A heat-resistant and salt-corrosion-resistant ysz-based composite ceramic coating and a preparation method thereof

Abstract

The application discloses a heat-resistant salt-corrosion YSZ-based composite ceramic coating and a preparation method thereof, and belongs to the technical field of thermal protection coatings. The method comprises the following steps: mixing YSZ powder and high-entropy rare earth aluminate powder to prepare a composite powder; first, preparing an alloy bonding layer on the surface of a substrate, and then spraying the composite powder on the alloy bonding layer by using a plasma spraying method to form a composite ceramic coating containing vertical cracks; preparing a YSZ precursor sol; coating the YSZ precursor sol on the surface of the composite ceramic coating containing vertical cracks, allowing the YSZ precursor sol to penetrate into the cracks, and then performing heat treatment to convert the YSZ precursor sol into solid YSZ to fill the cracks, so that a dense heat-resistant salt-corrosion YSZ-based composite ceramic coating is obtained. The composite ceramic coating structure simultaneously has high thermal cycle stability and high heat-resistant salt corrosion, significantly improves the service life of the coating, and is suitable for being used as a thermal barrier coating of a high-performance required hot end component.

Description

Technical Field

[0001] This invention belongs to the field of thermal protective coating technology, and specifically relates to a YSZ-based composite ceramic coating resistant to heat and salt corrosion and its preparation method. Background Technology

[0002] With the rapid development of aircraft technology, the performance requirements for its turbine engines are increasing daily, especially since the operating temperature of the hot-end parts exceeds 1000℃, making it difficult to meet the requirements using a single high-temperature alloy. Therefore, preparing thermal barrier coatings (TBCs) with high-temperature oxidation resistance and hot salt corrosion resistance on the surface of high-temperature alloy substrates has become a consensus among materials scientists.

[0003] Currently, representative thermal barrier coatings consist of two parts: an adhesive layer and a ceramic layer. The adhesive layer is mainly a metal or alloy adhesive layer, which serves to prevent high-temperature oxidation and alleviate interfacial stress. The ceramic layer mainly provides thermal insulation and corrosion resistance (commonly used materials include YSZ and rare earth silicates). When preparing yttrium-stabilized zirconia coatings (YSZ, commonly 7%~8% Y2O3 stabilizing ZrO2) using thermal spraying, residual stress is generated between the YSZ layer and the adhesive layer due to the difference in thermal expansion coefficients, leading to a decrease in the coating's internal strain tolerance and fracture toughness. During service, this residual stress is more easily released through crack propagation, ultimately causing large-area coating detachment and significantly reducing the service life of the YSZ.

[0004] The presence of vertical cracks can increase the strain tolerance of the thermal barrier coating (TBC) system and reduce the residual stress accumulated inside the coating due to the difference in thermal expansion coefficients between the ceramic layer and the binder layer. Therefore, applying vertical cracks to TBCs can improve their thermal cycling stability and extend their service life. Although vertical cracks can optimize the performance of TBCs, it is difficult to prepare vertical cracks using thermal spraying. It requires high substrate temperature and increased stress caused by layer-by-layer quenching to achieve the formation of vertical cracks. Since it is difficult to precisely control the cooling rate of molten ceramic powder during spraying, how to prepare thermal barrier coatings with a rated number and depth of cracks is a major challenge in its development. In addition, although TBCs with vertical crack structures have excellent thermal cycling stability, the presence of vertical cracks also weakens the corrosion resistance of the coating in actual working environments. This is because vanadates and sulfates produced by incomplete combustion of fuel and dust inhaled by the turbine engine can form molten hot salts with low eutectic temperatures (usually including elements such as Na, S, Cl, V, and O), which will deposit on the surface of the ceramic layer and diffuse into the coating interior through vertical cracks, leading to premature coating failure. In addition, the presence of vertical cracks provides a channel for oxygen penetration, which accelerates the formation rate of thermally grown oxides on the bonding surface and causes abrupt changes in stress at the coating interface.

[0005] In summary, existing technologies lack an effective solution that can fundamentally and synergistically address the thermal cycling stability and resistance to hot salt corrosion of thermal barrier coatings. Therefore, there is an urgent need in the field for a novel coating design that retains the stress release advantages of vertical crack structures while effectively blocking the penetration path of corrosive media, thereby achieving a significant leap forward in the overall service performance of the coating. Summary of the Invention

[0006] To address the aforementioned problems, the main objective of this invention is to provide a YSZ-based composite ceramic coating resistant to hot salt corrosion and its preparation method. The YSZ-based composite ceramic coating of this invention possesses both high thermal cycling stability and high resistance to hot salt corrosion, significantly improving the service life of the coating.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a YSZ-based composite ceramic coating resistant to hot salt corrosion, comprising the following steps: We offer YSZ powder and high-entropy rare earth aluminate powder; YSZ powder and high-entropy rare earth aluminate powder are mixed to form a composite powder; First, an alloy bonding layer is prepared on the substrate surface, and then the composite powder is sprayed onto the alloy bonding layer by plasma spraying to form a composite ceramic coating containing vertical cracks. Preparation of YSZ precursor sol; The YSZ precursor sol is coated onto the surface of the composite ceramic coating containing vertical cracks, allowing it to penetrate into the cracks. Then, heat treatment is performed to transform the YSZ precursor sol into solid YSZ that fills the cracks, resulting in a dense YSZ-based composite ceramic coating that is resistant to heat and salt corrosion.

[0008] Furthermore, the high-entropy rare-earth aluminate is a perovskite-type compound with the structural formula (nRE). 1 / n AlO3; where RE is selected from n different rare earth elements among La, Nd, Sm, Gd, Eu, Er, and Y, and n=4 or 5.

[0009] Furthermore, in the composite powder, the mass ratio of high-entropy rare earth aluminate powder to YSZ powder is 10:1 to 10:3.

[0010] Furthermore, the YSZ powder is made of 7-8% Y2O3 and 92-93% ZrO2 in a molar ratio.

[0011] Furthermore, the plasma spraying adopts plasma flame spraying with a spraying power of 38~40kW.

[0012] Furthermore, the heat treatment temperature is 700~900℃, and the time is 1~4h.

[0013] Furthermore, the preparation of the YSZ precursor sol includes the following steps: A Zr source solution was prepared by dissolving zirconium isopropoxide in a solvent; Y source solution was prepared by dissolving yttrium nitrate in a solvent; After stirring and mixing the Zr source solution and the Y source solution, a complexing agent was added and the mixture was heated under reflux to obtain the YSZ precursor sol.

[0014] Furthermore, the high-entropy rare-earth aluminate powder provided is prepared using a self-made method, specifically including the following steps: After mixing n rare earth oxides with alumina by ball milling, the mixture is sintered. The sintered product is ball-milled or ground to obtain the high-entropy rare earth aluminate powder. The sintering treatment is carried out at a temperature of 1500~1700℃ for 6~15h; the ratio of the total molar amount of the n rare earth oxides to the molar amount of alumina is 1:1, and n=4 or 5.

[0015] Furthermore, the alloy bonding layer is a NiCrAlY bonding layer.

[0016] Secondly, the present invention also provides a YSZ-based composite ceramic coating resistant to heat and salt corrosion, which is prepared by the aforementioned method for preparing a YSZ-based composite ceramic coating resistant to heat and salt corrosion.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention innovatively utilizes the dual differences in the thermal expansion coefficients and dissolution kinetics of YSZ and high-entropy rare-earth aluminates during hot salt corrosion to design a composite ceramic coating structure that "first creates cracks, then fills them." This composite ceramic coating structure simultaneously possesses high thermal cycling stability and high resistance to hot salt corrosion, significantly improving the service life of the coating and making it suitable as a thermal barrier coating for high-performance hot-end components (such as aerospace engines).

[0018] Specifically, by utilizing the difference in thermal expansion coefficients between YSZ and high-entropy rare-earth aluminates, a composite ceramic coating containing vertical cracks is prepared by plasma spraying a mixture of YSZ powder and high-entropy rare-earth aluminates. This releases the internal stress of the coating and improves its thermal cycle life. Then, a YSZ precursor sol is used to fill the cracks, followed by heat treatment to form a dense coating, preventing hot salt solutions from penetrating into the coating along the cracks during corrosion.

[0019] Furthermore, during hot salt corrosion, the difference in dissolution rates between YSZ and high-entropy rare earth aluminates is utilized. In the molten salt corrosion environment, YSZ is rapidly and selectively dissolved, while high-entropy rare earth aluminates, due to their higher chemical stability and extremely slow element diffusion rate, dissolve at a much lower rate than YSZ. The rare earth ions released after YSZ dissolves react with the corrosive medium to generate solid reaction products. These products accumulate on the surface of high-entropy rare earth aluminates, thus forming a dense barrier layer in situ at the molten salt corrosion front. This effectively blocks further corrosion penetration by the hot salt solution, significantly improving hot salt corrosion resistance.

[0020] Other features and effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0022] Figure 1 The image shows a SEM image of the surface of the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating of Embodiment 1 of the present invention; Figure 2 The image shows a SEM image of the surface of the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating of Embodiment 2 of the present invention; Figure 3 The image shows a cross-sectional SEM image of the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating of Embodiment 2 of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a YSZ-based composite ceramic coating resistant to hot salt corrosion, comprising the following steps: We offer YSZ powder and high-entropy rare earth aluminate powder; YSZ powder and high-entropy rare earth aluminate powder are mixed to form a composite powder; First, an alloy bonding layer is prepared on the substrate surface, and then the composite powder is sprayed onto the alloy bonding layer by plasma spraying to form a composite ceramic coating containing vertical cracks. Preparation of YSZ precursor sol; The YSZ precursor sol is coated onto the surface of the composite ceramic coating containing vertical cracks, allowing it to penetrate into the cracks. Then, heat treatment is performed to transform the YSZ precursor sol into solid YSZ that fills the cracks, resulting in a dense YSZ-based composite ceramic coating that is resistant to heat and salt corrosion.

[0025] In some preferred embodiments of the present invention, the high-entropy rare-earth aluminate is a perovskite-type compound with the structural formula (nRE). 1 / n AlO3; wherein RE is selected from n different rare earth elements selected from La, Nd, Sm, Gd, Eu, Er, and Y, where n=4 or 5. This invention utilizes the random distribution and synergistic effect of multiple rare earth elements in the crystal lattice to control the crystal structure of rare earth aluminates through high entropy regulation, forming a perovskite-type compound with a stable crystal structure at high temperatures. Simultaneously, the aforementioned high entropy structure can regulate the coefficient of thermal expansion. By precisely controlling the coefficient of thermal expansion of high-entropy rare earth aluminates using different types of rare earth elements, and by utilizing the difference in the coefficient of thermal expansion between high-entropy rare earth aluminates and YSZ, cracks are generated to release stress.

[0026] In some preferred embodiments of the present invention, the mass ratio of high-entropy rare earth aluminate powder to YSZ powder in the composite powder is 10:1 to 10:3.

[0027] In some preferred embodiments of the present invention, the YSZ powder is made from a molar ratio of 7-8% Y₂O₃ and 92-93% ZrO₂. The YSZ provided by the present invention can be a commercially available product or can be prepared in-house. The in-house preparation method is as follows: 7-8% Y₂O₃ and 92-93% ZrO₂ are ball-milled and mixed for 10-24 hours, then sintered at 1200-1500℃ for 1-2 hours, and the sintered product is then ground or ball-milled to obtain YSZ powder. More preferably, the particle size of the YSZ powder can be selected from 0.5-1 μm.

[0028] In some preferred embodiments of the present invention, the plasma spraying employs plasma flame spraying with a spraying power of 38-40 kW. The present invention achieves a suitable droplet velocity by rationally controlling the spraying power of the plasma spraying, and utilizes the thermal stress generated by the impact of high-temperature, high-speed droplets to induce the desired vertical crack structure, thereby releasing the internal stress of the coating and improving the thermal cycle life of the coating.

[0029] In some preferred embodiments of the present invention, the thickness of the composite ceramic coating containing vertical cracks is 300~600μm, more preferably 400~500μm.

[0030] In some optional embodiments of the present invention, when YSZ powder and high-entropy rare earth aluminate powder are mixed to form a composite powder, the above-mentioned mixing process can be carried out by directly grinding and mixing YSZ powder and high-entropy rare earth aluminate powder to obtain the composite powder, or by mixing YSZ powder and high-entropy rare earth aluminate powder and then spray granulating to obtain the composite powder (spherical particles, preferably with a particle size of 40~60μm). Exemplarily, the spray granulation process specifically involves: mixing YSZ powder, high-entropy rare earth aluminate powder, and polyvinyl alcohol to obtain a mixed solution, granulating the mixed solution, and then subjecting it to drying and heat treatment to obtain the composite powder.

[0031] In some preferred embodiments of the present invention, the heat treatment temperature is 700~900℃, more preferably 800~850℃, and the time is 1~4h, more preferably 2~3h. Through the above heat treatment, the solvent and organic components in the YSZ precursor sol can be decomposed and volatilized into solid YSZ, thereby filling vertical cracks and obtaining a dense composite ceramic coating. Furthermore, to achieve a denser crack filling, the YSZ precursor sol can be coated and heat-treated multiple times (e.g., 2~4 times).

[0032] In some preferred embodiments of the present invention, the preparation of YSZ precursor sol includes the following steps: dissolving zirconium isopropoxide in a solvent to obtain a Zr source solution; Y source solution was prepared by dissolving yttrium nitrate in a solvent; After stirring and mixing the Zr source solution and the Y source solution, a complexing agent was added and the mixture was heated under reflux to obtain the YSZ precursor sol.

[0033] In the preparation process of the YSZ precursor sol described above, the complexing agent can be, for example, citric acid.

[0034] In the above-mentioned YSZ precursor sol preparation process, the preferred temperature for the heating and reflux treatment is 70~90℃, and the preferred time is 2~6h.

[0035] In the above YSZ precursor sol, the preferred molar ratio of Zr to Y is 10:1.

[0036] In some preferred embodiments of the present invention, the high-entropy rare-earth aluminate powder can be a commercially available product or prepared by a self-made method, specifically including the following steps: After mixing n rare earth oxides with alumina by ball milling, the mixture is sintered. The sintered product is ball-milled or ground to obtain the high-entropy rare earth aluminate powder.

[0037] More preferably, the sintering temperature is 1500~1700℃, more preferably 1600~1650℃, and the time is 6~15h, more preferably 9~12h; the ratio of the total molar amount of the n rare earth oxides to the molar amount of alumina is 1:1, and n=4 or 5. The particle size of the high-entropy rare earth aluminate powder can be selected from 0.5~1μm.

[0038] In some preferred embodiments of the present invention, the alloy bonding layer is a NiCrAlY bonding layer.

[0039] A second aspect of the present invention provides a YSZ-based composite ceramic coating resistant to heat and salt corrosion, which is prepared by the aforementioned method for preparing a YSZ-based composite ceramic coating resistant to heat and salt corrosion.

[0040] Based on the reasons mentioned above, the YSZ-based composite ceramic coating prepared by this invention has both high thermal cycling stability and high resistance to hot salt corrosion, which significantly improves the service life of the coating and is suitable as a thermal barrier coating for high-performance hot-end components (such as aerospace engines).

[0041] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0042] Example 1 A YSZ-based composite ceramic coating resistant to heat and salt corrosion is prepared by the following method: (a) Preparation of YSZ powder: 8% Y2O3 and 92% ZrO2 were mixed and ball-milled for 24 h, followed by sintering at 1400 °C for 2 h. The calcined powder usually agglomerates severely and needs to be ball-milled again to break up the agglomerates, so as to obtain YSZ powder with a particle size in the range of 0.5~1 μm.

[0043] (b) (Nd) 1 / 5 Sm 1 / 5 Eu 1 / 5 Gd 1 / 5 Y 1 / 5 AlO3 powder preparation: Five rare earth oxides (Nd2O3, Sm2O3, Eu2O3, Gd2O3, Y2O3) in equimolar ratio were ball-milled with alumina for 24 h, sintered at 1600℃ for 10 h, crushed and then ball-milled to a particle size of 0.5~1 μm, wherein the total molar amount of rare earth oxides to the molar amount of alumina was 1:1.

[0044] (c) Preparation of composite powder: YSZ powder is combined with (Nd) 1 / 5 Sm 1 / 5Eu 1 / 5 Gd 1 / 5 Y 1 / 5 AlO3 powder was mixed at a mass ratio of 10:1 for 24 hours, then mixed with 5wt% polyvinyl alcohol, and granulated into spherical particles with a particle size of 50μm at an inlet temperature of 200℃, and then heat-treated at 1200℃ for 5 hours.

[0045] (d) Plasma spraying preparation of coating: Plasma flame spraying (power 34kW, Ar and H2 mixture) was used to preheat the substrate to 800°C and then NiCrAlY alloy bonding layer was sprayed on the substrate surface; then plasma flame spraying (power 40kW, Ar and H2 mixture) was used to spray the above composite powder on the bonding layer surface to prepare a composite ceramic coating with vertical cracks with a deposition thickness of 400μm.

[0046] (e) Preparation of YSZ precursor sol: Zirconium isopropoxide and Y(NO3)3 were added to a mixed solution of anhydrous ethanol and deionized water, respectively, and stirred vigorously to dissolve them, obtaining a Zr source solution and a Y source solution. The two solutions were then mixed in a specific ratio, and citric acid was added as a complexing agent. The mixture was heated to 85°C, refluxed, and stirred for 4 hours to obtain a clear and transparent YSZ sol; the molar ratio of Zr to Y in the YSZ sol was 10:1.

[0047] (f) YSZ filling of coating cracks: YSZ precursor sol is applied to the coating surface to allow the sol to penetrate into the cracks, followed by heat treatment at 800℃ for 1 hour to allow the solvent and organic components to decompose and volatilize. This step is repeated 4 times to obtain a dense, heat-resistant, salt-corrosion-resistant YSZ-based composite ceramic coating.

[0048] Performance test data: The surface structure of the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating prepared in this embodiment is as follows: Figure 1 As shown, the porosity of the coating is 5.2%. Compared with the existing traditional YSZ coating (a crack-free coating prepared by plasma spraying of single YSZ powder), the thermal cycling (1300℃-room temperature) life of the YSZ-based composite ceramic coating resistant to hot salt corrosion in this embodiment is increased by 1 time, and the hot salt corrosion resistance (tested according to HB20401-2016 standard, hot salt is NaCl+Na2SO4+V2O5) is greatly improved, and the corrosion depth is reduced by 67%.

[0049] Example 2 A YSZ-based composite ceramic coating resistant to heat and salt corrosion is prepared by the following method: (a) Preparation of YSZ powder: 8% Y2O3 and 92% ZrO2 were mixed and ball-milled for 24 h, followed by sintering at 1400 °C for 2 h. The calcined powder usually agglomerates severely and needs to be ball-milled again to break up the agglomerates, so as to obtain YSZ powder with a particle size in the range of 0.5~1 μm.

[0050] (b) (Y) 1 / 4 Eu 1 / 4 Nd 1 / 4 Sm 1 / 4 AlO3 powder preparation: Four rare earth oxides (Nd2O3, Sm2O3, Eu2O3, Y2O3) in equimolar ratio were ball-milled with alumina for 24 h, sintered at 1600℃ for 10 h, crushed and then ball-milled to a particle size of 0.5~1 μm, wherein the total molar amount of rare earth oxides to the molar amount of alumina was 1:1.

[0051] (c) Preparation of composite powder: YSZ powder is combined with (Y 1 / 4 Eu 1 / 4 Nd 1 / 4 Sm 1 / 4 AlO3 powder was mixed at a mass ratio of 10:2 for 24 hours, then mixed with 5wt% polyvinyl alcohol, and granulated into spherical particles with a particle size of 50μm at an inlet temperature of 200℃, and then heat-treated at 1200℃ for 5 hours.

[0052] (d) Plasma spraying preparation of coating: Plasma flame spraying (power 34kW, mixed gas of Ar and H2) was used to preheat the substrate to 800°C and then NiCrAlY alloy bonding layer was sprayed on the substrate surface; then plasma flame spraying (power 38kW, mixed gas of Ar and H2) was used to spray the above composite powder on the bonding layer surface to prepare a composite ceramic coating containing vertical cracks with a deposition thickness of 600μm.

[0053] (e) Preparation of YSZ precursor sol: Zirconium isopropoxide and Y(NO3)3 were added to a mixed solution of anhydrous ethanol and deionized water, respectively, and stirred vigorously to dissolve them, obtaining a Zr source solution and a Y source solution. The two solutions were then mixed in a specific ratio, and citric acid was added as a complexing agent. The mixture was heated to 85°C, refluxed, and stirred for 4 hours to obtain a clear and transparent YSZ sol, wherein the molar ratio of Zr to Y in the YSZ sol was 10:1.

[0054] (f) YSZ filling of coating cracks: The above-mentioned YSZ precursor sol is applied to the coating surface to allow the sol to penetrate into the cracks. Then, it is heat-treated at 800℃ for 1 hour to allow the solvent to decompose and volatilize. This step is repeated twice to obtain a dense YSZ-based composite ceramic coating that is resistant to heat and salt corrosion.

[0055] Performance test data: The surface structure and cross-sectional structure of the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating prepared in this embodiment are as follows: Figure 2 , Figure 3 As shown, the porosity of the coating is 5.6%. Compared with the existing traditional YSZ coating (a crack-free coating prepared by plasma spraying of single YSZ powder), the thermal cycling (1300℃-room temperature) life of the YSZ-based composite ceramic coating resistant to hot salt corrosion in this embodiment is increased by 1.2 times, and the hot salt corrosion resistance (tested according to HB20401-2016 standard, hot salt is NaCl+Na2SO4+V2O5) is greatly improved, and the corrosion depth is reduced by 80%.

[0056] Example 3 A YSZ-based composite ceramic coating resistant to heat and salt corrosion is prepared by the following method: (a) Preparation of YSZ powder: Y2O3 and ZrO2 with a molar ratio of 8% were mixed and ball-milled for 24 h, and then sintered at 1400 °C for 2 h. The calcined powder usually agglomerates severely and needs to be ball-milled again to break up the agglomerates, so as to obtain YSZ powder with a particle size in the range of 0.5~1 μm.

[0057] (b) (Y) 1 / 5 Er 1 / 5 Gd 1 / 5 Eu 1 / 5 La 1 / 5 AlO3 powder preparation: Five rare earth oxides (Nd2O3, Er2O3, Eu2O3, La2O3, Y2O3) in equimolar ratio were ball-milled with alumina for 24 h, sintered at 1600℃ for 10 h, crushed and then ball-milled to a particle size of 0.5~1 μm, wherein the total molar amount of rare earth oxides to the molar amount of alumina was 1:1.

[0058] (c) Preparation of composite powder: YSZ powder is combined with (Y 1 / 5 Er 1 / 5 Gd 1 / 5 Eu 1 / 5 La 1 / 5 AlO3 powder was mixed at a mass ratio of 10:3 for 24 hours, then mixed with 5wt% polyvinyl alcohol, and granulated into spherical particles with a particle size of 50μm at an inlet temperature of 200℃, and then heat-treated at 1200℃ for 5 hours.

[0059] (d) Plasma spraying preparation of coating: Ar / H2 plasma flame spraying (power 34kW) was used, the substrate was preheated to 800℃, and a NiCrAlY alloy bonding layer was sprayed on the substrate surface; then Ar / H2 plasma flame spraying (power 40kW) was used to spray the above composite powder on the bonding layer surface to prepare a composite ceramic coating with vertical cracks with a deposition thickness of 300μm.

[0060] (e) Preparation of YSZ precursor sol: Zirconium isopropoxide and Y(NO3)3 were added to a mixed solution of anhydrous ethanol and deionized water, respectively, and stirred vigorously to dissolve them, obtaining a Zr source solution and a Y source solution. The two solutions were then mixed in a certain ratio, and citric acid was added as a complexing agent. The mixture was heated to 85°C, refluxed, and stirred for 4 hours to obtain a clear and transparent YSZ sol; wherein the molar ratio of Zr to Y in the YSZ sol was 10:1.

[0061] (f) YSZ filling of coating cracks: YSZ precursor sol is applied to the coating surface to allow the sol to penetrate into the cracks. Then, it is heat-treated at 800℃ for 1 hour to allow the solvent to decompose and volatilize. This step is repeated 4 times to obtain a dense YSZ-based composite ceramic coating that is resistant to heat and salt corrosion.

[0062] Performance test data: The porosity of the YSZ-based composite ceramic coating resistant to hot salt corrosion prepared in this embodiment is 3.9%. Compared with the existing traditional YSZ coating (a crack-free coating prepared by plasma spraying of single YSZ powder), the hot salt corrosion resistant YSZ-based composite ceramic coating in this embodiment has a thermal cycle (1300℃-room temperature) life increased by about 1 times, and the hot salt corrosion resistance (tested according to HB20401-2016 standard, hot salt is NaCl+Na2SO4+V2O5) is greatly improved, and the corrosion depth is reduced by 76%.

[0063] 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a YSZ-based composite ceramic coating resistant to heat and salt corrosion, characterized in that, Includes the following steps: We offer YSZ powder and high-entropy rare earth aluminate powder; YSZ powder and high-entropy rare earth aluminate powder are mixed to form a composite powder; First, an alloy bonding layer is prepared on the substrate surface, and then the composite powder is sprayed onto the alloy bonding layer by plasma spraying to form a composite ceramic coating containing vertical cracks. Preparation of YSZ precursor sol; The YSZ precursor sol is coated onto the surface of the composite ceramic coating containing vertical cracks, allowing it to penetrate into the cracks. Then, heat treatment is performed to transform the YSZ precursor sol into solid YSZ that fills the cracks, resulting in a dense YSZ-based composite ceramic coating that is resistant to heat and salt corrosion.

2. The method for preparing the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating according to claim 1, characterized in that, The high-entropy rare-earth aluminate is a perovskite-type compound with the structural formula (nRE). 1 / n AlO3; where RE is selected from n different rare earth elements among La, Nd, Sm, Gd, Eu, Er, and Y, and n=4 or 5.

3. The method for preparing the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating according to claim 1, characterized in that, In the composite powder, the mass ratio of high-entropy rare earth aluminate powder to YSZ powder is 10:1 to 10:

3.

4. The method for preparing the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating according to claim 1, characterized in that, The YSZ powder is made from a molar ratio of 8% Y2O3 and 92% ZrO2.

5. The method for preparing the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating according to claim 1, characterized in that, The plasma spraying adopts plasma flame spraying with a spraying power of 38~40kW.

6. The method for preparing the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating according to claim 1, characterized in that, The heat treatment is performed at a temperature of 700~900℃ for 1~4 hours.

7. The method for preparing the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating according to claim 1, characterized in that, The preparation of the YSZ precursor sol includes the following steps: A Zr source solution was prepared by dissolving zirconium isopropoxide in a solvent; Y source solution was prepared by dissolving yttrium nitrate in a solvent; After stirring and mixing the Zr source solution and the Y source solution, a complexing agent was added and the mixture was heated under reflux to obtain the YSZ precursor sol.

8. The method for preparing the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating according to claim 1, characterized in that, The high-entropy rare-earth aluminate powder provided is prepared by a self-made method, specifically including the following steps: After mixing n rare earth oxides with alumina by ball milling, sintering is performed. The sintered product is ball-milled or ground to obtain the high-entropy rare earth aluminate powder. The sintering treatment is carried out at a temperature of 1500~1700℃ for 6~15h; the ratio of the total molar amount of the n rare earth oxides to the molar amount of alumina is 1:1, and n=4 or 5.

9. The method for preparing the heat-resistant salt corrosion-resistant YSZ-based composite ceramic coating according to claim 1, characterized in that, The alloy bonding layer is a NiCrAlY bonding layer.

10. A YSZ-based composite ceramic coating resistant to heat and salt corrosion, characterized in that, The coating is prepared by the method described in any one of claims 1 to 9 for the preparation of a YSZ-based composite ceramic coating resistant to hot salt corrosion.

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