A preparation method of a turbine blade surface temperature measuring assembly of a combustion engine

Abstract

This invention discloses a method for preparing a temperature measurement component on the surface of a gas turbine blade. The method includes the following steps: confirming the measurement point location and lead wire path on the turbine blade; pre-treating the test area with sandblasting; applying a NiCoCrAlY-containing composite insulating underlayer to the test area using plasma spraying; arranging and initially fixing φ0.1mm K-type micro thermocouples on the insulating underlayer; then fixing and surface-treating the measurement points with a zirconia protective coating applied by plasma spraying; finally, performing lead wire conversion at a suitable location on the turbine blade, converting the micro thermocouples into high-temperature resistant insulated compensating wires. This invention optimizes the sandblasting and plasma spraying process parameters through orthogonal experiments, while introducing a NiCoCrAlY-containing composite insulating underlayer material, reducing irreversible damage to the turbine blade body. This improves the coating's service reliability while ensuring temperature measurement accuracy, meeting the core requirements of gas turbine engineering applications.

Description

Technical Field

[0001] This invention relates to the field of gas turbine blade temperature measurement technology, specifically to a method for preparing a temperature measuring component on the surface of a gas turbine blade, and more particularly to a method for preparing a high-reliability temperature measuring component using a plasma-sprayed composite insulating underlayer. Background Technology

[0002] Gas turbine blade temperature measurement technology can accurately reveal the temperature distribution of turbine blades, providing important guidance for blade performance evaluation, failure analysis, and optimized design. For gas turbines, the combustion chamber outlet temperature directly reflects the turbine's sophistication. As turbine inlet temperatures continue to rise, higher demands are placed on the accuracy, reliability, and adaptability of gas turbine blade temperature measurement technology. Because the turbine inlet is located in an extremely high-temperature gas combustion environment, the service conditions of the turbine's hot-end components are extremely harsh, posing significant technical challenges to turbine blade temperature measurement.

[0003] Existing contact temperature measurement technology for gas turbine blades can effectively collect the surface temperature of the blades and the near-surface airflow temperature. The mainstream technologies currently include micro thermocouple wires, thin film thermocouples, armored thermocouples, temperature measuring crystals, and temperature-indicating paint.

[0004] High-temperature adhesive or welding methods are used to fix thermocouples on the complex curved surfaces of turbine blades. However, the introduction of high-temperature adhesive increases thermal resistance, severely affecting temperature measurement accuracy. Welding is only suitable for certain metal materials, limiting its application range, and the welding process may damage the blade surface. Thin-film thermocouple fabrication methods integrate thin-film thermocouples in situ onto the turbine blade surface using magnetron sputtering, RF sputtering, or MEMS technology. However, thin-film electrode fabrication processes are complex and costly, making them unsuitable for the short project cycles and cost control requirements of gas turbine engineering applications. Pre-embedded armored thermocouples require creating pre-embedded grooves approximately 1mm wide and 1mm deep on the turbine blades via EDM, which can cause irreversible damage to the structural strength and cooling structure of the turbine blades, affecting their service life.

[0005] A search revealed that prior art CN106768441A discloses a method for measuring turbine blade temperature based on plasma spraying. This method involves pre-treating the turbine blade surface (including sandblasting), plasma spraying an Al2O3 insulating layer, fixing a micro-thermocouple to the insulating layer, plasma spraying a protective layer, and leading out test leads to achieve turbine blade surface temperature measurement. However, this method uses Al2O3 as the insulating base material. The significant difference in thermal expansion coefficients between the Al2O3 coating and the nickel-based superalloy blade substrate can easily lead to interfacial thermal stress under the high-temperature cyclic conditions of frequent start-stop operations in gas turbines, causing the insulating layer to crack or peel off. Furthermore, the insulation resistance of Al2O3 decreases exponentially with increasing temperature, severely affecting the accuracy and reliability of the temperature measurement signal. In addition, this prior art only describes the sandblasting and spraying steps in general terms, without providing optimization schemes for specific process parameters, and lacks standardized guidance for engineering applications.

[0006] Therefore, there is an urgent need to develop a method for preparing a gas turbine blade surface temperature measurement structure that has a short preparation cycle, low cost, and minimal damage to the blade body. Summary of the Invention

[0007] To address the problems of insufficient high-temperature insulation resistance, easy cracking and peeling of coatings, and lack of standardization in the preparation process in existing technologies, this invention provides a method for preparing a temperature measuring component on the surface of a gas turbine blade.

[0008] To address the aforementioned technical problems, this invention, through in-depth research and process optimization, proposes the following technical solution: a method for preparing a surface temperature measuring component for a gas turbine blade, comprising the following steps: A. Turbine blade pretreatment: Confirm the test point position and lead wire path on the turbine blade, clean and protect the test area and sandblast it to remove the coating on the test area and increase the surface roughness of the substrate. B. Spraying the insulating underlayer: Using plasma spraying technology, an insulating underlayer containing NiCoCrAlY (nickel-cobalt-chromium-aluminum-yttrium alloy) is sprayed onto the pre-treated test area to achieve insulation isolation between the micro thermocouple and the blade substrate. C. Test point installation: After the insulation layer has cured, micro thermocouples are placed in the test area. High-temperature resistant protective tape is used to initially fix the micro thermocouples so that the thermocouple measuring ends are in close contact with the test area. D. Spraying a protective coating: Using plasma spraying technology, a zirconium oxide protective coating is sprayed on the test area where micro thermocouples have been placed to fix and protect the test points and make the surface of the test area flush with the surface of the non-test area. E. Lead wire conversion: After the surface protective coating is applied, the micro thermocouple is converted into a high-temperature resistant insulated compensation wire at a suitable position on the turbine blade.

[0009] This invention is based on the Benuch principle. The φ0.1mm K-type micro thermocouple used is made of fused filaments of two different metal materials. By detecting the thermoelectric potential generated by the temperature difference between the reference end and the measuring end, it achieves accurate measurement of the surface temperature of the gas turbine blade. Through five core steps—turbine blade pretreatment, spraying an insulating underlayer, laying measuring points, spraying a protective coating, and lead wire connection—combined with plasma spraying technology, the efficient and low-cost fabrication of the temperature measuring component is achieved.

[0010] As a further improvement of the present invention, the abrasive material used in step A is one of white fused alumina, silicon carbide, or brown fused alumina, with a mesh size of 16-60 mesh, a blasting distance of 50-150 mm, a blasting time of 10-20 s, and an air source pressure of 0.8 MPa. The parameters of the blasting treatment directly affect the adhesion of the subsequent insulating underlayer and surface protective coating, and are the core of the pretreatment process. The inventors controlled variables using orthogonal experimental design, selecting four core influencing factors: specimen material, abrasive type, abrasive mesh size, and blasting distance, and employing L9(3)... 4 An orthogonal array was used to simplify the experimental scheme. Surface roughness, cleanliness, coating adhesion, hardness, and porosity were used as comprehensive verification indicators to ultimately select the optimal parameter combination for sandblasting effect and solidify it to form a standardized sandblasting process scheme. The optimal sandblasting parameter combination (for high-temperature alloy GH30 substrate) is: white fused alumina, 24 mesh, sandblasting distance 100mm, and sandblasting time 15s.

[0011] As a further improvement of the present invention, the process parameters for plasma spraying in step B are: equipment current 400-500A, spraying distance 100-150mm, and spray gun moving speed 60-200mm / s. By controlling variables through orthogonal experimental design, three core influencing factors—equipment current, spraying distance, and moving speed—were selected. The spraying material was fixed, and an L9(3³) orthogonal array was used to design the experimental scheme. Pull-out tests were conducted to detect coating adhesion and other performance indicators. Finally, the optimal combination of spraying parameters was selected: equipment current 450A, spraying distance 120mm, and moving speed 60mm / s. These parameters balance the coating's adhesion and density.

[0012] Furthermore, the insulating substrate material in step B is a composite insulating substrate composed of a high-entropy rare-earth zirconate composite and NiCoCrAlY, wherein the chemical composition of the high-entropy rare-earth zirconate composite is (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7. The inventors discovered that when the high-entropy rare-earth zirconate composite and NiCoCrAlY are used in combination, they produce a significant synergistic effect. The coefficient of thermal expansion of the high-entropy rare-earth zirconate composite lies between that of NiCoCrAlY and the zirconium oxide protective coating, forming a gradient thermal expansion transition from the metal bonding layer to the ceramic insulating layer and then to the ceramic protective layer. This effectively alleviates interfacial thermal stress during high-temperature thermal cycling and extends the thermal cycle life of the coating. The synergistic effect is most significant when the volume ratio of the high-entropy rare-earth zirconate composite to NiCoCrAlY is in the range of 1:3 to 1:2. If the content of high-entropy rare earth zirconate composite is too low, the improvement in high-temperature insulation performance will not be significant; if the content is too high, the metal adhesion performance of the composite coating will decrease, affecting the bonding strength with the substrate.

[0013] The specific preparation method of the above-mentioned high-entropy rare earth zirconate complex is as follows: Weigh La(NO3)3·6H2O, Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, Gd(NO3)3·6H2O, Yb(NO3)3·5H2O, and ZrO(NO3)2·2H2O (all with a purity ≥ 99.9%) according to the stoichiometric ratio of their chemical compositions, dissolve them in deionized water to prepare a 0.5 mol / L solution; mix the six solutions in equal molar amounts, and then add the chelating agent citric acid (… A transparent sol was formed by adjusting the pH to 6.5–7.5 with ammonia water (total metal ions to citric acid molar ratio 1:1.5) and magnetically stirring at 60–80℃ for 2–3 hours. The sol was dried at 80–100℃ for 12–24 hours to obtain a dry gel. After grinding, the gel was placed in a muffle furnace and heated to 350–400℃ at a rate of 3–5℃ / min, held for 2–3 hours to remove organic matter, and then calcined at 900–1000℃ for 3–5 hours. After natural cooling to room temperature, the gel was ground to obtain a high-entropy rare-earth zirconate composite powder. In step B, during plasma spraying of the insulating underlayer, the high-entropy rare-earth zirconate composite powder and NiCoCrAlY powder were simultaneously fed into the plasma stream via a dual-path powder feeder for co-deposition, or the two powders were pre-mixed in a specific ratio and then fed into the plasma stream via a single-path powder feeder for deposition.

[0014] As a further improvement of the present invention, the micro thermocouple mentioned in step C is a φ0.1mm K-type micro thermocouple made of nickel-chromium-nickel-silicon material. This thermocouple is made of fused filaments of two different metal materials, with one end as the reference end and the other end as the measuring end. By detecting the thermoelectric potential generated by the temperature difference between the reference end and the measuring end, the precise measurement of the blade surface temperature is achieved based on the Bernoulli principle.

[0015] As a further improvement of the present invention, the zirconia protective coating in step D is 8% yttrium-stabilized zirconia (8YSZ), sprayed 3 to 4 times, with a coating thickness of 250 to 350 μm. 8YSZ zirconia has a low thermal conductivity (approximately 2.5 W / m·K) and excellent thermal shock resistance, which can effectively resist the erosion of combustion gases and thermal cycling stress. At the same time, its high toughness can prevent the coating from delaminating and peeling off.

[0016] As a further improvement of the present invention, the lead wire connection method in step E is as follows: the micro thermocouple is wound and fixed with a high-temperature resistant insulated compensating wire, and a high-temperature resistant asbestos pad is used to wrap the connection position to achieve insulation isolation. The outermost layer is fixed by spot welding with a high-temperature alloy skin. The insulation performance and lead wire strength of the micro thermocouple itself cannot adapt to the harsh working environment outside the test area. Through the above three-layer protective connection structure, the reliability and insulation problems of the signal lead end in high-temperature and harsh environments are effectively solved.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1) This invention achieves efficient and low-cost preparation of temperature measurement structures for gas turbine blades through five core steps: pretreatment of turbine blades, spraying of insulating underlayer, laying of measuring points, spraying of surface protective coating, and lead wire connection. Combined with process verification and curing of optimal parameters, it realizes efficient and low-cost preparation of temperature measurement structures for gas turbine blades. The cost of preparing a single measuring point is reduced by more than 50%, and the preparation cycle is shortened by more than 60%. 2) This invention uses plasma-sprayed NiCoCrAlY as the insulating underlayer material, which has matching thermophysical properties with the high-temperature alloy blade substrate, reducing irreversible damage to the turbine blade body, while simplifying the preparation process, shortening the cycle and reducing costs. 3) The present invention further combines high-entropy rare earth zirconate composite with NiCoCrAlY to form a composite insulating underlayer material. The synergistic effect of the two exhibits excellent thermal shock resistance and coating adhesion. 4) This invention verifies and solidifies the optimal process parameters for sandblasting and plasma spraying through orthogonal experiments, significantly reducing the operating threshold and defect rate (the defect rate is reduced to below 5%), forming a standardized process flow, and operators can master the preparation process through simple training. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall process for preparing the temperature measurement structure on the surface of the gas turbine blade according to the present invention.

[0019] Figure 2 A schematic diagram showing the marking of measuring point positions and lead wire paths on the surface of a turbine blade.

[0020] Figure 3 This is a comparison image of the surface of the test area of ​​the blade before and after sandblasting treatment.

[0021] Figure 4 This diagram illustrates the principle of plasma spraying for insulating undercoat and shows a comparison of the effects before and after spraying.

[0022] Figure 5 A schematic diagram illustrating the process and implementation effect of laying measuring points of micro thermocouples on the surface of an insulating substrate.

[0023] Figure 6 A schematic diagram of the process flow for plasma spraying an 8YSZ surface protective coating.

[0024] Figure 7 Photos showing the effect after the plasma spraying surface protective coating is completed.

[0025] Figure 8 This diagram shows the installation location and implementation example of the lead wire adapter on the turbine blade.

[0026] Figure 9 This is a schematic diagram illustrating the principle and effect of the lead-connection process between a micro thermocouple and a high-temperature resistant insulated compensating wire.

[0027] Figure 10 A schematic diagram illustrating the process of verifying sandblasting process parameters using the orthogonal experimental method.

[0028] Figure 11 This is a schematic diagram illustrating the process of verifying plasma spraying process parameters using the orthogonal experimental method.

[0029] Figure 12 A schematic diagram of the testing system and principle for the coating adhesion pull-out test. Detailed Implementation

[0030] To enable those skilled in the art to better implement the present invention, the present invention will be further described below with reference to embodiments. However, it should be understood that the present invention is not limited to the following embodiments.

[0031] For ease of comparison, the raw materials used in the following examples and comparative examples are all from the same batch, and the specific parameters of the raw materials are as follows: NiCoCrAlY alloy powder: particle size 15-53μm, purity ≥99.5%, Sulzer Metco; φ0.1mm K-type micro thermocouple (nickel-chromium / nickel-silicon): OMEGA Engineering; 8YSZ (8% Yttrium-stabilized Zirconia) powder: particle size 20–63 μm, purity ≥99.5%, Sulzer Metco; White corundum abrasive grains: 24 mesh, purity ≥99.0%, Zhengzhou Yufa Abrasives Co., Ltd.; Silicon carbide abrasive grains: 24 mesh, purity ≥99.0%, Zhengzhou Yufa Abrasives Co., Ltd. High-temperature resistant protective tape: 3M™ Aluminum Foil Tape 425, withstanding temperatures ≥150℃; High-temperature resistant insulated compensating wire: OMEGA Engineering, K-type thermocouple compensating wire, temperature resistance ≥260℃; High-temperature resistant asbestos pad: 0.5mm thick, temperature resistance ≥1000℃; High-temperature alloy skin: GH30 nickel-based high-temperature alloy sheet, 0.1mm thick; Lanthanum nitrate (La(NO3)3·6H2O), neodymium nitrate (Nd(NO3)3·6H2O), samarium nitrate (Sm(NO3)3·6H2O), gadolinium nitrate (Gd(NO3)3·6H2O), ytterbium nitrate (Yb(NO3)3·5H2O), zirconium oxynitrate (ZrO(NO3)2·2H2O): analytical grade, purity ≥99.9%, Sinopharm Chemical Reagent Co., Ltd. Citric acid: analytical grade, purity ≥99.5%, Sinopharm Chemical Reagent Co., Ltd.; Ammonia solution: analytical grade, concentration 25%–28%, Sinopharm Chemical Reagent Co., Ltd. Deionized water: prepared in the laboratory, resistivity ≥18.2MΩ·cm.

[0032] Example 1: The surface temperature sensing structure of the gas turbine blade was prepared according to the following method: S1. Pretreatment of turbine blades: S1-1. Marking of measuring points: According to the design requirements, use a height gauge and positioning fixture to mark the corresponding test positions on the GH30 nickel-based high-temperature alloy turbine blade and determine the lead wire path.

[0033] S1-2 Cleaning and Protection: After the test point marking is completed, acetone is used as a cleaning agent to thoroughly clean the blade surface, completely removing surface impurities, oil stains and oxide layers; after cleaning, aluminum foil tape is used to fully wrap and protect the non-test areas on the blade except for the test point positions and lead wire paths.

[0034] S1-3, Sandblasting: White corundum abrasive (24 mesh) is used to sandblast the test area of ​​the blade using a sandblasting machine. The sandblasting distance is 100mm, the sandblasting time is 15s, and the air source pressure is 0.8MPa. This removes the original coating of the test area and increases the surface roughness of the substrate.

[0035] S2, Spraying insulating base layer: S2-1. Pre-treatment before spraying: After sandblasting, remove the aluminum foil tape used for protection on the blade surface, and use acetone to clean the residual sand particles, impurities and dust on the blade surface; after cleaning, use high temperature resistant protective tape to wrap the non-test areas completely for secondary protection.

[0036] S2-2, Spraying the insulating undercoat: Place the properly protected turbine blades on the plasma spraying equipment (SulzerMetco 9MB plasma spray gun), and use the equipment's spray gun head to perform a spraying test program according to the blade lead wire path; after confirming that the spraying path and spraying parameters are correct, start the equipment to spray the NiCoCrAlY insulating undercoat. The spraying parameters are: equipment current 450A, spraying distance 120mm, spray gun moving speed 60mm / s, main gas Ar flow rate 40L / min, auxiliary gas H2 flow rate 12L / min, powder feeding rate 22±2g / min, spray 8 times, and the coating thickness is about 220μm.

[0037] S3. Measurement point installation: After the insulating undercoat is sprayed and cured, φ0.1mm K-type micro thermocouples are precisely placed in the test area where the insulating undercoat has been sprayed. Thin strips of high-temperature resistant protective tape are used to initially fix the micro thermocouples to ensure that the thermocouple measuring ends are in close contact with the blade test area.

[0038] S4. Apply a protective coating to the surface: The 8YSZ zirconia protective coating was applied using plasma spraying. The spraying path control program was the same as that used for the insulating undercoat. The spraying parameters were: equipment current 450A, spraying distance 120mm, spray gun moving speed 60mm / s, main gas Ar flow rate 40L / min, auxiliary gas H2 flow rate 12L / min, powder feeding rate 20±2g / min, 4 coats, and a coating thickness of approximately 300μm.

[0039] S5, Lead Adapter: After the surface protective coating is applied, lead wires are connected at appropriate positions on the turbine blades: the micro thermocouple is wound and fixed with high-temperature resistant insulated compensating wires, and the connection position is wrapped with a high-temperature resistant asbestos pad to achieve insulation isolation. The outermost layer is fixed by spot welding with a high-temperature alloy skin, thus obtaining a temperature measuring structure sample, which is denoted as sample 1.

[0040] Example 2: The same steps as in Example 1 are followed, except that the type of abrasive particles used in the sandblasting process and the spraying parameters in step S2-2 are adjusted. The specific scheme is as follows: S1-3, Sandblasting: Silicon carbide sand (24 mesh) is used to sandblast the test area of ​​the blade using a sandblasting machine. The sandblasting distance is 100mm, the sandblasting time is 15s, and the air source pressure is 0.8MPa.

[0041] S2-2, Spraying the insulating undercoat: Spraying parameters are as follows: equipment current 500A, spraying distance 100mm, spray gun moving speed 100mm / s, main gas Ar flow rate 40L / min, auxiliary gas H2 flow rate 12L / min, powder feeding rate 22±2g / min, spraying 8 times, coating thickness approximately 240μm.

[0042] The remaining steps are the same as in Example 1, and a temperature measuring structure sample is obtained, which is denoted as Sample 2.

[0043] Example 3: The procedure is the same as in Example 1, except that the sandblasting parameters in step S1-3 and the spraying parameters in step S2-2 are adjusted. The specific scheme is as follows: S1-3. Sandblasting treatment: White corundum abrasive (60 mesh) particles are used to sandblast the test area of ​​the blade using a sandblasting machine. The sandblasting distance is 150mm, the sandblasting time is 20s, and the air source pressure is 0.8MPa.

[0044] S2-2, Spraying the insulating underlayer: Spraying parameters are: equipment current 400A, spraying distance 150mm, spray gun moving speed 200mm / s, main gas Ar flow rate 40L / min, auxiliary gas H2 flow rate 12L / min, powder feeding rate 22±2g / min, spraying 8 times, coating thickness approximately 200μm.

[0045] The remaining steps are the same as in Example 1, and a temperature measuring structure sample is obtained, which is denoted as Sample 3.

[0046] Example 4: A temperature sensing structure for the surface of a gas turbine blade containing a composite insulating substrate was prepared using the following method: S1. Turbine blade pretreatment: Same as in Example 1.

[0047] S2, Spraying composite insulating base layer: Preparation of S2-0 and high-entropy rare earth zirconate composite powders: 0.02 mol each of La(NO3)3·6H2O, Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, Gd(NO3)3·6H2O, Yb(NO3)3·5H2O, and ZrO(NO3)2·2H2O were weighed according to stoichiometric ratios and dissolved in deionized water to prepare 0.5 mol / L solutions. The six solutions were then mixed equimolarly, and citric acid (total metal ions to citric acid molar ratio 1:1.5) was added as a chelating agent. The pH was adjusted to 7.0 with ammonia, and the mixture was magnetically stirred for 2.5 h in a 70℃ water bath to form a transparent sol. The sol was dried at 90℃ for 18 h to obtain a dry gel. After grinding, the gel was placed in a muffle furnace and heated to 380℃ at 4℃ / min and held for 2.5 h to remove organic matter. Then, the temperature was increased to 950℃ and calcined for 4 h. After naturally cooling to room temperature, the gel was ground to obtain a high-entropy rare earth zirconate composite powder ((La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7). The powder was granulated using a spray granulation process (inlet air temperature 220℃, atomizing disc speed 18000 rpm) and microspheres with a particle size of 15-45 μm were obtained through a 325-mesh sieve for later use.

[0048] S2-1. Pretreatment before spraying: Same as S2-1 in Example 1.

[0049] S2-2, Spraying the composite insulating underlayer: High entropy rare earth zirconate composite powder (particle size 15-45μm) and NiCoCrAlY alloy powder (particle size 15-53μm) are mixed in a V-type mixer at a volume ratio of 1:2 at 60rpm for 4h to obtain composite insulating underlayer powder; The uniformly mixed composite powder is fed into a plasma spraying equipment (SulzerMetco 9MB plasma spray gun) through a single-path powder feeder. The spraying parameters are the same as in Example 1 (equipment current 450A, spraying distance 120mm, spray gun moving speed 60mm / s), main gas Ar flow rate 40L / min, auxiliary gas H2 flow rate 12L / min, powder feeding rate 25±2g / min, spraying 8 times, coating thickness about 230μm.

[0050] S3. Measurement point laying: Same as in Example 1.

[0051] S4. Spraying a protective coating on the surface: Same as in Example 1.

[0052] S5. Lead wire connection: Same as in Example 1, a temperature measuring structure sample was prepared and denoted as Sample 4.

[0053] Comparative Example 1: This comparative example serves as a control experiment for Example 1 (Sample 1), and is conducted according to the same steps as Example 1, except that in step S2-2, the insulating underlayer material is not NiCoCrAlY, but Al2O3 (particle size 15-53 μm, purity ≥99.5%). The specific scheme is as follows: S2-2, Spraying the insulating underlayer: Al2O3 powder is fed into the plasma spraying equipment through a single-path powder feeder. The spraying parameters are the same as in Example 1 (equipment current 450A, spraying distance 120mm, spray gun moving speed 60mm / s), main gas Ar flow rate 40L / min, auxiliary gas H2 flow rate 12L / min, powder feeding rate 22±2g / min, spraying 8 times, and the coating thickness is about 210μm.

[0054] The remaining steps are the same as in Example 1, and a temperature measuring structure sample is obtained, which is denoted as Comparative Sample D1 (Al2O3 insulating bottom layer).

[0055] Comparative Example 2: This comparative example serves as a control experiment for Example 4 (sample 4), and was conducted according to the same steps as Example 4. The difference lies in that: no high-entropy rare-earth zirconate composite was added to the composite insulating substrate; that is, the insulating substrate was composed only of pure NiCoCrAlY (the same insulating substrate material as in Example 1). However, the total coating thickness, number of spray coats, and other process parameters were completely consistent with those of Example 4. The specific scheme is as follows: S2-2, Spraying the insulating underlayer: Pure NiCoCrAlY alloy powder is fed into the plasma spraying equipment through a single-path powder feeder. The spraying parameters are the same as in Example 1 (equipment current 450A, spraying distance 120mm, spray gun moving speed 60mm / s), main gas Ar flow rate 40L / min, auxiliary gas H2 flow rate 12L / min, powder feeding rate 25±2g / min, spraying 8 times, and the coating thickness is about 220μm.

[0056] The remaining steps are the same as in Example 4, and a temperature measuring structure sample is obtained, which is denoted as Comparative Sample D2 (pure NiCoCrAlY insulating underlayer, with a coating thickness comparable to that in Example 4).

[0057] Comparative Example 3: This comparative example serves as a control experiment for Example 4 (sample 4), conducted according to the same steps as Example 4. The difference lies in that NiCoCrAlY is not added to the composite insulating substrate; instead, the insulating substrate consists only of a high-entropy rare-earth zirconate composite. However, the total coating thickness, number of coating passes, and other process parameters are completely consistent with Example 4. The specific scheme is as follows: S2-2, Spraying the insulating underlayer: Pure high-entropy rare earth zirconate composite powder (particle size 15-45μm) is fed into the plasma spraying equipment through a single-path powder feeder. The spraying parameters are the same as in Example 1 (equipment current 450A, spraying distance 120mm, spray gun moving speed 60mm / s), main gas Ar flow rate 40L / min, auxiliary gas H2 flow rate 12L / min, powder feeding rate 25±2g / min, spraying 8 times, coating thickness about 240μm.

[0058] The remaining steps are the same as in Example 4, and a temperature measuring structure sample is obtained, which is denoted as Comparative Sample D3 (pure high-entropy rare earth zirconate composite insulating bottom layer).

[0059] Comparative Example 4: This comparative example is a control experiment of Example 4 (sample 4), carried out according to the same steps as Example 4, except that the volume ratio of high-entropy rare-earth zirconate composite to NiCoCrAlY in the composite insulating layer was adjusted so that the content of high-entropy rare-earth zirconate composite exceeds the preferred range of this invention. Specifically, the volume ratio of high-entropy rare-earth zirconate composite to NiCoCrAlY is 2:1. The specific scheme is as follows: S2-2, Spraying composite insulating underlayer: Mix high entropy rare earth zirconate composite powder with NiCoCrAlY alloy powder at a volume ratio of 2:1. The spraying parameters and steps are the same as in Example 4 S2-2. The powder feeding rate is 25±2g / min. Spray 8 times to achieve a coating thickness of about 250μm.

[0060] The remaining steps are the same as in Example 4, and a temperature measuring structure sample is obtained, which is denoted as control sample D4 (excess high-entropy rare earth zirconate).

[0061] Comparative Example 5: This comparative example is a control experiment of Example 4 (sample 4), carried out according to the same steps as Example 4, except that the volume ratio of high-entropy rare-earth zirconate composite to NiCoCrAlY in the composite insulating layer is adjusted so that the content of high-entropy rare-earth zirconate composite is lower than the preferred range of this invention, specifically, the volume ratio of high-entropy rare-earth zirconate composite to NiCoCrAlY is 1:5. The specific scheme is as follows: S2-2, Spraying composite insulating underlayer: Mix high entropy rare earth zirconate composite powder with NiCoCrAlY alloy powder at a volume ratio of 1:5. The spraying parameters and steps are the same as in Example 4 S2-2. The powder feeding rate is 25±2g / min. Spray 8 times to achieve a coating thickness of about 220μm.

[0062] The remaining steps are the same as in Example 4, and a temperature measuring structure sample is obtained, which is denoted as control sample D5 (insufficient high-entropy rare earth zirconate).

[0063] Performance verification experiment: The temperature-measuring structure samples prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were subjected to coating adhesion tests and thermal shock cycling tests, respectively. The specific test methods are as follows: Coating adhesion test: Pull-out test was conducted using a JHY-5000 electronic universal testing machine according to GB / T 8642-2002 standard to measure the adhesion strength between the insulating underlayer and the substrate.

[0064] Thermal shock cycle life test: After each sample is kept in an 800℃ muffle furnace for 15 minutes, it is taken out and forced to cool to room temperature (about 25℃). This is recorded as one thermal shock cycle. The number of cycles in which visible cracks or peeling of the insulation substrate appears is recorded.

[0065] Each experiment was repeated 5 times, and the average value was taken. The experimental results are shown in Table 1.

[0066] Table 1. Performance comparison of different samples

[0067] The results in Table 1 show that: 1. Verification of the effect of NiCoCrAlY insulating substrate: Comparing Example 1 (sample 1) and Comparative Example 1 (comparative sample D1), Example 1 uses NiCoCrAlY as the insulating substrate, and the coating adhesion reaches 41.3MPa, which is about 44.4% higher than that of Al2O3 coating (28.6MPa); the thermal shock cycle life reaches 523 cycles, which is about 145.5% higher than that of Al2O3 coating (213 cycles). This verifies that NiCoCrAlY as the insulating substrate is significantly better than traditional Al2O3 material in terms of adhesion performance and thermal shock resistance.

[0068] 2. Synergistic Effect of Composite Insulating Substrates: Under the premise of completely consistent total thickness and process parameters of the insulating substrates, after introducing a high-entropy rare-earth zirconate composite into NiCoCrAlY in Example 4 (Sample 4), the thermal shock cycle life reached 976 cycles, which is not only about 408% higher than that of pure high-entropy zirconate (comparative sample D3, 192 cycles), but also about 92% higher than that of pure NiCoCrAlY (comparative sample D2, 508 cycles). It can be seen that the thermal shock cycle life of the composite insulating substrates actually surpasses that of both, exhibiting a significant synergistic effect. At the same time, although the bonding strength of Sample 4 (31.9 MPa) is slightly lower than that of the pure NiCoCrAlY coating (40.2 MPa), it is significantly better than that of the pure high-entropy zirconate coating (14.7 MPa), achieving a leap in thermal shock resistance while ensuring good bonding strength. The inventors believe that the synergistic mechanism may be that the high-entropy rare-earth zirconate naturally forms a gradient transition interface order during the plasma co-deposition process. During thermal shock cycling, the intense thermal expansion of the 8YSZ surface layer and the reverse contraction of the NiCoCrAlY underlayer, constrained by the blade substrate, generate an alternating shear stress field at their interface. The high-entropy zirconate particles dispersed in the NiCoCrAlY matrix, due to the disordered mass and radius of the five rare-earth ions in their lattice, possess extremely high local strain tolerance. Under alternating stress, they preferentially undergo reversible lattice distortion, discretizing the originally concentrated two-dimensional thermal mismatch stress at the continuous interface into a large number of low-intensity micro-regions of stress redistribution. This is equivalent to introducing discrete stress buffer domains at the interface, suppressing the continuous propagation of cracks along the interface. Simultaneously, the tight coating of the NiCoCrAlY matrix provides three-dimensional constraint on the distortion, keeping it within the elastic reversible range; the 8YSZ coating further passivates the residual stress tips. This constitutes a closed-loop synergistic mechanism, enabling a nonlinear leap in the coating's thermal shock fatigue life, and its overall performance meets the stringent requirements of gas turbine blades under high-temperature conditions.

[0069] 3. Optimization and Verification of Composite Ratio: Comparing Example 4, Comparative Example 4 (excess HEZ, volume ratio 2:1), and Comparative Example 5 (insufficient HEZ, volume ratio 1:5), when the high-entropy zirconate content was too high (Comparative Example 4), the coating adhesion dropped to 19.6 MPa, and the thermal shock cycle life was only 337 cycles, representing decreases of 38.6% and 65.5% respectively compared to Example 4. When the high-entropy zirconate content was too low (Comparative Example 5), the thermal shock cycle life was 548 cycles, a decrease of approximately 43.8% compared to Example 4. Although the adhesion (36.5 MPa) was close to that of pure NiCoCrAlY, the improvement in thermal shock resistance was extremely limited. This indicates that there is an optimal range (1:3 to 1:2) for the volume ratio of the high-entropy rare earth zirconate composite to NiCoCrAlY. Within this range, the synergistic effect between the two is optimal. Example 4, with a volume ratio of 1:2, simultaneously achieved good coating adhesion (31.9 MPa) and excellent thermal shock cycle life (976 cycles), with both indicators being optimal overall. The data from Comparative Examples 4 and 5 respectively verified the significant degradation of one or more performance characteristics when the range was exceeded and exceeded, thus proving the necessity and critical significance of the proportion range defined by the present invention.

[0070] 4. Verification of the influence of sandblasting parameters: Comparing Example 1, Example 2 and Example 3, Example 1, which uses the optimal parameter combination of 24-mesh white corundum and a spray distance of 100mm, has better coating adhesion (41.3MPa) and thermal shock cycle life (523 cycles) than Example 2 (silicon carbide sandblasting, 38.2MPa / 477 cycles) and Example 3 (60-mesh sandblasting, 34.8MPa / 428 cycles), thus verifying the effectiveness of the optimal sandblasting parameters selected by orthogonal experiment.

Claims

1. A method of manufacturing a temperature measuring assembly for a turbine blade surface of a combustion engine, characterized in that Includes the following steps: A. Turbine blade pretreatment: Confirm the test point position and lead wire path on the turbine blade, clean and protect the test area and sandblast it to remove the coating on the test area and increase the surface roughness of the substrate. B. Spraying the insulating underlayer: Using plasma spraying technology, an insulating underlayer containing nickel-cobalt-chromium-aluminum-yttrium alloy is sprayed onto the pre-treated test area to achieve insulation isolation between the micro thermocouple and the blade substrate. C. Test point installation: After the insulation layer has cured, micro thermocouples are placed in the test area. High-temperature resistant protective tape is used to initially fix the micro thermocouples so that the thermocouple measuring ends are in close contact with the test area. D. Spraying a protective coating: Using plasma spraying technology, a zirconium oxide protective coating is sprayed on the test area where micro thermocouples have been placed to fix and protect the test points and make the surface of the test area flush with the surface of the non-test area. E. Lead wire conversion: After the surface protective coating is applied, the micro thermocouple is converted into a high-temperature resistant insulated compensation wire at a suitable position on the turbine blade.

2. The production method according to claim 1, characterized by, The sandblasting process described in step A uses one of the following abrasive materials: white corundum, silicon carbide, or brown corundum. The abrasive mesh size is 16–60 mesh, the sandblasting distance is 50–150 mm, the sandblasting time is 10–20 s, and the air source pressure is 0.8 MPa.

3. The preparation method according to claim 1, characterized in that, The process parameters for plasma spraying in step B are: equipment current 400-500A, spraying distance 100-150mm, and spray gun moving speed 60-200mm / s.

4. The production method according to claim 3, characterized by, The insulating substrate material mentioned in step B is a composite insulating substrate composed of a high-entropy rare earth zirconate composite and a nickel-cobalt-chromium-aluminum-yttrium alloy. The chemical composition of the high-entropy rare earth zirconate composite is (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7.

5. The production method according to claim 4, characterized by, In the composite insulating bottom layer, the volume ratio of the high-entropy rare earth zirconate composite to the nickel-cobalt-chromium-aluminum-yttrium alloy is 1:3 to 1:

2.

6. The preparation method according to claim 4, characterized in that, The preparation method of the high-entropy rare earth zirconate composite includes: weighing La(NO3)3·6H2O, Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, Gd(NO3)3·6H2O, Yb(NO3)3·5H2O and ZrO(NO3)2·2H2O according to the stoichiometric ratio of the chemical composition, dissolving them in deionized water, adding citric acid as a chelating agent, adjusting the pH to 6.5-7.5 with ammonia water, stirring at 60-80℃ to form a sol, drying, removing the sol at 350-400℃, and calcining at 900-1000℃ for 3-5 hours to obtain high-entropy rare earth zirconate composite powder.

7. The preparation method according to claim 4, characterized in that, In step B, during plasma spraying of the insulating underlayer, high-entropy rare-earth zirconate composite powder and nickel-cobalt-chromium-aluminum-yttrium alloy powder are simultaneously fed into the plasma flame for co-deposition via a dual-path powder feeder, or the two powders are pre-mixed in a uniform ratio and then fed into the plasma flame via a single-path powder feeder for deposition.

8. The method of claim 1, wherein, The micro thermocouple mentioned in step C is a φ0.1mm K-type micro thermocouple made of nickel-chromium-nickel-silicon material.

9. The preparation method according to claim 1, characterized in that, The zirconia protective coating described in step D is 8% yttrium-stabilized zirconia, applied in 3 to 4 coats, with a coating thickness of 250 to 350 μm.

10. The preparation method according to claim 1, characterized in that, The lead wire transfer method described in step E is as follows: the micro thermocouple is wound and fixed with the high-temperature resistant insulated compensating wire, the transfer position is wrapped with a high-temperature resistant asbestos pad to achieve insulation isolation, and the outermost layer is fixed by spot welding with a high-temperature alloy skin.

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