Alumina-based smooth coating resistant to salt spray corrosion, resistant to thermal shock

Abstract

The application belongs to the technical field of refractory materials, and particularly relates to an alumina-based smooth coating with salt mist corrosion resistance and thermal shock resistance. The alumina-based smooth coating uses alumina powder as the powder of the smooth coating; the particle size of the alumina powder ranges from 0.1 to 10 microns; the alumina powder is uniformly mixed with a binder to form a slurry; a YSZ substrate sample prepared by thermal spraying is completely immersed in the slurry or the slurry is uniformly brushed on the surface of the sample; after the slurry on the surface of the sample is naturally leveled, the sample is dried; after the slurry on the surface of the sample is solidified, the sample is subjected to heat treatment; and after the heat treatment is completed, the sample is detected by using a screw micrometer and a surface roughness detector. The smooth coating has the characteristics of low roughness, high reflectivity, excellent salt mist corrosion resistance and thermal shock resistance, and effectively improves the service life of the thermal barrier coating in the current complex environment of an aviation gas turbine and an aviation engine.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a smooth alumina-based coating that is resistant to salt spray corrosion and thermal shock. Background Technology

[0002] Thermal barrier coatings (TBCs) are an indispensable key technology in the design and manufacturing of aero-gas turbines and aero-engines, playing a crucial role in reducing blade temperatures, improving engine efficiency, and extending service life. Currently, yttrium-stabilized zirconia (YSZ) is a key technology for the development of these engines due to its excellent thermodynamic properties, and its application in TBCs is the most widespread. However, as aero-gas turbines develop towards higher flow ratios, higher thrust-to-weight ratios, and higher inlet temperatures, the damage caused by high-temperature oxidation and molten salt deposits (mainly composed of Na₂SO₄, V₂O₅, and NaCl) to TBCs is becoming increasingly severe, affecting the structural integrity of high-temperature components. The integrity of the structure and service safety are crucial; however, YSZ does not have excellent oxidation resistance and molten salt corrosion resistance at high temperatures, which can no longer meet the requirements of current aero-gas turbines and aero-engines in complex environments. Therefore, it is urgent to prepare a smooth coating with salt spray corrosion resistance and thermal shock resistance on the surface of the thermal barrier coating. On the one hand, the alumina-based smooth coating can effectively reduce the adhesion and penetration of molten salt in the environment on the surface of the thermal barrier coating. On the other hand, due to its high reflectivity, it can reflect most of the external heat radiation, reduce the heat conducted to the substrate, thereby improving its thermal shock resistance and molten salt corrosion resistance in high-temperature oxidation and high-temperature corrosion environments, and extending its service life. Summary of the Invention

[0003] The purpose of this invention is to provide an alumina-based smooth coating that is resistant to salt spray corrosion and thermal shock, giving it excellent thermal shock resistance and salt spray corrosion resistance in the service environment of gas turbines, thereby ensuring the structural integrity and service safety of high-temperature components.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A smooth alumina-based coating resistant to salt spray corrosion and thermal shock is disclosed. The smooth alumina-based coating uses alumina powder as the smoothing agent; the particle size of the alumina powder ranges from 0.1 to 10 μm. The alumina powder is uniformly mixed with a binder to form a slurry. A YSZ substrate sample prepared by thermal spraying is completely immersed in the slurry or the slurry is uniformly brushed onto the sample surface. After the slurry on the sample surface naturally levels, it is dried. After the slurry on the sample surface solidifies, heat treatment is performed. After heat treatment, a micrometer and a surface roughness tester are used for testing. The thickness of the smooth coating is 10–60 μm; the roughness of the smooth coating is 0–2 μm.

[0005] The binder is at least one of aluminum dihydrogen phosphate, silica sol, zirconium sol, and aluminum sol.

[0006] The mass ratio of alumina powder to aluminum dihydrogen phosphate, silica sol, zirconium sol and aluminum sol is 1:0~1:0~0.8:0~1:0~0.4.

[0007] The immersion time for the matrix sample to be completely immersed in the slurry is 0.1 to 5 minutes.

[0008] The drying temperature is 15-150℃, and the drying time is 5-55 hours.

[0009] The heat treatment temperature is 300–600℃, and the heat treatment time is 1–5 hours.

[0010] This invention proposes an alumina-based smooth coating that resists salt spray corrosion and thermal shock. Using the above technical solution, the alumina-based smooth coating can effectively reduce the adhesion and penetration of molten salt at high temperatures and reflect most of the external heat radiation. This improves both the coating's resistance to salt spray corrosion and ensures its excellent thermal shock resistance, thus significantly extending the service life of the thermal barrier coating in current complex environments. It exhibits excellent resistance to salt spray corrosion and thermal shock under high-temperature conditions; under conditions of 1400℃, flame velocity of Mach 0.5, constant temperature for 20s, and air cooling for 15s, the thermal shock life is not less than 2500 cycles; at 900℃ and 1.5 mg / cm³, the thermal shock life is also excellent. 2 Under high-concentration salt spray (Na2SO4-V2O5-NaCl, etc.) corrosion conditions, the coating life is not less than 150 hours. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the cross-sectional structure of a smooth coating prepared on the surface of a thermal barrier coating, as an embodiment of the present invention.

[0012] Figure 2 In one embodiment of the present invention, a schematic diagram of the coating cross-sectional structure after 2300 thermal shocks under the conditions of 1400°C, flame velocity of Mach 0.5, constant temperature for 20s, and air cooling for 15s is provided.

[0013] Figure 3 In one embodiment of the present invention, at 900°C and 1.5 mg / cm³... 2 A schematic diagram of the cross-sectional structure of the coating after 150 hours of corrosion under high-concentration salt spray (Na2SO4-V2O5-NaCl, etc.) conditions. Detailed Implementation

[0014] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments. Embodiments of the present invention include, but are not limited to, the following examples. Example 1

[0015] According to the method described, alumina powder, aluminum dihydrogen phosphate, silica sol, zirconium sol, and aluminum sol were selected and mixed evenly in a mass ratio of 1:0.6:0.2:0.2:0.1 to form a slurry. The sample was then immersed in the slurry for 3 minutes, removed, and placed in an oven to dry at 30°C for 25 hours. Following this, it was heat-treated at 350°C for 4.5 hours to obtain a smooth coating with a thickness of 43 μm. This coating exhibited 2531 thermal shock cycles under conditions of 1400°C, a flame velocity of Mach 0.5, a constant temperature for 20 seconds, and air cooling for 15 seconds. At 900°C and 1.5 mg / cm³, the coating also showed good thermal shock resistance. 2 Under high-concentration salt spray (Na2SO4-V2O5-NaCl, etc.) corrosion conditions, the coating life reaches 176 hours. Example 2

[0016] According to the method described, alumina powder, aluminum dihydrogen phosphate, silica sol, zirconium sol, and aluminum sol were selected and mixed evenly in a mass ratio of 1:0.3:0.3:0.3:0.1 to form a slurry. The slurry was then brushed onto the sample surface to form a coating, and the sample was placed in an oven and dried at 50°C for 20 hours, followed by heat treatment at 470°C for 2 hours to obtain a smooth coating with a thickness of 20 μm. This sample coating withstood 2505 thermal shocks under conditions of 1400°C, flame velocity of Mach 0.5, constant temperature for 20 seconds, and air cooling for 15 seconds; and under conditions of 900°C and 1.5 mg / cm³... 2 Under high-concentration salt spray (Na2SO4-V2O5-NaCl, etc.) corrosion conditions, the coating life reaches 187 hours. Example 3

[0017] According to the method described, alumina powder, aluminum dihydrogen phosphate, silica sol, zirconium sol, and aluminum sol were selected and mixed evenly in a mass ratio of 1:0.7:0:0.2:0 to form a slurry. The sample was then immersed in the slurry for 1 minute, removed, and placed in an oven to dry at 100°C for 30 hours, followed by heat treatment at 320°C for 5 hours to obtain a smooth coating with a thickness of 38 μm. This coating exhibited 2921 thermal shock cycles under conditions of 1400°C, a flame velocity of Mach 0.5, a constant temperature for 20 seconds, and air cooling for 15 seconds; and under conditions of 900°C and 1.5 mg / cm³... 2 Under high-concentration salt spray (Na2SO4-V2O5-NaCl, etc.) corrosion conditions, the coating life reaches 168 hours. Example 4

[0018] According to the method described, alumina powder, aluminum dihydrogen phosphate, silica sol, zirconium sol, and aluminum sol were selected and mixed evenly in a mass ratio of 1:0.2:0:0.5:0.3 to form a slurry. The slurry was then brushed onto the sample surface to form a coating, and the sample was placed in an oven and dried at 130℃ for 20 hours, followed by heat treatment at 600℃ for 1 hour to obtain a smooth coating with a thickness of 16 μm. This sample coating withstood 2758 thermal shocks under conditions of 1400℃, flame velocity of Mach 0.5, constant temperature for 20 seconds, and air cooling for 15 seconds; and under conditions of 900℃ and 1.5 mg / cm³... 2 Under high-concentration salt spray (Na2SO4-V2O5-NaCl, etc.) corrosion conditions, the coating life reaches 154 hours.

[0019] The present invention has the following beneficial effects: the alumina-based smooth coating prepared by the preparation process described in this invention exhibits excellent corrosion resistance under high-concentration salt spray corrosion at 900℃, and also maintains good thermal shock resistance at an service temperature of 1400℃. The materials used in this invention inherently possess good high-temperature service performance; the preparation process employed yields a smooth alumina coating with a roughness of less than 2μm. The smooth surface reduces the adhesion and penetration of molten salt and has high reflectivity, reflecting most of the external thermal radiation, thereby reducing the heat conducted to the substrate, effectively improving thermal shock resistance, and giving the coating a longer service life.

[0020] For those skilled in the art, without departing from the concept of the technical solution of this invention, several modifications and improvements can be made, and these should also be considered within the scope of protection of this invention. These will not affect the effectiveness of the implementation of this patent or the practicality of the patent.

Claims

1. A smooth alumina-based coating resistant to salt spray corrosion and thermal shock, characterized in that: The alumina-based smooth coating uses alumina powder as the smoothing agent; the particle size range of the alumina powder is 0.1–10 μm; the alumina powder is mixed evenly with a binder to form a slurry, and the YSZ substrate sample prepared by thermal spraying is completely immersed in the slurry or the slurry is evenly brushed onto the sample surface. After the slurry on the sample surface naturally levels, it is dried, and after the slurry on the sample surface solidifies, it is heat-treated. After the heat treatment, a micrometer and a surface roughness tester are used for testing; the thickness of the smooth coating is 10–60 μm; the roughness of the smooth coating is 0–2 μm; the binder is a combination of aluminum dihydrogen phosphate, silica sol, zirconium sol, and aluminum sol, and the mass ratio of alumina powder to aluminum dihydrogen phosphate, silica sol, zirconium sol, and aluminum sol is 1:0–1:0–0.8:0–1:0–0.4; the heat treatment temperature is 300–600℃, and the heat treatment time is 1–5 h.

2. The alumina-based smooth coating resistant to salt spray corrosion and thermal shock as described in claim 1, characterized in that: The immersion time for the matrix sample to be completely immersed in the slurry is 0.1 to 5 minutes.

3. The alumina-based smooth coating resistant to salt spray corrosion and thermal shock as described in claim 1, characterized in that: The drying temperature is 15-150℃, and the drying time is 5-55 hours.

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