Insulation test method and test equipment for thin film HFS
The insulation of the film HFS is optimized through high-temperature sintering welding joints and magnetron sputtering technology, and the problem of enhanced conductivity of the alumina insulating layer at high temperatures is solved, and the high-temperature insulation performance in aerospace bearings is improved.
Patent Information
- Application Number
- CN202410843842.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-27
- Publication Date
- 2024-12-13
AI Technical Summary
The insulation attenuation of existing thin film heat flow sensors (HFS) in high temperature environments leads to limited application in aerospace bearings, especially the alumina insulating layer has increased electrical conductivity at high temperatures, making it difficult to provide sufficient electrical insulation.
High-temperature sintered solder joints are used to change the resistance between the pads of the NiCrAlY-TGO-Al2O3 film layer, and the insulation performance of the thin film HFS is detected through high-temperature electrical insulation test. The aluminum oxide insulation layer is prepared in combination with magnetron sputtering technology and high-temperature chemical vapor deposition technology, and optimized Method for preparing thin film HFS to improve insulation.
It realizes good insulation performance of film HFS in high temperature environments, ensures its application in smart bearings, and improves the heat conduction performance and life of the bearings.
Smart Images
Figure CN119125674A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of thin film HFS, and in particular to a method and equipment for testing the insulation properties of thin film HFS. Background Art
[0002] Bearings play a crucial role in the aerospace industry, such as in aircraft engines and spacecraft propulsion systems. The performance and reliability of bearings directly impact the safety and lifespan of aerospace equipment. Therefore, aerospace bearings undergo rigorous design, manufacturing, and testing. In these applications, bearing operating temperatures reach over 1000°C, far exceeding the melting point of bearing materials such as nickel-based alloys. To protect bearings from erosion by high-temperature airflow, cooling channels are required to reduce surface temperatures and ensure proper operation when the hot air flows through them. Heat flux density is a key indicator for evaluating the effectiveness of cooling structures. Heat flux density refers to the amount of heat passing through a bearing per unit time. Applying a thin-film heat flux sensor (HFS) to the surface of a high-temperature bearing can measure its heat flux density, providing further insight into the bearing's heat conduction in high-temperature environments. This allows for optimized bearing design and improved performance and lifespan.
[0003] Based on the boundary conditions of the heat conduction differential equation, there are two approaches to measuring thin-film HFS: 1) Devices based on the general assumption of semi-infinite heat flux calculate the heat flux by integrating the temperature over time, such as coaxial thermocouples and thin-film resistors. However, these devices based on the general assumption of semi-infinite heat flux must be used in conditions with rapidly varying heat fluxes; otherwise, integration drift may occur. While these devices have the advantages of simple structure and easy fabrication, they also have the disadvantages of low sensitivity, long response time, and inability to measure steady-state heat flux.
[0004] Devices based on Fourier's law calculate heat flux based on the temperature gradient across the film thickness. They offer excellent dynamic and static performance and are the primary method for measuring thin-film HFS. The sensitive structure of Fourier's law-based thin-film HFS includes both thermoelectric and thermal resistors, typically designed as a thermopile or bridge structure to enhance sensitivity. This means that thin-film HFS devices have higher internal resistance than other thin-film devices, requiring higher electrical insulation in high-temperature environments.
[0005] The preparation and performance of thin-film heat flow sensors on the surface of nickel-based alloys were studied, among which the high-temperature insulation of the insulating layer is one of the key factors. There are three problems with the conventional magnetron sputtering method for preparing the aluminum oxide insulating layer: 1) In the magnetron sputtering process, the maximum preparation temperature of the aluminum oxide insulating layer cannot exceed 600°C. In order to convert the aluminum oxide crystal form into the α-phase structure, a long heat treatment of more than 1000°C is required. During this period, the main metal elements of the transition layer and the substrate diffuse into the aluminum oxide insulating layer to form NiFe compounds and Cr2O3. These substances have certain conductivity at high temperatures, resulting in a sharp attenuation of the high-temperature electrical insulation of the aluminum oxide film; 2) The volume shrinkage of the aluminum oxide crystal form during the phase change destroys the adhesion of the film layer on the alloy surface; 3) Due to the limitations of the magnetron sputtering equipment, the aluminum oxide deposition thickness is too thin (1μm), which cannot provide sufficient electrical insulation under high temperature conditions. In this case, the thickness of the aluminum oxide film needs to be increased; for the prepared thin film HFS, the insulation performance needs to be tested to ensure its application in bearings. Summary of the Invention
[0006] The purpose of the present invention is to provide a method and equipment for testing the insulation properties of thin film HFS, which can detect the insulation properties of thin film HFS so as to adjust the thin film HFS preparation method and prepare thin film HFS with good insulation properties suitable for smart bearings.
[0007] In order to achieve the above objectives, the technical solution adopted by the present invention is: a method for testing the insulation properties of a thin film HFS, comprising the following steps: Step 1: Prepare thin film HFS as a test sample; Step 2: Change the resistance between the NiCrAlY-TGO-Al2O3 film pads by high-temperature sintering solder joints, and test the relationship between the resistance between the film pads and temperature. Based on the test results and the temperature range of the thin film HFS, determine whether the pad position of the thin film HFS is reasonable. If reasonable, continue testing. If not, re-produce the thin film HFS sample. Step 3: The thin film HFS that has completed the test in step 2 and has a reasonable pad position is subjected to a high-temperature electrical insulation test at 900° C. to test the insulation performance of the thin film HFS.
[0008] Preferably, the preparation steps of the thin film HFS in step 1 are as follows: 1) Substrate preparation: HTCVD (high temperature chemical vapor deposition) technology is used to prepare CVD-Al2O3 thin film structure on the surface of nickel-based alloy as the substrate; 2) Cleaning process: Clean the CVD-Al2O3 substrate with acetone, ethanol and deionized water to remove impurities and oil on the surface; 3) Sputtering thermopile, ITO and In2O3: On the cleaned CVD-Al2O3 substrate, an ITO / In2O3 thermopile is deposited by magnetron sputtering technology to form the sensitive layer of the sensor. ITO and In2O3 serve as the p-type and n-type materials of the thermopile, respectively, and a mask is used to form alternating thermocouple pairs; 4) Sputtering thermal resistance layer: Aluminum oxide and YSZ are deposited at the hot and cold ends of the sensitive layer through magnetron sputtering technology to form the thermal resistance layer of the sensor; 5) Welding: On the outside of the thermal resistance layer, weld the pads using high-temperature welding technology.
[0009] Preferably, after completing step 2), a platinum electrode is clamped on the upper surface of the coating to measure the longitudinal insulation resistance of the aluminum oxide film, and the coating is repeatedly heated at 850°C for 9 cycles to measure the electrical insulation performance of the aluminum oxide insulating layer at high temperature. If the performance is good, proceed to subsequent steps 3) to 5). If the performance is not good, the aluminum oxide film is remade, and the thickness of this aluminum oxide film is greater than that of the aluminum oxide film with poor performance. Then, the electrical insulation performance of the aluminum oxide insulating layer at high temperature is measured again until the measured performance is good.
[0010] Another technical solution of the present invention: an insulation test device for a thin film HFS includes a test box capable of adjusting the internal temperature. A test bench is provided in the test box 1 for placing the thin film HFS. A resistance meter is provided on the test box, and a tester of the resistance meter is inserted into the test box.
[0011] Preferably, a measuring cylinder is installed in the upper part of the test box, a vertical measuring rod is provided in the measuring cylinder, the measuring rod is connected to a measuring frame, two columns of the measuring frame pass through the lower part of the measuring cylinder, and a measuring platinum sheet is installed at the lower end of the column passing through the lower part of the measuring cylinder, the measuring platinum sheet is connected to a wiring harness that passes through the column of the measuring frame and passes through the measuring cylinder, and the wiring harness is electrically connected to the resistance measurer.
[0012] Preferably, a vertically oriented wire tube is further provided in the measuring cylinder, and the center of the wire tube and the center of the corresponding measuring frame column are on the same vertical line.
[0013] Preferably, the measuring pull rod is connected to a measuring lifting block, the measuring lifting block is connected to the measuring frame via a buffer spring, and the measuring frame is provided with a guide rod passing through the measuring lifting block.
[0014] The technical solution adopted in the present invention is: The thin film HFS, aluminum oxide film and pad position can be detected, so that the thin film HFS preparation method can be adaptively adjusted to prepare a thin film HFS with good insulation and suitable for smart bearings.
[0015] The test equipment of the present invention, through the design of the measuring tube, can not only realize automatic contact measurement between the measuring platinum sheet and the thin film HFS, but also prevent the heat of the test box from affecting the resistance measuring device. The design of the buffer spring can prevent the thin film HFS from being crushed during the measurement process. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 The longitudinal insulation resistance of aluminum oxide film changes with temperature.
[0017] Figure 2 The diagram showing the change in insulation resistance during thermal cycling of CVD-Al2O3 film and the EDS analysis diagram.
[0018] Figure 3 This is a test diagram of the intrinsic high-temperature insulation properties of the NiCrAlY-TGO-Al2O3 film deposited by physical vapor deposition (PVD).
[0019] Figure 4 This is the electrical insulation test diagram of the thin film HFS.
[0020] Figure 5 Schematic diagram of the structure of the insulation test equipment of thin film HFS.
[0021] The text labels shown in the figure indicate: 1. test box; 2. test bench; 3. resistance meter. DETAILED DESCRIPTION
[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present invention. Example 1
[0023] The method for preparing the HFS thin film comprises the following steps: Step 1: Substrate preparation: Use HTCVD (high temperature chemical vapor deposition) technology to prepare a CVD-Al2O3 thin film structure on the surface of a nickel-based alloy as a substrate; Step 2: Cleaning process: Clean the CVD-Al2O3 substrate with acetone, ethanol and deionized water to remove impurities and oil stains on the surface; Step 3: Clamp a platinum electrode on the upper surface of the coating to measure the longitudinal insulation resistance of the aluminum oxide film. Repeat heating at 850°C for 9 cycles to measure the electrical insulation performance of the aluminum oxide insulation layer at high temperature. If the performance is good, proceed to the subsequent steps 3) to 5). If the performance is not good, re-make the aluminum oxide film, and the thickness of this aluminum oxide film is greater than the aluminum oxide film with poor performance. Then measure the electrical insulation performance of the aluminum oxide insulation layer at high temperature until the measured performance is good. After measurement, the performance is good when the thickness of the CVD-Al2O3 film is 7μm. Step 4: Sputtering the thermopile, ITO, and In2O3: On the cleaned CVD-Al2O3 substrate, an ITO / In2O3 thermopile is deposited using magnetron sputtering technology to form the sensor's sensitive layer. ITO and In2O3 serve as the p-type and n-type materials of the thermopile, respectively, and alternating thermocouple pairs are formed through a mask. Step 5: Sputtering thermal resistance layer: Aluminum oxide and YSZ are deposited at the hot and cold ends of the sensitive layer using magnetron sputtering technology to form the thermal resistance layer of the sensor. Step 6: Welding: Weld the pads on the outside of the thermal resistance layer using high-temperature welding technology. Step 7: Change the resistance between the NiCrAlY-TGO-Al2O3 film pads by high-temperature sintering solder joints, and test the relationship between the resistance between the film pads and temperature. Based on the test results and the temperature range of the thin film HFS, determine whether the pad position of the thin film HFS is reasonable. If reasonable, continue testing. If not, re-produce the thin film HFS sample. Step 8: The thin film HFS that has completed the test in step 7 and has a reasonable pad position is subjected to a high-temperature electrical insulation test at 900° C. to test the insulation performance of the thin film HFS.
[0024] The 7 μm CVD-Al2O3 film obtained in this example was repeatedly heated at 850°C for 9 cycles. The experimental results are as follows: Figure 1 As shown in the figure, when the test temperature is less than 600℃, the insulation resistance exceeds the test range of the data collector, so no accurate value is obtained. When the temperature increases from 600℃ to 750℃, the insulation resistance drops sharply from 120 MΩ to 20 MΩ. At 830℃, the insulation resistance drops slowly from 20 MΩ to 10 MΩ. It can be seen that the 7μm aluminum oxide insulating layer prepared by HTCVD has good electrical insulation properties at high temperatures, which ensures the stability of the thin film HFS film on the nickel alloy.
[0025] The high temperature insulation of CVD-Al2O3 film in thermal cycle was further studied. The 7μm CVD-Al2O3 film was repeatedly heated for 4 cycles to measure the insulation resistance in the thickness direction of the film in the range of 1000℃. Figure 2As shown in Figure 2, the insulation resistance changes during the heating process. It can be seen that the insulation resistance does decrease with the increase in the number of cycles. In the fourth cycle, it is about 1MΩ at 1000℃. After the cyclic insulation resistance test at 1000℃, the morphology and element analysis of the coating were carried out using a scanning electron microscope. The test results show that the microstructure of CVD-Al2O3 is dense, which is beneficial to blocking the diffusion of metal ions in nickel alloys, as analyzed by EDS.
[0026] Compare the insulation effects of films prepared by physical vapor deposition (PVD) process, such as Figure 3 The figure shows that the longitudinal resistance of the NiCrAlY-TGO-Al2O3 film decreases with increasing temperature but remains at a high level, indicating that the film prepared by the physical vapor deposition (PVD) process has good high-temperature insulation properties. However, the longitudinal resistance of the film is affected by the oxidation and loosening of the metal pad in the high-temperature environment, resulting in resistance fluctuations and the appearance of breakpoints, indicating that the stability and reliability of the PVD-Al2O3 film needs further improvement.
[0027] Changing the inter-pad resistance of the NiCrAlY-TGO-Al2O3 film layer by high-temperature sintering solder joints; Figure 4 It shows that the resistance between pads decreases significantly with increasing temperature, from 1MΩ to 7Ω, indicating that the diffusion of silver atoms under high temperature conditions causes the insulation of the film layer to decrease. In order to avoid the influence of silver atomic diffusion, the pads of the sensor prepared by magnetron sputtering should be designed in the low temperature area to ensure the high-temperature insulation performance of the sensor, thereby ensuring the high-temperature insulation performance of the prepared thin film HFS.
[0028] After the wire bonding is completed, a heat treatment is performed at 500° C. for 4 hours in a nitrogen environment, and then a heat treatment is performed at 1000° C. for 1 hour in an air environment to form a thermally grown oxide layer.
[0029] The heat treatment device used includes a heat treatment box, which is equipped with a sealing cover and has a nitrogen charging and discharging interface and an air charging and discharging interface installed on the side. A heat treatment frame is provided in the heat treatment box, a support plate is installed in the middle of the heat treatment frame, a heat source is installed at the lower part of the heat treatment frame, and the heights of the nitrogen charging and discharging interface and the air charging and discharging interface are lower than the upper end of the heat treatment frame. In this way, during the heat treatment process, when nitrogen is charged and discharged, the airflow will not affect the film HFS in the heat treatment frame. Example 2
[0030] The insulation testing equipment of the thin film HFS includes a test box 1 capable of adjusting the internal temperature. A test table 2 is provided in the test box 1, and the test table 2 is used to place the thin film HFS. A resistance meter 3 is provided on the test box 1, and the test of the resistance meter 3 is inserted into the test box 1. A measuring cylinder is inserted into the upper part of the test box 1, and a vertical measuring pull rod is provided in the measuring cylinder. The measuring pull rod is connected to a measuring frame. The two columns of the measuring frame pass through the lower part of the measuring cylinder 4, and a measuring platinum sheet is installed at the lower end of the column passing through the lower part of the measuring cylinder. The measuring platinum sheet is connected to a wiring harness that passes through the measuring frame column and passes through the measuring cylinder, and the wiring harness is electrically connected to the resistance meter 3. A vertical wire pipe is also provided in the measuring cylinder, and the center of the wire pipe and the corresponding measuring frame column are on the same vertical line. The measuring pull rod is connected to a measuring lifting block, which is connected to the measuring lifting block through a buffer spring, and a guide rod passing through the measuring lifting block is provided on the measuring frame.
[0031] This embodiment is a testing device. The specific test is as follows: first, the thin film HFS to be tested is placed on the test table 2. Then, the measuring pull rod is activated, driving the measuring lifting block and the measuring frame to descend. This causes the measuring platinum sheet to descend and then contact the pad of the thin film HFS to be tested. In this way, the thin film HFS is electrically connected to the resistance meter 3 through the measuring platinum sheet and the wiring harness. Then, the test box 1 is controlled to perform text and graphics adjustment according to the required test conditions. Then, the high-temperature insulation performance of the thin film HFS can be measured by the resistance change measured by the resistance meter 3.
[0032] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.
[0033] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method of the present invention and its core ideas. The above is only a preferred implementation method of the present invention. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of the present invention, they can make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the scope of protection of the present invention.
Claims
1. Test method for insulation properties of thin film HFS, It is characterized in that The steps include: Step 1: Prepare a thin film HFS as a test sample; Step 2: Change NiCrAlY-TGO-Al by high temperature sintering solder joints 2 O 3 Resistance between film pads, and test the relationship between resistance between film pads and temperature. According to the test results and the temperature range of the film HFS, judge whether the pad position of the film HFS is reasonable. If it is reasonable, continue to test. If not, re-make the film HFS sample. Step 3: Perform a high-temperature electrical insulation test on the thin film HFS that has completed the test in step 2 and has a reasonable pad position within a range of 900° C. to test the insulation performance of the thin film HFS.
2. The insulation testing method of the thin film HFS according to claim 1, It is characterized in that The preparation steps of the thin film HFS in step 1 are as follows: 1) Substrate preparation: HTCVD (high temperature chemical vapor deposition) technology is used to prepare CVD-Al on the surface of nickel-based alloy 2 O 3 Thin film structures, as substrates; 2) Cleaning process: CVD-Al 2 O 3 The substrate was cleaned with acetone, ethanol and deionized water to remove impurities and oil on the surface; 3) Sputtering thermal pile, ITO and In 2 O 3 : After cleaning CVD-Al 2 O 3 On the substrate, ITO / In is deposited by magnetron sputtering technology. 2 O 3 Thermopile, forming the sensitive layer of the sensor, ITO and In 2 O 3 The p-type and n-type materials of the thermopile are used to form alternatingly arranged thermocouple pairs through a mask; 4) Sputtering thermal resistance layer: Aluminum oxide and YSZ are deposited at the hot and cold ends of the sensitive layer through magnetron sputtering technology to form the thermal resistance layer of the sensor; 5) Welding: On the outside of the thermal resistance layer, weld the pads using high-temperature welding technology.
3. The insulation testing method of the thin film HFS according to claim 2, It is characterized in that After completing step 2), clamp a platinum electrode on the upper surface of the coating to measure the longitudinal insulation resistance of the aluminum oxide film, heat it repeatedly at 850°C for 9 cycles, and measure the electrical insulation performance of the aluminum oxide insulation layer at high temperature. If the performance is good, proceed to subsequent steps 3)-step 5). If the performance is not good, remake the aluminum oxide film, and the thickness of this aluminum oxide film is greater than that of the aluminum oxide film with poor performance. Then measure the electrical insulation performance of the aluminum oxide insulation layer at high temperature again until the measured performance is good.
4. The insulation testing device of the thin film HFS used in the insulation testing method of the thin film HFS according to claims 1 to 3, It is characterized in that The test box comprises a test box 1 capable of adjusting the internal temperature. A test bench is arranged in the test box. The test bench is used to place the thin film HFS. A resistance measuring device is arranged on the test box, and the test of the resistance measuring device is inserted into the test box.
5. The insulation test equipment of the thin film HFS according to claim 4, It is characterized in that A measuring cylinder is inserted into the upper part of the test box 1, and a vertical measuring rod is arranged in the measuring cylinder. The measuring rod is connected to a measuring frame. Two columns of the measuring frame pass through the lower part of the measuring cylinder, and a measuring platinum sheet is installed at the lower end of the column passing through the lower part of the measuring cylinder. The measuring platinum sheet is connected to a wiring harness that passes through the column of the measuring frame and passes through the measuring cylinder, and the wiring harness is electrically connected to the resistance measurer.
6. The insulation test equipment of the thin film HFS according to claim 5, It is characterized in that A vertical wire tube is also arranged in the measuring cylinder, and the center of the wire tube and the corresponding measuring frame column are on the same vertical line.
7. The insulation testing device of the thin film HFS according to claim 6, It is characterized in that The measuring pull rod is connected with a measuring lifting block, the measuring lifting block is connected with the measuring frame via a buffer spring, and the measuring frame is provided with a guide rod passing through the measuring lifting block.