Method for testing heat conductivity coefficient of thermal barrier coating
By utilizing the difference in ignition point between graphite and thermal barrier coating, the graphite is separated from the substrate at high temperatures, thus enabling the application of thermal barrier coating thermal conductivity measurement technology. This solves the problem of accurate measurement of thermal barrier coating thermal conductivity in existing technologies, resolves the technical issues of thermal barrier coatings in existing technologies, realizes the application of thermal barrier coatings, and achieves accurate measurement of thermal barrier coating thermal conductivity. It avoids testing errors caused by composite materials, and is simple to operate and low in cost.
Patent Information
- Application Number
- CN202511383087.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-26
- Publication Date
- 2025-12-23
AI Technical Summary
Existing technologies make it difficult to accurately measure the thermal conductivity of thermal barrier coatings, especially since they are tightly bonded to the substrate material and cannot be tested directly using traditional methods, resulting in large testing errors.
By taking advantage of the difference in ignition point between graphite and thermal barrier coating, the graphite is separated from the substrate material at high temperature, and then its thermal conductivity is tested separately using conventional laboratory equipment.
It enables accurate measurement of the thermal conductivity of thermal barrier coatings, avoids testing errors caused by composite materials, and is simple to operate and inexpensive.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of aero-engine technology, specifically relating to a method for testing the thermal conductivity of a thermal barrier coating. Background Technology
[0002] Thermal barrier coatings, as a type of ceramic coating, are deposited on the surface of high-temperature resistant metals or alloys to provide thermal insulation, reduce the substrate temperature, and enable engine components to operate at high temperatures. Spraying thermal barrier coatings onto the surfaces of engine components such as aerospace engines or gas turbines can not only improve the engine's thermal efficiency but also reduce its fuel consumption and extend its service life.
[0003] Currently, the combustion temperature of aero-engine exhaust gas is 1500~1600℃, and the surface temperature of turbine blades is about 1100℃. As the thrust-to-weight ratio of aero-engines continues to increase, the temperature and pressure of the exhaust gas in the combustion chamber will continue to rise. In the future, the combustion chamber temperature of aero-engines will reach 1800℃, or even above 2000℃, and the surface temperature of turbine blades will be about 1500℃. The thermal barrier coating material must withstand temperatures up to this level. Since the thermal conductivity of a material largely determines its heat insulation performance, determining the actual thermal conductivity of the thermal barrier coating material is crucial.
[0004] Determining the thermal conductivity of thermal barrier coatings on aerospace engine turbine blades is currently quite difficult. On the one hand, although thermal barrier coatings are ceramic coatings, their special preparation methods differ from traditional ceramic materials, and their microstructures are quite different from ordinary ceramics, resulting in a difference in their thermal conductivity compared to ceramic materials prepared by traditional molding methods. On the other hand, since thermal barrier coatings are mostly firmly bonded to the substrate material and belong to multilayer composite materials, it is not possible to directly use the traditional methods for testing the thermal conductivity of ceramic materials.
[0005] With the continuous development of my country's aviation technology, the operating environment temperature of gas turbines is constantly increasing. This also places higher demands on the thermal insulation of thermal barrier coatings. Therefore, determining the true and effective thermal conductivity of thermal barrier coatings is helpful for studying existing thermal barrier coating insulation technologies and accumulating experience for the development of new thermal barrier coating materials. Summary of the Invention
[0006] The purpose of this invention is to propose a method for testing the thermal conductivity of thermal barrier coatings. This method mainly utilizes the difference in ignition points between graphite and ordinary ceramic materials to separate the coating material from the substrate material. When testing the thermal conductivity, only the coating material is tested. This method provides more accurate testing conditions and avoids large errors in the thermal conductivity test caused by the thermal barrier coating being a composite material. Furthermore, it can use common laboratory equipment without the need for additional equipment, thus possessing high practical application value.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for testing the thermal conductivity of a thermal barrier coating, the method comprising the following steps: Step 1: Prepare a set of plasma flame spraying equipment and a graphite sheet. Spray a thermal barrier coating onto the surface of the graphite sheet to make a coating sample. Step 2: Place the prepared coating sample into an electric furnace for heat treatment; the heat treatment temperature is 1000℃ and the heat treatment time is not less than 6 hours; at a high temperature of 1000℃, the graphite sheet reacts chemically with oxygen to generate carbon dioxide and water, which then evaporate. The thermal barrier coating itself is an oxide and will not oxidize, thus allowing the thermal barrier coating and the graphite sheet to automatically peel off. Step 3: After the thermal barrier coating has cooled completely after being peeled off from the graphite sheet, use a cutting machine to prepare the heat-treated thermal barrier coating into a standard test sample. Step 4: Place the standard test sample into the laser thermal conductivity instrument for testing; repeat the above steps multiple times, record the test results, and take the average value as the thermal conductivity of the test sample.
[0008] The super plasma flame spraying equipment must include a spray gun, a powder feeder, and a robotic arm.
[0009] The graphite sheet is made of high-purity graphite and its size is not less than the minimum size of the standard sample required for the laser thermal conductivity instrument in step four.
[0010] The thickness of the thermal barrier coating in the coating sample shall not be less than the minimum thickness of the standard sample required for the laser thermal conductivity meter in step four.
[0011] This invention proposes a method for testing the thermal conductivity of thermal barrier coatings. This method is simple to operate and low in cost. Its principle utilizes the difference in ignition points between graphite and ordinary ceramic materials to separate the coating material from the substrate material. During thermal conductivity testing, only the coating material is tested. This provides more accurate testing conditions and avoids significant errors in thermal conductivity testing caused by the thermal barrier coating being a composite material. Furthermore, the equipment used in this experiment is all commonly used laboratory equipment, requiring no additional equipment, thus possessing high practical application value. Detailed Implementation
[0012] The present invention will be described in conjunction with the given embodiments: Example 1: Prepare a Praxair 7700 plasma flame spraying equipment equipped with an ABB robotic arm, a 500×500×100mm graphite plate, and spray the thermal barrier coating to be tested on one side of the plate with a coating thickness of 2mm; place the prepared coating sample in an electric furnace for heat treatment at 1000℃ for 6 hours; after the sample has cooled, use a cutting machine to cut the heat-treated sample into a standard circular sample of Φ20×2mm; place the standard sample in a laser thermal conductivity instrument for testing, repeat the above steps, record the test results and take the average value as the thermal conductivity of the test sample.
[0013] Example 2: Prepare a Praxair 100-HE plasma flame spraying equipment equipped with an ABB robotic arm, a 300×300×100mm graphite plate, and spray the thermal barrier coating to be tested on one side of the plate; the coating thickness is 3mm; place the prepared coating sample in an electric furnace for heat treatment at 1100℃ for 8 hours; after the sample has cooled, use a cutting machine to cut the heat-treated sample into a standard circular sample of Φ10×2mm; place the standard sample in a laser thermal conductivity instrument for testing, repeat the above steps, record the test results and take the average value as the thermal conductivity of the test sample.
Claims
1. A method for testing the thermal conductivity of a thermal barrier coating, characterized in that: The testing method includes the following steps: Step 1: Prepare a set of plasma flame spraying equipment and a graphite sheet. Spray a thermal barrier coating onto the surface of the graphite sheet to make a coating sample. Step 2: Place the prepared coating sample into an electric furnace for heat treatment; the heat treatment temperature is 1000℃ and the heat treatment time is not less than 6 hours; at a high temperature of 1000℃, the graphite sheet reacts chemically with oxygen to generate carbon dioxide and water, which then evaporate. The thermal barrier coating itself is an oxide and will not oxidize, thus allowing the thermal barrier coating and the graphite sheet to automatically peel off. Step 3: After the thermal barrier coating has cooled completely after being peeled off from the graphite sheet, use a cutting machine to prepare the heat-treated thermal barrier coating into a standard test sample. Step 4: Place the standard test sample into the laser thermal conductivity instrument for testing; repeat the above steps multiple times, record the test results, and take the average value as the thermal conductivity of the test sample.
2. The method for testing the thermal conductivity of a thermal barrier coating as described in claim 1, characterized in that: The graphite sheet is made of high-purity graphite and its size is not less than the minimum size of the standard sample required for the laser thermal conductivity instrument in step four.
3. The method for testing the thermal conductivity of a thermal barrier coating as described in claim 1, characterized in that: The thickness of the thermal barrier coating in the coating sample shall not be less than the minimum thickness of the standard sample required for the laser thermal conductivity meter in step four.