A method for preparing a thermal barrier coating resistant to non-penetrating vertical cracks in CMAS corrosion

Abstract

This invention discloses a method for preparing a thermal barrier coating with non-penetrating vertical cracks resistant to CMAS corrosion, belonging to the field of coating preparation technology. The preparation process consists of three steps: (1) high-energy plasma spraying of an MCrAlY underlayer; (2) high-energy plasma spraying of a non-penetrating vertical crack 8YSZ intermediate layer, with approximately 3-10 cracks / mm per cross-section and controllable crack density; (3) high-energy plasma spraying of a YSZ surface layer with high Y2O3 content and non-penetrating vertical cracks, with approximately 3-10 cracks / mm per cross-section and controllable crack density. The Y2O3 in the high-yttrium-content YSZ reacts rapidly with the CMAS components, forming reaction products on the surface. These products then rapidly block nanoscale vertical cracks through volume expansion, preventing rapid CMAS intrusion and ensuring the overall long-term effectiveness of the thermal barrier coating.

Description

Technical Field

[0001] This invention relates to the field of coating preparation technology, specifically to a method for preparing a thermal barrier coating for non-penetrating vertical cracks resistant to CMAS corrosion. Background Technology

[0002] High-thrust and high thrust-to-weight ratio aero-engines, considered the "heart" of aircraft, are among the most complex engineering technologies ever developed and a key area for the future development of my country's aviation equipment. Among these, the operating temperature and service life of thermal barrier coatings on the surface of high-temperature hot-end nickel-based superalloy turbine blades face increasingly stringent requirements. For a long time, YSZ has maintained an irreplaceable position in terms of overall performance among thermal barrier coatings. However, highly corrosive glassy deposits CaO-MgO-Al2O3-SiO2 (CMAS) can infiltrate the coating on the blade surface, causing blockage of the blade's cooling channels and even reacting with the coating to damage its composition and microstructure, accelerating performance degradation and ultimately leading to failure and spalling. Developing coating systems with novel structural anti-CAMS corrosion strategies based on optimal performance materials is a key bottleneck problem that needs to be solved in the development of high-performance high-temperature / ultra-high-temperature thermal barrier coatings. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a non-penetrating vertical crack thermal barrier coating resistant to CMAS corrosion. The method uses an Axial III system spraying equipment and a Met-tech Axiall III plasma spray gun. The dry powder feeding system of this equipment is used to spray and obtain an MCrAlY base layer / 8YSZ intermediate layer / 30~55YSZ top layer structure system.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a thermal barrier coating resistant to non-penetrating vertical cracks in CMAS corrosion is disclosed. The method involves sequentially preparing an MCrAlY underlayer, a YSZ intermediate layer (8YSZ), and a YSZ top layer (30-55YSZ) on a substrate using plasma spraying technology to obtain the thermal barrier coating having an MCrAlY underlayer / 8YSZ intermediate layer / 30-55YSZ top layer structure system. The spraying equipment is an Axial III spraying equipment, and the spray gun is a Met-tech Axiall III plasma spray gun.

[0006] The method includes the following three steps:

[0007] (1) MCrAlY underlayer was prepared by plasma spraying technology. The process parameters were: spray gun power of 90-110kW, argon flow rate of 200-250slpm, hydrogen flow rate of 15-40slpm, nitrogen flow rate of 40-70slpm, spraying distance of 180-220mm, and spray gun moving speed of 300-1000mm / s.

[0008] (2) The 8YSZ intermediate layer was prepared by plasma spraying technology. The process parameters were: spray gun power of 110-130kW, argon flow rate of 140-170slpm, hydrogen flow rate of 30-60slpm, nitrogen flow rate of 40-80slpm, spraying distance of 70-100mm, and spray gun moving speed of 500-1000mm / s.

[0009] (3) A 30-55 YSZ surface layer was prepared by plasma spraying technology. The process parameters were: spray gun power of 110-130 kW, argon flow rate of 140-170 slpm, hydrogen flow rate of 30-60 slpm, nitrogen flow rate of 60-90 slpm, spraying distance of 70-100 mm, and spray gun moving speed of 500-1000 mm / s.

[0010] The Axial III spraying equipment is a high-energy dry powder spraying system that uses axial powder feeding.

[0011] In step (1) of plasma spraying MCrAlY substrate preparation, the particle size range of MCrAlY powder used is 30-70 μm; in steps (2) and (3) of plasma spraying YSZ preparation, the particle size range of YSZ powder used is 30-60 μm.

[0012] The YSZ intermediate layer and YSZ surface layer contain vertical cracks, with a vertical crack density of 3 to 10 cracks / mm. The cracks do not penetrate to the bottom of the layer and connect with the adjacent layer, and there are no accompanying transverse cracks.

[0013] During the application of this thermal barrier coating, the Y2O3 in the high yttrium content YSZ (30-55 YSZ surface layer) reacts rapidly with the CMAS components. After forming reaction products on the surface, the products quickly block nanoscale vertical cracks through volume expansion, thereby preventing the rapid intrusion of CMAS and ensuring the overall long-term effectiveness of the thermal barrier coating.

[0014] The advantages and beneficial effects of this invention are:

[0015] 1. This invention prepares a thermal barrier coating with a structure system of MCrAlY bottom layer / 8YSZ intermediate layer / 30-55YSZ top layer; wherein: 8YSZ is yttrium-stabilized zirconium oxide with a yttrium oxide content of 8 wt.%; the 30-55YSZ contains 30-35 wt.% yttrium oxide; in this thermal barrier coating, the Y2O3 in the high-yttrium-content YSZ top layer can rapidly react with CMAS molten salt, forming reaction products on the surface, which quickly block nanoscale vertical cracks through volume expansion, thereby preventing the rapid intrusion of CMAS and ensuring the overall long-term effectiveness of the thermal barrier coating. Furthermore, with the continuous addition of stress and reaction products, some of the reaction products will detach, and the remaining high-yttrium-content YSZ top layer containing vertical cracks can continue to repeat the above process.

[0016] 2. The formation of non-penetrating nanocracks in the thermal barrier coating of the present invention helps to improve the thermal shock resistance of the coating and makes it difficult for CMAS molten salt to directly penetrate to the substrate surface, thus providing a long-lasting and effective protective effect. Attached Figure Description

[0017] Figure 1 The SEM cross-sectional morphology of the thermal barrier coating system prepared in Example 1.

[0018] Figure 2 The SEM cross-sectional morphology of the thermal barrier coating system prepared in Example 2. Detailed Implementation

[0019] The present invention will be further described in detail below through examples.

[0020] This invention relates to a method for preparing a non-penetrating vertical crack thermal barrier coating resistant to CMAS corrosion. The method employs an AxialIII spraying system, specifically an axially fed plasma spraying system, using a Met-tech Axiall III plasma spray gun. The thermal barrier coating prepared by this method has a structure system of MCrAlY underlayer / 8YSZ intermediate layer / 30–55YSZ top layer. Specifically, both the YSZ intermediate layer and the YSZ top layer exhibit vertical crack morphology, with a vertical crack density of 3–10 cracks / mm. These cracks do not penetrate to the bottom of the layer and connect with adjacent layers, and no accompanying transverse cracks are present.

[0021] In the following examples, the number before YSZ represents the weight percentage of yttrium oxide in YSZ × 100%, such as YSZ meaning that the yttrium oxide content in YSZ is 8 wt.%.

[0022] Example 1

[0023] The substrate used was an N5 high-temperature alloy substrate, and the sample size was Φ16*5mm. After sandblasting and surface cleaning, the coating was prepared according to the following steps:

[0024] (1) Plasma-sprayed MCrAlY underlayer was prepared using AXIAL III plasma spraying equipment, wherein: the powder used was MCrAlY powder with a particle size of 50μm, the power of the plasma spray gun was 107KW, the spraying distance was 200mm, the spray gun moving speed was 500mm / s, the plasma gas used was Ar, N2 and H2, the argon flow rate was 200slpm, the hydrogen flow rate was 45slpm, the nitrogen flow rate was 60slpm, and the spraying thickness was 150μm;

[0025] (2) Plasma-sprayed 8YSZ intermediate layer was prepared using three-electrode suspension plasma spraying technology, wherein: the powder used was 8YSZ powder with a particle size of 50μm, the power of the plasma spray gun was 124KW, the spraying distance was 80mm, the spray gun moving speed was 1000mm / s, the plasma gas used was Ar, N2 and H2, the argon flow rate was 160slpm, the hydrogen flow rate was 50slpm, the nitrogen flow rate was 65slpm, and the spraying thickness was 260μm;

[0026] (3) Plasma-sprayed 55YSZ surface layer was prepared using three-electrode suspension plasma spraying technology, wherein: the powder used was 40YSZ powder with a particle size of 40μm, the power of the plasma spray gun was 118KW, the spraying distance was 80mm, the spray gun moving speed was 800mm / s, the plasma gas used was Ar, N2 and H2, the argon flow rate was 160slpm, the hydrogen flow rate was 40slpm, the nitrogen flow rate was 80slpm, and the spraying thickness was 140μm;

[0027] The SEM cross-sectional morphology of the multilayer non-penetrating vertical crack thermal barrier coating prepared in this embodiment is as follows: Figure 1 As shown, the vertical crack density is 4 cracks / mm. The cracks in the 8YSZ intermediate layer do not extend to the surface of the MCrAlY bottom layer, and no through cracks are formed between the 40YSZ surface layer and the 8YSZ intermediate layer. All cracks are nanoscale, which can effectively prevent CMAS molten salt from rapidly invading the bonding layer.

[0028] Example 2

[0029] The substrate used was a CMSX-4 single-crystal high-temperature alloy substrate, and the sample size was Φ18*5mm. After sandblasting and surface cleaning, the coating was prepared according to the following steps:

[0030] (1) Plasma-sprayed MCrAlY underlayer was prepared using three-electrode suspension plasma spraying technology, wherein: the powder used was MCrAlY with a particle size of 40μm, the power of the plasma spray gun was 110KW, the spraying distance was 220mm, the spray gun moving speed was 500mm / s, the plasma gas used was Ar, N2 and H2, the argon flow rate was 220slpm, the hydrogen flow rate was 30slpm, the nitrogen flow rate was 70slpm, and the spraying thickness was 200μm;

[0031] (2) Plasma-sprayed 8YSZ intermediate layer was prepared using three-electrode suspension plasma spraying technology, wherein: the powder used was 8YSZ powder with a particle size of 40μm, the power of the plasma spray gun was 118KW, the spraying distance was 85mm, the spray gun moving speed was 1000mm / s, the plasma gas used was Ar, N2 and H2, the argon flow rate was 150slpm, the hydrogen flow rate was 60slpm, the nitrogen flow rate was 60slpm, and the spraying thickness was 150μm;

[0032] (3) Plasma-sprayed 55YSZ surface layer was prepared using three-electrode suspension plasma spraying technology, wherein: the powder used was 55YSZ powder with a particle size of 50μm, the power of the plasma spray gun was 128KW, the spraying distance was 80mm, the spray gun moving speed was 1200mm / s, the plasma gas used was Ar, N2 and H2, the argon flow rate was 170slpm, the hydrogen flow rate was 40slpm, the nitrogen flow rate was 80slpm, and the spraying thickness was 150μm;

[0033] The SEM cross-sectional morphology of the multilayer non-penetrating vertical crack thermal barrier coating prepared in this embodiment is as follows: Figure 2 As shown, the vertical crack density is 8 cracks / mm. The cracks in the 8YSZ intermediate layer do not extend to the surface of the MCrAlY bottom layer, and no through cracks are formed between the 55YSZ surface layer and the 8YSZ intermediate layer. All cracks are nanoscale, which can effectively prevent CMAS molten salt from rapidly invading the bonding layer.

Claims

1. A method for preparing a thermal barrier coating resistant to non-penetrating vertical cracks in CMAS corrosion, characterized in that: The method employs plasma spraying technology to sequentially prepare an MCrAlY underlayer, a YSZ intermediate layer, and a YSZ top layer on a substrate, thereby obtaining the thermal barrier coating with a structure system of MCrAlY underlayer / 8YSZ intermediate layer / 30~55YSZ top layer; wherein: the spraying equipment is an Axial III spraying equipment, and the spray gun is a Met-tech Axiall III plasma spray gun; The method includes the following three steps: (1) MCrAlY underlayer was prepared by plasma spraying technology. The process parameters were: spray gun power of 90~110kW, argon flow rate of 200~250slpm, hydrogen flow rate of 15~40slpm, nitrogen flow rate of 40~70slpm, spraying distance of 180~220mm, and spray gun moving speed of 300~1000mm / s. (2) The 8YSZ intermediate layer was prepared by plasma spraying technology. The process parameters were: spray gun power of 110~130kW, argon flow rate of 140~170slpm, hydrogen flow rate of 30~60slpm, nitrogen flow rate of 40~70slpm, spraying distance of 70~100mm, and spray gun moving speed of 500~1000mm / s. (3) A 30~55YSZ surface layer was prepared by plasma spraying technology. The process parameters were: spray gun power of 110~130kW, argon flow rate of 140~170slpm, hydrogen flow rate of 30~60slpm, nitrogen flow rate of 75~90slpm, spraying distance of 70~100mm, and spray gun moving speed of 500~1000mm / s. The YSZ intermediate layer and YSZ surface layer contain vertical cracks with a density of 3~10 cracks / mm. The cracks do not penetrate to the bottom of the layer and connect with the adjacent layer, and there are no accompanying transverse cracks.

2. The method for preparing a non-penetrating vertical crack resistant thermal barrier coating against CMAS corrosion according to claim 1, characterized in that: The Axial III spraying equipment is a high-energy dry powder spraying system that uses axial powder feeding.

3. The method for preparing a non-penetrating vertical crack resistant thermal barrier coating for CMAS corrosion according to claim 1, characterized in that: In step (1) during the plasma spraying of the MCrAlY underlayer, the particle size range of the MCrAlY powder used is 30~70μm; in steps (2) and (3) during the plasma spraying of YSZ preparation, the particle size range of the YSZ powder used is 30~60μm.

4. The method for preparing a non-penetrating vertical crack resistant thermal barrier coating for CMAS corrosion according to claim 1, characterized in that: During the application of this thermal barrier coating, the Y2O3 in the high yttrium content YSZ, i.e., 30~55YSZ surface layer, reacts rapidly with the CMAS component. After forming reaction products on the surface, the product quickly blocks the nanoscale vertical cracks through volume expansion, thereby preventing the rapid invasion of CMAS and ensuring the overall long-term effectiveness of the thermal barrier coating.

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