Thermal barrier coating capable of realizing high-sensitivity measurement of internal stress as well as preparation method and application of thermal barrier coating

Abstract

The invention provides a thermal barrier coating capable of achieving high-sensitivity measurement of internal stress and a preparation method and application of the thermal barrier coating, and belongs to the technical field of thermal barrier coatings. The ceramic layer is formed by spraying mixed powder of yttria-stabilized zirconia (YSZ) powder and cerium-doped yttrium aluminum garnet (YAG: Ce) powder; the preparation method comprises the steps that the metal bonding layer is prepared on the high-temperature alloy matrix layer, then mixed powder is sprayed to form the ceramic layer, and finally the thermal barrier coating is obtained. The YSZ / YAG: Ce thermal barrier coating is prepared by doping YAG: Ce as a fluorescence stress sensing medium into YSZ based on the high stress sensitivity characteristic of Ce < 3 + > fluorescence, and nondestructive fine detection of internal stress of the YSZ / YAG: Ce thermal barrier coating is realized by adopting a fluorescence spectrometry, so that the problems that high-sensitivity stress measurement is difficult to carry out by adopting an existing thermal barrier coating technology, and the thermal barrier coating is difficult to detect are solved. And fine characterization of the internal stress of the thermal barrier coating cannot be realized.

Description

Technical Field

[0001] This invention relates to the field of thermal barrier coating technology, and in particular to a thermal barrier coating capable of highly sensitive measurement of internal stress, its preparation method, and its application. Background Technology

[0002] Thermal barrier coating (TBC) technology is a key technology for improving the service performance of heavy-duty gas turbines and aero-engines. It effectively enhances the high-temperature resistance of turbine blades by coating the surface of high-temperature alloys with ceramic composite materials that have low thermal conductivity and high thermal stability. This coating is typically a multi-layered heterogeneous structure, comprising a ceramic layer, a metal binder layer, and a high-temperature alloy matrix. Yttrium-stabilized zirconia (YSZ) has become the mainstream material for the ceramic layer due to its low thermal conductivity, thermal expansion coefficient matching that of high-temperature alloys, and excellent mechanical properties. Simultaneously, fluorescence spectroscopy, as a non-destructive testing technique, is used to measure the internal stress of the coating. Based on the piezometric effect, it measures stress by observing the linear relationship between the frequency shift of the characteristic peak of the emission spectrum of fluorescent active ions after laser excitation and the stress. The coefficient indicating this linear relationship is called the piezometric coefficient. Typically, YSZ materials do not contain fluorescent active ions suitable for stress measurement; therefore, fluorescent active ions must be incorporated as a sensing medium. Currently, Eu is commonly used. 3+ ion.

[0003] As engine service environments become increasingly harsh, the process stress and service stress generated within thermal barrier coatings due to high thermal gradients, differences in interlayer thermal expansion coefficients, and environmental erosion have a more significant impact on coating reliability. Therefore, the need for precise characterization of stress within the coating (especially at the interface between the ceramic and metal bonding layers) is becoming increasingly urgent. Fluorescence spectroscopy, due to its non-destructive and high-resolution characteristics, has become a major research direction in this field. The industry tends to improve the sensitivity and accuracy of stress measurements by optimizing the performance of the fluorescence sensing medium, thereby achieving precise monitoring and life assessment of the coating's service condition.

[0004] Eu is currently used for stress measurement of thermal barrier coatings. 3+ Ions with a pressure spectral coefficient of only 4–10 cm⁻¹ -1 The low sensitivity ( / GPa) makes it difficult to conduct highly sensitive stress measurements and achieve precise characterization of the internal stress of thermal barrier coatings. This restricts the effective evaluation of coating service performance and life prediction, becoming a major shortcoming of existing technologies. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a thermal barrier coating capable of highly sensitive measurement of internal stress, its preparation method, and its application, based on Ce. 3+The high stress sensitivity of fluorescence allows for the preparation of YSZ / YAG:Ce thermal barrier coatings by doping YAG:Ce into YSZ using YAG:Ce as the fluorescent stress sensing medium. Fluorescence spectroscopy is then used to achieve non-destructive and precise detection of the internal stress of these coatings, thus solving the technical problem that existing thermal barrier coating technologies cannot perform high-sensitivity stress measurements and cannot achieve precise characterization of the internal stress of thermal barrier coatings.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A thermal barrier coating capable of highly sensitive measurement of internal stress comprises a high-temperature alloy substrate layer, a metal bonding layer, and a ceramic layer stacked sequentially. The ceramic layer is formed by spraying a mixture of yttrium-stabilized zirconia (YSZ) powder and cerium-doped yttrium aluminum garnet (YAG:Ce) powder.

[0008] Preferably, in the mixture of YSZ powder and YAG:Ce powder, the mass percentage of YAG:Ce powder is 8% to 12%, and the mass percentage of YSZ powder is 88% to 92%; the thickness of the ceramic layer is 200 to 250 μm.

[0009] Preferably, the mass ratio of YSZ powder to YAG:Ce powder in the mixed powder is 90% and 10%, respectively.

[0010] Preferably, the YAG:Ce powder is mainly prepared from the following raw materials in molar percentage: Y3Al5O 12 98–99.5% and CeO2 0.5–2%.

[0011] Preferably, the YAG:Ce powder comprises the following raw materials in molar percentage: Y3Al5O 12 99.5% and CeO2 0.5%.

[0012] Preferably, the YSZ powder is mainly prepared from the following raw materials in molar percentage: ZrO2 92-94% and Y2O3 6-8%.

[0013] Preferably, the YSZ powder comprises the following raw materials in molar percentage: 92% ZrO2 and 8% Y2O3.

[0014] The present invention also provides a method for preparing the above-mentioned thermal barrier coating capable of highly sensitive measurement of internal stress, comprising the following steps:

[0015] S1. A metal bonding layer is prepared on a high-temperature alloy substrate by atmospheric plasma spraying.

[0016] S2. The YSZ powder and YAG:Ce powder are mechanically mixed according to a preset mass ratio for 4 to 8 hours to obtain a mixed powder with a particle size of 250 mesh to 700 mesh.

[0017] S3. A ceramic layer formed from the mixed powder is prepared on the metal bonding layer by an atmospheric plasma spraying process, and finally the thermal barrier coating is obtained.

[0018] The present invention also provides an application of the above-mentioned thermal barrier coating capable of highly sensitive measurement of internal stress in the field of stress measurement, which is suitable for achieving highly sensitive measurement of its internal stress using fluorescence spectroscopy.

[0019] Preferably, the stress measurement includes non-destructive precision testing of stress distribution and evolution within the thermal barrier coating ceramic layer and at the interface between the ceramic layer and the metal bonding layer.

[0020] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0021] (1) This invention uses YAG:Ce as the fluorescence stress sensing medium to dope YSZ, thereby improving the pressure spectral coefficient of fluorescence spectroscopy techniques suitable for YSZ thermal barrier coatings compared to traditional Eu. 3+ Fluorescence compression spectroscopy improves the accuracy of internal stress measurement by two orders of magnitude, thereby significantly enhancing the accuracy of stress measurement in thermal barrier coatings and enabling highly sensitive stress detection.

[0022] (2) This invention enables precise characterization and comprehensive monitoring of internal stress in thermal barrier coatings. By using fluorescence spectroscopy, the stress distribution and evolution inside the ceramic layer and at the interface between the ceramic layer and the metal bonding layer can be detected non-destructively and precisely, breaking the limitation of low stress sensitivity of traditional fluorescent doped media. It can capture local stress concentration and stress evolution induced by crack growth. At the same time, by using surface scanning, high-precision full-field stress distribution information inside the coating can be obtained, providing an effective means for comprehensive analysis of the stress state of the coating.

[0023] (3) This invention optimizes service performance evaluation and life prediction while ensuring the basic performance of the thermal barrier coating. The prepared YSZ / YAG:Ce thermal barrier coating has improved high-temperature phase stability and thermal insulation performance compared with traditional YSZ coating without affecting the basic service performance. Combined with highly sensitive stress measurement results, it can accurately detect the service performance of the coating and effectively evaluate the service life, which is conducive to optimizing the maintenance cycle and improving the operational reliability of heavy-duty gas turbines and aero engines. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of the thermal barrier coating that enables highly sensitive measurement of internal stress according to Embodiment 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of the micro-fluorescence spectroscopy system for stress measurement of the YSZ / YAG:Ce thermal barrier coating specimen provided in Embodiment 1 of the present invention.

[0027] Explanation of reference numerals in the attached figures:

[0028] 100. YSZ / YAG:Ce thermal barrier coating specimen; 101. Ceramic layer; 102. Metal bonding layer; 103. High-temperature alloy substrate layer; 200. Filter; 300. Microscope objective lens; 400. Spectrometer; 500. Laser. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] like Figure 1 As shown, the present invention provides a thermal barrier coating that enables highly sensitive measurement of internal stress, comprising a high-temperature alloy substrate layer 103, a metal bonding layer 102 and a ceramic layer 101 stacked sequentially, wherein the ceramic layer 101 is formed by spraying a mixture of yttrium-stabilized zirconium oxide (YSZ) powder and cerium-doped yttrium aluminum garnet (YAG:Ce) powder.

[0033] In a preferred embodiment of the present invention, the YSZ / YAG:Ce powder is mainly prepared by mechanically mixing the following raw materials in mass percentage: YAG:Ce 8-12% and YSZ 88-92%; specifically, in the raw materials for preparing the YSZ / YAG:Ce powder, the mass percentage of YSZ includes, but is not limited to, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5% or 92%; and the mass percentage of YAG:Ce includes, but is not limited to, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5% or 12%.

[0034] Furthermore, when the raw material molar percentage of YAG:Ce powder is Y3Al5O 12 The raw material molar percentages of YSZ powder are 99.5% ZrO2 and 0.5% CeO2; when the mass ratio of YSZ powder to YAG:Ce powder is 90%:10%, the ceramic layer 101 made from YSZ / YAG:Ce powder with this ratio exhibits more stable fluorescence signal and more accurate measurement of internal stress in the thermal barrier coating. Furthermore, the thermal barrier coating made from YSZ / YAG:Ce powder with this ratio shows improvements in high-temperature phase stability and thermal insulation performance compared to the YSZ coating without affecting service performance.

[0035] In another preferred embodiment of the present invention, the particle size of the YSZ / YAG:Ce powder is 250-700 mesh, so that when the YSZ / YAG:Ce powder is used to prepare a thermal barrier coating by spraying technology, it is easier to spray evenly. Compared to the above-mentioned powder particle size range, when the particle size of the YSZ / YAG:Ce powder is too small, the powder output efficiency of the spraying technology is low; when the particle size of the YSZ / YAG:Ce powder is too large, it will increase the internal porosity of the coating and reduce the service performance of the thermal barrier coating.

[0036] Specifically, the particle size of YSZ / YAG:Ce powder includes, but is not limited to, 250 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh, 500 mesh, 550 mesh, 600 mesh, 650 mesh, or 700 mesh.

[0037] In another preferred embodiment of the present invention, the mixing time of YSZ and YAG:Ce powder is 4-8 hours, so that the prepared YSZ / YAG:Ce powder is more stable and the fluorescent ion doping is more uniform.

[0038] Specifically, the mixing time of YSZ and YAG:Ce powders includes, but is not limited to, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h.

[0039] Based on the above, this embodiment also provides a method for preparing the above-mentioned thermal barrier coating capable of highly sensitive measurement of internal stress, namely, the method for preparing the YSZ / YAG:Ce thermal barrier coating includes the following steps:

[0040] S1. A metal bonding layer 102 is prepared on a high-temperature alloy substrate layer 103 by atmospheric plasma spraying process.

[0041] S2. The YSZ powder and YAG:Ce powder are mechanically mixed according to a preset mass ratio for 4 to 8 hours to obtain a mixed powder with a particle size of 250 mesh to 700 mesh.

[0042] S3. A ceramic layer 101 formed from the mixed powder is prepared on the metal bonding layer 102 by atmospheric plasma spraying process, and finally the thermal barrier coating is obtained.

[0043] Specifically, in step S3 above, the thickness of the YSZ / YAG:Ce ceramic layer 101 is 200-250 μm; further, the thickness of the ceramic layer 101 includes, but is not limited to, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, or 250 μm. Experimental verification shows that, relative to the above thickness range, if the thickness of the YSZ / YAG:Ce ceramic layer 101 is greater than 250 μm, it easily affects the fluorescence transmittance and reduces measurement accuracy; if the thickness of the ceramic layer 101 is less than 200 μm, it reduces the thermal insulation performance of the thermal barrier coating.

[0044] As another preferred embodiment of the present invention, the present invention also provides a method for preparing YSZ / YAG:Ce ceramic layers and a method for calibrating the pressure spectrum coefficients. The experimental operation steps are as follows:

[0045] A YSZ / YAG:Ce ceramic layer was prepared on the surface of an aluminum substrate by spraying. The aluminum substrate was then dissolved by a 20% NaOH solution to obtain a YSZ / YAG:Ce ceramic layer sample.

[0046] The fluorescence spectrum was excited by focusing incident light onto the surface of the YSZ / YAG:Ce ceramic layer sample, and the characteristic peaks of the YSZ / YAG:Ce ceramic layer under no-pressure conditions were determined.

[0047] The YSZ / YAG:Ce ceramic layer to be calibrated is placed under a given stress state with a stress magnitude of σ. Ce Fluorescence spectra were collected at multiple locations on the sample surface, and the average results were taken. The measured fluorescence spectra were compared with the initial characteristic peaks, and the data were processed to extract frequency shift information, thus obtaining the frequency shift Δ of the characteristic peaks of the fluorescence spectrum before and after stress generation. Ce Using the formula Δ Ce =Π Ce ·σ CeThe pressure spectral coefficient Π corresponding to the YSZ / YAG:Ce ceramic layer can then be obtained. Ce .

[0048] In the above steps, the spraying technology is atmospheric plasma spraying technology.

[0049] As another preferred embodiment of the present invention, the method for non-destructive fine detection of internal stress in YSZ / YAG:Ce thermal barrier coating should be noted that the pressure spectrum coefficient of the YSZ / YAG:Ce ceramic layer has been calibrated, and includes the following steps:

[0050] A micro-fluorescence spectroscopy system was used to excite fluorescence spectra with a laser beam of a specific wavelength, and the initial characteristic peak R0 of the YSZ / YAG:Ce thermal barrier coating under no-pressure conditions was determined.

[0051] Using a laser beam of the same wavelength as in the above steps, incident on and penetrate the ceramic layer to excite a fluorescence spectrum, and calibrate the specific characteristic peak R1 of the YSZ / YAG:Ce thermal barrier coating under a specific pressure.

[0052] Calculate the peak position shift between R1 and R0 in the characteristic fluorescence spectrum, using the linear expression Δ Ce =Π Ce ·σ Ce The internal stress σ of the thermal barrier coating is obtained. Ce .

[0053] In the above, stress distribution and evolution information of a large area (on the order of centimeters) within the thermal barrier coating can be obtained completely by performing single-point detection or surface scanning detection on the thermal barrier coating.

[0054] To further verify the feasibility of the above content, combined with Figure 2 The micro-fluorescence spectroscopy system for stress measurement of the YSZ / YAG:Ce thermal barrier coating specimens provided further describes the technical solution of the present invention.

[0055] like Figure 2 As shown, the micro-fluorescence spectroscopy system consists of a filter 200, a microscope objective lens 300, a spectrometer 400, and a laser 500. The YSZ / YAG:Ce thermal barrier coating specimen 100 consists of a ceramic layer 101, a metal bonding layer 102, and a high-temperature alloy substrate layer 103.

[0056] The working principle of the micro-fluorescence spectroscopy system is as follows: After the excitation signal is emitted by the laser 500, it is reflected by the filter 200 and focused onto the YSZ / YAG:Ce thermal barrier coating specimen 100 by the microscope objective lens 300. The microscope objective lens 300 collects the rare earth fluorescence emitted by the ceramic layer 101 before and after stress generation, and introduces it into the spectrometer 400 for fluorescence spectroscopy analysis. The internal stress is calculated using the linear relationship between the frequency shift in the fluorescence spectrum and the internal stress of the thermal barrier coating. The analytical expression for the linear relationship is: Δ Ce =Π Ce ·σ Ce , where Δ Ce σ represents the frequency shift of the fluorescence spectrum before and after the generation of internal stress. Ce Represents the internal stress of the thermal barrier coating, Π Ce The pressure spectrum coefficient of the YSZ / YAG:Ce ceramic layer is given.

[0057] In the above description, the YSZ / YAG:Ce thermal barrier coating specimen 100 was prepared using atmospheric plasma spraying technology; the ceramic layer 101 had a thickness of 200 μm; and the raw materials for preparing the YSZ / YAG:Ce powder were YSZ powder and YAG:Ce powder, with a mass ratio of 90%:10%. The YAG:Ce powder mainly consisted of Y3Al5O3 molar percentage. 12 The YSZ powder is prepared from raw materials containing 99.5% ZrO2 and 0.5% CeO2. The YSZ powder is mainly prepared from raw materials containing 92% ZrO2 and 8% Y2O3 by molar percentage. The metal binder layer 102 is made of NiCoCrAlY and has a thickness of 150 μm. The high-temperature alloy substrate layer 103 is made of Inconel 718 high-temperature alloy and has a thickness of 5 mm.

[0058] In this embodiment, the pressure spectral coefficient of the YSZ / YAG:Ce ceramic layer provided in the embodiment was measured using a laser beam with a wavelength of 473 nm, and the result was 1440 cm⁻¹. -1 / GPa, compared to the 4-10 cm⁻¹ pressure spectral coefficient of Eu-doped 8YSZ, i.e., 8YSZ:Eu ceramic layers. -1 The / GPa value has increased by two orders of magnitude, effectively improving the measurement accuracy of internal stress in thermal barrier coatings, which is conducive to accurate monitoring of coating service life and optimization of maintenance cycles for thermal barrier coatings.

[0059] Therefore, using the above-mentioned thermal barrier coating capable of highly sensitive measurement of internal stress, its preparation method, and its application, based on Ce 3+The high stress sensitivity of fluorescence allows for the preparation of YSZ / YAG:Ce thermal barrier coatings by doping YAG:Ce into YSZ using YAG:Ce as the fluorescent stress sensing medium. Fluorescence spectroscopy is then used to achieve non-destructive and precise detection of the internal stress of these coatings, thus solving the technical problem that existing thermal barrier coating technologies cannot perform high-sensitivity stress measurements and cannot achieve precise characterization of the internal stress of thermal barrier coatings.

[0060] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A thermal barrier coating capable of highly sensitive measurement of internal stress, characterized in that, It includes a high-temperature alloy substrate layer, a metal bonding layer and a ceramic layer stacked in sequence. The ceramic layer is formed by spraying a mixture of yttrium-stabilized zirconia (YSZ) powder and cerium-doped yttrium aluminum garnet (YAG:Ce) powder.

2. The thermal barrier coating capable of highly sensitive measurement of internal stress according to claim 1, characterized in that, In the mixture of YSZ powder and YAG:Ce powder, the mass percentage of YAG:Ce powder is 8% to 12%, and the mass percentage of YSZ powder is 88% to 92%; the thickness of the ceramic layer is 200 to 250 μm.

3. A thermal barrier coating capable of highly sensitive measurement of internal stress according to claim 1, characterized in that, The mass ratios of YSZ powder and YAG:Ce powder in the mixed powder are 90% and 10%, respectively.

4. A thermal barrier coating capable of highly sensitive measurement of internal stress according to claim 1, characterized in that, The YAG:Ce powder is prepared mainly from the following raw materials in terms of molar percentage: Y3Al5O 12 98-99.5% and CeO2 0.5-2%.

5. A thermal barrier coating capable of highly sensitive measurement of internal stress according to claim 4, characterized in that, The YAG:Ce powder comprises raw materials in terms of molar percentage: Y3Al5O 12 99.5% and CeO2 0.5%.

6. A thermal barrier coating capable of highly sensitive measurement of internal stress according to claim 1, characterized in that, The YSZ powder is mainly prepared from the following raw materials in molar percentage: ZrO2 92-94% and Y2O3 6-8%.

7. A thermal barrier coating capable of highly sensitive measurement of internal stress according to claim 6, characterized in that, The YSZ powder comprises the following raw materials in molar percentage: 92% ZrO2 and 8% Y2O3.

8. A method for preparing a thermal barrier coating capable of highly sensitive measurement of internal stress according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. A metal bonding layer is prepared on a high-temperature alloy substrate by atmospheric plasma spraying. S2. The YSZ powder and YAG:Ce powder are mechanically mixed according to a preset mass ratio for 4 to 8 hours to obtain a mixed powder with a particle size of 250 mesh to 700 mesh. S3. A ceramic layer formed from the mixed powder is prepared on the metal bonding layer by an atmospheric plasma spraying process, and finally the thermal barrier coating is obtained.

9. The application of a thermal barrier coating capable of highly sensitive internal stress measurement according to any one of claims 1 to 7 in the field of stress measurement, characterized in that, It is suitable for highly sensitive measurement of internal stress using fluorescence spectroscopy.

10. The application of a thermal barrier coating capable of highly sensitive internal stress measurement according to claim 9 in the field of stress measurement, characterized in that, The stress measurement includes non-destructive precision testing of stress distribution and evolution within the thermal barrier coating ceramic layer and at the interface between the ceramic layer and the metal bonding layer.

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