A hydrogen-doped thermal barrier coating suitable for high-temperature water and oxygen environments and its preparation method

Abstract

This invention relates to the technical field of functional coatings, and provides a hydrogen-doped thermal barrier coating suitable for high-temperature water and oxygen environments, as well as its preparation method. This invention uses Tb 3+ and Tb 4+ By forming dual-site doping of Gd₂Zr₂O₇, the two dopant ions synergistically improve the coating's resistance to water-oxygen corrosion and reduce its thermal conductivity. Combined with the synergistic water vapor resistance of the fluorine-containing top layer, a hydrogen-doped thermal barrier coating with high resistance to water-oxygen corrosion and low thermal conductivity can be prepared, using Gd₂Zr₂O₇ as the insulation layer. The hydrogen-doped Gd₂Zr₂O₇ thermal barrier coating prepared by this invention achieves a water-oxygen coupling corrosion lifetime of up to 830 hours at 1300℃ and a high-temperature thermal conductivity of 1.05 W / m·K at 1000℃.

Description

Technical Field

[0001] This invention relates to the technical field of functional coatings, and provides a hydrogen-doped thermal barrier coating suitable for high-temperature water and oxygen environments, as well as a method for its preparation. Background Technology

[0002] Gas turbines are widely used not only in traditional fields such as power energy, aerospace, shipbuilding, military, and oil and gas, but also in emerging scenarios such as hydrogen energy, AI data center power, and supercritical CO2 cycles. The efficiency and output power of gas turbines are highly dependent on the turbine inlet temperature. The combustion chamber outlet and turbine blade surface gas temperature can reach 1300℃, while the long-term service temperature limit of high-temperature alloy substrates is 1000-1150℃. Without coating protection, the alloy will quickly soften, creep, oxidize, and ablate, leading to failure in a short time.

[0003] Thermal barrier coatings provide insulation and cooling, protect the metal substrate, resist corrosion from complex media, improve overall efficiency and power, resist thermal shock, and extend the service life of components. Typical thermal barrier coatings consist of a base adhesive layer, an intermediate thermal barrier layer, and either no surface protective layer or a simple SiO2 layer. The thermal barrier layer is usually made of 8YSZ zirconium oxide with virtually no additional doping.

[0004] Hydrogen-doped thermal barrier coatings are thermal barrier coatings used on gas turbines that burn pure hydrogen or a hydrogen-natural gas mixture. Because hydrogen is added to the fuel, a large amount of high-temperature water vapor is generated, thus requiring higher performance from the coating. Compared to ordinary coatings, hydrogen-doped coatings replace part or all of the 8YSZ in the intermediate heat-insulating layer with rare-earth zirconate or rare-earth silicate, and have a fluorinated rare-earth anti-hydroxyl / water vapor modification layer on the surface. In terms of performance, hydrogen-doped coatings exhibit better high-temperature resistance, lower thermal conductivity, better resistance to water and oxygen corrosion, better thermal shock resistance, and lower hydrogen permeability and water vapor permeability.

[0005] Rare earth zirconates or rare earth silicates, such as Gd₂Zr₂O₇ and Yb₂Si₂O₇, are commonly used in hydrogen-doped thermal barrier coatings for ceramic insulation. The high-temperature water-oxygen corrosion life of Gd₂Zr₂O₇ is significantly lower than that of Yb₂Si₂O₇. At 1300℃, the water-oxygen corrosion life of Gd₂Zr₂O₇ coating is 250-400 hours, while that of Yb₂Si₂O₇ coating can reach 800-1200 hours. The high-temperature thermal conductivity of Gd₂Zr₂O₇ is higher than that of Yb₂Si₂O₇. For example, at 1000℃, the thermal conductivity of Gd₂Zr₂O₇ coating is 1.7-1.9 W / m·K, while that of Yb₂Si₂O₇ coating is 0.8-1.4 W / m·K. Summary of the Invention

[0006] To improve the high-temperature water-oxygen corrosion resistance and reduce the thermal conductivity of hydrogen-doped thermal barrier coatings using Gd₂Zr₂O₇ as the insulation layer, thereby expanding their application range, this invention proposes a hydrogen-doped thermal barrier coating suitable for high-temperature water-oxygen environments and its preparation method, aiming to obtain a Gd₂Zr₂O₇ hydrogen-doped thermal barrier coating with high resistance to water-oxygen corrosion and low thermal conductivity.

[0007] To achieve the above objectives, the specific technical solution involved in this invention is as follows: First, this invention provides a method for preparing a hydrogen-doped thermal barrier coating suitable for high-temperature water-oxygen environments, the specific preparation steps of which are as follows: S1, NiCoCrAlY or NiCrAlYCe or CoCrAlYCe spherical powder is sprayed onto the surface of the alloy substrate using plasma spraying technology, and then vacuum diffusion annealed to form a metal bonding layer. S2, Gd2Zr2O7 agglomerated granulated powder is sprayed onto the surface of the metal bonding layer using plasma spraying technology, and then air-cooled to room temperature to form a GZO ceramic insulation layer. S3. Spin-coat Gd / Tb-F fluorine-containing rare earth sol onto the surface of the ceramic heat insulation layer in 2-3 layers. First, pre-fire at 480-520℃, then perform solid-phase diffusion at 1200-1300℃ and allow to cool naturally to obtain a hydrogen-doped thermal barrier coating suitable for high-temperature water and oxygen environments.

[0008] Preferably, the particle size of the NiCoCrAlY, NiCrAlYCe, or CoCrAlYCe spherical powder used is 40-80 μm, and the particle size of the Gd2Zr2O7 agglomerated granulated powder is 40-80 μm.

[0009] As a preferred embodiment, in S1, the plasma spraying uses argon gas at a flow rate of 30-50 L / min, hydrogen gas at a flow rate of 6-10 L / min, a spraying distance of 100-150 mm, and a powder feeding speed of 15-25 g / min.

[0010] More preferably, in S1, the vacuum degree of vacuum diffusion annealing is not greater than 1×10⁻⁶. -3 Pa, heat to 1000-1100℃ at 4-6℃ / min, and hold for 120-150min.

[0011] As a preferred embodiment, in S2, the plasma spraying uses argon gas at a flow rate of 40-50 L / min, hydrogen gas at a flow rate of 8-12 L / min, a spraying distance of 100-150 mm, and a powder feeding speed of 15-30 g / min.

[0012] As a preferred embodiment, the preparation process of Gd / Tb-F fluorinated rare earth sol in S3 is as follows: T1, add Gd(NO3)3, Tb(NO3)3, and Tb(NO3)4 to an ethanol / water solvent, stir to dissolve, then add citric acid, continue stirring to form a complex solution, place in a 25°C water bath, and add NH4F solution dropwise while stirring, and continue stirring for 20-40 minutes after the addition is complete. T2, adjust the pH to 4.5 with ammonia, then stir until completely transparent; T3, transfer to a sealed bottle, age in a water bath at 45-55℃ for 18-36 hours, then cool to room temperature.

[0013] In the preparation of Gd / Tb-F fluorinated rare earth sol, the preferred molar ratio of Gd(NO3)3, Tb(NO3)3, Tb(NO3)4, citric acid, and NH4F is 8:1.5:0.5:20:18-20.

[0014] As a preferred embodiment, in S3, the spin coating speed is 3000-4000 r / min; the preheating rate is 4-6℃ / min; and the time is 90-150 min.

[0015] Preferably, in S3, the solid-phase diffusion heating rate is 2-4℃ / min, and the time is 12-15h.

[0016] More preferably, the thickness of the spray coating in S1 is 80-150 μm; the thickness of the spray coating in S2 is 200-400 μm; and the thickness of each wet film layer in the spin coating in S3 is 0.5-1 μm.

[0017] This invention also provides a hydrogen-doped thermal barrier coating prepared by the above-described method. As previously mentioned, when Gd₂Zr₂O₇ is used as the ceramic insulation layer in a hydrogen-doped thermal barrier coating, the high-temperature water-oxygen lifetime needs to be improved, and the thermal conductivity needs to be reduced. To solve this problem, this invention uses a Gd / Tb-F fluorinated rare earth sol spin-coated onto the surface of the ceramic insulation layer. The sol contains Tb... 3+ It also contains Tb 4+ Through solid-phase diffusion, a fluorine-containing gradient top layer is formed, while Tb 3+ and Tb 4+ Fluorine-containing rare-earth sol can diffuse from the top layer into the ceramic insulation layer, doping rare-earth zirconate Gd₂Zr₂O₇. The fluorine-containing top layer causes the formation of numerous rare-earth -F or rare-earth -OF chemical bonds on the coating surface, replacing the original rare-earth -O chemical bonds. This significantly inhibits the adsorption and dissociation of water vapor / hydroxyl groups on the coating surface, thereby improving the water-oxygen corrosion life. In Gd₂Zr₂O₇, Gd… 3+ The ionic radius of Zr is 93.8 pm. 4+ The ionic radius is 72 pm, Tb 3+ The ionic radius is 92.3 pm, similar to Gd. 3+Similar, while Tb 4+ The ionic radius is 76 pm, similar to that of Zr. 4+ Similar, therefore, after solid-phase diffusion, Tb 3+ Replace Gd 3+ Location, Tb 4+ Replace Zr 4+ The position of Tb forms a dual-site doping. This invention, by employing this dual-site doping method, can both reduce thermal conductivity and further improve high-temperature stability, enhance resistance to water and oxygen corrosion, and extend service life. This is because, on the one hand, Tb... 3+ mass, radius and Gd 3+ There are differences; after substitution, a large number of point defects / lattice distortions are formed, which can significantly scatter heat-transferring phonons, thereby reducing thermal conductivity; on the other hand, Tb 4+ Replace Zr 4+ It can also reduce thermal conductivity, but this effect is relatively minor, Tb 4+ The core function of the replacement is to improve resistance to water and oxygen corrosion, because Tb 4+ It is a high-valence, high-field-strength cation, which can enhance the stability of lattice oxygen, inhibit lattice oxygen escape and water vapor dissociation, reduce the formation of ·OH, and improve structural compactness, thereby reducing the volatilization rate of Gd(OH)3. - It can not only form a high-bonding surface, but also with Tb 4+ It has a synergistic effect in resisting water and oxygen, and can also promote Tb 3+ and Tb 4+ Solid-phase diffusion. Additionally, Tb 4+ It is unstable in Gd₂Zr₂O₇. In the system of this invention, F - With Tb 4+ Co-doping occurs, F - Partial O in the replacement zirconate 2- It can reduce lattice oxygen activity and inhibit Tb 4+ Restore, increase Tb 4+ Doping stability.

[0018] This invention provides a hydrogen-doped thermal barrier coating suitable for high-temperature water-oxygen environments and its preparation method. The beneficial effects are: this invention uses Tb... 3+ and Tb 4+ By forming dual-site doping of Gd₂Zr₂O₇, the two dopant ions synergistically improve the coating's resistance to water-oxygen corrosion and reduce its thermal conductivity. Combined with the synergistic water vapor resistance of the fluorine-containing top layer, a hydrogen-doped thermal barrier coating with high resistance to water-oxygen corrosion and low thermal conductivity can be prepared, using Gd₂Zr₂O₇ as the insulation layer. The hydrogen-doped Gd₂Zr₂O₇ thermal barrier coating prepared by this invention achieves a water-oxygen coupling corrosion lifetime of up to 830 hours at 1300℃ and a high-temperature thermal conductivity of 1.05 W / m·K at 1000℃. Detailed Implementation

[0019] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the invention to the following examples. Various substitutions or modifications made based on ordinary technical knowledge and conventional methods in the art without departing from the above-described methodological spirit of the invention should be included within the scope of the invention. Example

[0020] Preparation of Gd / Tb-F fluorinated rare earth sol: T1, add Gd(NO3)3, Tb(NO3)3, and Tb(NO3)4 to an ethanol / water solvent, stir to dissolve, then add citric acid, continue stirring to form a complex solution, place in a 25°C water bath, and add NH4F solution dropwise while stirring, and continue stirring for 30 minutes after the addition is complete. T2, adjust the pH to 4.5 with ammonia, then stir until completely transparent; T3, transfer to a sealed bottle, age in a 50℃ water bath for 24 hours, then cool to room temperature.

[0021] The molar ratio of Gd(NO3)3, Tb(NO3)3, Tb(NO3)4, citric acid, and NH4F is 8:1.5:0.5:20:18.

[0022] Preparation of hydrogen-doped thermal barrier coating: S1, NiCoCrAlY spherical powder was plasma-sprayed onto the surface of an alloy substrate, followed by vacuum diffusion annealing to form a metal bonding layer; the average particle size of the NiCoCrAlY spherical powder was 50 μm; the plasma spraying used argon gas at a flow rate of 40 L / min and hydrogen gas at a flow rate of 8 L / min, with a spraying distance of 120 mm and a powder feed rate of 20 g / min; the vacuum degree of the vacuum diffusion annealing was 1 × 10⁻⁶. - 3 Pa, heated to 1000℃ at 5℃ / min, held for 150min; the coating thickness is 120μm; S2, Gd2Zr2O7 agglomerated granulated powder was sprayed onto the surface of the metal bonding layer using plasma spraying technology, and then air-cooled to room temperature to form a GZO ceramic insulation layer; the particle size of the Gd2Zr2O7 agglomerated granulated powder was 60μm; the plasma spraying used argon gas 45L / min, hydrogen gas 10L / min, the spraying distance was 120mm, the powder feeding speed was 20g / min; the spraying thickness was 300μm; S3, Gd / Tb-F fluorinated rare earth sol was spin-coated onto the surface of a ceramic heat insulation layer in three layers. The coating was first pre-fired at 500℃, then solid-phase diffusion was performed at 1200℃, followed by natural cooling to obtain a hydrogen-doped thermal barrier coating suitable for high-temperature water and oxygen environments. The spin-coating speed was 3500 r / min; the pre-fired heating rate was 5℃ / min for 120 min; the solid-phase diffusion heating rate was 3℃ / min for 15 h; and the wet film thickness of each spin-coated layer was 0.8 μm. Comparative Example 1

[0023] Preparation of Gd / Tb-F fluorinated rare earth sol: T1, add Gd(NO3)3 and Tb(NO3)3 to ethanol / water solvent, stir to dissolve, then add citric acid, continue stirring to form a complex solution, place in a 25℃ water bath, add NH4F solution dropwise while stirring, and continue stirring for 30 min after the addition is complete. T2, adjust the pH to 4.5 with ammonia, then stir until completely transparent; T3, transfer to a sealed bottle, age in a 50℃ water bath for 24 hours, then cool to room temperature.

[0024] The molar ratio of Gd(NO3)3, Tb(NO3)3, citric acid, and NH4F is 8.5:1.5:20:18.

[0025] Preparation of hydrogen-doped thermal barrier coating: same as in the example. Comparative Example 2

[0026] Preparation of Gd / Tb-F fluorinated rare earth sol: T1, add Gd(NO3)3 and Tb(NO3)4 to ethanol / water solvent, stir to dissolve, then add citric acid, continue stirring to form a complex solution, place in a 25℃ water bath, add NH4F solution dropwise while stirring, and continue stirring for 30 min after the addition is complete. T2, adjust the pH to 4.5 with ammonia, then stir until completely transparent; T3, transfer to a sealed bottle, age in a 50℃ water bath for 24 hours, then cool to room temperature.

[0027] The molar ratio of Gd(NO3)3, Tb(NO3)4, citric acid, and NH4F is 9.5:0.5:20:18.

[0028] Preparation of hydrogen-doped thermal barrier coating: same as in the example. Comparative Example 3

[0029] Preparation of Gd / Tb-F fluorinated rare earth sol: T1, add Gd(NO3)3 to ethanol / water solvent, stir to dissolve, then add citric acid, continue stirring to form a complex solution, place in a 25℃ water bath, and add NH4F solution dropwise while stirring, and continue stirring for 30 min after the addition is complete. T2, adjust the pH to 4.5 with ammonia, then stir until completely transparent; T3, transfer to a sealed bottle, age in a 50℃ water bath for 24 hours, then cool to room temperature.

[0030] The molar ratio of Gd(NO3)3, citric acid, and NH4F is 10:20:18.

[0031] Preparation of hydrogen-doped thermal barrier coating: same as in the example.

[0032] Performance testing: (1) Water-oxygen coupled corrosion life at 1300℃: A 25mm×10mm×3mm coating sample was ultrasonically cleaned with anhydrous ethanol for 10min, dried, cooled, and weighed initially. Simulated hydrogen mixed fuel gas turbine operating conditions: air + water vapor mixed atmosphere, water vapor accounted for 20 vol%, carrier gas flow rate 2L / min, atmospheric pressure inside the furnace. Test process: The temperature was increased to 1300℃ at 5℃ / min, and an air + water vapor mixed atmosphere was introduced. Timing was started. The coating was judged to fail when any of the following conditions were met, and the cumulative time was the water-oxygen coupled corrosion life: macroscopic cracking, large-area peeling, and flaking of the coating; obvious local ablation and interconnected pores in the coating, exposing the base metal; the increase in the unit area weight loss rate of the sample was greater than 1.0 mg / cm. 2 • 100h; the interface between the fluorine-containing top layer and the ceramic insulation layer delaminates and separates.

[0033] (2) Thermal conductivity at 1000℃: The sample was processed into a circular piece with a diameter of 12.7 mm and a thickness of 2 mm. A thin graphite coating was sprayed on the surface and allowed to dry at room temperature. Test atmosphere: high-purity argon gas, flow rate 0.5 L / min, heated to 1000℃ at 4℃ / min, held for 30 min, and tested using a laser flash thermal conductivity meter.

[0034] The obtained data is shown in Table 1.

[0035] Table 1: Example 830 1.05 Comparative Example 1 310 1.14 Comparative Example 2 770 1.78 Comparative Example 3 280 1.82 .

Claims

1. A method for preparing a hydrogen-doped thermal barrier coating suitable for high-temperature water-oxygen environments, characterized in that, The preparation steps of the hydrogen-doped thermal barrier coating are as follows: S1, NiCoCrAlY or NiCrAlYCe or CoCrAlYCe spherical powder is sprayed onto the surface of the alloy substrate using plasma spraying technology, and then vacuum diffusion annealed to form a metal bonding layer. S2, Gd2Zr2O7 agglomerated granulated powder is sprayed onto the surface of the metal bonding layer using plasma spraying technology, and then air-cooled to room temperature to form a GZO ceramic insulation layer. S3. Spin-coat Gd / Tb-F fluorine-containing rare earth sol onto the surface of the ceramic heat insulation layer in 2-3 layers. First, pre-fire at 480-520℃, then perform solid-phase diffusion at 1200-1300℃ and allow to cool naturally to obtain a hydrogen-doped thermal barrier coating suitable for high-temperature water and oxygen environments.

2. The preparation method according to claim 1, characterized in that, The particle size of NiCoCrAlY, NiCrAlYCe, or CoCrAlYCe spherical powder is 40-80 μm; the particle size of Gd2Zr2O7 agglomerated granulated powder is 40-80 μm.

3. The preparation method according to claim 1, characterized in that, In S1, plasma spraying uses argon gas at a flow rate of 30-50 L / min and hydrogen gas at a flow rate of 6-10 L / min, with a spraying distance of 100-150 mm and a powder feeding rate of 15-25 g / min.

4. The preparation method according to claim 1, characterized in that, In S1, the vacuum degree of vacuum diffusion annealing is no greater than 1×10⁻⁶. -3 Pa, heat to 1000-1100℃ at 4-6℃ / min, and hold for 120-150min.

5. The preparation method according to claim 1, characterized in that, In S2, plasma spraying uses argon gas at a flow rate of 40-50 L / min and hydrogen gas at a flow rate of 8-12 L / min, with a spraying distance of 100-150 mm and a powder feeding rate of 15-30 g / min.

6. The preparation method according to claim 1, characterized in that, In S3, the preparation process of Gd / Tb-F fluorinated rare earth sol is as follows: T1, add Gd(NO3)3, Tb(NO3)3, and Tb(NO3)4 to an ethanol / water solvent, stir to dissolve, then add citric acid, continue stirring to form a complex solution, place in a 25°C water bath, and add NH4F solution dropwise while stirring, and continue stirring for 20-40 minutes after the addition is complete. T2, adjust the pH to 4.5 with ammonia, then stir until completely transparent; T3, transfer to a sealed bottle, age in a water bath at 45-55℃ for 18-36 hours, then cool to room temperature.

7. The preparation method according to claim 6, characterized in that, The molar ratio of Gd(NO3)3, Tb(NO3)3, Tb(NO3)4, citric acid, and NH4F is 8:1.5:0.5:20:18-20.

8. The preparation method according to claim 1, characterized in that, In S3, the spin coating speed is 3000-4000 r / min; the pre-calcination heating rate is 4-6℃ / min, and the time is 90-150 min; the solid-phase diffusion heating rate is 2-4℃ / min, and the time is 12-15 h.

9. The preparation method according to claim 1, characterized in that, The thickness of the spray coating in S1 is 80-150μm; the thickness of the spray coating in S2 is 200-400μm; and the thickness of each wet film layer in the spin coating in S3 is 0.5-1μm.

10. The hydrogen-doped thermal barrier coating prepared by the preparation method according to any one of claims 1-9.