Hydroxyl-resistant surface passivation thermal barrier coating for hydrogen-mixed fuel environment and preparation method of hydroxyl-resistant surface passivation thermal barrier coating

Abstract

The invention discloses an anti-hydroxyl surface passivation thermal barrier coating for a hydrogen mixed fuel environment and a preparation method of the anti-hydroxyl surface passivation thermal barrier coating. The anti-hydroxyl surface passivation thermal barrier coating aims at solving the problem that a coating is degraded under hydrogen combustion and hydrogen / natural gas mixed combustion working conditions through water vapor induction. According to the hydroxyl-resistant surface passivation thermal barrier coating, a metal bonding layer, a ceramic surface layer and a fluorine-containing enrichment gradient layer are sequentially arranged on a metal matrix from bottom to top, the ceramic surface layer is a rare earth oxide doped zirconium dioxide ceramic layer and / or a rare earth doped lanthanum zirconate ceramic layer, and the fluorine-containing enrichment gradient layer is a fluorine-containing enrichment gradient layer. The fluorine-containing enriched gradient layer is formed by spraying fluorine-containing rare earth sol and then carrying out heat treatment and solid-phase activation diffusion treatment. Through the fluorine-containing enrichment layer, the chemical affinity of the surface to high-temperature water vapor and hydroxyl can be remarkably reduced, generation of volatile matter such as RE (OH) 3 and loss of a rare earth stabilizer are inhibited, and water vapor induced surface layer sintering densification and heat conductivity rising are weakened; therefore, the heat insulation performance maintaining capability and the heat cycle life of the thermal barrier coating under the hydrogen combustion / hydrogen mixed combustion working condition are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of thermal barrier coatings and high-temperature protective materials, specifically relating to a method for resisting hydroxyl passivation on the surface of a zirconium oxide-based rare earth modified thermal barrier coating for high-temperature water vapor / hydrogen co-combustion conditions, which can be applied to the surface protection of high-temperature components such as gas turbines. Background Technology

[0002] Key hot-end components of gas turbines, aero-engines, and industrial gas turbines endure prolonged exposure to high-temperature combustion gases and intense thermal cycling during service. To reduce the temperature of the metal substrate and extend component life, thermal barrier coating systems consisting of a metal bonding layer and a ceramic surface layer are commonly used. Among these, rare-earth-doped zirconium dioxide (RE₂O₃-ZrO₂, typically YSZ) and rare-earth-doped lanthanum zirconate (RE-doped La₂Zr₂O₇) have become mainstream surface layer materials due to their low thermal conductivity, good high-temperature phase stability, and thermal expansion coefficients that match those of nickel-based superalloys. As gas turbines evolve towards higher temperatures, higher efficiency, and lower carbon emissions, hydrogen combustion and hydrogen / natural gas co-combustion are increasingly being applied to next-generation gas turbines. This significantly increases the volume fraction of water vapor and the concentration of active groups such as H and OH in the combustion products, placing the coating surface in a high-temperature, high-partial-pressure water vapor environment for extended periods. Under these conditions, high-temperature water vapor is prone to adsorption and dissociation on the ceramic surface, generating a large number of hydroxyl groups and inducing the formation of volatile or soluble substances such as RE(OH)3. This leads to the migration and loss of rare earth stabilizers from the surface, phase structure transformation, and degradation of coating hardness and strength. At the same time, water vapor significantly accelerates surface and grain boundary diffusion, causing the sprayed porous structure to accelerate sintering and pore shrinkage, increasing thermal conductivity and reducing heat insulation capacity. Furthermore, it couples with the formation and evolution of molten salt and thermally grown oxides, further weakening the service reliability of the coating under hydrogen co-firing and water vapor-rich conditions.

[0003] To address the issue of moisture-induced coating degradation, existing technologies primarily employ two approaches: First, introducing multi-element rare earth elements, high-entropy compounds, or aluminates into the ZrO2 or La2Zr2O7 system to form novel ceramics, thereby improving the coating's phase stability and anti-sintering ability. Second, constructing a glassy phase sealing layer, a rare earth silicate / glass-ceramic outer coating, or densifying the surface pores to weaken the direct erosion by moisture and corrosive media. While these solutions can improve corrosion resistance and anti-sintering performance, they often require replacing mature material systems or employing complex multi-layer structures, which can easily damage the porous microstructure of the sprayed coating and reduce strain compliance. Furthermore, the processes involve numerous steps and long cycles, hindering the engineering application of components. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of water vapor-induced coating degradation under hydrogen combustion and hydrogen / natural gas mixed combustion conditions, and to provide a hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments and its preparation method.

[0005] The present invention provides an anti-hydroxyl surface passivation thermal barrier coating for hydrogen mixed fuel environments, comprising a metal bonding layer, a ceramic surface layer, and a fluorine enrichment gradient layer. The metal bonding layer, ceramic surface layer, and fluorine enrichment gradient layer are arranged sequentially from bottom to top on a metal substrate. The ceramic surface layer is a rare earth oxide-doped zirconium dioxide ceramic layer and / or a rare earth-doped lanthanum zirconate ceramic layer. The fluorine enrichment gradient layer contains a gradually decreasing fluorine content from the surface inward.

[0006] The fluorine-enriched gradient layer is formed by spraying fluorine-containing rare earth sol and then heat treatment and solid-phase activation diffusion treatment. The fluorine-containing rare earth sol contains rare earth precursors, fluorine sources and solvents. The rare earth precursors are RE(NO3)3 and / or RE(CH3COO)3, and the fluorine sources are NH4F and / or NH4HF2. The molar ratio (F / RE) of the F element in the fluorine source to the rare earth RE element in the rare earth precursor is 1 to 3.

[0007] The fluorine-enriched gradient layer of this invention contains a RE-Zr-OF solid solution phase and / or yttrium fluoride REOF and rare earth fluoride REF3 phase, wherein RE is a rare earth element, forming a hydroxyl-resistant surface passivation layer with low affinity for high-temperature water vapor and high chemical stability, used to suppress the corrosion and deterioration of ceramic surface layer by high-temperature water vapor in a hydrogen mixed fuel environment.

[0008] This invention provides a fluorine-enriched gradient surface layer (mainly composed of RE-Zr-OF solid solution phase with fluorite or defective fluorite as the main phase, supplemented by REOF / REF3 dispersed phase) formed after the construction of a fluorine-containing rare earth sol precursor layer and solid-phase activation and diffusion treatment. This layer serves as a functional layer with low affinity and high chemical stability to high-temperature water vapor and hydroxyl groups. It is applied to the surface thermal protection of high-temperature metal components under hydrogen / hydrogen co-combustion conditions such as gas turbines, aero engines, and industrial gas turbines, thereby improving the performance and expanding the engineering applications of traditional rare earth modified thermal barrier coating systems.

[0009] The method for preparing the hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments according to the present invention is implemented according to the following steps:

[0010] Step 1: Grind, sandblast, and clean the surface of the metal substrate in sequence. Prepare a metal bonding layer on the surface of the metal substrate using a spraying process or a physical vapor deposition process to obtain a substrate with a metal bonding layer.

[0011] Step 2: Prepare a ceramic surface layer on the substrate surface with a metal bonding layer using a spraying process or a physical vapor deposition process;

[0012] Step 3: Prepare a fluorinated rare earth sol by using rare earth precursor and fluorine source, then uniformly spray the fluorinated rare earth sol onto the surface of the ceramic surface layer, and obtain a fluorinated precursor layer by multiple spraying and drying processes.

[0013] Step 4: Under the protection of an inert gas or air atmosphere, heat the material to 400-700℃ and hold it for heat treatment, then heat it to 900-1000℃ and hold it for solid-phase activation and diffusion treatment, so that the fluorine-containing precursor layer is transformed into a fluorine-enriched gradient layer.

[0014] Step 5: After cooling under an inert atmosphere or air, a hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments is obtained.

[0015] In step two, the ceramic surface layer is a rare earth oxide-doped zirconium dioxide ceramic layer and / or a rare earth-doped lanthanum zirconate ceramic layer; in step three, the rare earth precursor is RE(NO3)3 and / or RE(CH3COO)3, and the fluorine source is NH4F and / or NH4HF2.

[0016] This invention provides a method for preparing a hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments. A fluorine-containing rare-earth sol precursor layer is constructed on the surface of a rare-earth oxide-doped zirconium dioxide or rare-earth-doped lanthanum zirconate thermal barrier coating ceramic layer. Following solid-phase activation and diffusion treatment, a fluorine-enriched gradient layer is in-situ constructed within a limited depth range on the outermost side of the coating, achieving surface passivation against high-temperature water vapor and hydroxyl groups. This method features a simple process route, short preparation cycle, and compatibility with existing thermal spraying processes and material systems. While maintaining the porous / layered microstructure and thermal shock compliance of the sprayed coating, it significantly improves the coating's resistance to water vapor degradation and service life in hydrogen mixed fuel environments.

[0017] The present invention provides a hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments and its preparation method, which has the following beneficial effects:

[0018] (1) This invention constructs a fluorine-containing rare earth sol precursor layer on the surface of sprayed rare earth-doped zirconium dioxide and rare earth-doped lanthanum zirconate ceramic surface layer and performs solid-phase activation and diffusion treatment. In situ, a fluorine-enriched gradient layer with RE-Zr-OF solid solution phase as the main component and REOF / REF3 dispersed phase is constructed within a limited depth range of the outermost layer of the coating. This transforms a large number of MO bonds on the surface into high bond energy MF and MOF structures, significantly reducing the surface Lewis acidity and chemical affinity for water molecules / hydroxyl groups. This inhibits the adsorption and dissociation of high-temperature water vapor on the coating surface from the source, reduces the generation of volatile hydrated species such as RE(OH)3 and the outward migration of rare earth stabilizers, thereby effectively slowing down the phase stability degradation and mechanical property deterioration induced by water vapor in the hydrogen mixed fuel environment.

[0019] (2) The fluorine-enriched gradient layer formed by the present invention is introduced by F doping and YOF / REF3 dispersed phase, which reduces the effective concentration of oxygen vacancies on the surface, inhibits surface and grain boundary diffusion and neck growth, weakens the sintering and densification effect of high temperature water vapor on the pores between sprayed layers, improves the retention of the porous / layered structure of the ceramic surface layer during long-term service, delays the increase of thermal conductivity, the decay of thermal insulation performance and the development of thermal stress concentration, and significantly improves the thermal barrier coating's ability to maintain thermal insulation performance and thermal cycle life in a hydrogen mixed fuel environment.

[0020] (3) The present invention uses a fluorine-containing rare earth sol precursor layer combined with solid-phase activation diffusion as a post-treatment process, which only acts on the outermost 2-30 μm range of the ceramic surface layer. It does not change the original rare earth modified ZrO2 / lanthanum zirconate material system and thermal spraying preparation process. It has little disturbance to the microstructure of the coating body, the process route is simple, and it can be used for coatings prepared by conventional plasma spraying or EB-PVD. At the same time, the thickness of the fluorine-enriched gradient layer and the F content can be controlled by adjusting parameters such as sol formulation, precursor layer thickness and activation diffusion heat treatment temperature and time, which has good process applicability.

[0021] (4) The anti-hydroxyl surface passivation thermal barrier coating constructed in this invention is compatible with existing Ni-based high-temperature alloy and conventional metal bonding layer systems. It is suitable for surface protection of combustion chambers, guide vanes, dynamic and static blades and high-temperature sealing components in hydrogen / hydrogen co-fired conditions such as gas turbines, aero engines and industrial gas turbines. It can significantly improve the service reliability and life of high-temperature components in high-temperature water vapor environment without significantly increasing structural complexity and manufacturing cost. It has important engineering application value and promotion prospects. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments according to the present invention.

[0023] Figure 2 A schematic diagram of the process flow for preparing a hydroxyl-resistant surface passivation thermal barrier coating. Detailed Implementation

[0024] Specific Implementation Method 1: The anti-hydroxyl surface passivation thermal barrier coating for hydrogen mixed fuel environments in this implementation method includes a metal bonding layer, a ceramic surface layer, and a fluorine enrichment gradient layer. The metal bonding layer, ceramic surface layer, and fluorine enrichment gradient layer are arranged from bottom to top on the metal substrate. The ceramic surface layer is a rare earth oxide-doped zirconium dioxide ceramic layer and / or a rare earth-doped lanthanum zirconate ceramic layer. The fluorine enrichment gradient layer has a gradually decreasing fluorine content from the surface to the inside.

[0025] The fluorine-enriched gradient layer is formed by spraying fluorine-containing rare earth sol and then heat treatment and solid-phase activation diffusion treatment. The fluorine-containing rare earth sol contains rare earth precursors, fluorine sources and solvents. The rare earth precursors are RE(NO3)3 and / or RE(CH3COO)3, and the fluorine sources are NH4F and / or NH4HF2. The molar ratio (F / RE) of the F element in the fluorine source to the rare earth RE element in the rare earth precursor is 1 to 3.

[0026] Under hydrogen / natural gas mixed combustion conditions of 900–1200℃, the fluorine-enriched gradient layer inhibits the adsorption and dissociation of high-temperature water vapor on the ceramic surface, exhibits a significant chemical passivation effect on high-temperature water vapor and hydroxyl groups, slows down the loss of rare earth stabilizers and sintering densification, maintains the stability of the porous / layered structure and phase composition of the ceramic surface, thereby improving the thermal insulation performance and thermal cycling life of the thermal barrier coating.

[0027] This embodiment constructs a fluorine-enriched gradient layer on the coating surface by post-fluorination treatment, which is mainly composed of RE-Zr-OF solid solution phase and supplemented by REOF and REF3 dispersed phases. It only performs directional chemical regulation on a limited depth area on the outermost part of the ceramic surface layer, and constructs a passivation layer with low affinity for high-temperature water vapor and hydroxyl groups and high chemical stability in situ on the surface. It can improve the corrosion resistance and service life of the coating under high-temperature water vapor / hydrogen co-combustion conditions without sacrificing the porous structure and thermal shock performance, and has good engineering application prospects.

[0028] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the metal bonding layer is a NiCoCrAlY bonding layer, and the thickness of the metal bonding layer is 50~200μm.

[0029] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the general chemical formula of the rare earth oxide-doped zirconium dioxide ceramic layer is represented as (Zr... 1-x RE x )O 2-δ x = 0.01~0.3; the general chemical formula of the rare earth-doped lanthanum zirconate ceramic layer is (La 1-y RE y )2Zr2O7, y=0.01~1.0.

[0030] Specific Implementation Method Four: This implementation method differs from one of the specific implementation methods one to three in that the thickness of the ceramic surface layer is 50 to 500 μm.

[0031] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that the thickness of the fluorine enrichment gradient layer is 2 to 30 μm, and the atomic fraction of F element in the fluorine enrichment gradient layer is 0.1 to 10 at..

[0032] In this embodiment, the main phase in the fluorine-enriched gradient layer is a fluorite-type or defective fluorite-type RE-Zr-OF solid solution, supplemented with 1 to 30 volume fractions of REOF or REF3 dispersed phase.

[0033] Specific Implementation Method Six: The preparation method of the hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments in this implementation method is carried out according to the following steps:

[0034] Step 1: Grind, sandblast, and clean the surface of the metal substrate in sequence. Prepare a metal bonding layer on the surface of the metal substrate using a spraying process or a physical vapor deposition process to obtain a substrate with a metal bonding layer.

[0035] Step 2: Prepare a ceramic surface layer (thickness approximately 50–500 μm) on the substrate surface with a metal bonding layer using a spraying process or a physical vapor deposition process.

[0036] Step 3: Prepare a fluorinated rare earth sol by using rare earth precursor and fluorine source, then uniformly spray the fluorinated rare earth sol onto the surface of the ceramic surface layer, and obtain a fluorinated precursor layer by multiple spraying and drying processes.

[0037] Step 4: Under the protection of an inert gas or air atmosphere, heat the material to 400-700℃ and hold it for heat treatment, then heat it to 900-1000℃ and hold it for solid-phase activation and diffusion treatment, so that the fluorine-containing precursor layer is transformed into a fluorine-enriched gradient layer.

[0038] Step 5: After cooling under an inert atmosphere or air, a hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments is obtained.

[0039] In step two, the ceramic surface layer is a rare earth oxide-doped zirconium dioxide ceramic layer and / or a rare earth-doped lanthanum zirconate ceramic layer, and maintains a sprayed lamellar and / or columnar porous structure; in step three, the rare earth precursor is RE(NO3)3 and / or RE(CH3COO)3, and the fluorine source is NH4F and / or NH4HF2.

[0040] In step three of this embodiment, complexing agents such as citric acid and acetylacetone, as well as pH adjusters such as ammonia and acetic acid, can be added as needed during the preparation of the fluorinated rare earth sol to stabilize the sol structure and improve coating uniformity.

[0041] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the metal matrix in step one is a nickel-based high-temperature alloy.

[0042] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Six or Seven in that the spraying process described in step one is atmospheric plasma spraying, vacuum plasma spraying, or suspension plasma spraying, and the physical vapor deposition process is electron beam physical vapor deposition.

[0043] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods Six to Eight in that the spraying process described in step two is an atmospheric plasma spraying process, a vacuum plasma spraying process, or a suspension plasma spraying process, and the physical vapor deposition process is an electron beam physical vapor deposition process.

[0044] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 6 to 9 in that the thickness of the fluorine-containing precursor layer in step 3 is 1 to 10 μm.

[0045] Specific Implementation Method Eleven: This implementation method differs from Specific Implementation Methods Six to Ten in that in step four, the temperature is increased to 400-700°C at a heating rate of 5-15°C / min, and heat treatment is carried out for 0.5-2 hours to form a RE-Zr-OF gel framework. Then, the temperature is increased to 900-1000°C and heat treatment is carried out for 1-3 hours to activate solid-phase diffusion treatment.

[0046] In this embodiment, the fluorine (F) element in the precursor layer undergoes a solid-phase reaction with the surface layer of the underlying rare-earth modified ceramic surface layer and diffuses inward, forming a fluorine-enriched gradient layer with decreasing F content along the thickness direction within a depth of 2–30 μm on the outermost side of the ceramic surface layer. Subsequently, the layer is cooled to room temperature in an inert gas or air furnace without further densification sintering, thus preserving the original porous / lamellar microstructure of the ceramic surface layer. This gradient layer contains a RE-Zr-OF solid solution phase as well as stable phases such as REOF and REF3, which have low affinity for high-temperature water vapor and hydroxyl groups.

[0047] Example 1: The preparation method of the hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments in this example is carried out according to the following steps:

[0048] Step 1: Using a nickel-based high-temperature alloy sample (25mm×10mm×3mm) as the metal substrate, the surface of the metal substrate is successively polished and sandblasted, ultrasonically cleaned with acetone and anhydrous ethanol, and dried for later use.

[0049] Step 2: An NiCoCrAlY bonding layer is prepared on a metal substrate using atmospheric plasma spraying. The spraying current is controlled at 450A, the voltage at 60V, and the distance between the spray gun and the substrate is 100mm, resulting in a bonding layer with a thickness of approximately 150μm. Then, a YSZ ceramic surface layer (8mol% Y2O3 stabilized ZrO2) is prepared using atmospheric plasma spraying. The thickness of the NiCoCrAlY bonding layer is controlled at approximately 150μm, and the thickness of the YSZ ceramic surface layer is controlled at approximately 300μm, totaling approximately 450μm. This forms a layered microstructure with a porosity of approximately 8%–12%, ensuring good thermal insulation performance and thermal shock compliance.

[0050] Step 3: Dissolve Y(NO3)3·6H2O in a mixed solvent of deionized water and anhydrous ethanol to prepare a Y(NO3)3·6H2O solution with a total concentration of approximately 0.1 mol / L. 3+ The solution was prepared by adjusting the F / Y molar ratio to 2:1 using NH4F as the fluorine source, adding a small amount of citric acid as a complexing agent if necessary, and adjusting the pH of the system to 3-4 by adding dilute ammonia. After stirring evenly, the solution was aged at room temperature for 2 hours to obtain a stable fluorinated rare earth sol. The metal substrate with the NiCoCrAlY / 8YSZ coating was fixed on a heating stage. The fluorinated rare earth sol was uniformly sprayed onto the surface of the YSZ layer using a pneumatic spray gun at a distance of about 150 mm between the spray gun and the substrate and a spray flow rate of about 0.5 mL / min. After each spraying, the solution was dried at 100℃ for 10 minutes to evaporate the solvent and form a gel thin layer. Through 5 spraying-drying cycles, a fluorinated precursor layer with a thickness of about 4 μm was constructed on the outermost side of the ceramic surface layer.

[0051] Step 4: Under the protection of an inert gas or air atmosphere, heat the mixture to 500℃ at a heating rate of 5℃ / min and hold for 1 hour to decompose the organic components and form a YOF gel skeleton. Then heat the mixture to 900℃ and hold for 2 hours to allow the F element in the precursor layer to undergo a solid-phase reaction and diffusion with the surface layer of the lower YSZ surface layer, transforming the fluorine-containing precursor layer into a fluorine-enriched gradient layer. This gradient layer contains a RE-Zr-OF solid solution phase and stable phases such as REOF and REF3 that have low affinity for high-temperature water vapor and hydroxyl groups.

[0052] Step 5: Cool the ceramic surface to room temperature in an inert atmosphere without further densification sintering to maintain the original porous / lamellae microstructure and thermal expansion compliance, thus obtaining a hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments.

[0053] As can be seen from the cross-section of this embodiment, a fluorine-enriched gradient layer is formed on the outermost 5-10 μm of the YSZ surface layer. The fluorine element gradually decreases from the surface inward. YOF solid solution phase and a small amount of YOF / YF3 dispersed phase were detected on the surface layer. The main body of the coating still maintains the original lamellar porous structure.

[0054] In a simulated hydrogen-fueled water vapor environment, a furnace thermal cycling test was conducted on the hydroxyl-resistant surface passivation thermal barrier coating at 1100℃. Each cycle involved holding at high temperature for 30 minutes followed by air cooling to approximately 200℃. The results showed that, under the same conditions, the fluorinated gradient layer coating had approximately 1.3 times the number of failure cycles compared to the untreated YSZ. The surface porosity was more intact, and the increase in thermal conductivity was smaller, indicating that the fluorinated layer effectively inhibited water vapor-induced hydroxylation and sintering densification, thus improving thermal insulation retention and thermal cycling life.

[0055] Example 2: The preparation method of the hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments in this example is carried out according to the following steps:

[0056] Step 1: Using a nickel-based high-temperature alloy sample (25mm×10mm×3mm) as the metal substrate, the surface of the metal substrate is successively polished and sandblasted, ultrasonically cleaned with acetone and anhydrous ethanol, and dried for later use.

[0057] Step 2: An NiCoCrAlY bonding layer is prepared on a metal substrate using atmospheric plasma spraying. The spraying current is controlled at 550A, the voltage at 65V, and the distance between the spray gun and the substrate is 100mm, resulting in a bonding layer with a thickness of approximately 100μm.

[0058] Then, a 150 μm thick YSZ (8 mol% Y₂O₃ stabilized ZrO₂) ceramic transition layer was prepared using atmospheric plasma spraying. A rare-earth-doped lanthanum zirconate topcoat was then prepared by spraying, using powder with the composition of (La) 0.5 Sm 0.25 Gd 0.25 )2Zr2O7, with a spraying thickness of about 150μm, makes the total thickness of the double ceramic layer about 300μm, forming a double ceramic surface layer with obvious lamellar and porous structure;

[0059] Step 3: Dissolve Y(NO3)3·6H2O and (La,Sm,Gd) nitrate in a mixed solvent of deionized water and anhydrous ethanol to prepare a rare earth solution with a total concentration of approximately 0.1 mol / L. Adjust the F / RE molar ratio to 2:1 using NH4F and NH4HF2 as fluorine sources. Add a small amount of citric acid as a complexing agent, stir thoroughly, and age at room temperature for 2 hours to obtain a stable fluorinated rare earth sol. Then, add NiCoCrAlY / YSZ / (La... 0.5 Sm 0.25 Gd 0.25 The metal substrate of the 2Zr2O7 coating was fixed on a heating table (heated to 80°C). Using a pneumatic spray gun, the fluorine-containing rare earth sol was uniformly sprayed onto the outermost rare earth-doped lanthanum zirconate surface at a distance of about 150 mm between the spray gun and the substrate and a spray flow rate of about 0.5 mL / min. After each spraying, the surface was dried at 100°C for 10 min to evaporate the solvent and form a gel layer. Through 5 spraying-drying cycles, a fluorine-containing precursor layer with a thickness of about 6 μm was constructed on the outermost side of the ceramic surface.

[0060] Step 4: Under the protection of an inert gas or air atmosphere, heat to 500℃ at a heating rate of 5℃ / min and hold for 1 hour to decompose the organic components and form a YOF gel framework; then continue heating to 950℃ and hold for 2 hours to allow the F element in the precursor layer to undergo a solid-phase reaction and diffusion with the surface layer of the lower rare earth-doped lanthanum zirconate layer, transforming the fluorine-containing precursor layer into a fluorine-enriched gradient layer (thickness of about 10-15 μm). This gradient layer contains a RE-Zr-OF solid solution phase and a small amount of stable phases such as REOF and REF3, which have low affinity for high-temperature water vapor and hydroxyl groups.

[0061] Step 5: Cool to room temperature in an inert atmosphere without further densification sintering to maintain the original porous / lamellae microstructure and thermal expansion compliance of the ceramic surface layer, resulting in a hydroxyl-resistant surface passivation double ceramic thermal barrier coating for hydrogen mixed fuel environments.

[0062] The cross-sectional SEM and EDS results of this embodiment show that a continuous fluorine-enriched region is formed in the outermost rare earth-doped lanthanum zirconate surface layer. The fluorine element is significantly enriched in the range of about 10 to 15 μm and decays inward. XRD detected the RE-Zr-OF solid solution phase and a small amount of REOF / REF3 diffraction peaks. The main body of the double ceramic layer still maintains the original porous layer structure, indicating that a stable fluorine-enriched gradient layer can be obtained on the surface of the double ceramic layer coating system through the construction of the fluorine-containing precursor layer and the solid phase activation diffusion method.

[0063] In a simulated hydrogen-fuel mixture with water vapor environment, the coating underwent a furnace thermal cycling test at 1100℃. Each cycle was held at high temperature for 30 minutes before air cooling to approximately 200℃. The results showed that, compared to the untreated YSZ / rare-earth-doped lanthanum zirconate bi-ceramic coating, the coating in this embodiment exhibited approximately 1.4 times more failure cycles, retained a more intact surface pore structure, and showed a smaller increase in thermal conductivity. This further demonstrates that the constructed fluorine-enriched gradient layer can effectively suppress high-temperature water vapor-induced hydroxylation and sintering densification, thereby improving the coating's thermal insulation performance and thermal cycling life under hydrogen-fuel mixture conditions.

[0064] In summary, under hydrogen / natural gas mixed combustion or hydrogen combustion conditions, high-temperature water vapor and hydrogen-containing active groups first come into contact with the fluorine-enriched gradient layer. The stable RE-F / RE-Zr-OF bonds and YOF, REF3, etc. in this gradient layer have a relatively low affinity for water molecules and hydroxyl groups, thereby significantly reducing the probability of chemical adsorption and dissociation of water vapor on the coating surface, inhibiting the formation of volatile hydrated species such as RE(OH)3 and the outward migration of rare earth stabilizers, and weakening the sintering and densification effect of water vapor on the surface and grain boundaries. This maintains the long-term stability of the porous / lamellae microstructure and phase composition of the ceramic surface layer, achieving in-situ passivation and chemical shielding against the high-temperature water vapor / hydroxyl environment. Consequently, it significantly improves the thermal barrier coating's ability to maintain thermal insulation performance, corrosion resistance, and thermal cycle service life under hydrogen mixed fuel environment, providing more reliable long-term thermal protection for high-temperature metal substrates.

Claims

1. A hydroxyl resistant surface passivated thermal barrier coating for a hydrogen- blended fuel environment, characterized by The anti-hydroxyl surface passivation thermal barrier coating facing hydrogen mixed fuel environment comprises a metal bonding layer, a ceramic surface layer and a fluorine-rich gradient layer, and the metal bonding layer, the ceramic surface layer and the fluorine-rich gradient layer are sequentially arranged on the metal substrate from bottom to top, the ceramic surface layer is a rare earth oxide doped zirconia ceramic layer and / or a rare earth doped lanthanum zirconate ceramic layer, and the content of F element in the fluorine-rich gradient layer gradually decreases from the surface to the inside. The fluorine-rich gradient layer is formed by spraying a fluorine-containing rare earth sol and then performing heat treatment and solid-phase activation diffusion treatment, the fluorine-containing rare earth sol contains a rare earth precursor and a fluorine source, the rare earth precursor is RE(NO3)3 and / or RE(CH3COO)3, the fluorine source is NH4F and / or NH4HF2, and the molar ratio of F element in the fluorine source to rare earth RE element in the rare earth precursor is 1-3.

2. The hydroxyl group oriented fuel environment for hydrogen fueling surface passivated thermal barrier coating according to claim 1, wherein The metal bonding layer is a NiCoCrAlY bonding layer, and the thickness of the metal bonding layer is 50-200 μm.

3. The hydroxyl group oriented fuel environment for hydrogen fueling surface passivated thermal barrier coating of claim 1 wherein The general chemical formula of the rare earth oxide doped zirconia ceramic layer is (Zr 1-x RE x )O 2-δ , x = 0.01-0.3; the general chemical formula of the rare earth doped lanthanum zirconate ceramic layer is (La 1-y RE y )2Zr2O7, y = 0.01-1.

0.

4. The hydroxyl group facing environmental hydrogen fuel resistant passive heat barrier coating according to claim 1, wherein The thickness of the ceramic surface layer is 50-500 μm.

5. The hydroxyl group oriented fuel environment for hydrogen fueling surface passivated thermal barrier coating of claim 1 wherein The thickness of the fluorine-rich gradient layer is 2-30 μm, and the atomic fraction of F element in the fluorine-rich gradient layer is 0.1-10 at.%.

6. The method for preparing a hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments as described in claim 1, characterized in that... The preparation method of the anti-hydroxyl surface passivation thermal barrier coating is realized according to the following steps: Step one: the surface of the metal substrate is sequentially polished, sandblasted and cleaned, a metal bonding layer is prepared on the surface of the metal substrate by using a spraying process or a physical vapor deposition process, and a substrate with a metal bonding layer is obtained; Step two: a ceramic surface layer is prepared on the surface of the substrate with the metal bonding layer by using a spraying process or a physical vapor deposition process; Step three: a fluorine-containing rare earth sol is prepared by configuring a rare earth precursor and a fluorine source, the fluorine-containing rare earth sol is uniformly sprayed on the surface of the ceramic surface layer, and a fluorine-containing precursor layer is obtained through multiple spraying-drying treatments; Step four: under the protection of an inert gas or air atmosphere, heat treatment is performed by heating to 400-700 ℃ and holding, and then solid-phase activation diffusion treatment is performed by heating to 900-1000 ℃ and holding, so that the fluorine-containing precursor layer is converted into a fluorine-rich gradient layer; Step five: after cooling in an inert atmosphere or air, an anti-hydroxyl surface passivation thermal barrier coating facing a hydrogen mixed fuel environment is obtained; In step two, the ceramic surface layer is a rare earth oxide doped zirconia ceramic layer and / or a rare earth doped lanthanum zirconate ceramic layer; in step three, the rare earth precursor is RE(NO3)3 and / or RE(CH3COO)3, and the fluorine source is NH4F and / or NH4HF2.

7. The method for preparing a hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments according to claim 6, characterized in that... In step one, the metal substrate is a nickel-based superalloy.

8. The method for preparing a hydroxyl-resistant surface passivation thermal barrier coating for hydrogen mixed fuel environments according to claim 6, characterized in that: In steps one and two, the spraying process is an atmospheric plasma spraying process, a vacuum plasma spraying process or a suspension plasma spraying process; and the physical vapor deposition process is an electron beam physical vapor deposition process.

9. The method of claim 6, wherein the hydrogen-facing, mixed-fuel environment, hydroxyl- resistant, passivated thermal barrier coating is prepared by In step three, the thickness of the fluorine-containing precursor layer is 1-10 μm.

10. The method of claim 6, wherein the hydrogen-facing, mixed-fuel environment, hydroxyl- resistant, passivated thermal barrier coating is prepared by In step four, the heat treatment is performed by heating to 400-700 ℃ at a heating rate of 5-15 ℃ / min and holding for 0.5-2 h, and then the solid-phase activation diffusion treatment is performed by heating to 900-1000 ℃ and holding for 1-3 h.

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