A thickness-adjustable thermal barrier / high-emissivity dual ceramic coating and a method for preparing the same

Abstract

This invention belongs to the field of surface thermal protection coating technology, and relates to a thermal barrier / high emissivity dual ceramic coating with adjustable thickness and its preparation method. The coating has a multi-layered structure, comprising, from the inside out, a metal bonding layer, a thermal barrier ceramic layer, and a high emissivity layer. The metal bonding layer is a NiCrAlY alloy bonding layer or a CoNiCrAlY alloy bonding layer. The ceramic layer is a multi-principal rare earth zirconate (RE2Zr2O7, RE=La / Nd / Sm / Eu / Gd) ceramic layer with low thermal conductivity. The high emissivity layer is a Sr-doped lanthanum ferrite layer. The dual ceramic coating of this invention has a gradient structure design, which can effectively alleviate the thermal mismatch stress caused by the difference in thermal expansion coefficients between the materials in each layer. Combining the high emissivity material, the low thermal conductivity material, and the metal bonding layer can reduce the heat conduction of high-temperature airflow to the substrate while enhancing the thermal radiation of the coating surface, greatly reducing the thermal load on the substrate.

Description

Technical Field

[0001] This invention belongs to the field of surface thermal protection coating technology, and relates to a thermal barrier / high emissivity dual ceramic coating with adjustable thickness and its preparation method. Background Technology

[0002] With the development of science and technology, the metal materials used in hot-end components must be able to operate stably under extreme temperatures and harsh conditions to meet the stringent requirements of emerging application scenarios. For example, aero-engines with high thrust-to-weight ratios operate at temperatures reaching 1200℃. These components frequently experience high temperatures and thermal shocks during normal use, making their surfaces prone to oxidation corrosion, stress concentration, coating cracking, or peeling, thus reducing their service life. Thermal barrier coatings can effectively resist adverse conditions such as high temperatures, oxidation, and corrosion. The low thermal conductivity of the coating can insulate heat from the outside, protecting turbine blades for normal operation at high temperatures. When the thickness of the thermal barrier coating is 0.1mm~0.5mm, a temperature reduction of 100~300℃ can be achieved.

[0003] Minimizing heat transfer to the metal substrate while reducing thermal conduction and enhancing thermal radiation are advanced techniques for improving the lifespan of hot-end components. A typical thermal barrier ceramic material, La₂Zr₂O₇, possesses a high melting point (2300℃) and low thermal conductivity (1.56 W·m⁻¹). -1 ·K -1 Rare earth zirconates (REEs) are highly valuable thermal insulation materials for high-temperature service conditions due to their oxygen impermeability and other properties. However, the multi-principal element design at RE sites leads to a mismatch in atomic mass and ionic radius, as well as an increase in phonon scattering centers caused by chemical bond fluctuations and local lattice distortions, directly reducing the phonon mean free path. Therefore, multi-principal element REEs can further reduce thermal conductivity. Common high-emissivity materials include spinel, cordierite, and La-based perovskites, and lattice doping can effectively improve their emissivity in the near-infrared band. LaFeO3 has a high emissivity in the 3-5 μm band and a thermal expansion coefficient close to that of high-temperature alloy substrates, exhibiting good stability under high-temperature service conditions. It remains very stable even after 50 cycles of thermal shock at 800℃. Furthermore, for the near-infrared band, lattice doping can introduce impurity energy levels, thereby reducing the band gap width, increasing the possibility of electron transitions, enhancing free carrier absorption, and further improving the material's emissivity. To achieve this goal, the thermal barrier coating is designed as a multi-layer structure, including a thermal barrier ceramic layer and a high-emissivity surface layer. However, interfacial failures due to thermal mismatch between multilayer structures can lead to shortened service life. Therefore, fabricating a thermal barrier coating with long service life and high emissivity and low thermal conductivity within a high temperature range is a technical challenge that researchers in this field need to overcome. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems mentioned in the background art and to provide a thermal barrier / high emissivity dual ceramic coating with adjustable thickness and its preparation method.

[0005] To achieve the above objectives, the present invention provides a thermal barrier / high emissivity dual ceramic coating with adjustable thickness. The coating has a multilayer stacked structure, comprising, from the inside out, a metal bonding layer, a thermal barrier ceramic layer, and a high emissivity layer. The metal bonding layer is a NiCrAlY alloy bonding layer or a CoNiCrAlY alloy bonding layer. The thermal barrier ceramic layer is a RE2Zr2O7 ceramic layer, wherein RE is one or more of La, Nd, Sm, Eu, and Gd. The high emissivity layer is a Sr-doped LaFeO3 layer.

[0006] Preferably, in the above-mentioned thermal barrier / high emissivity dual ceramic coating, the thickness of the metal bonding layer is 0.05mm~0.10mm, the thickness of the thermal barrier ceramic layer is 0.80mm~1.00mm, and the thickness of the high emissivity layer is 0.05mm~0.20mm.

[0007] Preferably, in the above-mentioned thermal barrier / high emissivity dual ceramic coating, the thermal barrier ceramic layer is a multi-principal rare earth zirconate ceramic layer doped with La, Nd, Sm, Eu, and Gd in a stoichiometric ratio, more specifically, (La... 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic layer.

[0008] Preferably, in the above-mentioned thermal barrier / high emissivity dual ceramic coating, the high emissivity layer is La. 0.8 Sr 0.2 FeO3 layer.

[0009] The composite coating design of this invention is mainly based on the following principles: rare earth zirconate materials, such as La2Zr2O7, have a high melting point (2300℃) and low thermal conductivity (1.56 W·m at 1000℃). -1 ·K -1 Furthermore, the thermal conductivity of the La2Zr2O7 coating prepared by APS is as low as 0.74 W·m. -1 ·K -1Furthermore, La2Zr2O7 exhibits good resistance to sintering, low oxygen ion permeability, and resistance to CMAS molten salt corrosion, thus it can be used as a thermal barrier layer to protect thermal barrier coating systems and extend their service life. The lattice distortion, structural disorder, and chemical bond inhomogeneity induced by multi-element rare earth element doping produce a "cocktail effect," significantly affecting the mechanical properties of materials. With the increase of the number of principal units in multi-element rare earth zircons, the material's thermal stability, thermal conductivity, and thermal expansion matching properties can be improved through lattice distortion and hysteresis diffusion effects. This is because the multi-principal unit design at RE sites leads to a mismatch in atomic mass and ionic radius, and the increase in phonon scattering centers caused by chemical bond fluctuations and local lattice distortion directly reduces the phonon mean free path. Therefore, most multi-element rare earth zircons can achieve lower thermal conductivity. LaFeO3 is a typical perovskite structure high-emissivity material with a melting point of 1900℃ and a stable crystal structure. By substituting A-sites with ions of similar radius as impurities, the infrared emissivity of this material in the 3–5 μm wavelength range can be improved. Addressing the application requirements of aero-engines, and based on the thermophysical properties of high-temperature Ni-based alloys, this invention, following the design concept of thermal barrier coatings and combining atmospheric plasma spraying technology, utilizes the high emissivity of LaFeO3 material and the excellent thermal insulation and oxygen barrier properties of RE2Zr2O7 ceramic coating to prepare a thermal barrier / high emissivity integrated coating with adjustable thickness. This coating simultaneously possesses thermal insulation and heat dissipation properties, addressing the issues of low temperature resistance and short service life of alloy substrates under high-temperature service conditions. The coating thickness is adjustable, allowing for comprehensive control of coating thickness, thermal insulation performance, and mechanical properties to meet different application requirements, effectively improving the service reliability of aero-engines.

[0010] On the other hand, the present invention also provides a method for preparing the above-mentioned thermal barrier / high emissivity dual ceramic coating, comprising the following steps: (1) Preparation of RE2Zr2O7 ceramic spray powder and Sr-doped LaFeO3 spray powder; (2) The high-temperature Ni-based alloy substrate is placed in a sandblasting machine for roughening treatment, and an atmospheric plasma spraying process is used to prepare a metal bonding layer on the surface of the substrate after sandblasting. (3) The RE2Zr2O7 ceramic powder is coated onto the surface of the metal bonding layer obtained in step (2) by atmospheric plasma spraying process to obtain the thermal barrier ceramic layer; (4) The Sr-doped LaFeO3 spray powder is coated onto the surface of the thermal barrier ceramic layer obtained in step (3) by atmospheric plasma spraying process to obtain a high emissivity layer.

[0011] Preferably, in the above preparation method, the process parameters for sandblasting in step (2) are: pressure of 0.3~0.5MPa, sandblasting distance of 80~150mm, sand size of 12~306 mesh, and sandblasting time of 1~5min; the parameters for preparing the metal bonding layer are: argon flow rate of 30~50L / min, hydrogen flow rate of 1~3L / min, current control of 500~550A, power of 25~40kW; powder feeding amount of 10~35 g / min, and spraying distance of 80~130mm.

[0012] Preferably, in the above preparation method, in step (3), the atmospheric plasma spraying parameters are: argon flow rate of 30~50L / min, current of 500~600A, power of 35~45kW; hydrogen flow rate of 1.0~3.0L / min, powder feeding amount of 10~30g / min; and spraying distance of 80~120mm.

[0013] Preferably, in the above preparation method, in step (4), the atmospheric plasma spraying parameters are: argon flow rate of 30~70L / min, current of 350~650A, power of 25~65kW; hydrogen flow rate of 2.0~8.0L / min, powder feeding amount of 15~40g / min; and spraying distance of 80~140mm.

[0014] Preferably, in the above preparation method, step (1) of preparing RE2Zr2O7 ceramic spray powder and Sr-doped LaFeO3 ceramic powder includes the following steps: ① Synthesis of RE2Zr2O7 ceramic powder: Rare earth oxide (RE2O3) and zirconium oxide (ZrO2) raw material powders are subjected to high-temperature heat treatment to remove excess impurities and crystal water. The rare earth oxide, zirconium oxide and deionized water are mixed evenly according to the stoichiometric ratio. The mixture is then obtained by wet ball milling. The mixture is then dried in a forced-air drying oven, ground and sieved to obtain a mixed powder. The mixed powder is then placed in a muffle furnace for high-temperature solid-state reaction. After the reaction, the powder obtained is ground and sieved to obtain RE2Zr2O7 ceramic powder. ② Synthesis of Sr-doped LaFeO3 ceramic powder: Lanthanum oxide raw material powder was subjected to high-temperature heat treatment to remove excess impurities and water of crystallization. Lanthanum oxide (La2O3), iron oxide (Fe2O3), strontium carbonate (SrCO3), and deionized water were mixed evenly according to stoichiometric ratio. The mixture was then wet-milled to obtain a homogeneous slurry. The slurry was then dried in a forced-air drying oven, ground, and sieved to obtain a mixed powder. The mixed powder was then placed in a muffle furnace for a high-temperature solid-state reaction. After the reaction, the resulting powder was ground and sieved to obtain Sr-doped LaFeO3 ceramic powder. ③ The RE2Zr2O7 ceramic powder and Sr-doped LaFeO3 ceramic powder synthesized in steps ① and ② are mixed with deionized water, gum arabic, and triammonium citrate in proportion, respectively. The mixture is then uniformly mixed by wet ball milling and centrifugal spray drying to prepare RE2Zr2O7 ceramic spray powder and Sr-doped LaFeO3 ceramic powder with certain flowability and uniform particle size distribution, respectively.

[0015] Preferably, in the above preparation method, in step ①, the heat treatment temperature is 800~1200℃, the heat treatment time is 2~4h, the raw material powder is mixed evenly using a horizontal ball mill, the mass ratio of deionized water:ceramic powder:zirconia grinding beads is 1:1:1.5, the ball mill speed is 300~500r / min, the ball milling time is 12~72h, the ceramic slurry drying temperature is 80~150℃, the drying time is 24~72h, and the ground powder is sieved through an 80~100 mesh sieve; the high-temperature solid-phase synthesis temperature is 800~1600℃, and the synthesis time is 12~48h. In step ②, the heat treatment temperature is 800~1200℃, the heat treatment time is 2~4h, the raw material powder is mixed evenly using a horizontal ball mill, the mass ratio of deionized water:ceramic powder:zirconia grinding beads is 1:1:1.5, the ball mill speed is 300~500 r / min, the ball milling time is 12~72h, the slurry drying temperature is 80~150℃, the drying time is 24~72h, and the ground powder is sieved through an 80~100 mesh sieve. The high-temperature solid-phase synthesis temperature is 800~1400℃, and the synthesis time is 12~48h. In step ③, when RE2Zr2O7 ceramic powder or Sr-doped LaFeO3 ceramic powder is mixed with deionized water, gum arabic, and triammonium citrate into the ball mill jar, the mass fraction of deionized water is controlled to be 40-80%, the mass fraction of gum arabic powder is 1-5%, the mass fraction of triammonium citrate is 1-5%, and the remainder is RE2Zr2O7 ceramic powder or Sr-doped LaFeO3 ceramic powder. The wet ball milling process is carried out on a horizontal ball mill with a rotation speed of 300-800 r / min and a stirring time of 36-72 h. In the spray drying process, the inlet temperature is controlled to be 200-270℃ and the outlet temperature is controlled to be 120-160℃.

[0016] Compared with existing technologies, the present invention has the following advantages: 1. This invention utilizes the low thermal conductivity, high thermal conductivity coefficient, high temperature phase stability characteristics of multi-principal rare earth zirconates and the high emissivity characteristics of Sr-doped LaFeO3 to enable the double ceramic coating to have both heat insulation and heat dissipation functions in high-temperature service environments.

[0017] 2. The thermal barrier / high emissivity dual ceramic coating of the present invention is designed with a gradient structure, which helps to alleviate the thermal stress caused by the thermal expansion mismatch at the interface, improves the bonding strength between the coating and the substrate, and enhances the thermal shock resistance of the coating.

[0018] 3. The thickness of the thermal barrier / high emissivity dual ceramic coating in this invention is adjustable. The thickness of the coating can be adjusted to meet the requirements of different service environments in order to control the heat dissipation and heat insulation performance.

[0019] 4. The thermal barrier / high emissivity dual ceramic coating preparation process of this invention is simple, mature and stable. The coating thickness is uniform on the surface of complex and irregular curved components. It is low in cost and easy to scale up production and application. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the adjustable-thickness thermal barrier / high-emissivity dual ceramic coating structure in this invention; Figure 2 The surface morphology of the coating in the embodiments of the present invention are as follows: (a) Comparative Example 1; (b) Example 1; (c) Example 2; Figure 3 The following are the thermal insulation performance curves of the thermal barrier / high emissivity dual ceramic coating in Embodiment 1 of the present invention: (b) 1200℃; (c) 1400℃.

[0022] Key diagram descriptions: 1-Substrate, 2-Metal bonding layer, 3-Thermal barrier ceramic layer, 4-High emissivity layer. Detailed Implementation

[0023] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in the present invention are commercially available or can be prepared by existing methods.

[0024] Example 1 like Figure 1As shown, a dual-ceramic coating with adjustable thickness, consisting of a thermal barrier / high emissivity layer, is a multi-layered structure. From the inside out, it comprises a NiCrAlY metal binder layer, a thermal barrier ceramic layer, and a high emissivity layer. The thermal barrier ceramic layer is (La...) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 The ceramic layer is 2Zr2O7, and the high emissivity layer is La. 0.8 Sr 0.2 FeO3 ceramic layer.

[0025] The thickness of the metal bonding layer is 0.1 mm, the thickness of the thermal barrier ceramic layer is 0.9 mm, the thickness of the high emissivity layer is 0.1 mm, and the total coating thickness is 1.1 mm.

[0026] A method for preparing a thermal barrier / high emissivity dual ceramic coating with adjustable thickness includes the following steps: (1) (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 spray powder and La 0.8 Sr 0.2 Synthesis of FeO3: ① ZrO2 and raw material powders of Sm2O3, La2O3, Gd2O3, Nd2O3, and Eu2O3 are subjected to high-temperature heat treatment to remove excess impurities and water of crystallization. ZrO2, Sm2O3, La2O3, Gd2O3, Nd2O3, Eu2O3, and deionized water are then mixed uniformly according to stoichiometric ratios. A uniformly mixed slurry is obtained through wet ball milling. The slurry is then dried in a forced-air drying oven, ground, and sieved to obtain a mixed powder. The mixed powder is then subjected to a high-temperature solid-state reaction in a muffle furnace. After the reaction, the resulting powder is ground and sieved to obtain (La2O3)2O3 powder. 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic powder; ②La 0.8 Sr 0.2 Synthesis of FeO3 ceramic powder: La2O3 raw material powder is subjected to high-temperature heat treatment to remove excess impurities and water of crystallization. La2O3, Fe2O3, SrCO3, and deionized water are mixed uniformly according to stoichiometric ratios. A uniformly mixed slurry is obtained through wet ball milling. The slurry is then dried in a forced-air drying oven, ground, and sieved to obtain a mixed powder. This mixed powder is then subjected to a high-temperature solid-state reaction in a muffle furnace. After the reaction, the resulting powder is ground and sieved to obtain La2O3 ceramic powder. 0.8 Sr0.2 FeO3 ceramic powder; ③ Powder synthesis: The powder synthesized in steps ① and ② (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic powder and La 0.8 Sr 0.2 FeO3 ceramic powder was mixed with deionized water, gum arabic, and triammonium citrate in specific proportions, and then uniformly mixed using a wet ball milling process. Finally, it was prepared into a powder with certain flowability and uniform particle size distribution using a centrifugal spray drying process. 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 spray powder and La 0.8 Sr 0.2 FeO3 spray powder; In step ①, the heat treatment temperature is 1000℃, the heat treatment time is 2h, the raw material powder is mixed evenly using a horizontal ball mill, the mass ratio of deionized water:ceramic powder:zirconia ball mill beads is 1:1:1.5, the ball mill speed is 400r / min, the stirring time is 72h, the slurry drying temperature is 150℃, the drying time is 48h, and the ground powder is sieved through an 80-mesh sieve; the high-temperature solid-phase synthesis temperature is 1600℃, and the synthesis time is 48h. In step ②, the heat treatment temperature is 1000℃, the heat treatment time is 2 hours, and the raw material powder is mixed evenly using a horizontal ball mill. The mass ratio of deionized water:ceramic powder:zirconia grinding beads is 1:1:1.5. The ball mill speed is 400 r / min, the stirring time is 24 hours, the slurry drying temperature is 150℃, and the drying time is 72 hours. The ground powder is then sieved through an 80-mesh sieve. The high-temperature solid-phase synthesis temperature is 1300℃, and the synthesis time is 12 hours. In step ③, (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic powder or La 0.8 Sr 0.2 When FeO3 ceramic powder is mixed with deionized water, gum arabic, and triammonium citrate in a ball mill jar, the mass fraction of deionized water is 50%, the mass fraction of gum arabic powder is 3%, the mass fraction of triammonium citrate is 1%, and the remainder is (La... 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd0.2 )2Zr2O7 ceramic powder or La 0.8 Sr 0.2 FeO3 ceramic powder; the wet ball milling process involves mixing in a horizontal ball mill with a deionized water:ceramic powder:zirconia balls mass ratio of 1:1:1.5, the rotation speed of the horizontal ball mill being 480 r / min, and the stirring time being 48 h; the spray drying process controls the inlet temperature to be 250℃ and the outlet temperature to be 120℃.

[0027] (2) Substrate roughening: The high-temperature Ni-based alloy substrate was placed in a sandblasting machine for roughening treatment. The sandblasting process parameters were: pressure of 0.4 MPa, sandblasting distance of 100 mm, sand size of 24 mesh, and sandblasting time of 3 min. An atmospheric plasma spraying process was used to prepare a metal bonding layer on the surface of the substrate after sandblasting. The metal bonding layer preparation parameters were: argon flow rate of 46 L / min, hydrogen flow rate of 2.6 L / min, current control of 550 A, power of 38 kW, powder feeding rate of 25 g / min, and spraying distance of 120 mm. (3) (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 Preparation of the 2Zr2O7 ceramic layer: The (La) ceramic layer was prepared using an atmospheric plasma spraying process. 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 spray powder is applied to the surface of the metal bonding layer obtained in step (2) to obtain (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 thermal barrier ceramic layer. Atmospheric plasma spraying parameters are: argon flow rate 36 L / min, current control 600A, power 42kW; hydrogen flow rate 1.5 L / min, powder feed rate 24 g / min; spraying distance 120mm; (4) La 0.8 Sr 0.2 Preparation of a high emissivity FeO3 layer: La was coated using an atmospheric plasma spraying process. 0.8 Sr 0.2 FeO3 spray powder coating is applied to the (La) obtained in step (3). 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2La was obtained on the surface of the 2Zr2O7 thermal barrier ceramic layer. 0.8 Sr 0.2 FeO3 high emissivity layer. Atmospheric plasma spraying parameters are: argon flow rate 50 L / min, current control 400 A, power 40 kW; hydrogen flow rate 2 L / min, powder feed rate 20 g / min; spraying distance 130 mm. The morphology of the thermal barrier / high emissivity dual ceramic coating prepared in this embodiment is as follows: Figure 2 As shown in (b), the total coating thickness is 1.1 mm, the bonding strength of the coating at room temperature is 11.2 MPa, and the coating has a lifespan of 35 cycles after water cooling at 900℃. The infrared emissivity of the coating at 1100℃ is 0.85. The measured temperature differences between the upper and lower surfaces of the coating at 1200℃ and 1400℃ are 224.35℃ and 209.62℃, respectively. Figure 3 As shown in the figure, the surface temperature and internal temperature refer to the upper and lower surface temperatures of the coating, respectively. The internal temperature is measured by a thermocouple through a pre-set temperature measuring hole near the coating end of the metal substrate. The results show that the thermal barrier / high emissivity dual ceramic coating prepared in this embodiment has excellent thermal shock resistance and thermal insulation performance.

[0028] Example 2 A multi-layered, adjustable-thickness thermal barrier / high emissivity dual-ceramic coating comprises, from the inside out, a NiCrAlY metal binder layer, a thermal barrier ceramic layer, and a high emissivity layer. The thermal barrier ceramic layer is (La... 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 The ceramic layer is 2Zr2O7, and the high emissivity layer is La. 0.8 Sr 0.2 FeO3 ceramic layer.

[0029] The thickness of the metal bonding layer is 0.1 mm, the thickness of the thermal barrier ceramic layer is 0.8 mm, the thickness of the high emissivity layer is 0.2 mm, and the total coating thickness is 1.1 mm.

[0030] A method for preparing a thermal barrier / high emissivity dual ceramic coating with adjustable thickness includes the following steps: (1) (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 Synthesis of Zr2O7 ceramic powder: ① ZrO2 and raw material powders of Sm2O3, La2O3, Gd2O3, Nd2O3, and Eu2O3 are subjected to high-temperature heat treatment to remove excess impurities and water of crystallization. ZrO2, Sm2O3, La2O3, Gd2O3, Nd2O3, Eu2O3, and deionized water are then mixed uniformly according to stoichiometric ratios. A uniformly mixed slurry is obtained through wet ball milling. The slurry is then dried in a forced-air drying oven, ground, and sieved to obtain a mixed powder. The mixed powder is then subjected to a high-temperature solid-state reaction in a muffle furnace. After the reaction, the resulting powder is ground and sieved to obtain (La2O3)2O3 powder. 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic powder; ②La 0.8 Sr 0.2 Synthesis of FeO3 ceramic powder: La2O3 raw material powder is subjected to high-temperature heat treatment to remove excess impurities and water of crystallization. La2O3, Fe2O3, SrCO3, and deionized water are mixed uniformly according to stoichiometric ratios. A uniformly mixed slurry is obtained through wet ball milling. The slurry is then dried in a forced-air drying oven, ground, and sieved to obtain a mixed powder. This mixed powder is then subjected to a high-temperature solid-state reaction in a muffle furnace. After the reaction, the resulting powder is ground and sieved to obtain La2O3 ceramic powder. 0.8 Sr 0.2 FeO3 ceramic powder; ③ Powder synthesis: The powder synthesized in steps ① and ② (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic powder and La 0.8 Sr 0.2 FeO3 ceramic powder was mixed with deionized water, gum arabic, and triammonium citrate in specific proportions, and then uniformly mixed using a wet ball milling process. Finally, it was prepared into a powder with certain flowability and uniform particle size distribution using a centrifugal spray drying process. 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 spray powder and La 0.8 Sr 0.2 FeO3 spray powder; In step ①, the heat treatment temperature is 1000℃, the heat treatment time is 2 hours, and the raw material powder is mixed evenly using a horizontal ball mill. The mass ratio of deionized water:ceramic powder:zirconia grinding beads is 1:1:1.5. The ball mill speed is 400 r / min, the stirring time is 72 hours, the slurry drying temperature is 150℃, and the drying time is 48 hours. The ground powder is then sieved through an 80-mesh sieve. The high-temperature solid-phase synthesis temperature is 1600℃, and the synthesis time is 48 hours. In step ②, the heat treatment temperature is 1000℃, the heat treatment time is 2 hours, and the raw material powder is mixed evenly using a horizontal ball mill. The mass ratio of deionized water:ceramic powder:zirconia grinding beads is 1:1:1.5. The ball mill speed is 400 r / min, the stirring time is 24 hours, the slurry drying temperature is 150℃, and the drying time is 72 hours. The ground powder is then sieved through an 80-mesh sieve. The high-temperature solid-phase synthesis temperature is 1300℃, and the synthesis time is 12 hours. In step ③, (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic powder or La 0.8 Sr 0.2 When FeO3 ceramic powder is mixed with deionized water, gum arabic, and triammonium citrate in a ball mill jar, the mass fraction of deionized water is 50%, the mass fraction of gum arabic powder is 3%, the mass fraction of triammonium citrate is 1%, and the remainder is (La... 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic powder or La 0.8 Sr 0.2 FeO3 ceramic powder; the wet ball milling process involves mixing in a horizontal ball mill with a rotation speed of 480 r / min and a stirring time of 48 h; the spray drying process controls the inlet temperature to be 250℃ and the outlet temperature to be 120℃.

[0031] (2) Substrate roughening: The high-temperature Ni-based alloy substrate was placed in a sandblasting machine for roughening treatment. The sandblasting process parameters were: pressure of 0.4 MPa, sandblasting distance of 100 mm, sand size of 24 mesh, and sandblasting time of 3 min. An atmospheric plasma spraying process was used to prepare a metal bonding layer on the surface of the substrate after sandblasting. The metal bonding layer preparation parameters were: argon flow rate of 46 L / min, hydrogen flow rate of 2.6 L / min, current control of 550 A, power of 38 kW, powder feeding rate of 25 g / min, and spraying distance of 120 mm. (3) (La)0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 Preparation of the 2Zr2O7 ceramic layer: The (La) ceramic layer was prepared using an atmospheric plasma spraying process. 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 spray powder is applied to the surface of the metal bonding layer obtained in step (2) to obtain (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 thermal barrier ceramic layer. Atmospheric plasma spraying parameters are: argon flow rate 36L / min, current control 600A, power 42kW; hydrogen flow rate 1.5L / min, powder feed rate 24g / min; spraying distance 120mm; (4) La 0.8 Sr 0.2 Preparation of a high emissivity FeO3 layer: La was coated using an atmospheric plasma spraying process. 0.8 Sr 0.2 FeO3 spray powder coating is applied to the (La) obtained in step (3). 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 La was obtained on the surface of the 2Zr2O7 thermal barrier ceramic layer. 0.8 Sr 0.2 FeO3 high emissivity layer. Atmospheric plasma spraying parameters are: argon flow rate 50 L / min, current control 400 A, power 40 kW; hydrogen flow rate 2 L / min, powder feed rate 20 g / min; spraying distance 130 mm. The morphology of the thermal barrier / high emissivity dual ceramic coating prepared in this embodiment is as follows: Figure 2 As shown in (c), the total coating thickness is 1.1 mm, the bonding strength of the coating at room temperature is 12.2 MPa, and the coating has a lifespan of 45 cycles after water cooling at 900℃. The infrared emissivity of the coating at 1100℃ is 0.88, and the measured temperature difference between the upper and lower surfaces of the coating at 1400℃ is 160.35℃. The results indicate that the thermal barrier / high emissivity dual-ceramic coating prepared in this embodiment has excellent thermal shock resistance and thermal insulation performance.

[0032] Comparative Example 1 A thermal barrier coating has a multi-layered structure, comprising, from the inside out, a NiCrAlY metal binder layer and a thermal barrier ceramic layer, wherein the thermal barrier ceramic layer is (La...0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic layer.

[0033] The thickness of the metal bonding layer is 0.1 mm, the thickness of the thermal barrier ceramic layer is 1 mm, and the total coating thickness is 1.1 mm.

[0034] A method for preparing a thermal barrier coating includes the following steps: (1) (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 Synthesis of Zr2O7 ceramic powder: ① ZrO2 and raw material powders of Sm2O3, La2O3, Gd2O3, Nd2O3, and Eu2O3 are subjected to high-temperature heat treatment to remove excess impurities and water of crystallization. ZrO2, Sm2O3, La2O3, Gd2O3, Nd2O3, Eu2O3, and deionized water are then mixed uniformly according to stoichiometric ratios. A uniformly mixed slurry is obtained through wet ball milling. The slurry is then dried in a forced-air drying oven, ground, and sieved to obtain a mixed powder. The mixed powder is then subjected to a high-temperature solid-state reaction in a muffle furnace. After the reaction, the resulting powder is ground and sieved to obtain (La2O3)2O3 powder. 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic powder; ② Powder synthesis: The powder synthesized in step ① (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 Zr₂O₇ ceramic powder was mixed with deionized water, gum arabic, and triammonium citrate in a specific ratio, and then uniformly mixed using a wet ball milling process. Finally, it was prepared into a (La) powder with certain flowability and uniform particle size distribution using a centrifugal spray drying process. 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 spray powder; In step ①, the heat treatment temperature is 1000℃, the heat treatment time is 2h, the raw material powder is mixed evenly using a horizontal ball mill, the mass ratio of deionized water:ceramic powder:zirconia ball mill beads is 1:1:1.5, the ball mill speed is 400 r / min, the stirring time is 72h, the slurry drying temperature is 150℃, the drying time is 48h, and the ground powder is sieved through an 80-mesh sieve; the high-temperature solid-phase synthesis temperature is 1600℃, and the synthesis time is 48h. In step ②, (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 When Zr₂O₇ ceramic powder is mixed with deionized water, gum arabic, and triammonium citrate in a ball mill jar, the mass fraction of deionized water is 50%, the mass fraction of gum arabic powder is 3%, the mass fraction of triammonium citrate is 1%, and the remainder is (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 ceramic powder; the wet ball milling process is carried out on a horizontal ball mill with a rotation speed of 480 r / min and a stirring time of 48h; the spray drying process controls the inlet temperature to be 250℃ and the outlet temperature to be 120℃.

[0035] (2) Substrate roughening: The high-temperature Ni-based alloy substrate was placed in a sandblasting machine for roughening treatment. The sandblasting process parameters were: pressure of 0.4 MPa, sandblasting distance of 100 mm, sand size of 24 mesh, and sandblasting time of 3 min. An atmospheric plasma spraying process was used to prepare a metal bonding layer on the surface of the substrate after sandblasting. The metal bonding layer preparation parameters were: argon flow rate of 46 L / min, hydrogen flow rate of 2.6 L / min, current control of 550 A, power of 38 kW, powder feeding rate of 25 g / min, and spraying distance of 120 mm. (3) (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 Preparation of the 2Zr2O7 ceramic layer: The (La) ceramic layer was prepared using an atmospheric plasma spraying process. 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )2Zr2O7 powder is coated onto the surface of the metal bonding layer obtained in step (2) to obtain (La 0.2 Nd 0.2 Sm 0.2 Eu0.2 Gd 0.2 )2Zr2O7 thermal barrier ceramic layer. Atmospheric plasma spraying parameters are: argon flow rate 36 L / min, current control 600A, power 42kW; hydrogen flow rate 1.5 L / min, powder feed rate 24 g / min; spraying distance 120mm; The (La) prepared in this comparative example 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 The 2Zr2O7 thermal barrier ceramic coating served as a blank control group, with the morphology as shown below. Figure 2 As shown in (a), the total coating thickness is 1.1 mm, the bonding strength of the coating at room temperature is 10.8 MPa, and the coating has a lifespan of 35 cycles after water cooling at 900℃. The infrared emissivity of the coating at 900℃ and 1100℃ is 0.44 and 0.53, respectively, and the measured temperature difference between the upper and lower surfaces of the coating at 1400℃ is 145.35℃.

[0036] Comparative Example 2 A ceramic coating has a multi-layered structure, comprising, from the inside out, a NiCrAlY metal binder layer and a high-emissivity layer. The high-emissivity layer is La. 0.8 Sr 0.2 FeO3 ceramic layer.

[0037] The thickness of the metal bonding layer is 0.1 mm, and the thickness of the high emissivity layer is 1 mm.

[0038] A method for preparing a thermal barrier / high emissivity dual ceramic coating with adjustable thickness includes the following steps: (1) La 0.8 Sr 0.2 Synthesis of FeO3: ①La 0.8 Sr 0.2 Synthesis of FeO3 ceramic powder: La2O3 raw material powder is subjected to high-temperature heat treatment to remove excess impurities and water of crystallization. La2O3, Fe2O3, SrCO3, and deionized water are mixed uniformly according to stoichiometric ratios. A uniformly mixed slurry is obtained through wet ball milling. The slurry is then dried in a forced-air drying oven, ground, and sieved to obtain a mixed powder. This mixed powder is then subjected to a high-temperature solid-state reaction in a muffle furnace. After the reaction, the resulting powder is ground and sieved to obtain La2O3 ceramic powder. 0.8 Sr 0.2 FeO3 ceramic powder; ② Synthesis of the powder to be sprayed: The La synthesized in step ① 0.8 Sr 0.2FeO3 ceramic powder was mixed with deionized water, gum arabic, and triammonium citrate in specific proportions, and then uniformly mixed using a wet ball milling process. Finally, it was prepared into La ceramic powder with certain flowability and uniform particle size distribution using a centrifugal spray drying process. 0.8 Sr 0.2 FeO3 spray powder; In step ①, the heat treatment temperature is 1000℃, the heat treatment time is 2 hours, and the raw material powder is mixed evenly using a horizontal ball mill. The mass ratio of deionized water:ceramic powder:zirconia grinding beads is 1:1:1.5. The ball mill speed is 400 r / min, the stirring time is 24 hours, the slurry drying temperature is 150℃, and the drying time is 72 hours. The ground powder is then sieved through an 80-mesh sieve. The high-temperature solid-phase synthesis temperature is 1300℃, and the synthesis time is 12 hours. In step ②, La 0.8 Sr 0.2 When FeO3 ceramic powder is mixed with deionized water, gum arabic, and triammonium citrate in a ball mill jar, the mass fraction of deionized water is 50%, the mass fraction of gum arabic powder is 3%, the mass fraction of triammonium citrate is 1%, and the remainder is La. 0.8 Sr 0.2 FeO3 ceramic powder; the wet ball milling process involves mixing in a horizontal ball mill with a rotation speed of 480 r / min and a stirring time of 48 h; the spray drying process controls the inlet temperature to be 250℃ and the outlet temperature to be 120℃.

[0039] (2) Substrate roughening: The high-temperature Ni-based alloy substrate was placed in a sandblasting machine for roughening treatment. The sandblasting process parameters were: pressure of 0.4 MPa, sandblasting distance of 100 mm, sand size of 24 mesh, and sandblasting time of 3 min. An atmospheric plasma spraying process was used to prepare a metal bonding layer on the surface of the substrate after sandblasting. The metal bonding layer preparation parameters were: argon flow rate of 46 L / min, hydrogen flow rate of 2.6 L / min, current control of 550 A, power of 38 kW, powder feeding rate of 25 g / min, and spraying distance of 120 mm. (2) La 0.8 Sr 0.2 Preparation of a high emissivity FeO3 layer: La was coated using an atmospheric plasma spraying process. 0.8 Sr 0.2 FeO3 spray powder coating is applied to the (La) obtained in step (3). 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 La was obtained on the surface of the 2Zr2O7 thermal barrier ceramic layer. 0.8 Sr 0.2FeO3 high emissivity layer. Atmospheric plasma spraying parameters are: argon flow rate 50 L / min, current control 400 A, power 40 kW; hydrogen flow rate 2 L / min, powder feed rate 20 g / min; spraying distance 130 mm. The ceramic coating prepared in this comparative example has a thickness of 1.1 mm. At room temperature, the coating exhibits a bonding strength of 9.5 MPa and a lifespan of 32 cycles after water cooling at 900℃. The infrared emissivity of the coating at 1100℃ is 0.88, and the measured temperature difference between the upper and lower surfaces of the coating at 1400℃ is 101.40℃.

[0040] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A dual ceramic coating with adjustable thickness for thermal barrier and high emissivity, characterized in that, The coating is a multi-layered structure, consisting of a metal bonding layer, a thermal barrier ceramic layer, and a high emissivity layer from the inside out. The thermal barrier ceramic layer is a RE2Zr2O7 ceramic layer, where RE is one or more of La, Nd, Sm, Eu, and Gd. The high emissivity layer is a Sr-doped LaFeO3 layer.

2. The thermal barrier / high emissivity dual ceramic coating according to claim 1, characterized in that, The thickness of the metal bonding layer is 0.05mm to 0.10mm, the thickness of the thermal barrier ceramic layer is 0.80mm to 1.00mm, and the thickness of the high emissivity layer is 0.05mm to 0.20mm.

3. The thermal barrier / high emissivity dual ceramic coating according to claim 2, characterized in that, The thickness of the thermal barrier ceramic layer is 0.90mm~1.00mm, and the thickness of the high emissivity layer is 0.05mm~0.1mm.

4. The thermal barrier / high emissivity dual ceramic coating according to claim 1, characterized in that, The metal bonding layer is a NiCrAlY alloy bonding layer or a CoNiCrAlY alloy bonding layer, and the thermal barrier ceramic layer is (La) 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 The high emissivity layer is a 2Zr2O7 ceramic layer, wherein the high emissivity layer is La. 0.8 Sr 0.2 FeO3 layer.

5. A method for preparing a thickness-adjustable thermal barrier / high emissivity dual ceramic coating as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Preparation of RE2Zr2O7 ceramic spray powder and Sr-doped LaFeO3 spray powder; (2) Substrate roughening and bonding layer preparation: The alloy substrate was roughened in a sandblasting machine, and an atmospheric plasma spraying process was used to prepare a metal bonding layer on the surface of the sandblasted substrate. (3) Preparation of thermal barrier ceramic layer: RE2Zr2O7 ceramic powder was coated onto the surface of the metal bonding layer obtained in step (2) using atmospheric plasma spraying process to obtain a thermal barrier ceramic layer. (4) Preparation of high emissivity layer: Sr-doped LaFeO3 powder was coated onto the surface of the thermal barrier ceramic layer obtained in step (3) using an atmospheric plasma spraying process to obtain a high emissivity layer.

6. The preparation method according to claim 5, characterized in that, In step (1), the preparation of RE2Zr2O7 ceramic spraying powder include: ZrO2 and RE2O3 raw material powders were subjected to high-temperature heat treatment. The heat-treated raw material powders and deionized water were mixed evenly according to the stoichiometric ratio. The mixture was then wet-milled to obtain a uniformly mixed slurry, which was dried and ground to obtain a mixed powder. The mixed powder was subjected to a high-temperature solid-state reaction to obtain RE2Zr2O7 ceramic powder. The RE2Zr2O7 ceramic powder was mixed with deionized water, gum arabic, and triammonium citrate in a certain proportion and mixed evenly by wet-milling. The mixture was then centrifugally spray-dried to prepare RE2Zr2O7 coating powder. The preparation of Sr-doped LaFeO3 spray coating powder includes: subjecting La2O3 raw material powder to high-temperature heat treatment; mixing La2O3, Fe2O3, SrCO3 and deionized water uniformly according to stoichiometric ratio; obtaining a uniformly mixed slurry through wet ball milling; drying, grinding and sieving to obtain mixed powder; subjecting the mixed powder to a high-temperature solid-state reaction; grinding and sieving the powder obtained after the reaction to obtain Sr-doped LaFeO3 spray coating powder.

7. The preparation method according to claim 6, characterized in that, In the preparation of the RE2Zr2O7 ceramic spray powder, the high-temperature solid-state synthesis temperature is 800~1600℃ and the synthesis time is 12~48h; in the preparation of the Sr-doped LaFeO3 spray powder, the synthesis temperature is 800~1400℃ and the synthesis time is 12~48h.

8. The preparation method according to claim 5, characterized in that, In step (2), the process parameters for sandblasting are: pressure of 0.3~0.5MPa, sandblasting distance of 80~150mm, sand size of 12~36 mesh, and sandblasting time of 1~5min; the parameters for preparing the metal bonding layer are: argon flow rate of 30~50L / min, hydrogen flow rate of 1~3L / min, current control of 500~550A, power of 25~40kW; powder feeding rate of 10~35 g / min, and spraying distance of 80~130mm.

9. The preparation method according to claim 5, characterized in that, In step (3), the atmospheric plasma spraying parameters are as follows: argon flow rate is 30~50L / min, current is controlled at 500~600A, power is 35~45kW; hydrogen flow rate is 1.0~3.0L / min, powder feeding amount is 10~30g / min; spraying distance is 80~120mm.

10. The preparation method according to claim 5, characterized in that, In step (4), the atmospheric plasma spraying parameters are as follows: argon flow rate is 30~70L / min, current is controlled at 350~650A, power is 25~65kW; hydrogen flow rate is 2.0~8.0L / min, powder feeding amount is 15~40g / min; spraying distance is 80~140mm.

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