Evaluation method for service performance of thermal barrier coating under impact of flames with different hydrogen-oxygen ratios

Abstract

The invention aims to provide a method for evaluating the service performance of a thermal barrier coating under the impact of flames with different hydrogen-oxygen ratios. According to the method, the real-time temperature of the surface of the sample does not need to be dynamically monitored by an infrared thermometer, the distance between the surface of the sample and the spray gun opening at the test temperature is determined, and the thermal shock test is carried out in a distance fixing manner, so that the problem of infrared temperature measurement misalignment caused by real-time change of the emissivity of the coating in the oxyhydrogen flame environment is successfully avoided. Unification of test conditions under thermal shock of different hydrogen-oxygen proportions is realized, the consistency, comparability and reliability of thermal shock life test results are remarkably improved, a more stable and practical test means is provided for performance evaluation of the thermal barrier coating in a hydrogen-doped environment, and the method is suitable for popularization and application. And a reliable basis is provided for fair screening and performance optimization of the thermal barrier coating in the hydrogen combustion environment.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature protective coating testing technology, specifically relating to a method for evaluating the service performance of thermal barrier coatings under flame impact with different hydrogen-oxygen ratios. Background Technology

[0002] Thermal barrier coatings are a key protective technology for high-temperature hot-end components such as aero-engines and gas turbines. Their excellent thermal insulation performance and resistance to environmental corrosion significantly improve the service temperature and service life of the base alloy. Clean fuels, represented by hydrogen, have become an important path for power equipment to achieve low-carbon transformation. However, the hydrogen combustion environment poses an unprecedented challenge to the service reliability of thermal barrier coatings: compared with traditional hydrocarbon fuels, the high partial pressure water vapor produced by hydrogen-oxygen combustion will drastically accelerate the sintering, phase transformation, and corrosion process of the ceramic layer. At the same time, the temperature of the hydrogen-oxygen flame increases significantly with the increase of hydrogen doping ratio, resulting in the coating being subjected to greater thermal stress, thereby aggravating the initiation and propagation of microcracks.

[0003] In such harsh environments, accurately evaluating the thermal shock life of thermal barrier coatings has become a key bottleneck in the development of hydrogen combustion technology. Currently, commonly used thermal shock testing methods largely rely on infrared thermometers for real-time monitoring and feedback control of the coating surface temperature. However, in a real oxyhydrogen flame environment, this method has significant limitations: First, gases such as water vapor in the high-temperature flame strongly absorb and re-radiate infrared signals, severely interfering with the accuracy of temperature measurement; second, and more importantly, the surface morphology and infrared emissivity of the coating continuously change during testing due to sintering, corrosion, and crack evolution, causing temperature measurements based on a fixed emissivity to deviate significantly from the true value. Furthermore, changes in the hydrogen doping ratio further cause fluctuations in flame temperature and heat flux, resulting in inconsistent thermal load conditions between different test batches, making objective comparison and cross-condition evaluation of life results difficult.

[0004] Therefore, there is an urgent need in this field for an evaluation method that can avoid real-time infrared temperature measurement errors, adapt to different hydrogen doping conditions, and achieve the service performance evaluation of thermal barrier coatings under uniform thermal load conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a method for evaluating the service performance of thermal barrier coatings under flame impact with different hydrogen-oxygen ratios. The method provided by this invention should be able to normalize the thermal shock test benchmarks under different hydrogen-oxygen ratios, thereby providing a reliable basis for studying the performance degradation behavior and life prediction of coating materials under varying hydrogen-oxygen environments.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for evaluating the service performance of thermal barrier coatings under flame impact with different hydrogen-oxygen ratios, comprising the following steps: Step 1: Provide a sample to be tested, which includes a metal substrate. The front side of the metal substrate is provided with a thermal barrier coating, and the back side is not provided with a thermal barrier coating. Obtain the infrared emissivity of the thermal barrier coating at the test temperature. Step 2: Place the sample to be tested in an oxyhydrogen flame thermal shock testing device. The back side of the sample is in contact with a contact thermocouple and is placed under a cooling gas. The front side of the sample is exposed to a flame with a specific hydrogen-oxygen ratio. Based on the infrared emissivity of the thermal barrier coating, adjust the distance between the spray gun and the sample. Use an infrared thermometer to monitor the temperature of the front side. When the temperature reaches the test temperature, record the temperature T of the back side at this time. 背 And the distance S1 between the spray gun and the sample under this hydrogen-oxygen ratio flame; Step 3: Adjust the hydrogen-oxygen ratio of the flame and the distance between the spray gun and the sample to be tested, so that the temperature on the back of the sample reaches T. 背 Record the distance S2 between the spray gun and the sample under this hydrogen-oxygen ratio flame. Step 4: Repeat steps 2 and 3 to obtain the relationship curve between the hydrogen-oxygen flame ratio and the distance between the spray gun and the sample to be tested; Step 5: Based on the relationship curve, thermal shock cycle tests under flames with different hydrogen-oxygen ratios are achieved by directly setting the distance between the spray gun and the sample to be tested.

[0007] Preferably, the test sample is a disc-shaped sample.

[0008] Preferably, the test temperature range is 1000~1400℃.

[0009] Preferably, the process of obtaining the infrared emissivity of the thermal barrier coating includes: The sample to be tested is placed in a high-temperature furnace and heated to the test temperature. The temperature of the thermal barrier coating surface is measured using an infrared thermometer. The infrared emissivity setting of the infrared thermometer is adjusted until the displayed temperature reaches the test temperature, and the infrared emissivity at this time is recorded.

[0010] Preferably, the infrared thermometer is a dual-color infrared thermometer, and the wavelength of the dual-color infrared thermometer is 1~3μm.

[0011] Preferably, the volume ratio of hydrogen to oxygen in the flame is 1:10 to 2:1, and the total flow rate of hydrogen and oxygen is 40 to 100 L / min.

[0012] Preferably, the temperature of the cooling gas is room temperature, and the flow rate of the cooling gas is no more than 100 L / min.

[0013] This invention provides a method for evaluating the service performance of thermal barrier coatings under flame shock with different hydrogen-oxygen ratios. By establishing a one-to-one correspondence between the hydrogen-oxygen ratio and the distance between the spray gun and the sample at a specific test temperature, it eliminates the need for dynamic monitoring of the sample surface temperature using an infrared thermometer. Instead, it determines the distance between the sample surface and the spray gun nozzle at the test temperature and performs thermal shock tests at a fixed distance, successfully avoiding the problem of inaccurate infrared thermometry caused by real-time changes in coating emissivity under hydrogen-oxygen flame conditions. This invention achieves uniformity in test conditions under thermal shock with different hydrogen-oxygen ratios, significantly improving the consistency, comparability, and reliability of thermal shock life test results. It provides a more stable and practical testing method for evaluating the performance of thermal barrier coatings under hydrogen-doped environments and a reliable basis for the fair selection and performance optimization of thermal barrier coatings under hydrogen combustion environments. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the spray gun and the sample to be tested. Detailed Implementation

[0015] This invention provides a method for evaluating the service performance of thermal barrier coatings under flame impact with different hydrogen-oxygen ratios, comprising the following steps: Step 1: Provide a sample to be tested, which includes a metal substrate. The front side of the metal substrate is provided with a thermal barrier coating, and the back side is not provided with a thermal barrier coating. Obtain the infrared emissivity of the thermal barrier coating at the test temperature. Step 2: Place the sample to be tested in an oxyhydrogen flame thermal shock testing device. The back side of the sample is in contact with a contact thermocouple and is placed under a cooling gas. The front side of the sample is exposed to a flame with a specific hydrogen-oxygen ratio. Based on the infrared emissivity of the thermal barrier coating, adjust the distance between the spray gun and the sample. Use an infrared thermometer to monitor the temperature of the front side. When the temperature reaches the test temperature, record the temperature T of the back side at this time. 背 And the distance S1 between the spray gun and the sample under this hydrogen-oxygen ratio flame; Step 3: Adjust the hydrogen-oxygen ratio of the flame and the distance between the spray gun and the sample to be tested, so that the temperature on the back of the sample reaches T. 背 Record the distance S2 between the spray gun and the sample under this hydrogen-oxygen ratio flame. Step 4: Repeat steps 2 and 3 to obtain the relationship curve between the hydrogen-oxygen flame ratio and the distance between the spray gun and the sample to be tested; Step 5: Based on the relationship curve, thermal shock cycle tests under flames with different hydrogen-oxygen ratios are achieved by directly setting the distance between the spray gun and the sample to be tested.

[0016] In this invention, the test sample is preferably a disc-shaped sample. This invention does not impose any special limitation on the size of the disc-shaped sample; any size well-known to those skilled in the art can be used. In this invention, the front side of the metal substrate is provided with a thermal barrier coating, while the back side is not. In a specific embodiment of this invention, the sample to be tested is preferably NiAl / YSZ, that is, the metal substrate is a NiAl alloy, and the thermal barrier coating is YSZ (yttrium-stabilized zirconium oxide).

[0017] In this invention, the preferred range of the test temperature is 1000~1400℃.

[0018] In this invention, the process of obtaining the infrared emissivity of the thermal barrier coating preferably includes: placing the sample to be tested in a high-temperature furnace, heating it to the test temperature, measuring the temperature of the surface of the thermal barrier coating using an infrared thermometer, adjusting the infrared emissivity setting value of the infrared thermometer until its displayed temperature reaches the test temperature, and recording the infrared emissivity at this time.

[0019] In this invention, the infrared thermometer is preferably a dual-color infrared thermometer, and the wavelength of the dual-color infrared thermometer is preferably 1~3μm.

[0020] In this invention, the volume ratio of hydrogen to oxygen in the flame is preferably 1:10 to 2:1, and the total flow rate of hydrogen and oxygen is preferably 40 to 100 L / min.

[0021] In this invention, the temperature of the cooling gas is preferably room temperature, and the flow rate of the cooling gas is preferably no more than 100 L / min; the cooling gas is preferably compressed air.

[0022] In this invention, in a single thermal shock test, the coating failure standard is defined as the peeling of 20% of the area of ​​the coating.

[0023] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0024] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] Example 1 NiAl / YSZ disc-shaped samples were used as the test samples, and 1050℃ was used as the test temperature. Step 1: Place the sample to be tested in the center of the high-temperature furnace and heat it to the test temperature (use a thermocouple to make close contact with the sample surface and wait for the displayed temperature to stabilize at 1050℃). Measure the surface temperature of the NiAl / YSZ coating with an infrared thermometer and adjust the emissivity setting of the dual-color infrared thermometer until its displayed temperature matches the actual temperature of 1050℃ measured by the thermocouple on the sample surface. At this point, record the infrared emissivity of the thermal barrier coating as 0.97. Step 2: Install the NiAl / YSZ sample with completed emissivity calibration in the oxy-hydrogen flame thermal shock test apparatus, ensuring close contact between the back side and the thermocouple. Introduce cooling gas (compressed air, flow rate 40 L / min, temperature 25°C) to the back side of the sample. Ignite the oxy-hydrogen burner, setting the hydrogen-oxygen volume ratio to 2:1 and the total flow rate to 40 L / min. Based on the infrared emissivity measured in Step 3 (0.97), when the distance between the spray gun and the sample is adjusted to 5.8 mm, the infrared thermometer outputs a temperature of 1050°C. At this point, the thermocouple outputs a temperature of 977°C (denoted as T). 背 ), and record the distance S1 between the spray gun and the sample under this condition; Step 3: Without changing other conditions, adjust the hydrogen-oxygen volume ratio to 1.5:1, the total flow rate to 40L / min, and adjust the distance between the spray gun and the sample to 32mm. The temperature output by the thermocouple on the back is 977℃. Record the distance S2 between the spray gun and the sample under this condition. Step 4: Repeat steps 2 and 3 to obtain the relationship curve between the hydrogen-oxygen flame ratio and the distance between the spray gun and the sample to be tested; Step 5: Based on the relationship curve, by directly setting the distance between the spray gun and the sample to be tested to S1 or S2, the sample to be tested is subjected to thermal shock cycle test under the conditions of hydrogen-oxygen ratio of 2:1 and hydrogen-oxygen ratio of 1.5:1 (heating for 300s and cooling for 300s under the same ratio is one cycle).

[0026] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for evaluating the service performance of thermal barrier coatings under flame impact with different hydrogen-oxygen ratios, characterized in that, Includes the following steps: Step 1: Provide a sample to be tested, which includes a metal substrate. The front side of the metal substrate is provided with a thermal barrier coating, and the back side is not provided with a thermal barrier coating. Obtain the infrared emissivity of the thermal barrier coating at the test temperature. Step 2: Place the sample to be tested in an oxyhydrogen flame thermal shock testing device. The back side of the sample is in contact with a contact thermocouple and is placed under a cooling gas. The front side of the sample is exposed to a flame with a specific hydrogen-oxygen ratio. Based on the infrared emissivity of the thermal barrier coating, adjust the distance between the spray gun and the sample. Use an infrared thermometer to monitor the temperature of the front side. When the temperature reaches the test temperature, record the temperature T of the back side at this time. 背 And the distance S1 between the spray gun and the sample under this hydrogen-oxygen ratio flame; Step 3: Adjust the hydrogen-oxygen ratio of the flame and the distance between the spray gun and the sample to be tested, so that the temperature on the back of the sample reaches T. 背 Record the distance S2 between the spray gun and the sample under this hydrogen-oxygen ratio flame. Step 4: Repeat steps 2 and 3 to obtain the relationship curve between the hydrogen-oxygen flame ratio and the distance between the spray gun and the sample to be tested; Step 5: Based on the relationship curve, thermal shock cycle tests under flames with different hydrogen-oxygen ratios are achieved by directly setting the distance between the spray gun and the sample to be tested.

2. The evaluation method according to claim 1, characterized in that, The test sample is a disc-shaped sample.

3. The evaluation method according to claim 1, characterized in that, The test temperature range is 1000~1400℃.

4. The evaluation method according to claim 1, characterized in that, The process of obtaining the infrared emissivity of the thermal barrier coating includes: The sample to be tested is placed in a high-temperature furnace and heated to the test temperature. The temperature of the thermal barrier coating surface is measured using an infrared thermometer. The infrared emissivity setting of the infrared thermometer is adjusted until the displayed temperature reaches the test temperature, and the infrared emissivity at this time is recorded.

5. The evaluation method according to claim 1 or 4, characterized in that, The infrared thermometer is a dual-color infrared thermometer with a wavelength of 1~3μm.

6. The evaluation method according to claim 1, characterized in that, The volume ratio of hydrogen to oxygen in the flame is 1:10 to 2:1, and the total flow rate of hydrogen and oxygen is 40 to 100 L / min.

7. The evaluation method according to claim 1, characterized in that, The temperature of the cooling gas is room temperature, and the flow rate of the cooling gas is no more than 100 L / min.

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