CN114295679B - Method and system for detecting internal cracks of thermal barrier coating - Google Patents
Method and system for detecting internal cracks of thermal barrier coating Download PDFInfo
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- CN114295679B CN114295679B CN202210014745.8A CN202210014745A CN114295679B CN 114295679 B CN114295679 B CN 114295679B CN 202210014745 A CN202210014745 A CN 202210014745A CN 114295679 B CN114295679 B CN 114295679B
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- 239000012720 thermal barrier coating Substances 0.000 title claims abstract description 116
- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000000013 phosphorescence detection Methods 0.000 claims abstract description 82
- 239000000919 ceramic Substances 0.000 claims abstract description 36
- 230000005284 excitation Effects 0.000 claims abstract description 36
- 229910052751 metal Inorganic materials 0.000 claims abstract description 31
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- 239000000463 material Substances 0.000 claims description 25
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- 238000012545 processing Methods 0.000 claims description 16
- 229910001233 yttria-stabilized zirconia Inorganic materials 0.000 claims description 7
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 4
- 229910052693 Europium Inorganic materials 0.000 claims description 4
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 claims description 3
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
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Abstract
The invention relates to a method and a system for detecting internal cracks of a thermal barrier coating, wherein the method comprises the following steps: projecting an excitation light beam to the thermal barrier coating to be detected at a set angle and generating a phosphorescence light beam on a phosphorescence detection layer of the thermal barrier coating to be detected; a phosphorescence detection layer is arranged between the metal bonding layer of the thermal barrier coating to be detected and the ceramic thermal insulation layer; the phosphorescence light beam passes through an optical beam splitter to obtain a first light beam and a second light beam; the first light beam and the second light beam have different wavelengths; obtaining a first light intensity of the first light beam; obtaining a second light intensity of the second light beam; determining the temperature distribution of a phosphorescence detection layer in the thermal barrier coating to be detected according to the light intensity ratio of the first light intensity and the second light intensity obtained at each point on the surface of the thermal barrier coating to be detected; according to the invention, whether cracks exist in the thermal barrier coating to be detected is judged according to the temperature difference of each point on the phosphorescence detection layer, and nondestructive detection of the cracks in the thermal barrier coating is realized by arranging the phosphorescence detection layer between the metal bonding layer and the ceramic heat insulation layer.
Description
Technical Field
The invention relates to the technical field of crack detection, in particular to a method and a system for detecting internal cracks of a thermal barrier coating.
Background
In order to increase the front temperature of the turbine of the aeroengine and the service life of the hot end component, the thermal barrier coating technology is widely applied in recent years. The thermal barrier coating technology realizes the protection effect on the hot end component by spraying ceramic materials on the surface of the turbine blade so as to ensure that the turbine blade can run at a higher temperature. The thermal barrier coating is generally composed of a nickel-based alloy substrate, a metal bonding layer and a ceramic layer, wherein the metal bonding layer is mainly made of MCrAlY or NiPtAl and is used for resisting oxidation and relieving the problem of unmatched thermal expansion coefficients of the metal substrate and the surface ceramic; the ceramic layer is typically yttria stabilized zirconia (8 YSZ), which is widely used for its good thermal cycling performance and relatively low thermal conductivity.
The thermal barrier coating works in extremely severe thermal and vibration environments in the aero-engine, and the complex structure and the severe working environment enable the thermal barrier coating to easily generate failures in the forms of cracking, falling and the like in the using process. The failure mechanism of the thermal barrier coating is complex, and the thermal barrier coating mainly comprises two aspects of TGO (Thermally grown oxide ) growth which occurs at the bonding layer interface to generate inside cracks and high-temperature erosion and CMAS corrosion which occur outside. The TGO refers to a series of thermally grown oxides which are generated by oxidation reaction of external oxygen elements and metal elements in the bonding layer after the external oxygen elements penetrate through the ceramic layer and diffuse to the bonding layer interface. TGO grows continuously at the interface of the bonding layer, gradually damages the original internal microstructure of the coating and causes stress concentration, and the abnormal concentrated stress causes microcracks to be generated on the inner side of the coating. The thermal physical property and mechanical property changes caused by microcracks further deepen stress concentration, and finally the whole coating is subjected to irreversible internal crack damage. The expansion of cracks plays a decisive role in the service life of the thermal barrier coating, so that nondestructive detection is carried out on cracks on the inner side of the thermal barrier coating to timely know the state of the internal cracks, and the evaluation of the residual service life is particularly important for safe and stable operation of the aeroengine.
In order to accurately evaluate the residual life of the thermal barrier coating, the detection of the inner side crack is required to be accurate to the micron level, however, the effective resolution is difficult to realize by the main nondestructive detection methods such as a penetration detection method, an infrared thermal imaging technology, an eddy current detection method and the like at present.
Disclosure of Invention
The invention aims to provide a method and a system for detecting internal cracks of a thermal barrier coating, which improve the detection accuracy of nondestructive detection of the internal cracks of the thermal barrier coating.
In order to achieve the above object, the present invention provides the following solutions:
a method for detecting cracks in a thermal barrier coating, comprising:
projecting an excitation light beam to the thermal barrier coating to be detected at a set angle and generating a phosphorescence light beam on a phosphorescence detection layer of the thermal barrier coating to be detected; the phosphorescence detection layer is arranged between the metal bonding layer of the thermal barrier coating to be detected and the ceramic thermal insulation layer; the material of the phosphorescence detection layer comprises a phosphorescence substance;
the phosphorescence light beam passes through an optical beam splitter to obtain a first light beam and a second light beam; the first light beam and the second light beam have different wavelengths;
obtaining the light intensity of the first light beam, and recording the light intensity as first light intensity; obtaining the light intensity of the second light beam, and recording the light intensity as second light intensity;
determining the temperature of each corresponding point on the phosphorescence detection layer in the thermal barrier coating to be detected according to the light intensity ratio of the first light intensity and the second light intensity obtained at each point on the surface of the thermal barrier coating to be detected;
judging whether cracks exist in the thermal barrier coating to be detected according to the temperature difference of each point on the phosphorescence detection layer.
Alternatively, the light intensity ratio is expressed as:
wherein FIR represents the light intensity ratio, I 1 Representing the first light intensity, I 2 Representing the second light intensity, B is a constant, K B The boltzmann constant is a temperature of the phosphorescence detection layer, and Δe is a constant.
Optionally, the thickness of the phosphorescence detection layer ranges from 10 μm to 20 μm; the thermal barrier coating to be detected comprises the metal bonding layer, the phosphorescence detection layer and the ceramic thermal insulation layer.
Optionally, the phosphorescent material includes at least one pair of thermally coupled energy levels.
Optionally, the phosphorescent substance is dysprosium or europium.
Optionally, the material of the metal bonding layer is MCrAlY.
Optionally, the material of the ceramic thermal insulation layer is yttria stabilized zirconia.
The invention discloses a thermal barrier coating internal crack detection system, which applies the thermal barrier coating internal crack detection method, and comprises the following steps: an excitation light source, an optical beam splitter, a photoelectric converter and a signal processing terminal;
the excitation light source is used for irradiating excitation light to the surface of the thermal barrier coating to be detected at a set angle and generating a phosphorescence light beam on the phosphorescence detection layer; the phosphorescence detection layer is arranged between the metal bonding layer of the thermal barrier coating to be detected and the ceramic thermal insulation layer; the material of the phosphorescence detection layer comprises a phosphorescence substance;
the optical beam splitter is used for receiving the phosphorescence light beam generated by the thermal barrier coating to be detected and dividing the phosphorescence light beam into a first light beam and a second light beam; the first light beam and the second light beam have different wavelengths;
the photoelectric converter is used for converting the received first light beam into a first electric signal and converting the received second light beam into a second electric signal;
the signal processing terminal is used for determining the light intensity of a first light beam according to the received first electric signal, marking the light intensity as the first light intensity, and determining the light intensity of a second light beam according to the received second electric signal, marking the light intensity as the second light intensity; the signal processing terminal is also used for determining the temperature of each corresponding point on the phosphorescence detection layer in the thermal barrier coating to be detected according to the light intensity ratio of the first light intensity and the second light intensity obtained at each point on the surface of the thermal barrier coating to be detected; and the signal processing terminal is also used for judging whether the thermal barrier coating to be detected has cracks or not according to the difference of the temperatures of all points on the phosphorescence detection layer.
Optionally, the photoelectric converter is a two-dimensional photoelectric converter.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
according to the invention, the phosphorescence detection layer doped with the phosphorescence substances is added at the joint of the metal bonding layer and the ceramic heat insulation layer, and the temperature distribution of the phosphorescence detection layer is determined according to the relation between the light intensity ratio of the phosphorescence light beams generated by the thermal barrier coating and the temperature, so that whether cracks exist in the thermal barrier coating is determined, and the detection accuracy of nondestructive detection of the cracks in the thermal barrier coating is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a method for detecting cracks in a thermal barrier coating according to the invention;
FIG. 2 is a schematic view of a thermal barrier coating structure of the present invention;
FIG. 3 is a one-dimensional heat transfer schematic diagram of a thermal barrier coating with internal cracks according to the present invention;
FIG. 4 is a schematic diagram of a system for detecting internal cracks of a thermal barrier coating according to the present invention;
symbol description:
the device comprises a 1-excitation light source, a 2-thermal barrier coating, a 3-optical beam splitter, a 4-photoelectric converter, a 5-signal processing terminal, a 21-ceramic heat insulation layer, a 22-phosphorescence detection layer, a 23-metal bonding layer and a 24-metal substrate.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a method and a system for detecting internal cracks of a thermal barrier coating, which realize nondestructive detection of the internal cracks of the thermal barrier coating.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
FIG. 1 is a schematic flow chart of a method for detecting internal cracks of a thermal barrier coating according to the present invention, as shown in FIG. 1, and the method for detecting internal cracks of the thermal barrier coating comprises:
step 101: projecting an excitation light beam to the thermal barrier coating to be detected at a set angle and generating a phosphorescence light beam on a phosphorescence detection layer of the thermal barrier coating to be detected; a phosphorescence detection layer is arranged between the metal bonding layer of the thermal barrier coating to be detected and the ceramic thermal insulation layer; the material of the phosphorescence detection layer comprises a phosphorescent substance.
As shown in fig. 2, the thermal barrier coating to be detected comprises a metal bonding layer 23, a phosphorescence detection layer 22 and a ceramic thermal insulation layer 21.
The metal bonding layer 23 is a metal transition layer connecting the metal substrate 24 and the ceramic layer; the phosphorescence detection layer 22 is positioned between the metal bonding layer 23 and the ceramic heat insulation layer 21, the phosphorescence detection layer 22 is made by mixing ceramic powder serving as a base material with phosphorescence substances, and the mixing does not influence the preparation process of the thermal barrier coating; the ceramic thermal insulation layer 21 is formed by spraying materials used for a common thermal barrier coating.
The material of the ceramic thermal insulation layer 21 is Yttria Stabilized Zirconia (YSZ), and is applied to the phosphorescence detection layer 22 by thermal spraying.
The interface between the metal adhesion layer 23 and the phosphorescence detection layer 22 is a site where the TGO is liable to grow to generate an inside crack, and when the phosphorescence detection layer 22 is thin, the phosphorescence signal generated by the phosphorescence detection layer 22 can reflect the inside crack information.
The thickness of the phosphorescence-detecting layer 22 ranges from 10 μm to 20 μm.
The original heat insulation performance of the thermal barrier coating is not changed by mixing the ceramic substrate and the phosphorescent substance. In order to ensure that the temperature of the phosphorescence detection layer 22 can accurately reflect the crack state at the interface of the bonding layer and the ceramic layer, the thickness of the phosphorescence detection layer 22 should be as thin as possible, and is recommended to be below 10% of the total thickness according to the practical application situation of the thermal barrier coating. At the same time, to ensure that the layer has sufficient phosphorescence intensity to be detected by the two-dimensional photoelectric converter, the thickness of the phosphorescence detection layer 22 should not be less than 5% of the total thickness.
Emitting excitation light from outside to the thermal barrier coating; based on the semi-permeability of the thermal barrier coating material to the excitation light and the band of phosphorescence, the excitation light can penetrate or partially penetrate through the ceramic thermal insulation layer 21 to reach the phosphorescence detection layer 22, the excitation light can heat the coating when propagating in the thermal barrier coating, and meanwhile, the excitation light can excite the phosphorescence substances mixed in the phosphorescence detection layer 22 to generate phosphorescence.
The phosphorescent material includes at least one pair of thermally coupled energy levels, and phosphorescence stimulated by the phosphorescent material is required to satisfy at least one set of wavelength-to-intensity ratios that are temperature dependent. The phosphorescent material is dysprosium (Dy) or europium (Eu).
The material of the metallic bond layer 23 is MCrAlY, where M represents cobalt, nickel or cobalt-nickel alloy, cr is chromium, al is aluminum, and Y is yttrium. The metal bonding layer 23 is used for relieving the mismatch of the thermal expansion coefficients of the metal substrate 24 and the surface ceramic, and prolonging the service life of the thermal barrier coating in the thermal cycle process. The reaction of the metallic bond coat 23 material with the oxygen element is the primary cause of crack formation inside the thermal barrier coating.
The YSZ material has semitransparent effect on light of 200-700nm wave band, when Dy or Eu is selected as the phosphorescent material, excitation light with 355nm and 405nm wavelength can be selected respectively, and the excitation light can effectively penetrate through the ceramic layer to reach the phosphorescence detection layer 22 to excite the phosphorescent material and simultaneously generate heating effect on the thermal barrier coating.
Step 102: the phosphorescence light beam passes through an optical beam splitter to obtain a first light beam and a second light beam; the first light beam and the second light beam have different wavelengths.
The first light beam and the second light beam are two light beams of phosphorescence characteristic wave bands.
Collecting the phosphorescence light beam by using an optical lens, dividing the collected phosphorescence light beam into two light beams by using an optical beam splitter 3, and keeping the two-dimensional information of the phosphorescence light beam in the collecting and beam dividing processes; the two-dimensional information is the light intensity distribution of the phosphorescent light beam on a plane.
Step 103: obtaining the light intensity of the first light beam, and recording the light intensity as the first light intensity; the intensity of the second light beam is obtained and noted as second intensity.
The first and second beams are filtered and the filtered beam is determined.
The filtering processing is carried out on the first light beam and the second light beam, and the filtered light beam is determined, which specifically comprises the following steps:
using a first characteristic wavelength band lambda of the phosphorescence beam 1 Filtering the first beam of light to obtain lambda 1 Band light beam (first light beam).
Using a second characteristic wavelength band lambda of the phosphorescence beam 2 Filtering the first beam of light to obtain lambda 2 Band beam (second beam).
The filtered beam includes lambda 1 Band light, lambda 2 Band light.
The first and second light intensities are determined from the filtered light beam.
Determining a first light intensity and a second light intensity according to the filtered light beam, specifically comprising:
lambda pair using a photosensor with two-dimensional photosensitive function 1 Band light, lambda 2 Measuring the wave band light, and obtaining a corresponding gray value after exposure; the corresponding gray values are respectively lambda 1 Is a first light intensity and a wavelength lambda 2 Is provided.
Step 104: and determining the temperature of each corresponding point on the phosphorescence detection layer in the thermal barrier coating to be detected according to the light intensity ratio of the first light intensity and the second light intensity obtained at each point on the surface of the thermal barrier coating to be detected.
Step 104 is to determine the temperature distribution of the phosphorescence detection layer in the thermal barrier coating to be detected according to the light intensity ratio.
The ratio of the phosphorescence intensities is determined according to the ratio relation between the first light intensity and the second light intensity.
The temperature of the phosphorescence detection layer 22 is obtained from the phosphorescence intensity ratio based on the light intensity ratio-temperature relationship of the phosphorescence signal obtained in the calibration.
The intensity ratio-temperature relationship is expressed as:
wherein FIR represents the light intensity ratio, I 1 Indicating a wavelength lambda 1 Is the first light intensity of I 2 Indicating a wavelength lambda 2 Is constant, K B The boltzmann constant, T, represents the temperature of the phosphorescence detection layer 22, Δe is a constant, and Δe specifically represents the energy difference between the energy levels. After the selected phosphorescence wave band is determined, the intensity ratio FIR is a single-value function of the temperature T, and the temperature distribution is calculated under the condition that the intensity ratio is known through calibration in advance.
Step 105: judging whether cracks exist in the thermal barrier coating to be detected according to the temperature difference of each point on the phosphorescence detection layer.
Because the thermal conductivity coefficients of the crack-free part and the crack-free part inside the thermal barrier coating are different, in step 105, if the temperature difference of each point on the phosphorescence detection layer exceeds the preset range, the crack inside the thermal barrier coating is indicated. The difference in temperature at each point on the phosphor detection layer in step 105 is due to the difference in thermal conductivity.
The crack condition is detected by temperature distribution acquisition, specifically comprising:
the heating effect generated by irradiation of excitation light to the thermal barrier coating is utilized, when cracks exist between the metal bonding layer 23 and the phosphorescence detection layer 22, the temperature distribution at the cracks is obviously different from the temperature distribution at the positions without cracks, and the crack condition of the detection layer can be obtained by analyzing the temperature information of the phosphorescence detection layer 22.
Based on the obvious difference of the temperature at the crack when the temperature at the inner side of the thermal barrier coating changes, the temperature distribution at the interface between the metal bonding layer 23 and the ceramic thermal insulation layer 21 (the phosphorescence detection layer 22) is measured according to the mapping relation between the phosphorescence intensity ratio and the temperature, and the crack condition of the interface between the metal bonding layer 23 and the ceramic thermal insulation layer 21 is judged according to the temperature distribution of the phosphorescence detection layer 22.
And acquiring the variance of the temperature distribution of the phosphorescence detection layer 22, if the variance is larger than a set value, judging that cracks exist in the thermal barrier coating, and if the variance is smaller than or equal to the set value, judging that no cracks exist in the thermal barrier coating.
The following describes a method for detecting cracks in a thermal barrier coating according to a specific embodiment.
Step1: the excitation light with specific wavelength is irradiated to the surface of the multi-layer structure phosphorescent thermal barrier coating from the outside, and the excitation wavelength is 405nm by taking a phosphorescent substance Eu as an example, so that the excitation light has a certain irradiation area or a beam expander is adopted to expand the excitation light beam in order to ensure that the whole region to be detected can be excited. Meanwhile, in order to ensure excitation efficiency, excitation light should have a certain intensity, and a laser is used as the excitation light source 1.
Step2: the excitation light can penetrate through the surface ceramic insulating layer 21 to reach the phosphorescence detection layer 22, and the phosphorescence substances mixed in the phosphorescence detection layer 22 are excited to generate phosphorescence.
For a phosphorescent substance having a thermally coupled energy level, when excited by excitation light, the ratio of the number of particles at the thermally coupled energy level satisfies the boltzmann distribution, that is:in N 1 And N 2 Respectively at wavelength lambda 1 And lambda (lambda) 2 Corresponding to the number of ions in the energy level state g 1 And g 2 Respectively the degeneracy of two transition energy levels of the phosphorescent substance, delta E is the energy extremely poor between energy levels, K B Is the boltzmann constant, and T is the temperature of the corresponding phosphorescence detection layer 22. When the specific wavelength lambda of the phosphorescent material is selected 1 And lambda (lambda) 2 After determination, g 1 、g 2 Delta E is constant.
The probability that a particle in a high-level state emits a photon to radiation of a certain energy level is unchanged, so that for phosphorescence of a certain wavelength, the phosphorescence intensity is proportional to the number of particles of the energy level corresponding to the wavelength, i.e. 1 ∝N 1 ,I 2 ∝N 2 。
Step3: the optical beam splitter 3 is used to perform beam processing on the phosphorescence beams with continuous wavelengths to determine two phosphorescence beams for the intensity ratio. The optical beam splitter 3 is an optical device for splitting one beam of light into two beams, and 50% of incident light passes through the beam splitter and the other 50% is reflected at an angle of 45 °.
Step4: and respectively filtering the two beams of light obtained in Step3 to obtain two beams of light with single wavelength for the intensity ratio. Specifically, the method comprises using a center wavelength lambda 1 And lambda (lambda) 2 The optical filter of (2) filters the two beams of light in Step3 to obtain the central wavelength lambda after the filtering 1 And lambda (lambda) 2 Is included in the phosphor layer.
Step5: the first and second intensities are determined from the Step4 filtered beam. The method specifically comprises the following steps: a photoelectric converter with two-dimensional photoelectric conversion function such as CCD (charge coupled device) or CMOS (Complementary Metal-Oxide-Semiconductor) is used for receiving the filtered light beam, and a two-dimensional gray value corresponding to the two light beams is obtained after exposure for a certain time. The gray value is lambda 1 Is of the first light intensity I 1 And a wavelength lambda 2 Is the second light intensity I of (2) 2 。
Step6: an intensity ratio is determined based on the first light intensity and the second light intensity. The intensity ratio is:
wherein FIR is intensity ratio, A 1 And A 2 Respectively the wavelength lambda 1 And lambda (lambda) 2 B is a constant. According to the formula in Step2, the ratio of the numbers of particles at the thermal coupling energy level is only related to temperature, and the phosphorescence intensity of a specific wavelength is in a proportional relation with the numbers of particles, so that the phosphorescence intensity ratio of two characteristic wave bands is a single-value function of temperature.
Based on the intensity ratio-temperature relationship obtained in the calibration, two-dimensional temperature information of the phosphorescence detection layer 22 is determined based on the intensity ratio obtained as described above.
The basic method for calibration work is as follows: the multi-layer thermal barrier coating which is manufactured by using a heating furnace with continuously adjustable temperature, is of the same type, the same thickness and the same process method during heating and temperature measurement, and the characteristic band light intensity ratio of the phosphorescence detection layer 22 at different temperatures is recorded by using the same excitation light and phosphorescence receiving device, so that the relation between the temperature and the light intensity ratio is obtained.
Step7: and acquiring the temperature distribution of the phosphorescence detection layer 22 based on the corresponding relation between the light intensity ratio and the temperature, and obtaining crack information according to the temperature distribution difference between the positions with and without cracks through data analysis, thereby realizing the nondestructive detection of the cracks on the inner side of the thermal barrier coating.
The principle of the difference of the temperature distribution at the position of cracks is shown in figure 3, the excitation light has a heating effect on the thermal barrier coating, so that the upper temperature of the coating is higher than the lower metal matrix temperature, and heat transfer and heat flux are generatedWhere Δt is the temperature difference and δ is the local thermal resistance. When a crack exists inside the thermal barrier coating, the thermal resistance delta at the crack is significantly increased, resulting in a change in the internal heat flow thereof, thereby causing a difference in the temperature distribution of the phosphorescence detection layer 22.
The invention is based on the semi-permeability of the ceramic coating to excitation light and phosphorescence, and based on the principle that the intensity of phosphorescence emitted by a ceramic-based phosphorescence substance in a characteristic wave band is compared with the sensitivity of temperature change at a crack of an internal phosphorescence detection layer 22, and the nondestructive detection of the crack at the inner side of the thermal barrier coating is realized by adding the phosphorescence detection layer 22 between the bonding layer and the ceramic layer.
According to the invention, a layer of phosphorescence detection layer 22 doped with phosphorescence substances is added between the metal bonding layer 23 and the ceramic heat insulation layer 21, excitation light can penetrate through the surface ceramic heat insulation layer 21 to reach the phosphorescence detection layer 22 to excite the phosphorescence substances to generate phosphorescence, then the sensitivity of the phosphorescence to temperature change at an internal crack is utilized by the intensity ratio of characteristic wave bands, and crack information at the inner side detection layer of the thermal barrier coating can be obtained by collecting and analyzing phosphorescence signals.
The invention discloses a thermal barrier coating internal crack detection system, which applies a thermal barrier coating internal crack detection method, as shown in fig. 4, and comprises the following steps: an excitation light source 1, an optical beam splitter 3, a photoelectric converter 4, and a signal processing terminal 5.
The excitation light source 1 is used for irradiating excitation light to the surface of the thermal barrier coating 2 to be detected at a set angle and generating a phosphorescence light beam on the phosphorescence detection layer 22; a phosphorescence detection layer 22 is arranged between the metal bonding layer 23 of the thermal barrier coating 2 to be detected and the ceramic thermal insulation layer 21; the material of the phosphorescence-detecting layer 22 includes a phosphorescent substance.
The optical beam splitter 3 is used for receiving the phosphorescence light beam generated by the thermal barrier coating 2 to be detected and dividing the phosphorescence light beam into a first light beam and a second light beam; the first light beam and the second light beam have different wavelengths.
The photoelectric converter 4 is configured to convert the received first light beam into a first electrical signal and convert the received second light beam into a second electrical signal.
The signal processing terminal 5 is configured to determine the light intensity of the first light beam according to the received first electrical signal, and record the light intensity as the first light intensity, and determine the light intensity of the second light beam according to the received second electrical signal, and record the light intensity as the second light intensity; the signal processing terminal 5 is further used for determining the temperature of each corresponding point on the phosphorescence detection layer 22 in the thermal barrier coating 2 to be detected according to the light intensity ratio of the first light intensity and the second light intensity obtained at each point on the surface of the thermal barrier coating 2 to be detected; the signal processing terminal 5 is further used for judging whether the thermal barrier coating 2 to be detected has cracks or not according to the difference of the temperatures of the points on the phosphorescence detection layer 22.
The photoelectric converter 4 is a two-dimensional photoelectric converter 4.
The excitation light source 1 generates luminescence and irradiates the thermal barrier coating with a multilayer structure from the outside, and a phosphorescence beam generated by the excitation of the phosphorescence substance in the phosphorescence detection layer 22 is divided into a wavelength lambda by the optical beam splitter 3 1 And lambda (lambda) 2 Is provided. The two beams of light are respectively detected and received by the photoelectric converter 4 after being filtered, optical signals are converted into electric signals retaining two-dimensional information, the electric signals are connected to the signal processing terminal 5 through the data line, and the crack state of the inner side of the thermal barrier coating is obtained after signal analysis.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.
Claims (9)
1. The method for detecting the internal cracks of the thermal barrier coating is characterized by comprising the following steps of:
projecting an excitation light beam to the thermal barrier coating to be detected at a set angle and generating a phosphorescence light beam on a phosphorescence detection layer of the thermal barrier coating to be detected; the phosphorescence detection layer is arranged between the metal bonding layer of the thermal barrier coating to be detected and the ceramic thermal insulation layer; the material of the phosphorescence detection layer comprises a phosphorescence substance; the thickness range of the phosphorescence detection layer is 10-20 mu m; the thickness of the phosphorescence detection layer should not be less than 5% of the total thickness;
the phosphorescence light beam passes through an optical beam splitter to obtain a first light beam and a second light beam; the first light beam and the second light beam have different wavelengths;
obtaining the light intensity of the first light beam, and recording the light intensity as first light intensity; obtaining the light intensity of the second light beam, and recording the light intensity as second light intensity;
determining the temperature of each corresponding point on the phosphorescence detection layer in the thermal barrier coating to be detected according to the light intensity ratio of the first light intensity and the second light intensity obtained at each point on the surface of the thermal barrier coating to be detected;
judging whether cracks exist in the thermal barrier coating to be detected according to the temperature difference of each point on the phosphorescence detection layer; and acquiring the variance of the temperature distribution of the phosphorescence detection layer, if the variance is larger than a set value, judging that cracks exist in the thermal barrier coating, and if the variance is smaller than or equal to the set value, judging that no cracks exist in the thermal barrier coating.
2. The method for detecting cracks inside a thermal barrier coating according to claim 1, wherein the light intensity ratio is expressed as:
wherein FIR represents the light intensity ratio, I 1 Representing the first light intensity, I 2 Representing the second light intensity, B is a constant, K B The boltzmann constant is a temperature of the phosphorescence detection layer, and Δe is a constant.
3. The method for detecting internal cracks of a thermal barrier coating according to claim 1, wherein the thermal barrier coating to be detected comprises the metal bonding layer, the phosphorescence detection layer and the ceramic thermal insulation layer.
4. The method of claim 1, wherein the phosphorescent substance comprises at least one pair of thermally coupled energy levels.
5. The method of claim 1, wherein the phosphorescent material comprises dysprosium or europium.
6. The method of claim 1, wherein the metallic bond coat material comprises MCrAlY.
7. The method of claim 1, wherein the material of the ceramic thermal barrier layer comprises yttria stabilized zirconia.
8. A thermal barrier coating internal crack detection system, characterized in that it applies the thermal barrier coating internal crack detection method according to any one of claims 1-7, comprising: an excitation light source, an optical beam splitter, a photoelectric converter and a signal processing terminal;
the excitation light source is used for irradiating excitation light to the surface of the thermal barrier coating to be detected at a set angle and generating a phosphorescence light beam on the phosphorescence detection layer; the phosphorescence detection layer is arranged between the metal bonding layer of the thermal barrier coating to be detected and the ceramic thermal insulation layer; the material of the phosphorescence detection layer comprises a phosphorescence substance; the thickness range of the phosphorescence detection layer is 10-20 mu m; the thickness of the phosphorescence detection layer should not be less than 5% of the total thickness;
the optical beam splitter is used for receiving the phosphorescence light beam generated by the thermal barrier coating to be detected and dividing the phosphorescence light beam into a first light beam and a second light beam; the first light beam and the second light beam have different wavelengths;
the photoelectric converter is used for converting the received first light beam into a first electric signal and converting the received second light beam into a second electric signal;
the signal processing terminal is used for determining the light intensity of a first light beam according to the received first electric signal, marking the light intensity as the first light intensity, and determining the light intensity of a second light beam according to the received second electric signal, marking the light intensity as the second light intensity; the signal processing terminal is also used for determining the temperature of each corresponding point on the phosphorescence detection layer in the thermal barrier coating to be detected according to the light intensity ratio of the first light intensity and the second light intensity obtained at each point on the surface of the thermal barrier coating to be detected; the signal processing terminal is also used for judging whether cracks exist in the thermal barrier coating to be detected according to the difference of the temperatures of all points on the phosphorescence detection layer; and acquiring the variance of the temperature distribution of the phosphorescence detection layer, if the variance is larger than a set value, judging that cracks exist in the thermal barrier coating, and if the variance is smaller than or equal to the set value, judging that no cracks exist in the thermal barrier coating.
9. The thermal barrier coating internal crack detection system of claim 8, wherein the photoelectric converter is a two-dimensional photoelectric converter.
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