. The method includes: controlling the distribution of eddy currents in the binder layer and substrate; expressing the coupling coefficient as an equivalent exponential relationship of the ceramic layer thickness; establishing an RLC parallel resonant circuit to obtain ΔL. ab The expression for the ceramic layer thickness; ΔL is obtained using two samples. ab By fitting the coefficients in the expression for ceramic layer thickness, the calibrated characteristic curve of the ceramic layer thickness is obtained. This provides an efficient solution to the challenge of accurate thickness measurement under multi-parameter coupling in thermal barrier coatings for aero-engines.

Description

Technical Field

[0001] This invention relates to the field of eddy current nondestructive testing, and specifically to an eddy current method for measuring the thickness of thermal barrier coating ceramic layers based on high-frequency resonance. Background Technology

[0002] Thermal barrier coatings are a material protection technology applied in high-temperature operating environments. They can reduce the operating temperature of hot-end components, prevent high-temperature corrosion, increase engine combustion temperature and thermal efficiency, reduce exhaust volume, thereby saving fuel and extending blade life. They are applied directly to a nickel-based superalloy substrate and typically consist of a ceramic thermal barrier layer and a metal bonding layer, such as... Figure 1 As shown, coating thickness and its uniformity are key indicators of bonding manufacturing quality and service condition, affecting coating thermal insulation performance, coating stress and bond strength, service life, coating material consumption, and cost. An excessively thin ceramic layer reduces its thermal insulation performance and increases the risk of blade damage. Conversely, an excessively thick ceramic layer results in a significant increase in interfacial stress due to the large difference in thermal expansion coefficients between the ceramic layer and the substrate, weakening the bond strength and making the coating prone to detachment. Therefore, ceramic layer uniformity testing is a crucial method for quality control and in-service performance evaluation of thermal barrier coatings.

[0003] Currently, common methods for measuring the thickness of thermal barrier coatings include ultrasonic, infrared, microwave, terahertz, and eddy current techniques. Because the ceramic layer in thermal barrier coatings has a porosity of 10%, its microstructure is highly inhomogeneous, often containing pores and unmelted particles. This significantly impacts other measurement methods besides eddy current thickness measurement. Eddy current technology, however, uses a field-like excitation mechanism, meaning the inhomogeneous microstructure of the ceramic layer does not affect the measurement results. Furthermore, eddy current technology is low-cost, fast, and requires a small probe size, making it ideal for assessing bonding quality and service condition.

[0004] Eddy current methods based on electromagnetic induction offer advantages such as low cost, high speed, and high accuracy, making them one of the ideal methods for non-destructive testing and evaluation of bond thickness. Bonded surfaces are characterized by complex structures, thin thickness, and low and small differences in conductivity between the bond layer and the substrate. Therefore, eddy current testing of thermal barrier coatings faces challenges such as strong signal coupling, weak signal, and low resolution. To improve thickness measurement resolution, many researchers have focused on increasing the excitation frequency. However, relying on high-frequency eddy currents to generate sufficient density of induced eddy currents to enhance impedance signal strength is problematic. As the excitation frequency increases, severe crosstalk and external interference are easily introduced during signal transmission in coaxial cables, leading to complex environmental noise effects and posing a significant challenge to obtaining high signal-to-noise ratio eddy current signals. Some researchers have also used resonant methods to improve thickness detection resolution. When the reactance is zero, the system is in a resonant state, exhibiting maximum response to excitation signals at specific frequencies. This enables directional signal selection and amplification, thereby enhancing the signal. This approach has been applied to the detection of debonding defects in thermal barrier coatings. However, capturing the resonant frequency shift through frequency sweeping is a relatively time-consuming method, making it difficult to meet the demands of rapid industrial testing. Furthermore, due to the lack of a mathematical mapping relationship between the physical properties of the test piece and its impedance characteristics, these methods are mostly applied to defect detection, and there is still a gap in thickness detection methods based on high-frequency resonance. Summary of the Invention

[0005] To address the above problems, this invention proposes an eddy current measurement method for the thickness of ceramic layers in thermal barrier coatings based on high-frequency resonance. This method utilizes high-frequency excitation to decouple the characteristics of ceramic layer thickness, suppressing the influence of the substrate and adhesive layer on the ceramic thickness measurement, and thus obtaining the ceramic layer thickness in thermal barrier coatings more accurately.

[0006] The technical solution of the present invention includes the following steps:

[0007] Step 1: Control the distribution of eddy currents in the adhesive layer and substrate;

[0008] By increasing the excitation angular frequency ω and using high-frequency excitation, the eddy currents are concentrated and penetrated into the adhesive layer, eliminating interference from the substrate.

[0009] Step 2: Express the coupling coefficient K as an exponential relationship of the ceramic layer thickness;

[0010] First, based on the equivalent transformer model, the analytical expressions for the probe inductance change ΔL and the mutual inductance index M in the transformer model are derived, and simplified to obtain the analytical expressions for ΔL and the coupling coefficient K, approximately eliminating eigenvalues ​​containing the adhesive layer thickness and conductivity. Then, based on the Neumann formula and Taylor series, the coupling coefficient K is equivalently expressed as the ceramic layer thickness h. t The exponential relationship is determined, and the fitting coefficients are obtained.

[0011] Step 3: Establish an RLC parallel resonant circuit and obtain the change in resonant inductance ΔL.ab An expression relating the thickness of the ceramic layer;

[0012] A capacitor is connected in parallel across the coil to form an RLC parallel resonant circuit. The resonant frequency is obtained by frequency sweeping, and the excitation frequency is fixed at 1 / 2 of the peak value of the resonant inductance. The change in resonant inductance ΔL of the current system output is used. ab The exponential expression represents the change in coil inductance ΔL in a conventional transformer model, establishing ΔL ab The expression for the ceramic layer thickness is derived, and the final fitting coefficients are obtained.

[0013] Step 4: Fabricate an integrated excitation, demodulation, and coil probe, and exchange digital signals and DC signals with the detection instrument through the input and output ports at the top of the probe;

[0014] Step 5: Prepare two thermal barrier coating samples with different coating thicknesses, and use a high-frequency resonant eddy current detector to measure the change in resonant inductance ΔL at the test point. ab The characteristics were identified, and the true thickness of the test point was obtained through metallographic experiments.

[0015] Step 6: Calculate ΔL using the two samples prepared in Step 5. ab The fitting coefficient in the expression for the ceramic layer thickness;

[0016] Step 7: Use a high-frequency resonant eddy current detector to measure the sample under test and obtain the change in its resonant inductance. Substitute this into the calibrated ceramic layer thickness characteristic curve to obtain the measured thickness of the ceramic layer of the sample.

[0017] Step 2 specifically includes:

[0018] Step 2.1: The analytical expression for ΔL-M can be derived as ΔL[1+(ΔR / ωΔL)]. 2 ]=L1K 2 Since the angular frequency ω is amplified in step 1, the analytical expression of ΔL-M is simplified to the analytical expression of ΔL-K, which is ΔL=L1K. 2 Where K is the coupling coefficient, L1 is the coil's own inductance, and ΔR and ΔL are the changes in resistance and inductance of the coil on the test piece and in air, respectively.

[0019] Step 2.2: Using the Neumann formula and Taylor series, the coupling coefficient K is equivalently expressed as the ceramic layer thickness h. t The exponential relationship ΔL=aL1·exp(bh t ), where a and b are fitting coefficients.

[0020] Step 3 specifically includes:

[0021] Step 3.1: Connect a capacitor in parallel across the coil to form an RLC parallel resonant circuit. Set the excitation frequency to 1 / 2 of the peak value of the resonant inductance and amplify the change in inductance through electromagnetic resonance.

[0022] Step 3.2: Establish the change in resonant inductance ΔL ab The exponential fitting expression for the change in coil inductance ΔL in a conventional transformer model. ab = c·exp(d·ΔL), where c and d are fitting coefficients;

[0023] Step 3.3: Combining the approximately exponential expression of the coupling coefficient K and ceramic layer thickness in Step 2, and the change in resonant inductance ΔL in Step 3.2. ab By fitting the exponential expression of ΔL in the conventional transformer model, the change in resonant inductance ΔL is established. ab With ceramic layer thickness h t Characteristic relation ΔL ab =a1·exp(b1·h t ), where a1 and b1 are the final fitting coefficients to be determined.

[0024] Step 4 specifically includes:

[0025] An integrated probe consisting of an excitation module, a demodulation module, and a coil is fabricated. Data is exchanged with the testing instrument through the input and output ports at the top of the probe. The input port transmits the digital signal controlling the excitation module. After excitation, the coil is controlled. Then, the differential signal of the bridge is demodulated and output. The output port transmits the demodulated amplitude and phase signals.

[0026] Step 6 uses the two known actual ceramic layer thicknesses and resonant inductance changes from Step 5 as calibration sample points to calibrate the ceramic layer thickness characteristic curve established in Step 3, and obtains ΔL. ab The fitting coefficients in the expression for the ceramic layer thickness; specifically including:

[0027] Let the thickness of the ceramic layer of calibration component 1 be h. t1 The change in resonant inductance is ΔL ab1 The ceramic layer thickness of calibration component 2 is h. t2 The change in resonant inductance is ΔL ab2 Substitute these values ​​into the characteristic curve expression ΔL for ceramic layer thickness detection. ab =a1·exp(b1·h t ), we can get a1=exp[(h t2 lnΔL ab1 -h t1 lnΔL ab2 ) / (h t2 -h t1 )],b1=1 / (h t1-h t2 )·(lnΔL ab1 -lnΔL ab2 ).

[0028] This invention addresses the problems of impedance coupling between the ceramic layer, adhesive layer, and substrate in traditional eddy current detection methods for ceramic layer measurement, as well as the weak eddy current characteristic signal changes and low detection sensitivity caused by the weak conductivity of the substrate. By combining the coupling characteristics of the ceramic layer, adhesive layer, and substrate in thermal barrier coatings, the eddy current attenuation law is analyzed. High-frequency excitation is used to decouple the ceramic layer thickness characteristics, suppressing the influence of the substrate and adhesive layer on ceramic thickness measurement. To address the low conductivity of the adhesive layer, the impedance signal change is increased through the near-resonant point inductance enhancement effect, establishing a novel resonant equivalent output inductance characteristic and constructing a mapping relationship between the new characteristic and the original impedance characteristic. Relying on the extremely high sensing capability of the new characteristic, the sensitivity of the characteristic signal is improved, and an integrated probe is designed to reduce signal interference from the coaxial cable under high-frequency excitation.

[0029] Compared with existing detection methods, the present invention has the following advantages:

[0030] I. Using eddy current to detect the thickness of thermal barrier coating ceramic layers can eliminate the influence of uneven microstructure in ceramic layers. In addition, it has advantages such as low cost, speed and small probe size.

[0031] Second, by simplifying the analytical expression of ΔL-K using high-frequency eddy currents, the influence of conductivity and thickness variation of the adhesive layer and substrate on the detection results is weakened, thereby improving the accuracy of ceramic layer thickness detection.

[0032] III. The change in resonant inductance ΔL at the near-resonant excitation position was established. ab An approximate mapping relationship with the change in coil inductance ΔL in a conventional transformer model was established, and this amplification relationship was used to improve the resolution of ceramic layer thickness detection.

[0033] Fourth, an integrated probe for excitation, demodulation, and coil was developed. This probe is completely immune to the influence of coaxial cable connections on the test results, thus improving the device's application capability in complex environments.

[0034] Therefore, this invention provides an accurate, efficient, and interference-resistant technical solution for detecting the thickness of thermal barrier coated ceramic layers. Based on an equivalent transformer model, it derives analytical expressions for the coil inductance change ΔL and the equivalent coupling coefficient K, and simplifies the expression for ΔL-K using high-frequency eddy currents, approximately eliminating characteristic values ​​containing adhesive layer thickness and conductivity. Near-resonant frequency excitation improves probe resolution and establishes ΔL... ab The relationship between K and the exponential expression is expressed through ΔL. abIt expresses the thickness of the ceramic layer; it fabricates an integrated probe for excitation, demodulation, and coiling, and realizes data interaction between the probe and the device through digital signals and DC signals, reducing deformation noise generated by coaxial cables.

[0035] Overall, this invention improves the accuracy of ceramic layer thickness detection, eliminates the influence of the adhesive layer and substrate on ceramic layer thickness detection, and avoids the impact of probe connection cables on thickness detection results, greatly enhancing the device's application capability in complex environments. Compared with traditional eddy current detection technology, it features high sensitivity, strong anti-interference ability, and high field applicability, providing an efficient solution to the challenge of accurate thickness measurement under multi-parameter coupling in thermal barrier coatings of aero-engines. Attached Figure Description

[0036] Figure 1 Schematic diagram of eddy current ceramic layer thickness detection principle, where L0 is the inductance of the coil, R0 is the resistance of the coil, K is the coupling coefficient, and L... b It is the equivalent inductance of the eddy current in the specimen, R b It is the equivalent resistance of the eddy current in the specimen, K is the coupling coefficient, C0 is the parallel capacitor, and the voltage source excitation is between ab.

[0037] Figure 2 : Plot showing the degree of fit between the change in resonant inductance and the change in probe inductance.

[0038] Figure 3 Flowchart of eddy current detection based on high-frequency resonance.

[0039] Figure 4 Integrated probe structure design diagram. Detailed Implementation

[0040] To clearly illustrate the technical features of this patent, the following detailed description is provided through specific embodiments and in conjunction with the accompanying drawings.

[0041] The detection principle diagram of this invention is as follows: Figure 1 As shown, the flowchart of the eddy current measurement method for the thickness of the thermal barrier coating ceramic layer based on high-frequency resonance is as follows: Figure 3 As shown, it includes the following steps:

[0042] Step 1: Control the distribution of eddy currents in the adhesive layer and substrate;

[0043] Increase the excitation angular frequency ω, for example, increase the value of the excitation angular frequency ω to 30MHz, and use high-frequency excitation to make the eddy currents concentrate and penetrate into the adhesive layer, thereby eliminating the interference of the substrate;

[0044] Step 2: Express the coupling coefficient K as an exponential relationship of the ceramic layer thickness;

[0045] First, based on the equivalent transformer model, the analytical expressions for the probe inductance change ΔL and the mutual inductance index M in the transformer model are derived, and simplified to obtain the analytical expressions for ΔL and the coupling coefficient K, approximately eliminating eigenvalues ​​containing the adhesive layer thickness and conductivity. Then, based on the Neumann formula and Taylor series, the coupling coefficient K is equivalently expressed as the ceramic layer thickness h. t The exponential relationship is determined, and the fitting coefficients are obtained.

[0046] Specifically:

[0047] Step 2.1: The analytical expression for ΔL-M can be derived as ΔL[1+(ΔR / ωΔL)]. 2 ]=L1K 2 Since the angular frequency ω is amplified in step 1, the analytical expression of ΔL-M is simplified to the analytical expression of ΔL-K, which is ΔL=L1K. 2 Where K is the coupling coefficient, L1 is the coil's own inductance, and ΔR and ΔL are the changes in resistance and inductance of the coil on the test piece and in the air, respectively. Considering that the ceramic layer is non-conductive, and ΔR is the measured value of the adhesive layer, the influence of ΔR on the expression is greatly reduced after the value of the angular frequency ω is amplified, thereby simplifying the analytical expression and achieving the purpose of eliminating the interference of the adhesive layer.

[0048] Step 2.2: Using the Neumann formula and Taylor series, the coupling coefficient K is equivalently expressed as the ceramic layer thickness h. t The exponential relationship ΔL=aL1·exp(bh t ), where a and b are fitting coefficients.

[0049] Step 3: Establish an RLC parallel resonant circuit and obtain ΔL. ab An expression relating the thickness of the ceramic layer;

[0050] Step 3 specifically considers that after the angular frequency ω is amplified, the change in coil inductance ΔL will decrease, which will be detrimental to subsequent calculations. Therefore, this design adds an RLC parallel resonant circuit to control the change in inductance ΔL. ab This is used to characterize the change in coil inductance ΔL, and to further accurately obtain the ceramic layer thickness;

[0051] A capacitor is connected in parallel across the coil to form an RLC parallel resonant circuit. The resonant frequency is obtained by frequency sweeping, and the excitation frequency is fixed at 1 / 2 of the peak value of the resonant inductance. The change in resonant inductance ΔL of the current system output is used. ab The exponential expression represents the change in coil inductance ΔL in a conventional transformer model, and its exponential relationship shows the goodness of fit as follows: Figure 2 As shown, the resolution of this feature is improved, and ΔL is established. ab The expression for the ceramic layer thickness is derived, and the final fitting coefficients are obtained.

[0052] Specifically:

[0053] Step 3.1: Connect a capacitor in parallel across the coil to form an RLC parallel resonant circuit. Set the excitation frequency to 1 / 2 of the peak value of the resonant inductance and amplify the change in inductance through electromagnetic resonance.

[0054] Step 3.2: Establish the change in resonant inductance ΔL ab The exponential fitting expression for the change in coil inductance ΔL in a conventional transformer model. ab = c·exp(d·ΔL), where c and d are fitting coefficients;

[0055] Step 3.3: Combining the approximately exponential expression of the coupling coefficient K and ceramic layer thickness in Step 2, and the change in resonant inductance ΔL in Step 3.2. ab By fitting the exponential expression of the change in coil inductance ΔL in a conventional transformer model, the change in resonant inductance ΔL is established. ab With ceramic layer thickness h t Characteristic relation ΔL ab =a1·exp(b1·h t ), where a1 and b1 are the final fitting coefficients to be determined.

[0056] Step 4: Fabricate an integrated excitation, demodulation, and coil probe, and exchange digital signals and DC signals with the detection instrument through the input and output ports at the top of the probe;

[0057] Considering that after the angular frequency ω is amplified, the coaxial cable originally used for connection between the coil and the instrument (including the excitation module and demodulation module) will be treated as a coil by the instrument, resulting in impedance changes when the coaxial cable deforms, which affects the detection accuracy, the following optimizations were made in this case:

[0058] Step 4 involves fabricating an integrated probe comprising an excitation module, a demodulation module, and a coil. Data exchange with the testing instrument occurs through the input and output ports at the probe's tip. The input port transmits the digital signal controlling the excitation module, which, after excitation, controls the coil. The differential signal from the bridge circuit is then demodulated and output, while the output port transmits the demodulated amplitude and phase signals. The probe structure is as follows: Figure 4 As shown, this eliminates the need for a coaxial cable, reducing the impact of deformation noise generated by the coaxial cable.

[0059] Step 5: Prepare two thermal barrier coating samples with different coating thicknesses, and use a high-frequency resonant eddy current detector to measure the change in resonant inductance ΔL at the test point. ab The characteristics were identified, and the true thickness of the test point was obtained through metallographic experiments.

[0060] Step 6: Calculate ΔL using the two samples prepared in Step 5. abThe fitting coefficient in the expression for the ceramic layer thickness;

[0061] Step 6 uses the two known actual ceramic layer thicknesses and resonant inductance changes from Step 5 as calibration sample points to calibrate the ceramic layer thickness characteristic curve established in Step 3, and obtains ΔL. ab The fitting coefficients in the expression for the ceramic layer thickness; specifically:

[0062] Let the thickness of the ceramic layer of calibration component 1 be h. t1 The change in resonant inductance is ΔL ab1 The ceramic layer thickness of calibration component 2 is h. t2 The change in resonant inductance is ΔL ab2 Substitute these values ​​into the characteristic curve expression ΔL for ceramic layer thickness detection. ab =a1·exp(b1·h t ), we can get a1=exp[(h t2 lnΔL ab1 -h t1 lnΔL ab2 ) / (h t2 -h t1 )],b1=1 / (h t1 -h t2 )·(lnΔL ab1 -lnΔL ab2 ).

[0063] Step 7: Use a high-frequency resonant eddy current detector to measure the sample under test and obtain the change in its resonant inductance. Substitute this into the calibrated ceramic layer thickness characteristic curve to obtain the measured thickness of the ceramic layer of the sample.

[0064] This invention derives analytical expressions for the probe inductance change ΔL and the equivalent coupling coefficient K based on an equivalent transformer model, and simplifies the expression for ΔL-K using high-frequency eddy currents to approximately eliminate characteristic values ​​containing adhesive layer thickness and conductivity. Near-resonant frequency excitation improves probe resolution and establishes ΔL... ab The exponential relationship between ΔL and K is expressed through ΔL. ab This invention expresses the thickness of the ceramic layer by fabricating an integrated probe for excitation, demodulation, and coil control. Data interaction between the probe and the device is achieved through digital and DC signals, reducing deformation noise from coaxial cables. This invention improves the accuracy of ceramic layer thickness detection and avoids the influence of probe connection cables on the thickness measurement results, greatly enhancing the device's application capability in complex environments.

[0065] There are many specific ways to implement this invention. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A method for measuring the thickness of a thermal barrier coating ceramic layer based on high-frequency resonance using eddy current, characterized in that, Includes the following steps: Step 1: Control the distribution of eddy currents in the adhesive layer and substrate; By increasing the excitation angular frequency ω and using high-frequency excitation, the eddy currents are concentrated and penetrated into the adhesive layer, eliminating interference from the substrate. Step 2: Express the coupling coefficient K as an exponential relationship of the ceramic layer thickness; First, based on the equivalent transformer model, derive the analytical expressions for the change in coil inductance ∆L and the mutual inductance index M in the equivalent transformer model, and simplify to obtain the analytical expressions for ∆L and coupling coefficient K, thus approximately eliminating the characteristic values ​​containing the adhesive layer thickness and conductivity. Then, based on the Neumann formula and Taylor series, the coupling coefficient K is equivalently expressed as the ceramic layer thickness h. t The exponential relationship is determined, and the fitting coefficients are obtained. Step 3: Establish an RLC parallel resonant circuit and obtain the change in resonant inductance ∆L. ab The expression relating the thickness of the ceramic layer; A capacitor is connected in parallel across the coil to form an RLC parallel resonant circuit. The resonant frequency is obtained by frequency sweeping, and the excitation frequency is fixed at 1 / 2 of the peak value of the resonant inductance. The change in resonant inductance ∆L output by the RLC parallel resonant circuit is then used. ab The exponential expression represents the change in coil inductance ΔL derived in the equivalent transformer model in step 2, establishing ΔL ab The expression for the ceramic layer thickness is derived, and the final fitting coefficients are obtained. Step 4: Fabricate an integrated excitation, demodulation, and coil probe, and exchange digital signals and DC signals with the detection instrument through the input and output ports at the top of the probe; Step 5: Prepare two thermal barrier coating samples with different coating thicknesses, and use a high-frequency resonant eddy current detector to measure the change in resonant inductance ∆L at the test point. ab The true thickness of the test point is obtained through metallographic experiments. Step 6: Calculate ∆L using the two samples prepared in Step 5. ab The fitting coefficient in the expression for the ceramic layer thickness; Step 7: Measure the sample under test using a high-frequency resonant eddy current detector to obtain the change in its resonant inductance ∆L. ab Substitute the ∆L obtained from calibrating the fitting coefficients in step 6 ab The ceramic layer thickness of the sample is obtained by using the expression for the ceramic layer thickness. Step 2 specifically includes: Step 2.1: The analytical expression for ∆LM can be derived as follows: Since the angular frequency ω is amplified in step 1, the analytical expression of ∆LM is simplified to the analytical expression of ∆LK, which is: Where K is the coupling coefficient, L1 is the coil's own inductance, and ΔR and ΔL are the changes in resistance and inductance of the coil on the test piece and in air, respectively. Step 2.2: Using the Neumann formula and Taylor series, the coupling coefficient K is equivalently expressed as the ceramic layer thickness h. t exponential relationship , where a and b are fitting coefficients; Step 3 specifically includes: Step 3.1: Connect a capacitor in parallel across the coil to form an RLC parallel resonant circuit. Set the excitation frequency to 1 / 2 of the peak value of the resonant inductance and amplify the change in inductance through electromagnetic resonance. Step 3.2: Establish the change in resonant inductance ∆L ab The exponential fitting expression for the change in coil inductance ΔL derived in the equivalent transformer model in step 2. , where c and d are the fitting coefficients; Step 3.3: Combining the approximately exponential expression of the coupling coefficient K and ceramic layer thickness in Step 2, and the change in resonant inductance ∆L in Step 3.

2. ab By combining the exponential fitting expression for the change in coil inductance ΔL derived in the equivalent transformer model in step 2, the change in resonant inductance ΔL is established. ab With ceramic layer thickness h t Characteristic Relationship , where a1 and b1 are the final fitting coefficients to be determined; Step 4 specifically includes: An integrated probe consisting of an excitation module, a demodulation module, and a coil is fabricated. Data is exchanged with the testing instrument through the input and output ports at the top of the probe. The input port transmits the digital signal controlling the excitation module. After excitation, the coil is controlled. Then, the differential signal of the bridge is demodulated and output. The output port transmits the demodulated amplitude and phase signals.

2. The eddy current measurement method for the thickness of thermal barrier coating ceramic layer based on high-frequency resonance according to claim 1, characterized in that, Step 6 uses the two samples with known actual ceramic layer thicknesses and resonant inductance changes from Step 5 to calibrate the resonant inductance change and ceramic layer thickness expression established in Step 3, and obtains ∆L. ab The fitting coefficients in the expression for the ceramic layer thickness; specifically including: Let the thickness of the ceramic layer of calibration component 1 be h. t1 The change in resonant inductance is ∆L ab1 The ceramic layer thickness of calibration component 2 is h. t2 The change in resonant inductance is ∆L ab2 Substitute the change in resonant inductance ∆L into the values ​​respectively. ab With ceramic layer thickness h t Characteristic Relationship , can be obtained , .

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