阅读说明：本技术 一种重型燃气轮机热障涂层界面氧化物荧光信号增强方法 (Method for enhancing fluorescence signal of oxide on interface of thermal barrier coating of heavy-duty gas turbine ) 是由 江鹏 王铁军 李定骏 杨镠育 于 2019-09-17 设计创作，主要内容包括：本发明公开了一种重型燃气轮机热障涂层界面氧化物荧光信号增强方法,包括步骤：1)对重型燃气轮机热障涂层试样进行高温氧化处理,使其界面产生3-10μm厚度的热生长氧化物,随后取出试样；2)将氧化处理后的热障涂层试样放置于盛有矿物油或环氧树脂的容器中,将其整体置于密闭的真空箱中进行抽真空操作,并在10<Sup>-</Sup><Sup>4</Sup>Pa真空度下保持60～100分钟；3)使真空箱缓慢吸气,升压速率小于100Pa/min,直至真空箱内外压相持平,即可得到界面氧化物荧光信号增强后的重型燃气轮机热障涂层。本发明采用真空环境,将矿物油或环氧树脂会缓慢填充到重型燃气轮机热障涂层的孔隙和微缺陷之中,这将极大地缓解空气和氧化锆陶瓷的折射率,有效提升界面氧化物中Cr<Sup>3+</Sup>的荧光信号强度。(The invention discloses a method for enhancing a fluorescence signal of an oxide on a thermal barrier coating interface of a heavy-duty gas turbine, which comprises the following steps: 1) carrying out high-temperature oxidation treatment on a heavy-duty gas turbine thermal barrier coating sample to generate a thermal growth oxide with the thickness of 3-10 mu m on an interface of the heavy-duty gas turbine thermal barrier coating sample, and then taking out the sample; 2) placing the thermal barrier coating sample after oxidation treatment in a container containing mineral oil or epoxy resin, placing the whole in a closed vacuum box for vacuumizing operation, and performing vacuum-pumping operation at 10 DEG C ‑ 4 Keeping the vacuum degree of Pa for 60-100 minutes; 3) and (3) slowly sucking air in the vacuum box, wherein the pressure increasing rate is less than 100Pa/min until the internal pressure and the external pressure of the vacuum box are equal, and thus the thermal barrier coating of the heavy-duty gas turbine with the enhanced interface oxide fluorescence signal can be obtained. The invention adopts a vacuum environment, and mineral oil or epoxy resin can be slowly filled into the pores and microdefects of the thermal barrier coating of the heavy-duty gas turbine, which greatly relieves air and oxidationThe refractive index of the zirconium ceramic can effectively improve Cr in the interface oxide 3+ The intensity of the fluorescence signal of (a).)

1. A fluorescence signal enhancement method for an oxide on a thermal barrier coating interface of a heavy-duty gas turbine is characterized by comprising the following steps:

1) carrying out high-temperature oxidation treatment on a heavy-duty gas turbine thermal barrier coating sample to generate a thermal growth oxide with the thickness of 3-10 mu m on an interface of the heavy-duty gas turbine thermal barrier coating sample, and then taking out the sample;

2) placing the thermal barrier coating sample after oxidation treatment in a container containing mineral oil or epoxy resin, and integrating the thermal barrier coating samplePlacing in a sealed vacuum box for vacuum-pumping operation, and performing vacuum-pumping operation at 10 deg.C^-4Keeping the vacuum degree of Pa for 60-100 minutes;

3) and (3) slowly sucking air in the vacuum box, wherein the pressure increasing rate is less than 100Pa/min until the internal pressure and the external pressure of the vacuum box are equal, and thus the thermal barrier coating of the heavy-duty gas turbine with the enhanced interface oxide fluorescence signal can be obtained.

2. The method for enhancing the fluorescence signal of the oxide on the thermal barrier coating interface of the heavy-duty gas turbine as claimed in claim 1, wherein in the step 1), the sample of the thermal barrier coating of the heavy-duty gas turbine is prepared by an atmospheric plasma spraying method.

3. The method for enhancing the fluorescence signal of the oxide on the thermal barrier coating interface of the heavy-duty gas turbine as claimed in claim 1, wherein in the step 1), the sample of the thermal barrier coating of the heavy-duty gas turbine is processed at a temperature of 1000 ℃ to 1250 ℃ for 100 to 500 hours.

Technical Field

The invention belongs to the technical field of nondestructive measurement, and particularly relates to a method for enhancing a fluorescence signal of an oxide on a thermal barrier coating interface of a heavy-duty gas turbine.

Background

The heavy gas turbine (reburning) is a big national heavy equipment, is one of core power equipment of a clean and efficient thermal power energy system, and is concerned with national energy safety, national defense safety and industrial competition. The thermal barrier coating is one of key technologies for protecting the reburning high-temperature blade from being burnt by high-temperature fuel gas, and is considered as the most feasible method for improving the reburning service temperature at present. However, due to the large difference of the properties and dimensions of the layers of the thermal barrier coating system, the extremely complex interface between the layers, and the unusually severe service environment (high temperature, high pressure, impact, thermal gradient, etc.), the coating is prone to cracking and debonding in the extreme service environment, thereby causing the spalling failure of the coating. Not only does the spalling of the coating lose the protective effect of the metal substrate, but the collision of the fragments of the coating can also cause fatal threats to the turbine blades rotating at high speed and even the whole failure of the gas turbine, which becomes a bottleneck restricting the safety application of the heavy-duty gas turbine in all countries around the world. The spalling failure of the thermal barrier coating is influenced by various factors such as high-temperature oxidation, thermal shock fatigue, high-temperature creep, high-temperature sintering, phase change, high-temperature corrosion, high-temperature particle erosion and impact, and the influence of the factors can cause the accumulation of residual stress near an interface. When the residual stress built up in the coating, particularly near the interface, exceeds its own strength, crack initiation, propagation, and eventual spallation failure of the coating will be induced. The cracking and peeling of the thermal barrier coating always have no foreboding, and no effective means for accurately detecting the internal cracks of the coating in a large area exists at present.

The research shows that: the in-plane residual compressive stress generated by the thermal barrier coating in the cooling stage is a direct cause for inducing crack initiation and buckling and peeling above the coating interface. Although cracks in the coating are difficult to detect, residual stress in the coating is continuously accumulated and evolved. Therefore, the level and evolution of the residual stress of the interface of the thermal barrier coating can be detected, and the damage degree of the coating can be evaluated in a feedback mode.

The existing methods for measuring the stress of the material are many, but due to the characteristics of a thermal barrier coating system and the limitations of various measuring methods, the measurement of the stress inside the thermal barrier coating (especially at an interface) is still difficult. For example: the curvature method, the layer cutting method and the drilling method can only obtain the overall average stress of the thermal barrier coating and cannot obtain the local stress of an interface, and meanwhile, the methods are also contact and inevitably damage the coating in the measurement process; the digital image correlation method analyzes the evolution of strain based on the acquired two-dimensional image, but can only measure the surface strain; the digital volume correlation method analyzes the strain evolution based on the material internal three-dimensional structure image, but the current Computed Tomography (CT) technology can only be used for measuring the internal three-dimensional structure of the material with small size and is difficult to be used for large-area measurement of the residual stress of the TBC, and meanwhile, the precision of the three-dimensional image acquired based on the CT technology is often difficult to ensure; the conventional X-ray diffraction method is often used for detecting the stress, but the penetration depth of the TBC is limited to about 10 μm, and the stress at the inner depth cannot be measured; high-energy X-ray diffraction is a new method developed in recent years, and has higher energy than conventional X-rays, enough to penetrate through TBC of several hundred microns, but high-energy X-ray sources are extremely rare and expensive, and are difficult to popularize.

At present, the most successful method applied in the measurement of the internal stress of the thermal barrier coating is a fluorescence stress method based on the elastic stress luminescence property of a specific element, and the basic principle is as follows: in the matrix material doped with the fluorescence activator ions, the fluorescence activator ions can generate energy level transition and emit spectra under the excitation of laser; when the host material is under a stress load, the lattice parameter of the host material changes with the stress, so that the peak position of the fluorescence spectrum changes with the stress. In general, the fluorescence emission spectrum peak of a fluorescence activator ion is proportional to the stress to which it is subjected. Clarke, a professor of Harvard university, a well-known expert in thermal barrier coating materials, successfully used this method for the first time in the thermal barrier coating of an aeroengine by determining its interfacial thermally grown oxides (TGO, Al)₂O₃:Cr³⁺) Middle Cr³⁺Ion fluorescence peak shift feeds back its residual stress. The thermal barrier coating of the aeroengine is prepared by adopting an electron beam physical vapor deposition method, and the interior of the thermal barrier coating is of a columnar crystal structure vertical to an interface, so that the smooth penetration of a fluorescent signal can be ensured.

However, for heavy-duty gas turbines, thermal barrier coatings require high thermal insulation performance, large area spraying, and low cost production, and thus plasma thermal spraying processes are frequently used. The thermal barrier coating prepared by the thermal spraying process has a porous and lamellar structure, and a large number of micropores and defects exist. The attenuation of the fluorescence signal of the thermal barrier coating interface oxide is extremely serious when the fluorescence signal penetrates through the coating, the distribution rate and the detection efficiency of stress measurement are difficult to ensure, and the popularization and the application of a fluorescence stress method on the measurement of the thermal barrier coating interface residue of the heavy-duty gas turbine are seriously restricted.

Disclosure of Invention

In order to solve the problems, the invention provides a fluorescence signal enhancement method for an oxide on a thermal barrier coating interface of a heavy-duty gas turbine, which is used for realizing effective detection of residual stress on the thermal barrier coating interface of the heavy-duty gas turbine and service life evaluation of the coating.

The invention is realized by adopting the following technical scheme:

a fluorescence signal enhancement method for an oxide on an interface of a thermal barrier coating of a heavy-duty gas turbine comprises the following steps:

1) carrying out high-temperature oxidation treatment on a heavy-duty gas turbine thermal barrier coating sample to generate a thermal growth oxide with the thickness of 3-10 mu m on an interface of the heavy-duty gas turbine thermal barrier coating sample, and then taking out the sample;

2) placing the thermal barrier coating sample after oxidation treatment in a container containing mineral oil or epoxy resin, placing the whole in a closed vacuum box for vacuumizing operation, and performing vacuum-pumping operation at 10 DEG C^-4Keeping the vacuum degree of Pa for 60-100 minutes;

3) and (3) slowly sucking air in the vacuum box, wherein the pressure increasing rate is less than 100Pa/min until the internal pressure and the external pressure of the vacuum box are equal, and thus the thermal barrier coating of the heavy-duty gas turbine with the enhanced interface oxide fluorescence signal can be obtained.

The further improvement of the invention is that in the step 1), the thermal barrier coating sample of the heavy-duty gas turbine is prepared by adopting an atmospheric plasma spraying method.

The further improvement of the invention is that in the step 1), the sample of the thermal barrier coating of the heavy-duty gas turbine is treated for 100 to 500 hours at the temperature of 1000 to 1250 ℃.

The invention has the following beneficial technical effects:

the invention adopts a vacuum environment, and mineral oil or epoxy resin can be slowly filled into pores and microdefects of a thermal barrier coating of a heavy-duty gas turbine. Since the refractive indexes of the mineral oil and the epoxy resin are between that of air and the zirconia ceramic, the refractive indexes of the air and the zirconia ceramic are greatly relieved, and the interface oxide (TGO, Al) is effectively improved₂O₃:Cr³⁺) Middle Cr³⁺The maximum thickness of the detectable coating is not less than 300 μm.

Drawings

FIG. 1 is a graph of thermally grown oxide (TGO, Al) at thermal barrier coating interface for a heavy duty gas turbine engine₂O₃:Cr³⁺) Middle Cr³⁺The principle of measuring the fluorescence signal of the ions is shown schematically.

FIG. 2 illustrates thermal growth oxide (TGO, Al) at thermal barrier coating interface for heavy duty gas turbine engine₂O₃:Cr³⁺) Middle Cr³⁺Typical fluorescence spectra and fluorescence peak maps of ions.

FIG. 3 shows a degree of vacuum of 10^-4Pa, Cr before and after mineral oil vacuum infiltration³⁺Contrast graph of ion fluorescence signal intensity.

Detailed Description

The invention is further described below with reference to the following figures and examples.

The invention provides a method for enhancing a fluorescence signal of an oxide on a thermal barrier coating interface of a heavy-duty gas turbine, which comprises the following steps: firstly, preparing a thermal barrier coating sample of the heavy-duty gas turbine by adopting an atmospheric plasma spraying method; then, it was subjected to high-temperature oxidation treatment (1100 ℃ C., 100 hours) to generate a thermally grown oxide (TGO, Al) of sufficient thickness at the interface thereof₂O₃:Cr³⁺) Subsequently, the sample is taken out; then, the thermal barrier coating sample after oxidation treatment is placed in a beaker filled with mineral oil or epoxy resin, the whole is placed in a closed vacuum box for vacuum pumping operation, and the vacuum degree is 10^-4Keeping the vacuum degree of Pa for 60-100 minutes; then, the vacuum box is slowly sucked,and the boosting rate is less than 100Pa/min until the internal pressure and the external pressure of the vacuum box are leveled, and the thermal barrier coating of the heavy-duty gas turbine with the enhanced interface oxide fluorescence signal can be obtained.

The method comprises the following specific implementation steps:

step 1: performing sand blasting treatment on the surface of a nickel-based high-temperature alloy substrate (In718) by using a high-pressure sand blasting machine (STR-1212, STELLE, China), and controlling the surface roughness to be 4.5-5.5 mu m after being measured by a roughness tester (SJ-310, Mitutoyo, Japan);

step 2: spraying a metal bonding layer with the thickness of about 150 microns on the high-temperature alloy substrate by adopting a supersonic flame spraying method;

and 3, step 3: carrying out sand blasting treatment on the surface of the bonding layer by adopting the same method, and controlling the roughness of the bonding layer to be 4-5 mu m;

and 4, step 4: preparing a zirconia ceramic layer with the thickness of about 300 microns on the metal bonding layer by adopting an atmospheric plasma spraying method to finish the preparation of the thermal barrier coating of the heavy-duty gas turbine;

and 5, step 5: placing the mixture in a muffle furnace at 1100 ℃ for high-temperature oxidation for 100 hours to ensure that thermal growth oxide (TGO, Al) is formed at the interface of the mixture₂O₃:Cr³⁺) Subsequently, the sample is taken out;

and 6, step 6: measurement of thermal growth oxide (TGO, Al) of thermal barrier coating interface of heavy-duty gas turbine after high-temperature oxidation by fluorescence spectrometer (Horiba 800)₂O₃:Cr³⁺) Middle Cr³⁺Ion fluorescence signals are recorded, and fluorescence spectra near peak positions of 692nm and 694nm are recorded;

and 7, step 7: placing the oxidized thermal barrier coating sample in a beaker filled with mineral oil or epoxy resin, placing the whole sample in a closed vacuum box for vacuumizing operation, and performing vacuum-pumping operation at 10 DEG C^-4Keeping the vacuum degree of Pa for 60-100 minutes;

and 8, step 8: slowly sucking air into the vacuum box, wherein the pressure increasing rate is less than 100Pa/min until the internal pressure and the external pressure of the vacuum box are equal, and then obtaining the thermal barrier coating of the heavy-duty gas turbine with the enhanced interface oxide fluorescence signal;

step 9: measurement of vacuum Permeability to mineral oil by fluorescence Spectroscopy (Horiba 800)Interface oxide (TGO, Al) of thermal barrier coating of heavy-duty gas turbine₂O₃:Cr³⁺) Middle Cr³⁺Ion fluorescence spectra, and recording fluorescence spectra near peak positions of 692nm and 694 nm;

step 10: data were processed to compare thermal growth of oxides (TGO, Al) before and after vacuum infiltration of mineral oil₂O₃:Cr³⁺) Middle Cr^{3 +}692nm and 694nm fluorescence peak position signals, and the conclusion is reached.

FIG. 1 is a thermal growth oxide (TGO, Al) of thermal barrier coating interface for heavy duty gas turbine engine under laser excitation by fluorescence spectrometer (Horiba 800)₂O₃:Cr³⁺) Middle Cr³⁺The principle of measuring the fluorescence signal of the ions is shown schematically.

FIG. 2 illustrates thermal growth oxide (TGO, Al) at thermal barrier coating interface for heavy duty gas turbine engine₂O₃:Cr³⁺) Middle Cr³⁺Typical fluorescence spectra and fluorescence peak maps of the ions (692nm, 694 nm).

FIG. 3 shows a degree of vacuum of 10^-4Cr before (dotted line) and after (solid line) vacuum infiltration of mineral oil at Pa³⁺Contrast graph of ion fluorescence signal intensity. It can be found that: thermally grown oxide (TGO, Al) at thermal barrier coating interface for heavy duty gas turbine₂O₃:Cr³⁺) Middle Cr³⁺The fluorescence signal intensity of the ions is greatly improved after the mineral oil is infiltrated in vacuum. Wherein the mean intensity of fluorescence signals at 692nm peak position is increased from 3523.6 to 17634.9, which is increased by 5.0 times; the average intensity of the fluorescence signal at the peak position of 694nm is increased from 4105.3 to 24865.1, which is 6.1 times higher.