Double-ceramic rare earth modified thermal barrier coating and preparation method thereof

Abstract

The invention relates to a double-ceramic rare earth modified thermal barrier coating and a preparation method thereof, and belongs to the technical field of materials. The thermal barrier coating comprises a bottom layer, a transition layer and a surface layer, the bottom layer is made of nickel-based high-temperature alloy powder, the transition layer is made of YSZ, and the surface layer is made of rare earth modified zirconia powder; the thickness of the bottom layer, the thickness of the transition layer and the thickness of the surface layer are all 0.10-0.15 mm, and the total thickness of the double-ceramic rare earth modified thermal barrier coating is 0.30-0.45 mm. The preparation method comprises the following steps: pretreating the surface of the substrate, spraying the bottom layer by adopting high velocity oxy-fuel spraying equipment, and respectively spraying the transition layer and the surface layer by adopting atmospheric plasma spraying equipment. The bonding strength of the thermal barrier coating is larger than 35 MPa, thermal shock resistance is larger than 2000 times in the environment of 1300 DEG C, and the thermal barrier coating has excellent high-temperature stability and thermal shock resistance and is suitable for protection of high-temperature components such as aero-engines and gas turbines.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation coating technology, specifically to a dual-ceramic rare earth modified thermal barrier coating and its preparation method, which is used to coat the hot end components of aero engines and gas turbines with a heat-resistant and heat-insulating coating. Background Technology

[0002] Aero-engines and large ground-based gas turbines are core power systems for advanced equipment in various fields such as power, shipbuilding, aviation, aerospace, and energy. The performance improvement of these systems largely depends on increasing the turbine inlet temperature, as higher temperatures significantly enhance operational efficiency. However, this increase places extremely stringent requirements on the high-temperature resistance of critical hot-end components such as turbine blades. To address this challenge, dual-ceramic rare-earth modified thermal barrier coating technology has emerged and rapidly become an important means of protecting these hot-end components and extending their service life. Currently, third-generation dual-ceramic rare-earth modified thermal barrier coating technology is widely used, with its ceramic layer material being 7-8% (wt) Y₂O₃ partially stabilized ZrO₂ (YSZ, i.e., yttrium-stabilized zirconium oxide). YSZ coatings provide effective thermal insulation protection for hot-end components in high-temperature environments such as aero-engines and heavy-duty gas turbines, ensuring stable equipment operation.

[0003] Despite the significant achievements of third-generation dual-ceramic rare-earth modified thermal barrier coating technology, numerous challenges remain in practical applications. Among these, the most prominent issue is the stability and durability of the YSZ coating at high temperatures. Specifically, when the operating temperature exceeds 1200℃ for extended periods, the metastable tetragonal phase (t') in the YSZ coating decomposes into a tetragonal phase (t) and a cubic phase (c). During subsequent cooling, the t phase undergoes a phase transformation, converting into a monoclinic phase (m) accompanied by volume expansion. This transformation leads to internal cracking within the coating, ultimately causing coating failure. Furthermore, the YSZ coating is prone to sintering during use, resulting in densification, reduced strain tolerance, and decreased thermal insulation performance. These problems severely limit the application of third-generation dual-ceramic rare-earth modified thermal barrier coatings at higher temperatures and threaten their service life.

[0004] To address the problems existing in third-generation dual-ceramic rare-earth modified thermal barrier coatings, researchers have conducted extensive studies and attempted to improve coating performance through various methods. On one hand, researchers explored the effects of different stabilizers on the stability of the ZrO2 phase, trying to find stabilizers that can replace or supplement Y2O3 to improve the phase stability of the coating at high temperatures. On the other hand, researchers are also committed to developing novel coating structures, such as multilayer structures and gradient structures, to improve their crack propagation resistance by optimizing the internal stress distribution of the coating. In addition, researchers have attempted to improve the anti-sintering properties and thermal insulation properties of the coating by introducing nanotechnology and adding rare earth elements. These efforts have, to some extent, extended the service life of dual-ceramic rare-earth modified thermal barrier coatings and improved their stability under high-temperature environments.

[0005] However, despite numerous improvements made to third-generation dual-ceramic rare-earth modified thermal barrier coatings by existing technologies, some insurmountable problems remain. For example, the introduction of novel stabilizers may complicate the coating preparation process and increase production costs; while the design of multilayer or gradient structure coatings improves crack propagation resistance, it may also lead to a decrease in the bonding strength between the coating and the substrate; and although the addition of nanotechnology or rare earth elements can improve the coating's anti-sintering and thermal insulation properties, it may also adversely affect other properties of the coating. More importantly, these improvements often only effectively address specific problems and are unlikely to significantly enhance the overall performance of the coating. Therefore, developing a fourth-generation novel dual-ceramic rare-earth modified thermal barrier coating that can operate stably at higher temperatures and possesses excellent overall performance remains a crucial issue that urgently needs to be addressed in the current research field. Summary of the Invention

[0006] This invention provides a dual-ceramic rare-earth modified thermal barrier coating and its preparation method, solving the problem that existing thermal barrier coatings, when used above 1200℃, undergo sintering and phase transformation, leading to a significant increase in coating thermal conductivity, increased internal thermal stress, crack propagation, and ultimately, coating cracking and detachment. The dual-ceramic rare-earth modified thermal barrier coating of this invention can be used for high-temperature protection of combustion chamber components in aero-engines and ground-based gas turbines. It features good high-temperature stability, high bonding strength, and outstanding performance, with an operating temperature exceeding 1300℃, significantly improving coating life and high-temperature protection effectiveness.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a dual-ceramic rare-earth modified thermal barrier coating, comprising a base layer, a transition layer, and a top layer, wherein the base layer is nickel-based high-temperature alloy powder, the transition layer is YSZ, and the top layer is rare-earth modified zirconium oxide powder; the thickness of the base layer, the transition layer, and the top layer are all 0.10 mm to 0.15 mm, and the total thickness of the dual-ceramic rare-earth modified thermal barrier coating is 0.30 mm to 0.45 mm.

[0008] Furthermore, the nickel-based superalloy powder is NiCoCrAlY alloy powder with a particle size range of 15μm to 45μm; Based on the mass of NiCoCrAlY alloy powder as 100%, the NiCoCrAlY alloy powder includes: 18wt%-22wt% Co, 18wt%-22wt% Cr, 10wt%-12wt% Al, 0.5wt%-0.8wt% Y, and the balance is Ni.

[0009] Furthermore, YSZ is ZrO2·Y2O3, with a particle size range of 30μm to 70μm; Based on the mass of ZrO2·Y2O3 as 100%, ZrO2·Y2O3 includes: 92.5wt% ZrO2 + HfO2, 7wt% Y2O3, and the remainder is impurities.

[0010] Furthermore, the particle size range of rare earth modified zirconium oxide is 25 μm to 120 μm; Based on the mass of rare earth modified zirconium oxide as 100%, rare earth modified zirconium oxide includes: 10wt% Y2O3, 5wt% Gd2O3, 5wt% Yb2O3, and the balance is ZrO2 + HfO2.

[0011] Furthermore, the bonding strength of the dual ceramic rare earth modified thermal barrier coating is greater than 35 MPa, and it can withstand more than 2000 thermal shocks at 1300℃.

[0012] This invention also provides a method for preparing a dual-ceramic rare-earth modified thermal barrier coating, the specific steps of which are as follows: Substrate surface pretreatment; Nickel-based high-temperature alloy powder was sprayed onto the surface of a substrate using a supersonic flame spraying device to obtain a substrate with an underlying material. YSZ was sprayed onto a substrate with an underlying material using atmospheric plasma spraying equipment to obtain a substrate with a transition layer material. Rare earth modified zirconium oxide powder was sprayed onto a substrate with a transition layer material using atmospheric plasma spraying equipment to obtain a substrate with a surface layer material. The coating consists of a base layer, a transition layer, and a top layer, and is composed of dual ceramic rare earth modified thermal barrier materials.

[0013] Furthermore, the thickness of the bottom layer, transition layer, and top layer is 0.10 mm to 0.15 mm, and the total thickness of the dual ceramic rare earth modified thermal barrier coating is 0.30 mm to 0.45 mm.

[0014] Furthermore, the nickel-based superalloy powder is NiCoCrAlY alloy powder with a particle size range of 15μm to 45μm; Based on the mass of NiCoCrAlY alloy powder as 100%, NiCoCrAlY alloy powder includes: 20wt% Co, 20wt% Cr, 10wt% Al, 0.6wt% Y, and the balance is Ni. YSZ is ZrO2·Y2O3, with a particle size range of 30μm to 70μm; Based on the mass of ZrO2·Y2O3 as 100%, ZrO2·Y2O3 includes: 92.5wt% ZrO2 + HfO2, 7wt% Y2O3, and the remainder is impurities; The particle size range of rare earth modified zirconium oxide is 25μm to 120μm; Based on the mass of rare earth modified zirconium oxide as 100%, rare earth modified zirconium oxide includes: 10wt% Y2O3, 5wt% Gd2O3, 5wt% Yb2O3, and the balance is ZrO2 + HfO2.

[0015] Furthermore, the supersonic flame spraying uses kerosene and oxygen as the combustion spraying gases, wherein the oxygen flow rate is 1800 L / min to 2000 L / min, the kerosene flow rate is 15 L / min to 30 L / min, nitrogen is used as the carrier gas with a flow rate of 15 L / min to 35 L / min, the powder feeding rate is 30 g / min to 50 g / min, and the spraying distance is 200 mm to 450 mm; The plasma spraying uses hydrogen and argon as the main gases, with a hydrogen flow rate of 10 L / min to 15 L / min, an argon flow rate of 30 L / min to 55 L / min, a current of 550 A to 650 A, a power of 40 KW to 50 KW, a powder feeding rate of 30 g / min to 50 g / min, and a spraying distance of 90 mm to 110 mm.

[0016] Furthermore, the substrate surface pretreatment includes degreasing and roughening the substrate surface, with a surface roughness Ra greater than 2 μm.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: This invention provides a dual-ceramic rare-earth modified thermal barrier coating, which adopts a YSZ / GY-YSZ dual-ceramic structure and achieves performance optimization through functional layering. The surface layer is based on rare-earth modified zirconium oxide (GY-YSZ), which has excellent high-temperature thermal stability, effectively suppressing sintering and phase transformation, and has a thermal conductivity as low as <1.2W / (m·k), significantly reducing heat transfer efficiency. The intermediate transition layer YSZ acts as a buffer layer, balancing the difference in thermal expansion coefficients between the nickel-based alloy substrate and the GY-YSZ surface layer, while compensating for the low fracture toughness of the rare-earth ceramic layer. This significantly alleviates thermal stress concentration and extends the service life of the coating in ultra-high temperature environments of 1300℃. Furthermore, by introducing gadolinium oxide (Gd₂O₃) and ytterbium oxide (Yb₂O₃) into the surface layer, dual rare earth doping can stabilize the metastable tetragonal phase (t') of YSZ, inhibiting its decomposition into tetragonal (t) and cubic (c) phases at high temperatures, and blocking the catastrophic transformation to the monoclinic phase (m) during cooling, thus eliminating the problem of crack initiation and propagation caused by volume expansion at its root. Experiments show that the coating withstands more than 2000 thermal shock cycles at 1300℃, with a bonding strength exceeding 35MPa, far exceeding the 1200℃ service limit of existing technologies. In addition, the total thickness of the coating is only 0.30mm to 0.45mm, with the thickness of each layer precisely controlled between 0.10mm and 0.15mm, ensuring both thermal insulation performance and avoiding excessive weight gain. In practical applications, it can significantly reduce the surface temperature of combustion chamber components in aero-engines and gas turbines, improve oxidation and gas corrosion resistance, extend component lifespan several times, and enhance engine operational reliability, providing a revolutionary solution for high-temperature protection.

[0018] The method for preparing a dual-ceramic rare-earth modified thermal barrier coating provided by this invention has clear steps, involving sequential pretreatment of the substrate surface, spraying of the base layer, transition layer, and top layer material. The operation is relatively simple and can be achieved using existing supersonic flame spraying equipment and atmospheric plasma spraying equipment, making it easy to promote and apply in industrial production and possessing significant engineering application value. The coating prepared by this method has a bonding strength greater than 35 MPa and withstands more than 2000 thermal shock cycles at 1300℃, far exceeding the 1200℃ operating temperature limit of existing technologies, significantly improving the high-temperature stability and durability of the coating. Simultaneously, the coating has a low thermal conductivity (<1.2 W / (m·K)), which can significantly reduce the surface temperature of combustion chamber components, significantly extend the service life of components, improve engine reliability, and provide reliable high-temperature protection for combustion chamber components of aero-engines and ground-based gas turbines. Attached Figure Description

[0019] Figure 1 This invention relates to a microstructure of a dual-ceramic rare-earth modified thermal barrier coating. Figure 2 Photograph of a dual-ceramic rare-earth modified thermal barrier coating of the present invention after 2100 thermal shocks at 1300℃. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0021] This invention provides a dual-ceramic rare-earth modified thermal barrier coating. The coating has a three-layer structure, including a base layer, a transition layer, and a top layer. The thickness of each of the three layers is 0.10–0.15 mm, and the total thickness is 0.30–0.45 mm. Specifically, the base layer is MCrAlY alloy powder, the transition layer is YSZ, and the top layer is rare-earth modified (GY-YSZ) zirconium oxide powder. In order to effectively alleviate the difference in thermal expansion matching between the GY-YSZ coating and the MCrAlY alloy base layer, a YSZ / GY-YSZ dual-ceramic structure is adopted. The surface ceramic layer has the characteristics of good high-temperature thermal stability, anti-sintering, and low thermal conductivity. The middle YSZ layer acts as a buffer layer between the alloy layer and the GY-YSZ ceramic layer, which can effectively alleviate the shortcomings of poor thermal expansion coefficient matching and low fracture toughness of the new rare-earth ceramic layer, and is conducive to extending the ultra-high temperature service life of the thermal barrier coating. The thermal barrier coating prepared using this structure and technology has a bonding strength of over 35 MPa and can withstand more than 2000 thermal shocks at 1300℃.

[0022] Furthermore, the present invention is characterized in that: the nickel-based high-temperature alloy powder is NiCoCrAlY alloy powder, and based on the mass of the NiCoCrAlY alloy powder as 100%, the NiCoCrAlY alloy powder includes: 18wt%-22wt% cobalt (Co), 18wt%-22wt% chromium (Cr), 10wt%-12wt% aluminum (Al), 0.5wt%-0.8wt% yttrium (Y), and the balance is nickel (Ni).

[0023] Furthermore, the present invention is characterized in that: YSZ is ZrO2·Y2O3, and based on the mass of ZrO2·Y2O3 as 100%, ZrO2·Y2O3 includes: 92.5wt% zirconium oxide ZrO2 + hafnium dioxide HfO2, 7wt% yttrium oxide Y2O3, and the remainder is impurities.

[0024] Furthermore, the present invention is characterized in that: based on the mass of rare earth modified zirconium oxide as 100%, the rare earth modified zirconium oxide includes: 10 wt% yttrium oxide (Y₂O₃), 5 wt% gadolinium oxide (Gd₂O₃), 5 wt% ytterbium oxide (Yb₂O₃), and the balance is zirconium oxide (ZrO₂) + hafnium dioxide (HfO₂).

[0025] This invention also provides a method for preparing a dual-ceramic rare-earth modified thermal barrier coating. NiCoCrAlY alloy powder is sprayed onto a metal surface using a supersonic flame spraying device to prepare an underlayer coating. An atmospheric plasma spraying device is then used to prepare a ZrO2·Y2O3 transition layer and a rare-earth modified zirconia top layer, respectively. The final total coating thickness is 0.30~0.45 mm. Compared with plasma spraying of NiCoCrAlY alloy powder, supersonic flame spraying has extremely high spray velocity, relatively low flame temperature, and extremely high compressive stress, resulting in a denser, lower-oxidation, and higher-bonding-strength coating. Compared with low-pressure plasma (VPS / LPPS) spraying for preparing zirconia thermal barrier coatings, plasma spraying offers lower application costs, more flexible operation, higher production efficiency, and easier attainment of ideal thermal barrier coating structures, making it more suitable for batch production of parts.

[0026] Furthermore, the present invention is characterized in that: the supersonic flame spraying of the bottom layer uses kerosene and oxygen as the combustion spraying gas, or hydrogen and oxygen can be used as the combustion spraying gas, with an oxygen flow rate of 1800 L / min to 2000 L / min and a kerosene flow rate of 15 L / min to 30 L / min, or a hydrogen flow rate of 655±5 SLPM and an oxygen flow rate of 190±7 SLPM; nitrogen is used as the carrier gas with a flow rate of 15 L / min to 35 L / min, a powder feeding rate of 30 g / min to 50 g / min, and a spraying distance of 200 mm to 450 mm.

[0027] Furthermore, the present invention is characterized in that: the plasma spraying of the transition layer and the top layer uses hydrogen and argon as the main gases, with a hydrogen flow rate of 10 L / min to 15 L / min, an argon flow rate of 30 L / min to 55 L / min, a current of 550A to 650A, a power of 40 KW to 50 KW, a powder feeding rate of 30 g / min to 50 g / min, and a spraying distance of 90 mm to 110 mm.

[0028] Furthermore, the present invention is characterized in that the particle size range of the NiCoCrAlY alloy powder is 15μm to 45μm; Furthermore, the present invention is characterized in that the particle size range of the ZrO2·Y2O3 transition layer powder is 30μm to 70μm; Furthermore, the present invention is characterized in that the particle size range of the rare earth modified zirconia surface powder is 25μm to 120μm.

[0029] Furthermore, the present invention is characterized in that: before spraying the metal substrate surface, the substrate surface is degreased and roughened, and the surface roughness Ra needs to be greater than 2μm. It is recommended to use 60# alumina sand as the working medium, with an air pressure of 0.1 MPa to 0.3 MPa and a sandblasting distance of 200mm to 350mm.

[0030] Furthermore, the present invention is characterized in that: before spraying the surface of the metal substrate, the area outside the area to be sprayed is masked and protected.

[0031] Example 1 Taking the coating of the present invention's dual ceramic rare earth modified thermal barrier coating on floating tile parts as an example, the following description is provided: The bottom layer material of the dual-ceramic rare-earth modified thermal barrier coating of this invention is NiCoCrAlY alloy powder, the transition layer is ZrO2·Y2O3, and the top layer is rare-earth modified ZrO2. The particle size range of the NiCoCrAlY alloy powder is 15μm to 45μm, the particle size range of the ZrO2·Y2O3 transition layer powder is 30μm to 70μm, and the particle size range of the rare-earth modified zirconium oxide top layer powder is 25μm to 120μm. The prepared coating thicknesses are: bottom layer 0.11mm, transition layer 0.10mm, and top layer 0.11mm (see...). Figure 1 The bonding strength of the thermal barrier coating was tested using Q / AVIC06020 "Tension Bond Strength Test Method for Thermally Sprayed Coatings". The bonding strength was greater than 35 MPa. Using Q / AVIC 06016.2-2013 "Thermal Shock Test Method for Coatings - Part 2: Flame Heating Method", the coating withstood more than 2000 thermal shock cycles at 1300℃ without peeling (see...). Figure 2 In addition, the coating has good resistance to oxidation and gas corrosion, and has a low thermal conductivity (<1.2W / (m·k)) and can operate at temperatures up to 1300℃.

[0032] Example 2 The preparation method of the dual-ceramic rare-earth modified thermal barrier coating described in Example 1 includes the following steps: (1) Cleaning and protection: Use analytical grade acetone to clean the sprayed surface of the workpiece, and use high temperature tape to protect the non-sprayed areas.

[0033] (2) Surface roughening treatment: Clean and dry 60-mesh alumina sand is used to roughen the surface of the workpiece. The air pressure is 0.1 MPa and the sand blowing distance is 350 mm. The surface roughness Ra after roughening is greater than 2 μm.

[0034] (3) Preparation of the base coating: The base coating is prepared on the surface of the part after sandblasting by supersonic flame spraying equipment. The powder used is NiCoCrAlY alloy powder. The NiCoCrAlY alloy powder contains 20wt% Co, 20wt% Cr, 10wt% Al, 0.6wt% Y, and the balance is Ni.

[0035] The above-mentioned supersonic flame spraying process parameters are: oxygen flow rate of 1900 L / min, kerosene flow rate of 20 L / min, nitrogen as carrier gas with a flow rate of 25 L / min, powder feeding rate of 40 g / min, spraying distance of 350 mm, and coating thickness of 0.11 mm. (4) Preparation of transition layer and topcoat: The transition layer and topcoat were applied using plasma spraying equipment within 2 hours after the bottom coat was applied. The transition layer material was ZrO2·Y2O3, which, based on 100% ZrO2·Y2O3 mass, consisted of 92.5 wt% ZrO2 + HfO2, 7 wt% Y2O3, and the remainder being impurities. The topcoat material was rare earth modified zirconia powder, which, based on 100% rare earth modified zirconia mass, consisted of 10 wt% Y2O3, 5 wt% Gd2O3, 5 wt% Yb2O3, and the remainder being ZrO2 + HfO2. The transition layer thickness was 0.10 mm, and the topcoat thickness was 0.11 mm. The final total coating thickness was 0.32 mm.

[0036] The plasma spraying process parameters are as follows: hydrogen flow rate 11 L / min, argon flow rate 43 L / min, current 600A, power 45KW, powder feeding rate 40g / min, and spraying distance 100mm.

[0037] The three-layer rare earth modified thermal barrier coating prepared on floating tile parts using the above method has the advantages of stable phase structure, excellent thermal insulation performance and good thermal shock resistance at high temperature of 1300℃. It can solve the problem that traditional 7wt%~8wt% Y2O3 partially stable ZrO2 (YSZ) will cause sintering and phase transformation leading to coating failure after exceeding 1200℃.

[0038] Example 3 This invention provides a dual-ceramic rare-earth modified thermal barrier coating, comprising a base layer, a transition layer, and a top layer. The base layer is made of nickel-based high-temperature alloy powder, the transition layer is made of YSZ, and the top layer is made of rare-earth modified zirconium oxide powder.

[0039] The base layer uses NiCoCrAlY alloy powder, with a particle size ranging from 15μm to 45μm. Based on 100% by weight, the NiCoCrAlY alloy powder comprises: 20wt% Co, 20wt% Cr, 11wt% Al, 0.6wt% Y, with the balance being Ni. NiCoCrAlY alloy powder exhibits excellent high-temperature oxidation resistance and bonding properties with the matrix, effectively preventing the matrix from oxidizing at high temperatures.

[0040] The transition layer uses ZrO2·Y2O3 as the YSZ material, with a particle size ranging from 30μm to 70μm. Based on a 100% mass composition of ZrO2·Y2O3, it comprises: 92.5wt% zirconium oxide (ZrO2) + hafnium dioxide (HfO2), 7wt% yttrium oxide (Y2O3), and the remainder being impurities. The YSZ transition layer not only reduces the difference in thermal expansion coefficients between the base layer and the top layer but also improves the overall thermal barrier coating's bonding strength and thermal shock resistance.

[0041] The rare earth modified zirconia powder used in the surface layer has a particle size range of 25μm to 120μm. Based on 100% by mass, the rare earth modified zirconia comprises: 10wt% yttrium oxide (Y₂O₃), 5wt% gadolinium oxide (Gd₂O₃), 5wt% ytterbium oxide (Yb₂O₃), with the balance being zirconia (ZrO₂) + hafnium dioxide (HfO₂). The rare earth modified zirconia surface layer exhibits excellent high-temperature stability and low thermal conductivity, effectively isolating the substrate from heat transfer by high-temperature gases.

[0042] In this embodiment, the bottom layer thickness is 0.12 mm, the transition layer thickness is 0.13 mm, the top layer thickness is 0.15 mm, and the total thickness of the dual-ceramic rare-earth modified thermal barrier coating is 0.40 mm. By precisely controlling the thickness of each layer, the coating achieves optimal thermal barrier performance and structural stability.

[0043] In a preferred embodiment, the thickness of the bottom layer can be 0.10 mm, the thickness of the transition layer can be 0.10 mm, the thickness of the top layer can be 0.10 mm, and the total thickness is 0.30 mm; or the thickness of the bottom layer can be 0.15 mm, the thickness of the transition layer can be 0.15 mm, the thickness of the top layer can be 0.15 mm, and the total thickness is 0.45 mm.

[0044] The dual-ceramic rare-earth modified thermal barrier coating of this embodiment exhibits a bonding strength greater than 35 MPa and withstands more than 2000 thermal shock cycles at 1300℃. Through the rational design of the three-layer structure (base layer, transition layer, and top layer) and the optimized proportions of materials in each layer, this thermal barrier coating achieves excellent high-temperature protection performance and a long service life. Specifically, the base layer NiCoCrAlY alloy powder provides good bonding strength and oxidation resistance; the transition layer YSZ alleviates stress caused by differences in thermal expansion coefficients; and the top layer rare-earth modified zirconium oxide provides excellent thermal insulation performance and high-temperature stability. The synergistic effect of the three layers allows the coating to maintain structural integrity under high-temperature conditions, effectively extending its service life and the number of thermal cycles.

[0045] Example 4 Example 3 describes a method for preparing a dual-ceramic rare-earth modified thermal barrier coating, with the following specific steps: Step 1: Substrate Surface Pretreatment. The substrate surface is degreased and roughened to achieve a surface roughness Ra greater than 2μm. Roughening can be performed using sandblasting to ensure good adhesion to the substrate surface, providing a solid foundation for subsequent coating application.

[0046] Step Two: Base Material Spraying. Nickel-based superalloy powder (NiCoCrAlY) is sprayed onto the pretreated substrate surface using a supersonic flame spraying device to obtain a substrate with a base material. The NiCoCrAlY alloy powder has a particle size range of 15μm to 45μm, and its composition, by mass percentage, includes: 20wt% cobalt (Co), 20wt% chromium (Cr), 10wt% aluminum (Al), 0.6wt% yttrium (Y), with the balance being nickel (Ni). During the supersonic flame spraying process, kerosene and oxygen are used as the combustion gases, with an oxygen flow rate of 2000 L / min, a kerosene flow rate of 30 L / min, and nitrogen as the carrier gas at a flow rate of 35 L / min. The powder feed rate is 50 g / min, and the spraying distance is 450 mm.

[0047] Step 3: Transition Layer Material Spraying. YSZ is sprayed onto the substrate with the underlying material using atmospheric plasma spraying equipment to obtain a substrate with the transition layer material. YSZ is ZrO2·Y2O3, with a particle size range of 30μm to 70μm. Its composition, by mass percentage, includes: 92.5wt% zirconium oxide (ZrO2) + hafnium dioxide (HfO2), 7wt% yttrium oxide (Y2O3), and the remainder being impurities. During the plasma spraying process, hydrogen and argon are used as the main gases. The hydrogen flow rate is 15 L / min, the argon flow rate is 55 L / min, the current is 650A, the power is 50KW, the powder feed rate is 50g / min, and the spraying distance is 110mm.

[0048] Step 4: Topcoat Material Spraying. Rare earth modified zirconia powder is sprayed onto a substrate with a transition layer material using an atmospheric plasma spraying system to obtain a substrate with the topcoat material. The rare earth modified zirconia has a particle size range of 25μm to 120μm, and its composition, by mass percentage, includes: 10wt% yttrium oxide (Y₂O₃), 5wt% gadolinium oxide (Gd₂O₃), 5wt% ytterbium oxide (Yb₂O₃), with the balance being zirconia (ZrO₂) + hafnium dioxide (HfO₂). The plasma spraying parameters are the same as in Step 3.

[0049] Step 5: Forming a dual-ceramic rare-earth modified thermal barrier coating. Through the above steps, the base layer, transition layer, and top layer materials constitute a dual-ceramic rare-earth modified thermal barrier coating.

[0050] In a preferred embodiment, the bottom layer thickness is 0.10 mm, the transition layer thickness is 0.12 mm, the top layer thickness is 0.12 mm, and the total thickness is 0.34 mm. In another preferred embodiment, the bottom layer thickness is 0.15 mm, the transition layer thickness is 0.15 mm, the top layer thickness is 0.15 mm, and the total thickness is 0.45 mm.

[0051] This dual-ceramic rare-earth modified thermal barrier coating exhibits excellent thermal barrier performance and thermal shock resistance. The bottom NiCoCrAlY alloy powder has good adhesion to the substrate and effectively prevents oxidation; the transition layer YSZ material has good matching thermal expansion coefficients, reducing thermal stress; the top layer of rare-earth modified zirconia powder, with added gadolinium oxide and ytterbium oxide, significantly improves the coating's thermal shock resistance and ablation resistance. Through this three-layer structure design, a gradient transition of thermal expansion coefficients between the coating and the substrate is achieved, greatly improving the service life and reliability of the thermal barrier coating.

[0052] Efficacy verification tests show that after 200 cycles at a high temperature of 1300℃, the surface of the dual ceramic rare earth modified thermal barrier coating does not show obvious peeling. The thermal conductivity is reduced by about 25% compared with the traditional single-layer YSZ coating, and the thermal shock resistance is improved by about 30%.

[0053] In summary, the dual-ceramic rare-earth modified thermal barrier coating of the present invention has a bonding strength greater than 35 MPa, withstands more than 2000 thermal shocks at 1300℃, exhibits good oxidation and gas corrosion resistance, and has a low thermal conductivity (<1.2 W / (m·k)). The operating temperature can reach 1300℃, which is a significant improvement compared to the 1200℃ operating temperature limit of the prior art.

[0054] This invention adopts a YSZ / GY-YSZ dual ceramic structure. The surface ceramic layer has the characteristics of good high-temperature thermal stability, anti-sintering, and low thermal conductivity. The middle YSZ layer serves as a buffer layer between the alloy layer and the GY-YSZ ceramic layer, which can effectively alleviate the shortcomings of poor thermal expansion coefficient matching and low fracture toughness of the new rare earth ceramic layer, and is conducive to extending the ultra-high temperature service life of the thermal barrier coating.

[0055] This invention effectively suppresses the phase transformation and sintering phenomena of YSZ coating at high temperatures by adding rare earth elements gadolinium oxide (Gd₂O₃) and ytterbium oxide (Yb₂O₃) to the surface layer. It solves the problems in the prior art where the metastable tetragonal phase (t') of YSZ coating decomposes into tetragonal phase (t) and cubic phase (c) at high temperatures, and the tetragonal phase (t) transforms into monoclinic phase (m) during cooling, leading to volume expansion and crack generation.

[0056] The dual-ceramic rare-earth modified thermal barrier coating of the present invention can significantly reduce the surface temperature of combustion chamber parts, significantly improve the service life of combustion chamber parts, and improve engine reliability, and has important engineering application value.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual-ceramic rare-earth modified thermal barrier coating, characterized in that, It includes a base layer, a transition layer, and a top layer. The base layer is made of nickel-based high-temperature alloy powder, the transition layer is made of YSZ, and the top layer is made of rare earth modified zirconium oxide powder. The thickness of the base layer, the transition layer, and the top layer is 0.10 mm to 0.15 mm, and the total thickness of the dual ceramic rare earth modified thermal barrier coating is 0.30 mm to 0.45 mm.

2. The dual-ceramic rare-earth modified thermal barrier coating according to claim 1, characterized in that, The nickel-based superalloy powder is NiCoCrAlY alloy powder with a particle size range of 15μm to 45μm. Based on the mass of NiCoCrAlY alloy powder as 100%, the NiCoCrAlY alloy powder includes: 18wt%-22wt% Co, 18wt%-22wt% Cr, 10wt%-12wt% Al, 0.5wt%-0.8wt% Y, and the balance is Ni.

3. The dual-ceramic rare-earth modified thermal barrier coating according to claim 1, characterized in that, YSZ is ZrO2·Y2O3, with a particle size range of 30μm to 70μm; Based on the mass of ZrO2·Y2O3 as 100%, ZrO2·Y2O3 includes: 92.5wt% ZrO2 + HfO2, 7wt% Y2O3, and the remainder is impurities.

4. The dual-ceramic rare-earth modified thermal barrier coating according to claim 1, characterized in that, The particle size range of rare earth modified zirconium oxide is 25μm to 120μm; Based on the mass of rare earth modified zirconium oxide as 100%, rare earth modified zirconium oxide includes: 10wt% Y2O3, 5wt% Gd2O3, 5wt% Yb2O3, and the balance is ZrO2 + HfO2.

5. The dual-ceramic rare-earth modified thermal barrier coating according to claim 1, characterized in that, The bonding strength of the dual ceramic rare earth modified thermal barrier coating is greater than 35 MPa, and it can withstand more than 2000 thermal shocks at 1300℃.

6. A method for preparing a dual-ceramic rare-earth modified thermal barrier coating, characterized in that, The specific steps are as follows: Substrate surface pretreatment; Nickel-based high-temperature alloy powder was sprayed onto the surface of a substrate using a supersonic flame spraying device to obtain a substrate with an underlying material. YSZ was sprayed onto a substrate with a base material using atmospheric plasma spraying equipment to obtain a substrate with a transition layer material. Rare earth modified zirconium oxide powder was sprayed onto a substrate with a transition layer material using atmospheric plasma spraying equipment to obtain a substrate with a surface layer material. The coating consists of a base layer, a transition layer, and a top layer, and is composed of dual ceramic rare earth modified thermal barrier materials.

7. The method for preparing a dual-ceramic rare-earth modified thermal barrier coating according to claim 6, characterized in that, The thickness of the base layer, transition layer and top layer is 0.10 mm to 0.15 mm, and the total thickness of the dual ceramic rare earth modified thermal barrier coating is 0.30 mm to 0.45 mm.

8. The method for preparing a dual-ceramic rare-earth modified thermal barrier coating according to claim 6, characterized in that, The nickel-based superalloy powder is NiCoCrAlY alloy powder with a particle size range of 15μm to 45μm. Based on the mass of NiCoCrAlY alloy powder as 100%, NiCoCrAlY alloy powder includes: 20wt% Co, 20wt% Cr, 10wt% Al, 0.6wt% Y, and the balance is Ni. YSZ is ZrO2·Y2O3, with a particle size range of 30μm to 70μm; Based on the mass of ZrO2·Y2O3 as 100%, ZrO2·Y2O3 includes: 92.5wt% ZrO2 + HfO2, 7wt% Y2O3, and the remainder is impurities; The particle size range of rare earth modified zirconium oxide is 25μm to 120μm; Based on the mass of rare earth modified zirconium oxide as 100%, rare earth modified zirconium oxide includes: 10wt% Y2O3, 5wt% Gd2O3, 5wt% Yb2O3, and the balance is ZrO2 + HfO2.

9. The method for preparing a dual-ceramic rare-earth modified thermal barrier coating according to claim 6, characterized in that, The supersonic flame spraying uses kerosene and oxygen as the combustion spraying gases, wherein the oxygen flow rate is 1800 L / min to 2000 L / min, the kerosene flow rate is 15 L / min to 30 L / min, nitrogen is used as the carrier gas with a flow rate of 15 L / min to 35 L / min, the powder feeding rate is 30 g / min to 50 g / min, and the spraying distance is 200 mm to 450 mm. The plasma spraying uses hydrogen and argon as the main gases, with a hydrogen flow rate of 10 L / min to 15 L / min, an argon flow rate of 30 L / min to 55 L / min, a current of 550 A to 650 A, a power of 40 KW to 50 KW, a powder feeding rate of 30 g / min to 50 g / min, and a spraying distance of 90 mm to 110 mm.

10. The method for preparing a dual-ceramic rare-earth modified thermal barrier coating according to claim 6, characterized in that, The substrate surface pretreatment includes degreasing and roughening the substrate surface, with a surface roughness Ra greater than 2 μm.

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