High-entropy ceramic thermal barrier coating and method of making the same

Abstract

The application discloses a kind of high-entropy ceramic thermal barrier coatings and preparation method thereof, it is related to thermal barrier coating material technical field.The method includes that ZrO2, HfO2, Ta2O5 and multiple rare earth oxides are mixed, by high-energy wet ball milling, drying, solid solution sintering and crushing, and submicron high-entropy ceramic powder is prepared;Again, it is mixed with the aluminum sol obtained by the hydrolysis of aluminum isopropyl alcohol, rare earth nitrate etc., by dispersion, drying and heat treatment, and the modified powder coated with aluminum oxide nanoparticles on the surface is obtained;Then, spherical agglomerated powder is obtained by spray drying granulation;Finally, the DD6 single crystal high-temperature alloy substrate is sandblasted and pre-oxidized, and the agglomerated powder is deposited on the surface of the substrate by plasma spraying vapor deposition technology, forming a columnar crystal coating, and the finished product is prepared by vacuum annealing.The coating prepared by the method has uniform structure, high bonding strength, significantly improved thermal shock resistance and high-temperature phase stability, and is suitable for surface protection of the hot end parts of an aero-engine.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal barrier coating materials, in particular to a high-entropy ceramic thermal barrier coating and a preparation method thereof. BACKGROUND

[0002] As the core protective material of the high-temperature end components of high-temperature power equipment such as aircraft engines and gas turbines, the service performance of the thermal barrier coating directly determines the working temperature, thermal efficiency and service life of the equipment. With the continuous improvement of the requirements for the thrust-to-weight ratio and thermal efficiency of the equipment in the fields of aerospace and energy power, the gas inlet temperature continues to break through 1600℃, and the traditional thermal barrier coating material has been difficult to meet the service requirements of ultra-high temperature, long period and high reliability. As the core material of the traditional thermal barrier coating, yttria-stabilized zirconia (YSZ) has good mechanical properties and heat insulation effect, but it is prone to phase transition and sintering aging above 1200℃, which leads to coating peeling failure; single-component rare earth zirconate has better high-temperature phase stability, but it has defects such as insufficient toughness and low thermal expansion coefficient, which limits its application in extreme working conditions. In order to solve the performance bottleneck of traditional materials, the concept of "high entropy" is introduced into the field of ceramic thermal barrier coatings. By forming high-entropy ceramics with five or more main elements in equal or near-equal molar ratio, the high-entropy effect (configuration entropy, delayed diffusion effect, etc.) is used to realize the synergistic optimization of high-temperature phase stability, mechanical properties and heat insulation performance. However, the existing research and development of high-entropy ceramic thermal barrier coatings still has some core technical problems, that is, the entropy value is not sufficient, which cannot reach the theoretical optimal level, and seriously restricts the further breakthrough of the comprehensive performance of the coating. SUMMARY

[0003] The purpose of the present application is to provide a high-entropy ceramic thermal barrier coating and a preparation method thereof to solve the technical problems raised in the background.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] A preparation method of a high-entropy ceramic thermal barrier coating, comprising the following steps:

[0006] S1, taking oxide raw materials ZrO2, HfO2, Ta2O5, Y2O3, Sm2O3, Eu2O3, Gd2O3 and Yb2O3, drying, mixing the dried oxide raw materials with anhydrous ethanol medium and oleic acid dispersant, high-energy wet ball milling to obtain a composite slurry;

[0007] S2, drying and pressing the composite slurry into a green compact, and performing solid solution sintering in an air atmosphere to obtain a high-entropy ceramic block, and then mechanically crushing and wet grinding the high-entropy ceramic block to obtain a submicron high-entropy ceramic powder;

[0008] S3, dissolving aluminum isopropoxide in isopropyl alcohol, adding acetylacetone stabilizer and rare earth nitrate mixture, adjusting pH to be acidic, carrying out hydrolysis reaction, obtaining aluminum sol;

[0009] S4, mixing sub-micron high-entropy ceramic powder with aluminum sol, after dispersion and drying, carrying out heat treatment, obtaining modified high-entropy ceramic powder coated with alumina nanoparticles on the surface;

[0010] S5, preparing the modified high-entropy ceramic powder into water-based slurry, adding polyvinyl alcohol binder and ammonium polyacrylate dispersant, carrying out spray drying granulation, obtaining spherical agglomerated powder;

[0011] S6, carrying out sand blasting and pre-oxidation treatment on the DD6 single crystal high-temperature alloy substrate to obtain a pretreated substrate, depositing the spherical agglomerated powder on the surface of the pretreated substrate by plasma spraying vapor deposition to form a columnar crystal coating, and carrying out vacuum annealing treatment on the columnar crystal coating.

[0012] In the present application, the entropy value of the ceramic thermal barrier coating is improved from the following aspects: on the one hand, the configuration entropy of the coating is maximized by the cooperation of multi-main element raw materials and process. Specifically, eight oxides of high-purity ZrO2, HfO2, Ta2O5, Y2O3, Sm2O3, Eu2O3, Gd2O3 and Yb2O3 are selected to provide cations with different atomic sizes and valence states for the system, thereby providing a high-entropy basis from the thermodynamic aspect. Then, the raw materials are uniformly mixed at the sub-micron scale by high-energy wet ball milling with oleic acid as a dispersant, and then are sintered for a long time in a high-temperature air atmosphere to activate and drive the diffusion of multiple cations into the ZrO2 lattice, overcome the solid solution enthalpy resistance by virtue of the entropy driving effect, and finally form a single-phase fluorite structure solid solution without impurities, thereby obtaining a high-entropy ceramic substrate. On the other hand, the interface entropy is improved by constructing a nano-composite structure, and is coordinated with the above-mentioned configuration entropy: first, aluminum isopropoxide is hydrolyzed and stabilized to prepare aluminum sol with uniform particle size; the sol is mixed with high-entropy ceramic powder, and the sol is uniformly coated on the surface of the powder by ultrasonic and mechanical stirring. Then, the coating layer is in-situ dehydrated and converted into alpha-Al2O3 nano-crystal particles at high temperature, and these particles are uniformly pinned on the surface of the high-entropy substrate in the form of pomegranate structure, thereby greatly increasing the number of two-phase interfaces. The structural difference and atomic interaction between the high-entropy solid solution and alpha-Al2O3 at the interface significantly improve the atomic arrangement disorder degree (i.e. interface entropy) of the interface region. Finally, the high interface entropy introduced by nano-coating and the high configuration entropy of the substrate are synergistically coordinated, thereby enhancing the high-temperature thermal stability, sintering resistance and mechanical properties of the coating.

[0013] During the development of the present application, it is found that when the high-entropy ceramic matrix and the nano-aluminum oxide coating layer are in long-term action at high temperature, the "solute stripping effect" will be induced due to the serious imbalance of the chemical potential of rare earth elements on both sides of the interface. Specifically, the abundant rare earth cations (such as Y 3+ , Sm 3+ , Gd 3+ ) in the high-entropy matrix will diffuse to the pure nano-Al2O3 layer under the driving of the concentration gradient, and then react to generate a brittle rare earth aluminate phase at the interface. This process not only consumes the solid-solution rare earth elements in the matrix, destroys the high-entropy state established by the first modification, but also causes the coating layer to peel off due to the volume change of the new phase, resulting in a decrease in the interface entropy and reducing the overall synergistic modification effect. To further solve this technical problem, the present application pre-dopes rare earth nitrates (yttrium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate and nitric acid mixture) in the preparation of the aluminum sol coating agent, which balances the rare earth chemical potential on both sides of the interface through "homogeneous pre-saturation", effectively inhibits the high-temperature outward diffusion of the matrix components, and thus protects the high-entropy single-phase structure of the matrix. In addition, during the subsequent high-temperature heat treatment, the pre-doped rare earth ions will guide the in-situ formation of an entropy gradient transition zone between the nano-Al2O3 and the high-entropy matrix. This region has a highly disordered atomic arrangement, which further improves the interface entropy. At the same time, these rare earth ions act as atomic pinning points, which strengthen the interface bonding between the Al2O3 nanocrystals and the high-entropy ceramic at the atomic scale through mutual compensation of lattice distortion energy, prevent phase separation and peeling at high temperature, and ultimately achieve the stable coupling of the configurational entropy and the interface entropy across the scale, so that the single-phase structure retention rate of the composite powder after high-temperature heat treatment is improved, the nano-phase peeling rate is reduced, and the thermal stability and reliability of the coating are significantly improved.

[0014] Preferably, in step S2, the solid solution sintering temperature is 1600-1650℃, and the solid solution sintering time is 10-15h.

[0015] Preferably, in step S2, the sub-micron high-entropy ceramic powder D50 is 0.8-1.5μm.

[0016] Preferably, in step S3, the addition amount of rare earth nitrate is 2-5wt% of aluminum isopropoxide.

[0017] Preferably, in step S3, the rare earth nitrate is composed of yttrium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate and ytterbium nitrate.

[0018] Preferably, in step S4, the mass ratio of the sub-micron high-entropy ceramic powder to the aluminum sol is 9:7-8.

[0019] Preferably, in step S4, the heat treatment temperature is 1000-1050℃, and the heat treatment time is 3-5h.

[0020] Preferably, in step S5, the water-based slurry has a solid content of 60-68%.

[0021] Preferably, in step S6, the vacuum annealing temperature is 1080-1100℃, and the vacuum annealing time is 4-6h.

[0022] A high-entropy ceramic thermal barrier coating is prepared by the method.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. By multi-principal element raw material design and synergistic process, a single-phase high-entropy ceramic matrix with significantly improved configuration entropy is successfully prepared. The high-entropy state effectively suppresses the second phase precipitation and crystal transformation at high temperature, thereby greatly enhancing the long-term phase stability of the coating in high-temperature service environment.

[0025] 2. By constructing a nanometer alpha-Al2O3 coated "pomegranate-like" composite structure, the interface entropy is improved while the high configuration entropy of the matrix produces a synergistic effect. This structure not only effectively pins the grain boundaries and suppresses the sintering densification of the coating at high temperature, but also significantly improves the mechanical properties of the coating through the interface toughening mechanism.

[0026] 3. By pre-doping rare earth elements to balance the interface chemical potential, the high-temperature "solute stripping effect" is fundamentally suppressed. This not only protects the high-entropy structure of the matrix, but also forms a strong bonding entropy gradient transition zone, realizing the cross-scale stable coupling of configuration entropy and interface entropy, increasing the single-phase structure retention rate of the composite powder after high-temperature heat treatment, reducing the nanophase peeling rate, and significantly improving the thermal stability and reliability of the coating. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM image of the surface of the high-entropy ceramic thermal barrier coating prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] Example 1

[0030] A preparation method of a high-entropy ceramic thermal barrier coating, comprising the following steps:

[0031] Step 1: Weigh the following mass of oxide raw materials: 550g ZrO2, 60g HfO2, 40g Ta2O5, 50.5g Y2O3, 77.9g Sm2O3, 78.6g Eu2O3, 81.1g Gd2O3 and 88.2g Yb2O3, dry the raw materials at 120℃ for 24h under vacuum, then put them into a polyethylene mill jar, add 3kg high-purity zirconia balls (Φ3mm / Φ5mm grading), use anhydrous ethanol as the medium, add 15g oleic acid as a dispersant, run in a planetary ball mill at 400rpm for 24h to obtain a composite slurry.

[0032] Step 2: The composite slurry is vacuum evaporated to remove alcohol, pressed into a billet, placed in a high-purity zirconia crucible, and heated to 1630℃ at a rate of 5℃ / min in an air atmosphere electric furnace, held at constant temperature for 12h, and then cooled in the furnace to obtain a high-entropy ceramic block. The high-entropy ceramic block is first broken to less than 2mm by a jaw crusher, then dry ground to less than 50μm by a vibration mill, and finally put into a horizontal stirring mill (zirconia lining and medium) and ground for 6h at 3000rpm with anhydrous ethanol as the medium. After centrifugal drying, a sub-micron high-entropy ceramic powder with a D50 of 0.8-1.5μm is obtained.

[0033] Step 3: Dissolve 150g aluminum isopropoxide in 800mL isopropyl alcohol solution, add 30g acetylacetone as a stabilizer and 6.0g of a rare earth nitrate mixture, which consists of equal molar ratios of yttrium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate and ytterbium nitrate. Adjust the pH of the system to 2.0 by stirring and adding dilute nitric acid under a 85℃ water bath, and continue to reflux and stir for 6h to obtain an aluminum sol.

[0034] Step 4: Put 900g of sub-micron high-entropy ceramic powder into 780g of aluminum sol, ultrasonic (600W) combined with mechanical stirring for 2h, vacuum evaporate at 100℃ while stirring, and then heat treat at 1020℃ for 4h in an air furnace to obtain a modified high-entropy ceramic powder coated with aluminum oxide nanoparticles on the surface.

[0035] Step 5: Configure the above modified high-entropy ceramic powder into a water-based slurry with a solid content of 66%, add 20g of polyvinyl alcohol and 5g of ammonium polyacrylate, use a spray dryer (inlet air temperature 280℃, outlet air temperature 120℃) to granulate, and screen 40-60μm particles to obtain spherical agglomerated powder.

[0036] Step 6: Select DD6 single crystal superalloy as the substrate, after solid solution treatment, 120 mesh white corundum automatic sand blasting (0.4 MPa) is carried out, and then pre-oxidation is carried out at 1050℃ in a vacuum environment for 2h, the thickness of the generated TGO (thermal growth oxide layer) is controlled to be 0.5-0.8μm, and a pretreated substrate is obtained. The pretreated substrate is preheated to 950℃, a high helium proportion mixed gas (Ar:He=1:2) is used, and a plasma spraying gas phase deposition is used to deposit the spherical agglomerated powder on the surface of the pretreated substrate, wherein the chamber pressure is 150Pa, the plasma power is 120kW, the spraying distance is 1000mm, the gas phase deposition is carried out for 40min, a columnar crystal coating is formed, and then the columnar crystal coating is placed in a vacuum furnace, heated to 1090℃ at a rate of 3℃ / min, and kept for 5h, and then slowly cooled to room temperature at a rate of 2℃ / min.

[0037] Example 2

[0038] A preparation method of a high-entropy ceramic thermal barrier coating, comprising the following steps:

[0039] Step 1: weigh the following mass of oxide raw materials: 550g ZrO2, 60g HfO2, 40g Ta2O5, 50.5g Y2O3, 77.9g Sm2O3, 78.6g Eu2O3, 81.1g Gd2O3 and 88.2g Yb2O3, dry the raw materials in a vacuum at 120℃ for 24h, then put them into a polyethylene mill jar, add 3kg of high-purity zirconia balls (Φ3mm / Φ5mm grading), use anhydrous ethanol as the medium, add 15g of oleic acid as a dispersant, and run in a planetary ball mill at a speed of 400rpm for 24h to obtain a composite slurry.

[0040] Step 2: the composite slurry is vacuum rotary evaporated to remove alcohol, pressed into a billet, placed in a high-purity zirconia crucible, heated to 1630℃ at a rate of 5℃ / min in an air atmosphere electric furnace, kept at a constant temperature for 12h, and then cooled in the furnace to obtain a high-entropy ceramic block, which is first broken to below 2mm by a jaw crusher, then dry ground to below 50μm by a vibration mill, and finally put into a horizontal stirring mill (zirconia lining and medium) to grind for 6h at 3000rpm with anhydrous ethanol as the medium, centrifuged and dried to obtain a submicron high-entropy ceramic powder with a D50 of 0.8-1.5μm.

[0041] Step 3: dissolve 150g of aluminum isopropoxide in 800mL of isopropyl alcohol solution, add 30g of acetylacetone as a stabilizer and 4.0g of a rare earth nitrate mixture, and the rare earth nitrate mixture is composed of equal molar ratios of yttrium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate and ytterbium nitrate. Adjust the pH value of the system to 2.0 by stirring and adding dilute nitric acid under a 85℃ water bath, continue to reflux and stir for 6h to obtain an aluminum sol.

[0042] Step 4: 900 g of sub-micron high-entropy ceramic powder was put into 730 g of aluminum sol, and ultrasonic (600 W) combined with mechanical stirring was performed for 2 h. The mixture was vacuum evaporated at 100 ℃ while stirring, and then heat-treated at 1020 ℃ for 4 h in an air furnace to obtain modified high-entropy ceramic powder coated with aluminum oxide nanoparticles on the surface.

[0043] Step 5: The modified high-entropy ceramic powder was configured into a water-based slurry with a solid content of 62%, 20 g of polyvinyl alcohol and 5 g of ammonium polyacrylate were added, and spray drying was performed using a spray dryer (inlet air temperature 280 ℃, outlet air temperature 120 ℃) to obtain spherical agglomerated powder with a particle size of 40-60 μm.

[0044] Step 6: DD6 single crystal superalloy was selected as the substrate, and after solid solution treatment, 120 mesh white corundum automatic sandblasting (0.4 MPa) was performed, followed by pre-oxidation at 1050 ℃ in a vacuum environment for 2 h to control the thickness of the generated TGO (thermal growth oxide layer) to be 0.5-0.8 μm, thereby obtaining a pretreated substrate. The pretreated substrate was preheated to 950 ℃, and spherical agglomerated powder was deposited on the surface of the pretreated substrate using high-helium mixed gas (Ar:He = 1:2) by plasma spraying vapor deposition, wherein the chamber pressure was 150 Pa, the plasma power was 120 kW, the spraying distance was 1000 mm, the vapor deposition time was 40 min, and a columnar crystal coating was formed. Then, the columnar crystal coating was placed in a vacuum furnace and heated to 1090 ℃ at a rate of 3 ℃ / min, and then held for 5 h. After that, the columnar crystal coating was slowly cooled to room temperature at a rate of 2 ℃ / min, thereby obtaining the columnar crystal coating.

[0045] Example 3

[0046] A method for preparing a high-entropy ceramic thermal barrier coating, comprising the following steps:

[0047] Step 1: The following mass of oxide raw materials was weighed: 550 g of ZrO2, 60 g of HfO2, 40 g of Ta2O5, 50.5 g of Y2O3, 77.9 g of Sm2O3, 78.6 g of Eu2O3, 81.1 g of Gd2O3, and 88.2 g of Yb2O3. The raw materials were vacuum dried at 120 ℃ for 24 h, then put into a polyethylene mill jar, 3 kg of high-purity zirconia balls (Φ3 mm / Φ5 mm grading) were added, anhydrous ethanol was used as the medium, 15 g of oleic acid was added as a dispersant, and the planetary ball mill was operated at a speed of 400 rpm for 24 h to obtain a composite slurry.

[0048] Step 2: The composite slurry is vacuum distilled to remove alcohol, pressed into a billet, placed in a high-purity zirconia crucible, and heated to 1630°C at a rate of 5°C / min in an air atmosphere electric furnace. After 12 hours of constant temperature holding, the furnace is cooled down, and a high-entropy ceramic bulk is obtained. The high-entropy ceramic bulk is first broken to less than 2 mm by a jaw crusher, then dry ground to less than 50 μm by a vibration mill, and finally ground to less than 50 μm by a horizontal stirring mill (zirconia lining and medium). The powder is ground in anhydrous ethanol as medium at 3000 rpm for 6 hours, centrifuged and dried to obtain sub-micron high-entropy ceramic powder with a D50 of 0.8-1.5 μm.

[0049] Step 3: 150 g of aluminum isopropoxide is dissolved in 800 mL of isopropanol solution, 30 g of acetylacetone is added as a stabilizer, and 5.0 g of a rare earth nitrate mixture is added. The rare earth nitrate mixture is composed of equal molar ratios of yttrium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate, and ytterbium nitrate. The system is stirred at 85°C water bath and the pH value is adjusted to 2.0 by adding dilute nitric acid dropwise. The system is continuously stirred for 6 hours under reflux to obtain an aluminum sol.

[0050] Step 4: 900 g of sub-micron high-entropy ceramic powder is added to 750 g of aluminum sol, ultrasonic (600 W) combined with mechanical stirring for 2 hours, and then vacuum distilled at 100°C while stirring. Subsequently, the system is heat treated at 1020°C for 4 hours in an air furnace to obtain a modified high-entropy ceramic powder coated with aluminum oxide nanoparticles on the surface.

[0051] Step 5: The modified high-entropy ceramic powder is configured into a water-based slurry with a solid content of 64%, 20 g of polyvinyl alcohol and 5 g of ammonium polyacrylate are added, and the slurry is granulated by a spray dryer (inlet air temperature 280°C, outlet air temperature 120°C). The particles with a size of 40-60 μm are screened to obtain spherical agglomerated powder.

[0052] Step 6: DD6 single crystal superalloy is selected as the substrate, and after solid solution treatment, 120 mesh white corundum automatic sandblasting (0.4 MPa) is performed. Subsequently, the substrate is pre-oxidized at 1050°C in a vacuum environment for 2 hours to control the thickness of the TGO (thermal growth oxide layer) to be 0.5-0.8 μm, and a pretreated substrate is obtained. The pretreated substrate is preheated to 950°C, and a high-helium mixed gas (Ar:He=1:2) is used for plasma spraying vapor deposition to deposit the spherical agglomerated powder on the surface of the pretreated substrate. The chamber pressure is 150 Pa, the plasma power is 120 kW, the spraying distance is 1000 mm, and the vapor deposition time is 40 min. A columnar crystal coating is formed, and then the coating is placed in a vacuum furnace and heated to 1090°C at a rate of 3°C / min. After 5 hours of constant temperature holding, the system is slowly cooled to room temperature at a rate of 2°C / min to obtain the coating.

[0053] Example 4

[0054] A method for preparing a high-entropy ceramic thermal barrier coating, comprising the following steps:

[0055] Step 1: Weigh the following mass of oxide raw materials: 550 g of ZrO2, 60 g of HfO2, 40 g of Ta2O5, 50.5 g of Y2O3, 77.9 g of Sm2O3, 78.6 g of Eu2O3, 81.1 g of Gd2O3, and 88.2 g of Yb2O3, and dry the raw materials in a vacuum oven at 120°C for 24 hours, then put them into a polyethylene mill jar, add 3 kg of high-purity zirconia balls (Φ3 mm / Φ5 mm grading), use anhydrous ethanol as the medium, add 15 g of oleic acid as a dispersant, and run in a planetary ball mill at a speed of 400 rpm for 24 hours to obtain a composite slurry.

[0056] Step 2: The composite slurry is vacuum evaporated to remove alcohol, pressed into a billet, placed in a high-purity zirconia crucible, and heated to 1650°C at a rate of 5°C / min in an air atmosphere electric furnace, and then held at a constant temperature for 15 hours before cooling in the furnace to obtain a high-entropy ceramic block. The high-entropy ceramic block is first broken to less than 2 mm by a jaw crusher, then dry ground to less than 50 μm by a vibration mill, and finally ground to less than 50 μm by a horizontal stirring mill (zirconia lining and medium) at 3000 rpm with anhydrous ethanol as the medium for 6 hours. After centrifugal drying, a sub-micron high-entropy ceramic powder with a D50 of 0.8-1.5 μm is obtained.

[0057] Step 3: Dissolve 150 g of aluminum isopropoxide in 800 mL of isopropyl alcohol solution, add 30 g of acetylacetone as a stabilizer, and 7.5 g of a rare earth nitrate mixture composed of equal molar ratios of yttrium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate, and ytterbium nitrate. Adjust the pH of the system to 2.0 by stirring and adding dilute nitric acid under a 85°C water bath, and continue to reflux and stir for 6 hours to obtain an aluminum sol.

[0058] Step 4: Put 900 g of sub-micron high-entropy ceramic powder into 800 g of aluminum sol, ultrasonic (600 W) combined with mechanical stirring for 2 hours, and then vacuum evaporate at 100°C while stirring, followed by heat treatment at 1050°C for 5 hours in an air furnace to obtain a modified high-entropy ceramic powder coated with aluminum oxide nanoparticles on the surface.

[0059] Step 5: Configure the above modified high-entropy ceramic powder into a water-based slurry with a solid content of 68%, add 20 g of polyvinyl alcohol and 5 g of ammonium polyacrylate, use a spray dryer (inlet air temperature 280°C, outlet air temperature 120°C) to granulate, and screen 40-60 μm particles to obtain spherical agglomerated powder.

[0060] Step 6: Select DD6 single crystal superalloy as the substrate, after solid solution treatment, 120 mesh white corundum automatic sand blasting (0.4 MPa) is carried out, and then pre-oxidation is carried out at 1050℃ in a vacuum environment for 2h, the thickness of the generated TGO (thermal growth oxide layer) is controlled to be 0.5-0.8μm, and a pretreated substrate is obtained. The pretreated substrate is preheated to 950℃, a high helium proportion mixed gas (Ar:He=1:2) is used, and a plasma spraying gas phase deposition is used to deposit the spherical agglomerated powder on the surface of the pretreated substrate, wherein the chamber pressure is 150Pa, the plasma power is 120kW, the spraying distance is 1000mm, the gas phase deposition is carried out for 40min, a columnar crystal coating is formed, and then the columnar crystal coating is placed in a vacuum furnace, heated to 1100℃ at a rate of 3℃ / min, and kept for 6h, and then slowly cooled to room temperature at a rate of 2℃ / min.

[0061] Example 5

[0062] A preparation method of a high-entropy ceramic thermal barrier coating, comprising the following steps:

[0063] Step 1: weigh the following mass of oxide raw materials: 550g ZrO2, 60g HfO2, 40g Ta2O5, 50.5g Y2O3, 77.9g Sm2O3, 78.6g Eu2O3, 81.1g Gd2O3 and 88.2g Yb2O3, dry the raw materials in a vacuum at 120℃ for 24h, then put them into a polyethylene mill jar, add 3kg of high-purity zirconia balls (Φ3mm / Φ5mm grading), use anhydrous ethanol as the medium, add 15g of oleic acid as a dispersant, and run in a planetary ball mill at a speed of 400rpm for 24h to obtain a composite slurry.

[0064] Step 2: the composite slurry is vacuum rotary evaporated to remove alcohol, pressed into a billet, placed in a high-purity zirconia crucible, heated to 1600℃ at a rate of 5℃ / min in an air atmosphere electric furnace, kept at a constant temperature for 10h, and then cooled in the furnace to obtain a high-entropy ceramic block. The high-entropy ceramic block is first broken to below 2mm by a jaw crusher, then dry ground to below 50μm by a vibration mill, and finally put into a horizontal stirring mill (zirconia lining and medium) and ground for 6h at 3000rpm with anhydrous ethanol as the medium. Centrifugal drying is performed to obtain a submicron high-entropy ceramic powder with a D50 of 0.8-1.5μm.

[0065] Step 3: 150g of aluminum isopropanol is dissolved in 800mL of isopropanol solution, 30g of acetylacetone is added as a stabilizer, and 3.0g of a rare earth nitrate mixture is added. The rare earth nitrate mixture is composed of equal molar ratios of yttrium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate and ytterbium nitrate. Stirring is carried out under a 85℃ water bath, and the pH value of the system is adjusted to 2.0 by adding dilute nitric acid dropwise, and the system is continuously refluxed and stirred for 6h to obtain an aluminum sol.

[0066] Step 4: 900 g of sub-micron high-entropy ceramic powder was put into 700 g of aluminum sol, and ultrasonic (600 W) combined with mechanical stirring was performed for 2 h. The mixture was dried under vacuum at 100 ℃ while stirring, and then heat-treated at 1000 ℃ for 3 h in an air furnace to obtain modified high-entropy ceramic powder coated with aluminum oxide nanoparticles on the surface.

[0067] Step 5: The modified high-entropy ceramic powder was configured into a water-based slurry with a solid content of 60%, 20 g of polyvinyl alcohol and 5 g of ammonium polyacrylate were added, and spray drying was performed (inlet air temperature 280 ℃, outlet air temperature 120 ℃) to obtain spherical agglomerated powder with a particle size of 40-60 μm.

[0068] Step 6: DD6 single crystal superalloy was selected as the substrate, and after solid solution treatment, 120 mesh white corundum automatic sandblasting (0.4 MPa) was performed, followed by pre-oxidation at 1050 ℃ in a vacuum environment for 2 h to control the thickness of the generated TGO (thermal growth oxide layer) to be 0.5-0.8 μm, thereby obtaining a pretreated substrate. The pretreated substrate was preheated to 950 ℃, and spherical agglomerated powder was deposited on the surface of the pretreated substrate using high-helium mixed gas (Ar:He = 1:2) by plasma spraying vapor deposition, wherein the chamber pressure was 150 Pa, the plasma power was 120 kW, the spraying distance was 1000 mm, the vapor deposition time was 40 min, and a columnar crystal coating was formed. Then, the coating was placed in a vacuum furnace and heated to 1080 ℃ at a rate of 3 ℃ / min, and then held for 4 h. After that, the coating was slowly cooled to room temperature at a rate of 2 ℃ / min, thereby obtaining the coating.

[0069] Comparative Example 1: Comparative Example 1 differs from Example 1 in that traditional yttria-stabilized zirconia (8YSZ) was used as the raw material, and steps 1-4 were omitted. The thermal barrier coating was prepared by steps 5-6.

[0070] Comparative Example 2 (without aluminum sol coating treatment): Comparative Example 2 differs from Example 1 in that steps 3-4 were omitted, and the powder obtained in step 2 was directly granulated according to step 5, and then coated and deposited according to step 6.

[0071] Comparative Example 3: Comparative Example 3 differs from Example 1 in that no rare earth nitrate mixture was added when the aluminum sol was configured in step 3.

[0072] Comparative Example 4: Comparative Example 4 differs from Example 1 in that when the aluminum sol was configured in step 3, yttrium nitrate and samarium nitrate were replaced by equal amounts of europium nitrate and gadolinium nitrate, respectively.

[0073] Performance test:

[0074] 1. Total entropy test: The total entropy of the coating was calculated by the formula: S = ∑(xi ln xi). The molar fraction of each element was measured by energy dispersive spectroscopy (EDS) attached to a field emission scanning electron microscope (FESEM) on five randomly selected defect-free areas on the coating surface. The microstructure of the coating was observed by transmission electron microscopy (TEM), and the number density and average size of the α-Al2O3 nanoparticles were counted. The specific surface area of the coating was measured by a Brunauer-Emmett-Teller (BET) specific surface area analyzer. The interface entropy was calculated according to the interface entropy calculation model. The total entropy of the coating was obtained by directly summing the data of the configuration entropy and the interface entropy obtained by the above tests. The test results are shown in Table 1.

[0075] 2. High-temperature phase stability test: The coating sample was placed in a high-temperature box furnace and heat treated at 1700°C in air for 100h. After cooling to room temperature, the sample was analyzed by X-ray diffraction (XRD). The scanning range was 2θ = 10°-90°, and the scanning rate was 5° / min. The mass fraction of impurities was calculated by peak shape fitting and phase retrieval of the XRD pattern. The lower the impurity content, the better the high-temperature phase stability. The test results are shown in Table 1.

[0076] 3. Hardness test: The nanoindentation tester was used, and the Berkovich diamond indenter was selected. Eight test points were randomly selected on the coating surface. The indentation depth was set to 1 / 10 of the coating thickness (to avoid the influence of the substrate), the loading rate was 5mN / s, the maximum load was 50mN, and the holding time was 10s. The Vickers hardness of the coating was calculated according to the indentation load-displacement curve, and the average value of eight test results was taken. The test results are shown in Table 1.

[0077] 4. Thermal shock resistance test: The coating sample was placed in a muffle furnace and heated to 1100°C at a rate of 10°C / min. After heat treatment for 30min, it was quickly taken out and placed in room temperature air for natural cooling (temperature difference of about 1100°C). One thermal shock cycle was completed. After each cycle, the coating surface was observed by stereomicroscopy to determine whether there were defects such as cracking and peeling. The test was stopped when the peeling area of the coating exceeded 30%, and the cycle number at this time was recorded as the thermal shock life. The test results are shown in Table 1.

[0078] Table 1:

[0079] Total entropy value (R) Content of heterogeneous phase after 1700°C for 100h (%) Hardness (GPa) Thermal shock resistance life (times) Example 1 2.25 0.7 13.3 1356 Example 2 2.17 1.1 12.8 1285 Example 3 2.21 0.9 13.0 1322 Example 4 2.39 0.4 13.9 1483 Example 5 2.11 1.3 12.4 1227 Comparative Example 1 1.17 18.6 11.5 453 Comparative Example 2 1.53 3.2 12.1 855 Comparative Example 3 1.75 5.7 12.6 1107 Comparative Example 4 1.92 3.9 12.7 1181

[0080] Although the present application has been described in detail with reference to the foregoing embodiments, the technical solutions recorded in the foregoing embodiments can be modified, or some of the technical features can be replaced by equivalent features, by those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of making a high entropy ceramic thermal barrier coating, characterized by, The method comprises the following steps: S1, taking oxide raw materials ZrO2, HfO2, Ta2O5, Y2O3, Sm2O3, Eu2O3, Gd2O3 and Yb2O3, drying, mixing the dried oxide raw materials with anhydrous ethanol medium and oleic acid dispersant, and performing high-energy wet ball milling to obtain a composite slurry; S2, drying and pressing the composite slurry into a green body, and performing solid solution sintering in an air atmosphere to obtain a high-entropy ceramic block, and then mechanically crushing and wet grinding the high-entropy ceramic block to obtain a submicron high-entropy ceramic powder; S3, dissolving aluminum isopropoxide in isopropyl alcohol, adding acetylacetone stabilizer and a rare earth nitrate mixture, wherein the rare earth nitrate is composed of yttrium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate and ytterbium nitrate, adjusting the pH to be acidic, and performing hydrolysis reaction to obtain an aluminum sol; S4, mixing the submicron high-entropy ceramic powder with the aluminum sol, dispersing and drying, and then performing heat treatment to obtain a modified high-entropy ceramic powder coated with aluminum oxide nanoparticles on the surface; S5, preparing the modified high-entropy ceramic powder into a water-based slurry, adding polyvinyl alcohol binder and polyacrylammonium dispersant, and performing spray drying granulation to obtain spherical agglomerated powder; S6, performing sandblasting and pre-oxidation treatment on a DD6 single crystal high-temperature alloy substrate to obtain a pretreated substrate, depositing the spherical agglomerated powder on the surface of the pretreated substrate by plasma spraying vapor deposition to form a columnar crystal coating, and performing vacuum annealing treatment on the columnar crystal coating.

2. The method of claim 1, wherein the high entropy ceramic thermal barrier coating is prepared by a process comprising: In the step S2, the solid solution sintering temperature is 1600-1650°C, and the solid solution sintering time is 10-15h.

3. The method of claim 1, wherein the high entropy ceramic thermal barrier coating is prepared by a process comprising: In the step S2, the submicron high-entropy ceramic powder has a D50 of 0.8-1.5μm.

4. The method of claim 1, wherein the high entropy ceramic thermal barrier coating is prepared by a process comprising: In the step S3, the rare earth nitrate is added in an amount of 2-5wt% of the aluminum isopropoxide.

5. The method of claim 1, wherein the high entropy ceramic thermal barrier coating is prepared by a process comprising: In the step S4, the mass ratio of the submicron high-entropy ceramic powder to the aluminum sol is 9:7-8.

6. The method of claim 1, wherein the high entropy ceramic thermal barrier coating is prepared by a process comprising: In the step S4, the heat treatment temperature is 1000-1050°C, and the heat treatment time is 3-5h.

7. The method of claim 1, wherein the high entropy ceramic thermal barrier coating is prepared by a process comprising: In the step S5, the solid content of the water-based slurry is 60-68%.

8. The method of claim 1, wherein the high entropy ceramic thermal barrier coating is prepared by a process comprising: In the step S6, the vacuum annealing temperature is 1080-1100°C, and the vacuum annealing time is 4-6h.

9. A high entropy ceramic thermal barrier coating, characterized in that, Prepared by the method of any one of claims 1-8.

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