Method for preparing multi-interface alumina insulation layer of turbine blade surface thin film thermocouple

Abstract

The application provides a preparation method of a turbine blade surface thin film thermocouple multi-interface alumina insulation layer, which comprises the following steps: placing a turbine blade test piece in a vacuum environment, and performing ion etching on a blade back area of the test piece; maintaining the vacuum environment after the ion etching, and performing magnetron sputtering deposition on the blade back area to form a first layer; the target material of the magnetron sputtering is alumina; the test piece is transferred from the vacuum environment to an atmospheric environment after the sputtering deposition; the sputtering and annealing treatment are performed five times to form second to sixth layers of alumina in sequence; the test piece is transferred from the atmospheric environment to the vacuum environment, and the seventh layer of magnetron sputtering deposition is performed; and the test piece is transferred from the vacuum environment to the atmospheric environment after the sputtering deposition. The alumina thin film deposition process is adjusted, and the multi-interface alumina insulation layer with strong bonding force with a metal base, thin size and excellent insulation performance is prepared on the surface of the turbine blade without a metal adhesive layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the insulation film preparation technology, and relates to a turbine blade surface thin film thermocouple multi-interface aluminum oxide insulation layer preparation method. BACKGROUND

[0002] The development of an aero-engine is a core link in the development of an airplane. In the process of increasing the thrust-to-weight ratio of an aero-engine, the average temperature at the outlet of a combustion chamber and the inlet of a turbine is continuously increased. Therefore, it is extremely difficult to accurately measure the surface temperature of a key component such as a turbine blade under the extremely harsh conditions of high temperature, high pressure, high-speed erosion of strong oxidizing gas and intense heat exchange. The surface temperature parameter of these key components is a key technical parameter in engine design and material manufacturing, and is urgently needed in engine operation state monitoring and fault diagnosis, verification of cooling effect of film cooling technology, evaluation of heat insulation effect of thermal barrier coating, and evaluation of gas combustion efficiency. The thin film thermocouple temperature measurement technology is a new type of temperature measurement technology based on the Seebeck effect and developed on the basis of traditional thermocouple temperature measurement technology and thin film deposition technology. A thin film thermocouple is formed by attaching two types of thermoelectric materials to an insulating substrate to form a thin film. Compared with a traditional thermocouple, the thin film thermocouple has the characteristics of thin hot junction, small mass and small heat capacity, and therefore has the advantages of small disturbance to the working environment, fast response rate, temperature close to the surface, and no need to damage the measured workpiece. The thin film thermocouple is an important means for measuring the surface temperature of a turbine blade.

[0003] Before the functional layer of the thin film thermocouple is prepared, an insulation layer must be prepared to prevent the conduction between the turbine blade high-temperature alloy substrate and the thin film thermocouple from causing disorder of the electrical signal. It is expected that the thickness of the insulation layer can be as thin as possible under the condition of ensuring insulation, so that the thin film thermocouple can obtain the most real temperature of the turbine blade surface. Aluminum oxide is a commonly used material for preparing an insulation layer, but in order to ensure the bonding force between the aluminum oxide and the metal substrate, a layer of NiCrAlY metal bonding layer must be first prepared on the surface of the turbine blade, and then a thin layer of aluminum oxide is precipitated on the surface of the metal bonding layer by an aluminum precipitation process. The introduction of the metal bonding layer increases the distance between the thin film thermocouple and the surface of the turbine blade, resulting in a deviation between the measured temperature and the real wall temperature. By directly preparing an ultrathin aluminum oxide insulation layer on the surface of the turbine blade through process adjustment, the measurement of the surface temperature of the turbine blade can be more accurate, but the bonding force between the aluminum oxide insulation layer and the metal substrate of the turbine blade needs to be enhanced to solve the problem of easy falling off at high temperature caused by the large difference in thermal expansion coefficient and the large mismatch in lattice constant.

[0004] The S-K model growth (i.e. island-layer growth) is generally used in the deposition process of the alumina insulation layer film prepared by the magnetron sputtering process. In the initial stage of film formation, the growth is in a two-dimensional layer mode, and then the atomic island structure is formed on the layer film, which causes the film growth mode to transform into a three-dimensional island growth. The island growth causes the alumina to have a columnar crystal structure, and there are gaps between the crystal grains. The grain size is different at different deposition temperatures. In the deposition process of the functional thermoelectric arm of the film thermocouple, the thermoelectric material may also penetrate downward through the gaps between the crystal grains and conduct with the turbine blade, which causes the film thermocouple to fail. In the working process of the film thermocouple, the carriers in the functional thermoelectric arm are also easy to move downward through the gaps between the columnar crystals, which causes the electric leakage. By adjusting the process, the alumina film is prepared into a dense structure with multiple interfaces and different grain sizes, which can effectively improve the insulation performance of the alumina insulation layer and minimize the size of the alumina insulation layer. Overcoming the problems of stress matching of the multiple interface alumina insulation layer, stability and toughness of the interface is the key to preparation. SUMMARY

[0005] The purpose of the present application is to prepare a multiple interface alumina insulation layer with strong bonding force to the metal substrate, thin size and excellent insulation performance on the surface of the turbine blade under the condition of no metal adhesive layer by adjusting the deposition process of the alumina film.

[0006] The technical scheme of the present application is:

[0007] The present application provides a preparation method of a multiple interface alumina insulation layer of a film thermocouple on the surface of a turbine blade, which comprises the following steps:

[0008] Step 1: placing the turbine blade test piece in a vacuum environment and performing ion etching on the back region of the test piece; (the ion etching can remove the gas and organic matter attached to the surface of the turbine blade, which is conducive to the combination of the sputtering particles and the substrate, and can also increase the surface micro-roughness to some extent, thereby improving the bonding force of the alumina film on the surface of the turbine blade.

[0009] Step 2: maintaining the vacuum environment after ion etching and performing first layer magnetron sputtering deposition on the back region; the target material of the magnetron sputtering is alumina; after sputtering deposition, the turbine blade test piece is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 800-1000 DEG C and kept for at least 1 hour; the thickness of the first layer alumina after heat preservation is not more than 300 nm; (the annealing in the atmosphere can change the crystal structure and surface morphology of the alumina film, making it more dense and smooth, enhancing its high temperature stability, releasing the surface stress, and at the same time, the alumina film prepared in the vacuum may have poor insulation due to oxygen deficiency, and the annealing in the atmosphere can solve the problem of poor insulation caused by oxygen deficiency.

[0010] Step 3, sputtering and annealing treatment is carried out five times, and the second layer to the sixth layer of aluminum oxide is formed successively, each treatment process is: from the atmospheric environment to the vacuum environment, and the magnetron sputtering deposition is carried out; after sputtering deposition, it is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 800-1000℃, and the temperature is kept for at least 1h; the thickness of each layer of aluminum oxide after keeping warm is not more than 300nm; the sputtering process in each treatment process is different; (layer-by-layer annealing can overcome the problems of stress matching of multi-layer film, stability and toughness of interface in multi-interface aluminum oxide insulating layer.)

[0011] Step 4, from the atmospheric environment to the vacuum environment, and the seventh layer of magnetron sputtering deposition is carried out; after sputtering deposition, it is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 700-950℃, and the temperature is kept for at least 0.5h; the thickness of the seventh layer of aluminum oxide after keeping warm is not more than 50nm.

[0012] The deposition temperature of the first layer is constant temperature deposition selected from the range of 450-500℃; (at lower deposition temperature, the thin film and the turbine blade mainly rely on mechanical combination and van der waals force combination, and appropriate improvement of the deposition temperature makes the interatomic diffusion between the thin film and the turbine blade, forming diffusion adhesion and chemical bond adhesion, and improving the bonding force of the aluminum oxide film on the surface of the turbine blade.)

[0013] The deposition temperature of the second, fourth and sixth layers is variable temperature deposition from 200℃ to 450℃; (the variable temperature process is adopted to make the grain size continuously increase during the deposition process, the grain size is in an inverted trapezoidal structure, the barrier performance to carrier migration is enhanced, and the insulation performance of aluminum oxide is improved.)

[0014] The deposition temperature of the third, fifth and seventh layers is constant temperature deposition selected from the range of 200-250℃; (at low temperature, the grain size of aluminum oxide is smaller, which can significantly reduce the gap on the surface of aluminum oxide film and reduce the leakage point, and improve the insulation performance of aluminum oxide.)

[0015] The vacuum pressure of the vacuum environment corresponding to the deposition of the first layer is not less than 1.0×10 －4 Pa, and the vacuum pressure of the vacuum environment corresponding to the deposition of the second to seventh layers is not less than 5.0×10 －3 Pa; (the vacuum degree corresponding to the deposition of the first layer is higher, the number of atomic collisions incident on the surface of the turbine blade is reduced, the energy is higher, the diffusion ability of atoms during deposition is improved, and the density of the aluminum oxide film and the bonding force with the surface of the turbine blade are improved.)

[0016] The sputtering pressure in the magnetron sputtering of each layer satisfies 0.2-0.4Pa;

[0017] The first layer is sputter-deposited with a bias voltage of 850V-1000V, and the second to seventh layers are deposited without bias voltage.

[0018] The first to sixth layers are deposited for 5h, and the seventh layer is deposited for 0.5h. The short deposition time of the seventh layer causes the aluminum oxide film to only undergo layer growth, making the surface structure of the aluminum oxide film continuous and free of grain gaps, preventing diffusion of the functional layer material and improving the insulation of the aluminum oxide insulation layer.

[0019] Further, the total deposition thickness of the seven layers is not more than 1.8μm.

[0020] Further, the first layer magnetron sputtering parameters are that the distance d between the sample table and the radio frequency table is adjusted to 70mm; the vacuum chamber vacuum pressure is adjusted to be not less than 1.0x10 －4 Pa; the constant deposition temperature is selected from the range of 450℃-500℃; the argon flow rate is adjusted to adjust the sputtering gas pressure to [0.2Pa-0.4Pa], [360W-480W] radio frequency power and [850V-1000V] bias power are applied to the aluminum oxide target material; the sample table rotation speed is set to 3rpm; after sputter deposition for 5h, the sample is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 800℃-1000℃ and held for at least 1h; the thickness of the first layer of aluminum oxide after holding is not more than 300nm.

[0021] Further, the second layer, the fourth layer and the sixth layer magnetron sputtering parameters are that the distance d between the sample table and the radio frequency table is adjusted to 70mm; the vacuum chamber vacuum pressure is adjusted to be not less than 5.0x10 －3 Pa; the deposition temperature is set to vary during sputtering, and the deposition temperature is raised from 200℃ to 450℃ at a rate of 50℃ / h; the argon flow rate is adjusted to adjust the sputtering gas pressure to [0.2Pa-0.4Pa], [360W-480W] radio frequency power is applied to the aluminum oxide target material; the sample table rotation speed is set to 3rpm; after sputter deposition for 5h, the sample is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 800℃-1000℃ and held for at least 1h; the thickness of each layer of aluminum oxide after holding is not more than 300nm.

[0022] Further, the third layer and the fifth layer magnetron sputtering parameters are that the distance d between the sample table and the radio frequency table is adjusted to 70mm; the vacuum chamber vacuum pressure is adjusted to be not less than 5.0x10 －3Pa; the constant deposition temperature is selected from the range of 200-250℃; the sputtering gas pressure is adjusted to [0.2-0.4] Pa by adjusting the argon flow; the radio frequency power applied to the aluminum oxide target is [360-480] W; the rotation speed of the sample table is set to 3 rpm; the turbine blade test piece is transferred from the vacuum environment to the atmospheric environment after sputter deposition for 5 h; the deposited turbine blade test piece is heated to 800-1000℃ and kept for at least 1 h; and the thickness of each layer of aluminum oxide after keeping is not more than 300 nm.

[0023] Further, the seventh layer of magnetron sputtering parameters are as follows: the distance d between the sample table and the radio frequency table is adjusted to 70 mm; the vacuum pressure in the vacuum chamber is not less than 5.0x10 －3 Pa; the constant deposition temperature is selected from the range of 200-250℃; the sputtering gas pressure is adjusted to [0.2-0.4] Pa by adjusting the argon flow; the radio frequency power applied to the aluminum oxide target is [360-480] W; the rotation speed of the sample table is set to 3 rpm; the turbine blade test piece is transferred from the vacuum environment to the atmospheric environment after sputter deposition for 0.5 h; the deposited turbine blade test piece is heated to 700-950℃ and kept for at least 0.5 h; and the thickness of the seventh layer of aluminum oxide after keeping is not more than 50 nm.

[0024] Further, the turbine blade test piece is mechanically polished before step 1 to control the surface roughness to be 50-100 nm. The surface is cleaned after mechanical polishing, and the surface is sequentially washed with deionized water and ethanol and then dried. (Excessive surface roughness will affect the quality of the aluminum oxide film, the surface recess will make the gap between the aluminum oxides too large and reduce the insulation, and too small surface roughness will affect the adhesion between the aluminum oxide film and the turbine blade metal substrate.)

[0025] Further, the process parameters of the ion etching are as follows: the bias voltage is set to [700-800] V, and the ion source is set to [2000-2600] V.

[0026] Further, the purity of the aluminum oxide target is not less than 99.99%.

[0027] Further, each layer of aluminum oxide film needs to be cooled to room temperature before being transferred into the vacuum environment.

[0028] The advantages of the present application are: ① the selected insulating layer material, alumina, has high thermal conductivity, and compared with the thickness and thermal conductivity of the thermal barrier coating, the insulating layer has less effect on the temperature measurement error. ② By mechanical polishing, ion etching, increasing sputtering temperature, applying bias power, and improving vacuum degree, the adhesion between the alumina insulating layer and the metal substrate is improved, so that the alumina insulating layer can be directly prepared on the surface of the turbine blade metal without a metal adhesive layer, and the influence of the insulating layer on the thin film thermocouple temperature measurement process is eliminated. ③ The multi-interface alumina insulating layer prepared by controlling the microstructure has different grain sizes and structures in each alumina insulating layer, which greatly increases the insulation while reducing the film thickness, so that the thin film thermocouple can obtain the real temperature closest to the surface of the turbine blade. ④ The last layer of the multi-interface alumina insulating layer is only layered growth, so that the surface structure of the insulating layer is continuous and has no grain gap, which can effectively prevent the diffusion of functional layer materials and improve the insulation of the alumina insulating layer. ⑤ The layer-by-layer annealing process used in the preparation of the multi-interface alumina can release surface stress, which can well overcome the stress matching problem of the multi-layer film in the multi-interface alumina insulating layer. At the same time, surface cracks will appear on the surface of the last alumina film after annealing, and the next layer of alumina film will fill the defects when it grows, which enhances the interface connection and overcomes the stability and toughness problem of the interface. DETAILED DESCRIPTION

[0029] In fact, many different examples can be described and these examples should not be construed as limiting to the examples set forth herein. Rather, these examples are described so that the present disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0030] A turbine blade surface thin film thermocouple multi-interface alumina insulating layer preparation method is provided, comprising the following steps:

[0031] Step 1, place the turbine blade test piece in a vacuum environment, and perform ion etching on the back area of the test piece; (by ion etching, the gas and organic matter attached to the surface of the turbine blade can be removed, which is conducive to the combination of sputtering particles and the substrate, and can also increase the surface micro-roughness to some extent, thereby improving the adhesion of the alumina film on the surface of the turbine blade.

[0032] Step 2, after ion etching, keep vacuum environment, and perform first layer of magnetron sputtering deposition on the back region of the blade; the target material of magnetron sputtering is aluminum oxide; after sputtering deposition, transfer from vacuum environment to atmospheric environment; heat the deposited turbine blade test piece to 800-1000℃, and keep for at least 1 hour; the thickness of the first layer of aluminum oxide after keeping is not more than 300nm; (annealing under atmosphere can change the crystal structure and surface morphology of the aluminum oxide film, making it more dense and smooth, enhancing its high temperature stability, releasing surface stress, and at the same time, the aluminum oxide film prepared under vacuum may be poor in insulation due to oxygen deficiency, and annealing under atmosphere can solve the problem of poor insulation caused by oxygen deficiency.)

[0033] Step 3, sputter and anneal five times to form the second to sixth layers of aluminum oxide one by one, each process being: transfer from atmospheric environment to vacuum environment, and perform magnetron sputtering deposition; after sputtering deposition, transfer from vacuum environment to atmospheric environment; heat the deposited turbine blade test piece to 800-1000℃, and keep for at least 1 hour; the thickness of each layer of aluminum oxide after keeping is not more than 300nm; the sputtering process in each process is different; (layer-by-layer annealing can overcome the problems of multi-layer film stress matching, interface stability and toughness in multi-interface aluminum oxide insulating layer.)

[0034] Step 4, transfer from atmospheric environment to vacuum environment, and perform seventh layer of magnetron sputtering deposition; after sputtering deposition, transfer from vacuum environment to atmospheric environment; heat the deposited turbine blade test piece to 700-950℃, and keep for at least 0.5h; the thickness of the seventh layer of aluminum oxide after keeping is not more than 50nm.

[0035] The deposition temperature of the first layer is constant temperature deposition selected from the range of 450-500℃; (at lower deposition temperature, the thin film and the turbine blade mainly rely on mechanical bonding and van der Waals force bonding, and appropriate increase in deposition temperature makes the atoms of the thin film and the turbine blade interdiffuse, forming diffusion adhesion and chemical bond adhesion, and improving the bonding force of the aluminum oxide film on the surface of the turbine blade.)

[0036] The deposition temperature of the second, fourth and sixth layers is variable temperature deposition from 200-450℃; (the use of variable temperature process with increasing temperature makes the grain size increase during deposition, the grain has an inverted trapezoidal structure, the barrier property to carrier migration is enhanced, and the insulation performance of aluminum oxide is improved.)

[0037] The deposition temperature of the third, fifth and seventh layers is constant temperature deposition selected from the range of 200-250℃; (at low temperature, the aluminum oxide grain size is smaller, which can significantly reduce the surface gap of the aluminum oxide film and reduce the leakage point, improving the insulation performance of aluminum oxide.)

[0038] The vacuum pressure of the vacuum environment corresponding to the first layer deposition is not less than 1.0x10－4 Pa, the vacuum pressure of the corresponding vacuum environment of the second layer to the seventh layer is not less than 5.0*10 －3 Pa; (the first layer corresponds to a higher vacuum degree, the number of atomic collisions incident on the turbine blade surface is reduced, the energy is higher, the diffusion ability of the atom during deposition is improved, and the density of the aluminum oxide film and the binding force with the turbine blade surface are improved.)

[0039] The sputtering gas pressure of each layer satisfies 0.2Pa-0.4Pa;

[0040] The first layer is sputter deposited by applying a bias voltage of 850V-1000V, and the second layer to the seventh layer is deposited without bias voltage; (the bias voltage can effectively improve the binding force of the aluminum oxide film on the turbine blade surface.)

[0041] The deposition time of the first to the sixth layer is 5h, and the deposition time of the seventh layer is 0.5h. (The shorter deposition time of the seventh layer makes the aluminum oxide film only grow in layers, so that the surface structure of the aluminum oxide film is continuous and has no grain gap, preventing the diffusion of the functional layer material and improving the insulation of the aluminum oxide insulation layer.)

[0042] The total deposition thickness of the seven layers is not more than 1.8μm.

[0043] The first layer magnetron sputtering parameters are that the distance d between the sample table and the radio frequency table is adjusted to 70mm; the vacuum pressure of the vacuum chamber is adjusted to not less than 1.0*10 －4 Pa; the constant deposition temperature is selected from the range of 450℃-500℃; the argon flow rate is adjusted to adjust the sputtering gas pressure to [0.2Pa-0.4Pa], the aluminum oxide target is applied with [360W-480W] radio frequency power and [850V-1000V] bias power, the sample table rotation speed is set to 3rpm; after sputter deposition for 5h, the turbine blade test piece is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 800℃-1000℃ and kept for at least 1h; the thickness of the first layer of aluminum oxide after heat preservation is not more than 300nm.

[0044] The second layer, the fourth layer and the sixth layer magnetron sputtering parameters are that the distance d between the sample table and the radio frequency table is adjusted to 70mm; the vacuum pressure of the vacuum chamber is adjusted to not less than 5.0*10 －3 Pa; the deposition temperature is set to vary during sputtering, and the deposition temperature is increased from 200℃ to 450℃ at a rate of 50℃ / h; the argon flow rate is adjusted to adjust the sputtering gas pressure to [0.2Pa-0.4Pa], the aluminum oxide target is applied with [360W-480W] radio frequency power; the sample table rotation speed is set to 3rpm; after sputter deposition for 5h, the turbine blade test piece is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 800℃-1000℃ and kept for at least 1h; the thickness of each layer of aluminum oxide after heat preservation is not more than 300nm.

[0045] The magnetron sputtering parameters of the third layer and the fifth layer are as follows: the distance d between the sample table and the radio frequency table is adjusted to 70 mm; the vacuum pressure in the vacuum chamber is adjusted to be not less than 5.0*10 －3 Pa; the constant deposition temperature is selected from the range of 200℃ to 250℃; the argon flow rate is adjusted to adjust the sputtering gas pressure to [0.2Pa-0.4Pa], the radio frequency power applied to the aluminum oxide target is [360W-480W]; the sample table rotation speed is set to 3rpm; after sputtering deposition for 5h, the turbine blade test piece is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 800℃-1000℃ and kept for at least 1h; the thickness of each layer of aluminum oxide after keeping is not more than 300nm.

[0046] The magnetron sputtering parameters of the seventh layer are as follows: the distance d between the sample table and the radio frequency table is adjusted to 70 mm; the vacuum pressure in the vacuum chamber is adjusted to be not less than 5.0*10 －3 Pa; the constant deposition temperature is selected from the range of 200℃ to 250℃; the argon flow rate is adjusted to adjust the sputtering gas pressure to [0.2Pa-0.4Pa], the radio frequency power applied to the aluminum oxide target is [360W-480W]; the sample table rotation speed is set to 3rpm; after sputtering deposition for 0.5h, the turbine blade test piece is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 700℃-950℃ and kept for at least 0.5h; the thickness of the seventh layer of aluminum oxide after keeping is not more than 50nm.

[0047] Before step 1, the surface of the turbine blade test piece is mechanically polished to control the surface roughness to be 50nm-100nm. After mechanical polishing, the surface is cleaned by sequentially washing the surface with deionized water and ethanol, and then dried. (If the surface roughness is too large, the quality of the aluminum oxide film will be affected, the surface recess will make the gap between the aluminum oxides too large and reduce the insulation, and if the surface roughness is too small, the adhesion between the aluminum oxide film and the turbine blade metal substrate will be affected.)

[0048] The process parameters of the ion etching are as follows: the bias voltage is set to [700V-800V] and the ion source is set to [2000V-2600V].

[0049] The purity of the aluminum oxide target is not less than 99.99%.

[0050] After annealing of each layer of aluminum oxide film, the turbine blade test piece is cooled to room temperature and then transferred into the vacuum environment.

[0051] The description of the different advantageous arrangements has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the examples disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Moreover, different advantageous examples can provide different advantages as compared to other advantageous examples. The chosen examples are described to best explain the principles of the disclosure and its practical application to enable others skilled in the art to best utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated.

Claims

1. A method for preparing a multi-interface alumina insulating layer for a thin-film thermocouple on the surface of a turbine blade, characterized in that, Includes the following steps: Step 1: Place the turbine blade test piece in a vacuum environment and perform ion etching on the blade back area of ​​the test piece; Step 2: After ion etching, maintain a vacuum environment and perform magnetron sputtering deposition on the blade back area; the target material for magnetron sputtering is alumina; after sputtering deposition, transfer from the vacuum environment to the atmospheric environment; heat the deposited turbine blade test piece to 800℃~1000℃ and hold for at least 1 hour; The thickness of the first layer of alumina after insulation should not exceed 300nm; Step 3: Sputtering and annealing are performed in five stages to form the second to sixth layers of alumina. Each process is as follows: transfer from the atmospheric environment to the vacuum environment and magnetron sputtering deposition; transfer from the vacuum environment to the atmospheric environment after sputtering deposition; heat the deposited turbine blade test piece to 800℃~1000℃ and hold for at least 1 hour. After heat preservation, the thickness of each layer of alumina does not exceed 300nm; the sputtering process varies in each treatment process; Step 4: Transfer from the atmospheric environment to a vacuum environment and perform magnetron sputtering deposition of the seventh layer; after sputtering deposition, transfer from the vacuum environment to the atmospheric environment; heat the deposited turbine blade test piece to 700℃~950℃ and hold for at least 0.5h; the thickness of the seventh layer of alumina after holding for at least 0h should not exceed 50nm. The deposition temperature of the first layer was selected from the range of 450℃ to 500℃ for isothermal deposition; The deposition temperature of the second, fourth and sixth layers is a variable temperature deposition ranging from 200℃ to 450℃, with the deposition temperature increasing from 200℃ to 450℃ at a rate of 50℃ / h. The deposition temperatures of the third, fifth, and seventh layers were selected from isothermal deposition in the range of 200℃ to 250℃; The vacuum pressure of the vacuum environment corresponding to the first deposition layer is not less than 1.0 × 10⁻⁶. -4 The vacuum pressure of the vacuum environment corresponding to the second to seventh deposition layers is not less than 5.0 × 10 Pa. -3 Pa; The sputtering pressure in each layer of magnetron sputtering meets the requirements of 0.2 Pa to 0.4 Pa. The first layer of sputtering deposition is performed with a bias voltage of 850V to 1000V, while the second to seventh layers are deposited without a bias voltage. The deposition time for the first to sixth layers was 5 hours, and the deposition time for the seventh layer was 0.5 hours. The total deposition thickness of the seven layers does not exceed 1.8µm.

2. The method for preparing a multi-interface alumina insulating layer for a thin-film thermocouple on the surface of a turbine blade as described in claim 1, characterized in that: The parameters for the first layer of magnetron sputtering are as follows: adjust the distance between the sample stage and the RF stage to d = 70 mm; adjust the vacuum pressure in the vacuum chamber to be no less than 1.0 × 10⁻⁶ mm. -4 Pa; the constant deposition temperature is selected from the range of 450℃ to 500℃; the argon flow rate is adjusted to adjust the sputtering pressure to 0.2Pa to 0.4Pa, and 360W to 480W RF power and 850V to 1000V bias power are applied to the alumina target; the sample stage rotation speed is set to 3rpm; after sputtering deposition for 5 hours, the sample is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 800℃ to 1000℃ and held at that temperature for at least 1 hour; The thickness of the first layer of alumina after heat preservation should not exceed 300nm.

3. The method for preparing a multi-interface alumina insulating layer for a thin-film thermocouple on the surface of a turbine blade as described in claim 1, characterized in that: The magnetron sputtering parameters for the second, fourth, and sixth layers are as follows: adjust the distance between the sample stage and the RF stage to d = 70 mm; adjust the vacuum chamber pressure to be no less than 5.0 × 10⁻⁶ mm. -3 Pa; Adjust the argon flow rate to adjust the sputtering pressure to 0.2Pa~0.4Pa, and apply 360W~480W RF power to the alumina target; Set the sample stage rotation speed to 3rpm; Transfer from the vacuum environment to the atmospheric environment after sputtering deposition for 5 hours; Heat the deposited turbine blade test piece to 800℃~1000℃ and hold for at least 1 hour; The thickness of each layer of alumina after holding should not exceed 300nm.

4. The method for preparing a multi-interface alumina insulating layer for a thin-film thermocouple on the surface of a turbine blade as described in claim 1, characterized in that: The magnetron sputtering parameters for the third and fifth layers are as follows: adjust the distance between the sample stage and the RF stage to d = 70 mm; adjust the vacuum pressure in the vacuum chamber to be no less than 5.0 × 10⁻⁶ mm. -3 Pa; the constant deposition temperature is selected from the range of 200℃~250℃; the argon flow rate is adjusted to adjust the sputtering pressure to 0.2 Pa~0.4 Pa, and 360W~480W RF power is applied to the alumina target; the sample stage rotation speed is set to 3 rpm; after sputtering deposition for 5 h, it is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 800℃~1000℃ and held at that temperature for at least 1 h; the thickness of each layer of alumina after holding at that temperature does not exceed 300nm.

5. The method for preparing a multi-interface alumina insulating layer for a thin-film thermocouple on the surface of a turbine blade as described in claim 1, characterized in that: The seventh layer magnetron sputtering parameters are as follows: adjust the distance between the sample stage and the RF stage to d = 70 mm; adjust the vacuum pressure in the vacuum chamber to be no less than 5.0 × 10⁻⁶ mm. -3 Pa; the constant deposition temperature is selected from the range of 200℃~250℃; the argon flow rate is adjusted to adjust the sputtering pressure to 0.2Pa~0.4Pa, and 360W~480W RF power is applied to the alumina target; the sample stage rotation speed is set to 3rpm; after sputtering deposition for 0.5h, it is transferred from the vacuum environment to the atmospheric environment; the deposited turbine blade test piece is heated to 700℃~950℃ and held at that temperature for at least 0.5h; the thickness of the seventh layer of alumina after holding at that temperature does not exceed 50nm.

6. The method for preparing a multi-interface alumina insulating layer for a thin-film thermocouple on the surface of a turbine blade as described in claim 1, characterized in that: Before step 1, the surface of the turbine blade test piece is mechanically polished to control the surface undulation within 50nm to 100nm. After mechanical polishing, the surface is cleaned by washing the surface with deionized water and ethanol in sequence, and then dried.

7. The method for preparing a multi-interface alumina insulating layer for a thin-film thermocouple on the surface of a turbine blade as described in claim 6, characterized in that: The process parameters for the ion etching are as follows: bias voltage is set to 700V~800V, and ion source is set to 2000V~2600V.

8. The method for preparing a multi-interface alumina insulating layer for a thin-film thermocouple on the surface of a turbine blade as described in claim 1, characterized in that: The purity of the alumina target material is not less than 99.99%.

9. The method for preparing a multi-interface alumina insulating layer for a thin-film thermocouple on the surface of a turbine blade as described in claim 1, characterized in that: Each layer of alumina film must be cooled to room temperature after annealing before being transferred to a vacuum environment.