Method for testing flame impact resistance and CMAS coupling resistance of thermal barrier coating

Abstract

The invention relates to a method for testing flame impact resistance and CMAS coupling resistance of a thermal barrier coating, which is characterized by comprising the following steps of: preparing a set of supersonic flame spraying equipment, preparing a metal substrate with the diameter of 25mm and the thickness of 6mm, and spraying the thermal barrier coating on the surface of the metal substrate to prepare a test sample; preparing and mixing alumina powder, magnesium oxide powder, calcium oxide powder and silicon oxide powder, and putting the mixed powder into a powder feeder; placing a test sample on a mechanical arm, igniting a spray gun, starting a powder feeder, moving the test sample to the flame center of the spray gun by using the mechanical arm to impact, moving the test sample away after a period of time, waiting for natural cooling, taking down the metal substrate, and observing the damage and peeling conditions of the thermal barrier coating; the steps can be repeated for multiple times, and information such as the coating damage and stripping area is recorded as a basis for flame impact resistance and CMAS coupling resistance. The method is simple and convenient to operate and accurate in test condition, the coating preparation environment is utilized, so that the cost is saved, and the method has relatively high practical application value.

Description

Technical Field

[0001] The invention belongs to the technical field of aeroengines, and in particular relates to a method for testing flame impact resistance and CMAS coupling resistance of a thermal barrier coating. Background Art

[0002] As a ceramic coating, thermal barrier coating is deposited on the surface of high-temperature resistant metals or alloys, which acts as a heat insulator and reduces the substrate temperature, allowing engine components to operate at high temperatures. Spraying thermal barrier coating on the surface of engine components such as aerospace engines or gas turbines can not only improve the thermal efficiency of the engine, but also reduce its fuel consumption and increase its service life.

[0003] At present, the service working environment of thermal barrier coatings on aerospace engine turbine blades is extremely complex: on the one hand, the blades are constantly washed by the ultra-high temperature supersonic flame inside the engine, and they receive severe impact and huge temperature difference in a short period of time. The bonding strength of the coating and the degree of matching with the thermal expansion performance of the substrate are important factors affecting its life; on the other hand, in an extremely high temperature environment, particulate matter in the air and impurities in the fuel gas will melt at high speed and adhere to the surface of the turbine blades, forming a deposit with calcium magnesium aluminum silicon as the main component (referred to as CMAS); this deposit penetrates into the thermal barrier coating on the blade surface at high temperature and reacts with it, reducing the stability of the thermal barrier coating. Therefore, the corrosion resistance of the coating is also an important factor affecting its life.

[0004] With the continuous development of my country's aviation technology, the study of the failure mechanism of thermal barrier coatings in service working environments has received widespread attention. Therefore, finding a method that can be used to characterize the performance of thermal barrier coatings in high-temperature service environments will help study the existing thermal barrier coating life extension technology and accumulate experience in the development of new thermal barrier coating materials.

[0005] The existing methods for characterizing high-temperature service of thermal barrier coatings are as follows. High-temperature performance mainly adopts a self-made flame thermal shock device, the principle of which is to use oxygen and coal gas / propane / acetylene to burn to generate a flame flow, and intermittently impact the surface of the thermal barrier coating to characterize the impact resistance of the thermal barrier coating; the anti-CMAS performance mainly adopts to brush CMAS powder on the surface of the sample and react it in a high-temperature furnace to characterize the erosion resistance of the coating; both methods have a large deviation from the actual service environment conditions of the blade, and both can only test a single performance of the coating, and the accuracy of the experimental results is insufficient. Summary of the invention

[0006] The purpose of the present invention is to propose a test method for the flame impact resistance and CMAS coupling resistance of a thermal barrier coating, which utilizes the supersonic flame spraying equipment required in the coating preparation process to reduce the cost without the need for additional coating performance assessment equipment; in addition, the supersonic flame spray gun itself can be ignited using aviation kerosene, and its flame speed and temperature are closer to the real engine flame, and CMAS powder can be fed to the sample surface while igniting, so that the actual service conditions of the coating can be more accurately simulated.

[0007] The present invention adopts the following technical solutions to achieve the above-mentioned purpose: A method for testing flame shock resistance and CMAS coupling resistance of a thermal barrier coating, the testing method comprising the following steps: Step 1: prepare a set of supersonic flame spraying equipment and a metal substrate, and spray a thermal barrier coating on the surface of the substrate to prepare a test sample; the supersonic flame spraying equipment must include a spray gun, a powder feeder and a robotic arm; Step 2: Prepare alumina powder, magnesium oxide powder, calcium oxide powder, and silicon oxide powder; Step 3: Evenly mix aluminum oxide powder, magnesium oxide powder, calcium oxide powder and silicon oxide powder in a certain proportion to obtain CMAS powder, and put the mixed CMAS powder into the powder feeder of the thermal spraying equipment; Step 4: Place the test sample on the robotic arm, ignite the spray gun, and turn on the powder feeder. Use the robotic arm to move the sample to the center of the spray gun flame for impact. After a period of time, remove the sample and wait for it to cool naturally. Remove the metal substrate and observe the damage and peeling of the thermal barrier coating. The above steps can be repeated many times to record information such as the coating damage and peeling area, which will be used as a basis for the flame impact resistance and CMAS coupling resistance performance. The fuel of the spray gun is aviation kerosene and oxygen.

[0008] The metal substrate is made of high temperature resistant metal, has a shape consistent with the muzzle of a supersonic spray gun, is 1.5-2 times the size of the muzzle of the spray gun, and has a thickness of no less than 6 mm.

[0009] The purity of the aluminum oxide powder, magnesium oxide powder, calcium oxide powder and silicon oxide powder is ≥95%, and the particle size is ≤200 meshes.

[0010] The molar ratio of the aluminum oxide powder, magnesium oxide powder, calcium oxide powder and silicon oxide powder is 6.5:9:33:45.

[0011] The powder feeding rate of the powder feeder is set to 10±5g / min.

[0012] The period of time can be adjusted according to experimental requirements.

[0013] The purpose of the present invention is to provide a test method for the flame impact resistance and CMAS coupling resistance of a barrier coating, and the beneficial effects are as follows: the supersonic flame spraying equipment required in the coating preparation process is utilized, so that there is no need to additionally configure a coating performance assessment device, thereby reducing the cost to a certain extent; in addition, the supersonic flame spray gun itself can be ignited using aviation kerosene, and its flame speed and temperature are closer to the real engine flame, and CMAS powder can be fed to the sample surface while igniting, so that the actual service conditions of the coating can be more accurately simulated. DETAILED DESCRIPTION

[0014] The present invention is described in conjunction with the embodiments provided: Example 1: Prepare a set of Praxair JP8000 supersonic flame spraying equipment equipped with an ABB robotic arm, a Φ25×6mm nickel-based alloy disc, and spray the thermal barrier coating to be tested on one side of the disc; 45 parts of silicon oxide powder, 33 parts of calcium oxide powder, 9 parts of magnesium oxide, and 6.5 parts of aluminum oxide powder are evenly mixed and put into the powder feeder of the spray gun; the powder feeder feeding rate is set to 10g / min; the nickel-based alloy disc is placed on the robotic arm (the coating side faces the spray gun), the spray gun is ignited, and the powder feeder is turned on, and the robotic arm is used to move the sample to the center of the spray gun flame for impact, and after 5 minutes, the sample is removed and waited for natural cooling, and the nickel-based alloy sheet is removed to observe the damage and peeling of the thermal barrier coating, and the information such as the coating damage and peeling area is recorded, which is used as the basis for the flame impact resistance and CMAS coupling resistance of the thermal barrier coating.

[0015] Example 2: Prepare a set of Praxair jp8000 supersonic flame spraying equipment equipped with an abb robotic arm, a Φ20×6mm hafnium alloy disc, and spray the thermal barrier coating to be tested on one side of the disc; 90 parts of silicon oxide powder, 66 parts of calcium oxide powder, 18 parts of magnesium oxide, and 13 parts of aluminum oxide powder are evenly mixed and put into the powder feeder of the spray gun; the powder feeder feeding rate is set to 15g / min; the hafnium alloy disc is placed on the robotic arm (the coating side faces the spray gun), the spray gun is ignited, and the powder feeder is turned on. The robotic arm moves the sample to the center of the spray gun flame for impact, removes it after 20s and cools it for 20s, and then continues to impact it for 20s and then cools it, and repeats this process. Observe the damage and peeling of the thermal barrier coating, record the damage and peeling area of ​​the coating, and use this as the basis for the flame impact resistance and CMAS coupling resistance of the thermal barrier coating.

Claims

1. A method for testing the flame shock resistance and CMAS coupling resistance of thermal barrier coatings, characterized in that: The test method includes the following steps: Step 1: prepare a set of supersonic flame spraying equipment and a metal substrate, and spray a thermal barrier coating on the surface of the substrate to prepare a test sample; the supersonic flame spraying equipment must include a spray gun, a powder feeder and a robotic arm; Step 2: Prepare alumina powder, magnesium oxide powder, calcium oxide powder, and silicon oxide powder; Step 3: Evenly mix aluminum oxide powder, magnesium oxide powder, calcium oxide powder and silicon oxide powder in a certain proportion to obtain CMAS powder, and put the mixed CMAS powder into the powder feeder of the thermal spraying equipment; Step 4: Place the test sample on the robotic arm, ignite the spray gun, and turn on the powder feeder. Use the robotic arm to move the sample to the center of the spray gun flame for impact. After a period of time, remove the sample and wait for it to cool naturally. Remove the metal substrate and observe the damage and peeling of the thermal barrier coating. The above steps can be repeated many times to record information such as the coating damage and peeling area, which will be used as a basis for the flame impact resistance and CMAS coupling resistance performance. The fuel of the spray gun is aviation kerosene and oxygen.

2. The method for testing flame shock resistance and CMAS coupling resistance of a thermal barrier coating according to claim 1, characterized in that: The metal substrate is made of high temperature resistant metal, has a shape consistent with the muzzle of a supersonic spray gun, is 1.5-2 times the size of the muzzle of the spray gun, and has a thickness of not less than 6 mm.

3. The method for testing flame shock resistance and CMAS coupling resistance of a thermal barrier coating according to claim 1, characterized in that: The purity of the aluminum oxide powder, magnesium oxide powder, calcium oxide powder and silicon oxide powder is ≥95%, and the particle size is ≤200 meshes.

4. The method for testing flame shock resistance and CMAS coupling resistance of a thermal barrier coating according to claim 1, characterized in that: The molar ratio of the aluminum oxide powder, magnesium oxide powder, calcium oxide powder and silicon oxide powder is 6.5:9:33:

45.

5. The method for testing flame shock resistance and CMAS coupling resistance of thermal barrier coatings according to claim 1, characterized in that: The powder feeding rate of the powder feeder is set to 10±5g / min.