Gradient self-repairing sealing coating and preparation method thereof

Abstract

The invention provides a gradient self-repairing sealing coating and a preparation method thereof, and relates to a high-temperature protection material. The gradient self-repairing sealing coating comprises a bonding layer, a gradient middle layer, a transition layer and an abradable surface layer which are sequentially arranged from a base body to the surface. A bonding layer in the gradient self-repairing sealing coating contains silicate, so that the bonding strength and the heat-resistant stability of a matrix are improved; rare earth silicate and Ir elements are introduced into the gradient intermediate layer, so that high-temperature corrosion resistance is enhanced, and thermal stress is relieved; the transition layer contains zirconium oxide and graphene and has the functions of thermal isolation and stress regulation; the abradable surface layer is formed by combining rare earth silicate and graphite, low friction and preferential abrasion are achieved, and effective sacrifice protection is provided. The overall structure can have multiple properties of heat, corrosion resistance and abrasion resistance, and is suitable for the surface protection requirement under the complex hot end working condition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature protective materials, in particular to a gradient self-repairing sealing coating and a preparation method thereof. BACKGROUND

[0002] High-temperature protective coating is a kind of key material system that can be used on the surface of hot end components of aero-engine, gas turbine and high-temperature equipment, which can isolate heat conduction, resist corrosion and erosion and particle erosion, so as to prolong the service life of the key structure under extreme working conditions. With the continuous increase of the operating temperature of the hot end equipment, the coating system needs to meet multiple functional requirements such as thermal insulation, corrosion resistance, wear resistance and thermal cycle stability. In order to adapt to the service environment under multiple fields, high-temperature coating materials gradually evolve towards composite structure, gradient transition and functional integration, which become an important development direction in the field of surface engineering.

[0003] The existing high-temperature functional coating mostly uses zirconia material as the thermal barrier main layer, and cooperates with rare earth doping to improve the anti-phase change ability and thermal stability. There are also documents that use ceramic / metal composite system or introduce reinforcing phase in the functional layer to improve the mechanical response. In the above technical system, there are still many practical problems. On the one hand, the thermal expansion coefficient of each layer in the multi-layer structure is not matched, which is easy to produce interfacial thermal stress under cold and hot cycle, resulting in delamination or peeling phenomenon; on the other hand, although the rare earth oxide system has high temperature phase stability, it is still easy to react or penetrate corrosion in the molten slag (CMAS) or molten salt environment containing Ca-Mg-Al-Si, and the mechanical properties of the coating after corrosion quickly decay. In addition, although the traditional porous ceramic structure has certain thermal barrier performance, microcracks are easy to expand under long-term service conditions, and it lacks the response repair ability to local damage, which affects its service life.

[0004] In summary, the existing high-temperature functional coating still has many challenges in dealing with complex service environment, including insufficient structure thermal matching, limited corrosion resistance, irreversible local damage and short service period. These problems are more prominent in extreme working conditions such as high-frequency thermal shock, molten salt corrosion and multi-directional friction and wear, which restricts the wide application of coating technology in the new generation of high-performance power equipment.

[0005] Therefore, the present application is provided. SUMMARY

[0006] The purpose of the present application is to provide a gradient self-repairing sealing coating and a preparation method thereof. The gradient self-repairing sealing coating realizes the combination stability, corrosion resistance, stress buffering and wear protection in high-temperature environment through the synergistic design of multiple different functional layers. The functions of each layer are complementary, which helps to improve the thermal cycle stability and overall service life.

[0007] In order to achieve the above-mentioned object of the present application, the following technical solutions are adopted: In a first aspect, the present application provides a gradient self-repairing seal coating, comprising a bonding layer containing silicate, a gradient intermediate layer containing rare earth silicate and Ir element, a transition layer containing zirconia material and graphene, and an abradable surface layer containing rare earth silicate and graphite material, which are sequentially arranged from the substrate to the surface.

[0008] In an optional embodiment, the molar ratio of Ir element to Si element in the rare earth silicate is 0.2-0.5; and / or, the rare earth silicate material comprises Yb2Si2O7.

[0009] In an optional embodiment, the gradient intermediate layer is a gradient structure formed by a pulsed plasma spraying method based on the bonding layer; wherein the gradient structure satisfies at least one of the following conditions: A. The porosity of the gradient structure is 15%-25%; B. The content of Ir element in the gradient structure increases linearly from 0wt% to 15wt% along the thickness direction; C. The Rockwell hardness of the gradient structure decreases from 75 to 60 along the thickness direction.

[0010] In an optional embodiment, the zirconia material comprises 8YSZ; and / or, The volume fraction of the zirconia material in the transition layer is 80%-90%; and / or, The volume fraction of graphene in the transition layer is 3vol%; and / or, The porosity of the transition layer is 20%-30%; and / or, The high-temperature Rockwell hardness HR15Y of the transition layer is 80-90; and / or, The silicate in the bonding layer comprises HfSiO4; and / or, The bonding layer is formed by supersonic flame spraying; and / or, The thickness of the bonding layer is 300μm-500μm; and / or, The porosity of the bonding layer is not more than 5%; and / or, The Rockwell hardness HR45Y of the bonding layer is 65-75; and / or, The bonding strength of the bonding layer is not less than 40MPa; and / or, The temperature resistance of the bonding layer is not less than 1400℃; and / or, The graphite material in the abradable surface layer accounts for 10vol%-20vol%; and / or, The abradable surface layer is a connected honeycomb structure formed by cold spraying; and / or, The porosity of the abradable surface layer is 30% to 40%; and / or, The high-temperature Rockwell hardness HR15Y of the abradable surface layer is 70 to 80; and / or, The friction coefficient of the abradable surface layer is not greater than 0.12.

[0011] In an optional embodiment, at least part of the area of the gradient intermediate layer is provided with a ternary doped region; The ternary doped region comprises (Yb 1-x-y Y x Sc y )2SiO5. Wherein, x+y≤0.5; Preferably, when x-y≥0.1, the CMAS corrosion penetration resistance of the gradient intermediate layer under the condition of 1350℃ and 240 hours is ≤5μm; Preferably, when y-x≥0.1, the molten salt corrosion rate of the gradient intermediate layer under the condition of 1200℃ and 300 hours is ≤0.02% / h.

[0012] In an optional embodiment, a first composite layer is further provided between the bonding layer and the gradient intermediate layer; The first composite layer comprises HfO2-Yb2O3; and / or, the thickness of the first composite layer is 30μm to 60μm; and / or, the gradient change of the thermal expansion coefficient of the first composite layer is not greater than 2×10 -6 / ℃.

[0013] In an optional embodiment, a second composite layer is further provided between the gradient intermediate layer and the transition layer; the second composite layer comprises Al2O3-TiC; The second composite layer is a gradient structure; and in the gradient structure, the content of Al2O3 changes from 100% to 0% along the thickness direction; the content of TiC changes from 0% to 100%; and / or, the interfacial bonding strength between the gradient intermediate layer and the transition layer is not less than 35MPa.

[0014] In a second aspect, the present application provides a preparation method of the gradient self-repairing seal coating as described in any one of the preceding embodiments, comprising: A silicate-containing bonding layer is prepared on the surface of the substrate by using supersonic flame spraying; A gradient intermediate layer containing rare earth silicate and Ir is deposited on the bonding layer by using pulse plasma spraying process; A transition layer containing zirconia material and graphene is formed on the gradient intermediate layer by using plasma spraying method; An abradable surface layer containing rare earth silicate and graphite material is formed on the transition layer by using cold spraying process.

[0015] In a third aspect, the present application provides a method for preparing the gradient self-repairing seal coating as described in the preceding embodiments, the gradient intermediate layer is formed by depositing Yb2Si2O7-Ir nanopowder in a gradient structure through a pulsed plasma spraying process; wherein the Yb2Si2O7-Ir nanopowder is prepared by a sol-gel method; and / or, the particle size of the Yb2Si2O7-Ir nanopowder is 50nm-100nm; and / or, the Yb2Si2O7-Ir nanopowder is doped with at least 1vol% of carbon nanotubes; and / or, the main arc power of the pulsed plasma spraying process is 40kW-65kW; and / or, the pulse frequency of the pulsed plasma spraying process is 100Hz; and / or, the gas pressure of the cold spraying process is 2MPa; and / or, the temperature of the cold spraying process is not more than 100℃; and / or, the porosity of the abradable surface layer is 30%-40%; and / or, the plasma spraying method is a three-electrode plasma spraying process; and / or, after forming the abradable surface layer containing rare earth silicate and graphite material, further comprising: performing vacuum annealing treatment.

[0016] In a fourth aspect, the present application provides a product, the product comprising a thermal protection member; The thermal protection member is at least partially coated with the gradient self-repairing seal coating as described in any one of the preceding embodiments.

[0017] The present application provides a gradient self-repairing seal coating and a method for preparing the same. The gradient self-repairing seal coating is constructed by sequentially building a bonding layer, a gradient intermediate layer, a transition layer and an abradable surface layer from the substrate to the surface, which has a clear hierarchical functional synergy relationship and can provide comprehensive structural protection and performance guarantee in high-temperature service environment.

[0018] The bonding layer containing silicate in the gradient self-repairing seal coating helps to achieve stable bonding with the substrate material, improve the overall adhesion strength, and provide good high-temperature resistance foundation, so that the coating system has a stable bearing foundation. The presence of this layer helps to buffer the physical stress difference between the substrate and the upper functional structure, reducing the risk of interface peeling.

[0019] The gradient interlayer containing rare earth silicate and Ir element has excellent thermal stability and corrosion resistance of rare earth silicate, and the characteristics of forming an oxidation phase of noble metal elements under high temperature environment to lubricate and fill cracks. The introduction of gradient design makes the composition and performance gradually change in the thickness direction, which helps to relieve the thermal stress concentration caused by the mismatch of the thermal expansion coefficient, and improves the overall thermal cycle stability.

[0020] The transition layer containing zirconia material and graphene can provide excellent mechanical cushioning and fracture inhibition performance at high temperature. The zirconia material has good thermal isolation capacity, and the sheet structure and elastic characteristics of graphene make it have certain strain adjustment capacity under scraping or fretting load. The presence of the transition layer helps to further reduce the stress discontinuity between the gradient interlayer and the surface layer, and improve the integrity of the coating structure.

[0021] The outermost layer is an abradable surface layer containing rare earth silicate and graphite material, which can preferentially wear during operation, providing sacrificial protection to prevent direct exposure of the deep structure to extreme environments. The graphite composition gives it a low friction coefficient and good wear resistance, while maintaining a certain porosity, which is beneficial to maintaining lubrication and energy dissipation capacity during friction or erosion, prolonging the overall service life of the key components.

[0022] The overall structure has the characteristics of multi-layer composite, clear division of labor, and functional synergy, and can provide reliable support in multiple performance dimensions such as heat, corrosion resistance, and wear resistance, suitable for surface protection requirements in complex high-temperature operating environments. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0024] Figure 1 It is a cross-sectional structure schematic diagram of the gradient self-repairing seal coating in the embodiments of the present application; Figure 2 It is a flowchart schematic diagram of the preparation method of the gradient self-repairing seal coating in the embodiments of the present application.

[0025] Main element symbol explanation: 100-gradient self-repairing seal coating; 1-bonding layer; 2-gradient interlayer; 3-transition layer; 4-abradable surface layer; 200-substrate. DETAILED DESCRIPTION

[0026] The embodiments of the present application will be described in detail below with examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. The specific conditions not noted in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not noted by the manufacturer, which are all conventional products that can be obtained by purchase.

[0027] Reference Figure 1 In the embodiments of the present application, a gradient self-repairing seal coating is provided. From the substrate to the surface, the coating comprises a bonding layer, a gradient intermediate layer, a transition layer and an abradable surface layer in sequence. The coating adopts a multi-layer composite structure design, aiming to adapt to the complex stress field and corrosive medium under high temperature environment, and at the same time realize multiple protection functions.

[0028] Specifically, from the substrate to the surface, the coating comprises in sequence: (1) a bonding layer containing silicate; wherein the bonding layer contains silicate material, which is used to enhance the interfacial bonding strength between the coating and the substrate, and provide thermal stability support for the upper layer structure. The silicate material has good high-temperature resistance and is suitable for being used as a bottom substrate in high-temperature service environment.

[0029] (2) a gradient intermediate layer containing rare earth silicate and Ir element; the gradient intermediate layer contains rare earth silicate and Ir element, which constitutes the main protection structure. The rare earth silicate has good thermal stability and corrosion resistance, and is suitable for high-temperature oxidation and corrosive medium environment; the Ir element is a noble metal material, which can provide certain structural lubricity and self-sealing ability at high temperature, and is helpful to improve crack propagation inhibition and thermal stress release.

[0030] (3) a transition layer containing zirconia material and graphene; the transition layer contains zirconia material and graphene, which is used to establish a thermal expansion transition area between the functional layers. Zirconia has excellent thermal insulation performance, while graphene is a sheet structure material with high strength and flexibility, which can effectively buffer the thermal-mechanical mismatch between different layers and improve the overall structural integrity.

[0031] (4) an abradable surface layer containing rare earth silicate and graphite material. The abradable surface layer contains rare earth silicate and graphite material, which is set in the outermost layer and preferentially occurs controllable abrasion in actual service process. The graphite material has low friction characteristics, which can reduce the wear and tear between parts; the rare earth silicate maintains the structural stability and heat resistance, thereby prolonging the service life of the coating to a certain extent and protecting the lower structure from damage.

[0032] In summary, the coating structure provided in the embodiment realizes multiple protection requirements such as high-temperature resistance, corrosion resistance, stress buffering and controllable wear through multi-functional layer synergy on the basis of ensuring overall bonding performance, and is suitable for long-term service environment of high-temperature hot end components.

[0033] In some embodiments, the rare earth silicate material comprises Yb2Si2O7.

[0034] It should be noted that, in the coating system, Ir has more excellent high-temperature stability, self-repairing potential and structural compatibility than other platinum group metals such as Pt, Rh and Pd, and is therefore preferably selected as a doping component of the gradient intermediate layer.

[0035] Ir can stably generate lubricant IrO2 in an oxidation environment of ≥1200℃, and has more structural stability and crack filling capacity than oxides such as PtO2, Rh2O3 and PdO, which helps to realize dynamic self-repairing in the thermal cycle process.

[0036] Ir 3+ The ionic radius of Ir matches that of Yb 3+ and Si 4+ , can stably embed Yb2Si2O7lattice to form a three-dimensional network structure, enhance high-temperature strength and coating density, and at the same time, the gradient distribution can effectively control the overall thermal expansion coefficient of the coating, realize thermal matching with the substrate such as nickel-based alloy, and reduce the interfacial thermal stress.

[0037] In addition, Ir has good high-temperature CMAS and molten salt corrosion resistance, and can form a stable barrier layer on the surface, which cooperates with the ternary doping system to play a protective effect. In terms of process, the high melting point and low vapor pressure of Ir make it suitable for pulse plasma spraying process, which is convenient for realizing composition control and uniform deposition in the gradient structure.

[0038] In terms of thermal performance, corrosion stability and process compatibility, Ir has more comprehensive advantages than other platinum group elements in the structure, and can effectively support the high-temperature protection requirements of "self-repairing-thermal matching-corrosion resistance" integration.

[0039] In addition, the Yb2Si2O7-Ir intermediate layer can generate IrO2lubricating phase in an oxidation environment of ≥1200℃, fill cracks of ≤100μm, and the repair rate is ≥95%.

[0040] In some embodiments, the molar ratio of Ir element to Si element in the rare earth silicate is 0.2-0.5. For example, it can be 0.2, 0.3, 0.4, 0.5, etc.

[0041] The above molar ratio range comprehensively considers the self-repairing capacity, thermal physical matching, structural stability and engineering applicability of the coating.

[0042] When the molar ratio is between 0.2 and 0.5, the Ir element can stably form an IrO2 lubricating phase in a high-temperature oxidation environment, has good crack filling capacity and self-repairing effect, and the repair rate can reach more than 95%, and the thermal shock resistance will not decrease due to the liquid film caused by excessive IrO2.

[0043] The thermal expansion coefficient of the bonding layer can be 8.5×10 -6 / k, and the thermal expansion coefficient of the transition layer is 10.5×10 -6 / k, so the thermal expansion coefficient of the intermediate layer needs to be adjusted by the gradient distribution of Ir: when the molar ratio of Ir / Si is 0.2, the thermal expansion coefficient of the intermediate layer is approximately 7.8×10 -6 / k; when the molar ratio of Ir / Si is 0.5, the thermal expansion coefficient is approximately 9.2×10 -6 / k; and the range can make the thermal expansion coefficient gradient change from the bonding layer to the transition layer be ≤2×10 -6 / ℃, and the thermal stress is reduced by 40% (the thermal stress difference of the traditional three-layer structure is >5×10 -6 / ℃).

[0044] Therefore, by being limited in the molar ratio range, the thermal expansion coefficient of the intermediate layer can be controlled in the range of 7.8×10 -6 / k to 9.2×10 -6 / k, which is beneficial to alleviate the thermal expansion difference with the adjacent layers, so that the overall thermal expansion gradient change is controlled within 2×10 -6 / ℃, and the interface thermal stress is significantly reduced.

[0045] In terms of process adaptability, for example, in the PS-PVD process, a molar ratio lower than 0.2 can easily lead to insufficient Ir component during deposition, making it difficult to form a stable gradient distribution; and a molar ratio higher than 0.5 can cause powder agglomeration and an increase in porosity, and excessive evaporation can lead to powder agglomeration (particle size >200 nm), coating porosity >30%, and a decrease in bonding strength (<30 MPa). In addition, this ratio range can effectively control the raw material cost while ensuring performance optimization, has a higher performance-price ratio compared to a pure Ir system, and is convenient for engineering application promotion.

[0046] In some embodiments, the gradient intermediate layer is a gradient structure formed based on the bonding layer by a pulsed plasma spraying method; wherein the gradient structure satisfies at least one of the following conditions: A. The porosity of the gradient structure is 15% to 25%; for example, it can be 15%, 18%, 20%, 22%, 23%, 25%, and the like.

[0047] By controlling the porosity of the gradient interlayer to be 15% to 25%, the thermal stress relief capacity of the structure can be improved while maintaining certain thermal insulation performance, thereby enhancing the thermal shock resistance and structural stability under high-temperature working conditions.

[0048] B. The content of Ir in the gradient structure linearly increases from 0wt% to 15wt% along the thickness direction.

[0049] The content of Ir linearly increases from 0wt% to 15wt% along the thickness direction, realizing the continuous transition of the thermal physical properties (such as the coefficient of thermal expansion) of the coating, which helps to relieve the interfacial stress caused by the mismatch of the thermal expansion of the layers, improve the bonding stability of the layers, and enhance the overall thermal cycle life.

[0050] C. The Rockwell hardness of the gradient structure decreases from 75 to 60 along the thickness direction.

[0051] The Rockwell hardness of the gradient structure gradually transitions from 75 in the inner layer to 60 in the outer layer, presenting a mechanical gradient distribution from hard to soft, which is beneficial to dispersing external mechanical impact loads, reducing the risk of surface cracking and peeling, and improving the surface scratch resistance and wear resistance.

[0052] In some embodiments, the zirconia material includes 8YSZ.

[0053] The zirconia material is selected as 8YSZ (8mol% Yttria-Stabilized Zirconia, 8mol% Y2O3 stabilized zirconia), which has excellent thermal stability and thermal insulation performance and is a commonly used thermal barrier material. The 8YSZ-graphene transition layer can absorb scratching stress through the "nanospring" effect of graphene, and the high-temperature wear rate fluctuation is ≤10%.

[0054] In some embodiments, the volume fraction of the zirconia material in the transition layer is 80% to 90%. For example, it can be 80%, 82%, 84%, 86%, 88%, 90%, etc.

[0055] In some embodiments, the volume fraction of graphene in the transition layer is 3vol%.

[0056] It should be noted that the volume fraction of the zirconia material (such as 8YSZ) in the transition layer is 80% to 90%, and the volume fraction of graphene is 3vol%. Since this volume ratio is counted with respect to the solid phase component, and the total porosity of the entire transition layer is 20% to 30%, it can be concluded that the solid phase accounts for 70% to 80% of the total volume of the transition layer. On this basis, the zirconia material accounts for about 56% to 72% of the total layer volume, and the graphene accounts for about 2.1% to 2.4%.

[0057] The remaining unlisted solid phase components (about 7% to 17% of the volume of the solid phase) are mainly derived from (may include but not limited to) the following several categories of trace ingredients: (1) stabilizer Y2O3 in the 8YSZ raw material (8 mol%, corresponding to about 5% to 8% of the volume of the solid phase); (2) residual sintering aids (such as Al2O3, generally not more than 2vol%) in the nanometer powder preparation process; (3) process-induced residues such as graphene surface oxygen-containing functional groups or dispersants (total amount generally not more than 1vol%).

[0058] Since these components are inevitable trace impurities or aids in the preparation process, their total content is low (usually ≤5vol%), and they have limited impact on the main performance of the coating, so they are not labeled separately in this embodiment, and only the volume fraction of the main functional materials (8YSZ and graphene) is limited.

[0059] The zirconia material in the above transition layer is 8mol% Y2O3 stabilized ZrO2 (i.e. 8YSZ), with a volume fraction of 80% to 90%. This design, on the one hand, 8YSZ has excellent high-temperature crystal phase stability, can inhibit the phase transformation expansion of ZrO2 under thermal cycling conditions above 1200℃, and maintain the integrity of the coating structure; on the other hand, its low thermal conductivity (1.5W / m·K~2.0W / m·K) helps to effectively block heat transfer to the substrate, and in combination with a 20% to 30% porosity design, the thermal resistance performance can be significantly improved (about 30%) compared to pure 8YSZ.

[0060] When the 8YSZ content is less than 80%, the continuity of the ceramic phase skeleton decreases, which easily leads to insufficient high-temperature compressive strength; if it is higher than 90%, the overall toughness decreases, which is not conducive to resisting external force impact such as scraping, so 80% to 90% is a reasonable interval for comprehensive strength and toughness.

[0061] In addition, the volume fraction of graphene in the transition layer is preferably 3vol%. This content range is conducive to forming a uniformly dispersed nanosheet structure, and under ultrasonic dispersion conditions, a "ceramic-carbon nanometer network" can be constructed at the grain boundaries, improving the elastic modulus and fracture toughness.

[0062] When the content exceeds 3vol%, the graphene sheets are prone to agglomeration, causing local stress concentration and weakening the structural performance. At the same time, after vacuum annealing at 800℃ / 2h, 3vol% of graphene and 8YSZ can form a stable interface through C-O-Zr chemical bonds, with a binding energy of 4.2eV, significantly improving the interface stability in high-temperature environments.

[0063] In terms of thermal property synergy, graphene has excellent in-plane thermal conductivity (>1500 W / m·K), which helps to accelerate heat diffusion and smooth the thermal expansion difference between each layer of the coating (ensuring a gradient change of ≤2x10 -6 / ℃); at the same time, graphene slip can also play a solid lubricating role during the scraping process (friction coefficient ≤0.12), forming a multi-scale synergy with the IrO2 lubricating phase in the intermediate layer, further improving the overall wear resistance and self-repairing ability. Therefore, the above volume fraction design of 8YSZ and graphene provides comprehensive protection for the coating in terms of structural stability, thermal insulation, and self-repairing function.

[0064] In some embodiments, the porosity of the transition layer is 20% to 30%. For example, it can be 20%, 22%, 24%, 26%, 28%, 30%, and the like.

[0065] The above porosity range is not simply caused by component deficiency, but is formed through the synergistic regulation of material ratio and spraying process, and has a clear structure-function role.

[0066] During the spraying process (such as three-electrode plasma spraying), the carbon elements in graphene are partially pyrolyzed into CO / CO2 gas that escapes in the high-temperature plasma jet, forming nanopores with a diameter of about 50 nm to 200 nm. The content of graphene is positively correlated with the porosity: when the content of graphene is controlled at 3vol%, the pores can be uniformly distributed; if the content is too high (such as more than 5vol%), the pores are easy to connect and form macroscopic cracks of >1 μm, thereby damaging the air tightness and structural integrity of the coating.

[0067] The porosity of 20% to 30% not only helps to reduce the overall thermal conductivity of the coating and improve the thermal insulation performance, but also provides diffusion channels for the IrO2 lubricating phase generated in the intermediate layer under high-temperature working conditions, enhancing the self-repairing efficiency. In addition, the pore structure in this range also has a certain "stress buffering" ability, which can absorb energy through pore collapse under the action of external scraping and other mechanical stresses, reducing the damage to key components such as blades. Therefore, this porosity design achieves an effective balance between structural stability, thermal protection ability, and self-repairing mechanism.

[0068] In some embodiments, the high-temperature Rockwell hardness HR15Y of the transition layer is 80 to 90. For example, it can be 80, 81, 82, 83, 85, 88, 90, and the like.

[0069] In some embodiments, the silicate in the bonding layer includes HfSiO4.

[0070] In some embodiments, the bonding layer is formed by supersonic flame spraying.

[0071] The high velocity oxy-fuel spraying (HVOF) is a commonly used thermal spraying technology, and the core purpose is to deposit coating particles at high speed without melting the material, so as to obtain a coating with high density, high bonding strength and good mechanical properties.

[0072] In some embodiments, the thickness of the bonding layer is 300-500 μm. For example, it can be 300 μm, 400 μm, 500 μm, etc.

[0073] In some embodiments, the porosity of the bonding layer is not more than 5%.

[0074] In some embodiments, the Rockwell hardness HR45Y of the bonding layer is 65-75. For example, it can be 65, 66, 67, 68, 69, 70, 71, 73, 75, etc.

[0075] In some embodiments, the bonding strength of the bonding layer is not less than 40 MPa.

[0076] In some embodiments, the temperature resistance of the bonding layer is not less than 1400℃.

[0077] In some embodiments, the graphite material in the abradable surface layer accounts for 10vol%-20vol%. For example, it can be 10vol%, 12vol%, 14vol%, 16vol%, 18vol%, 20vol%, etc.

[0078] In some embodiments, the abradable surface layer is a connected honeycomb structure formed by cold spraying.

[0079] In some embodiments, the porosity of the abradable surface layer is 30%-40%. For example, it can be 30%, 32%, 34%, 36%, 38%, 40%, etc.

[0080] In some embodiments, the high-temperature Rockwell hardness HR15Y of the abradable surface layer is 70-80. For example, it can be 70, 72, 74, 76, 78, 80, etc.

[0081] In some embodiments, the friction coefficient of the abradable surface layer is not more than 0.12.

[0082] In some embodiments, at least part of the area in the gradient intermediate layer is provided with a ternary doped region; The ternary doped region includes (Yb 1-x-y Y x Sc y )2SiO5; wherein x+y≤0.5.

[0083] The embodiment proposes introducing a ternary doped zone (Yb 1-x-y Y x Sc y )2SiO5, aiming to achieve double adaptability to high-temperature corrosion environment, including CMAS (molten silicate) and molten salt (such as Na2SO4 / NaVO3) corrosion, by regulating the doping combination of rare earth elements.

[0084] The ternary doped environmental barrier layer of Y and Sc in the gradient intermediate layer aims to regulate the thermophysical and chemical properties of the ceramic phase through the synergistic substitution of rare earth ions, making up for the deficiencies of Yb2Si2O7 or Yb2Si2O7-Ir system in service stability.

[0085] It should be noted that the partial substitution of Y 3+ (1.01 Å) and Sc 3+ (0.75 Å) to Yb 3+ (0.98 Å) can adjust the lattice constant and crystal distortion, and then optimize the thermal expansion coefficient of the ceramic phase, making it closer to the thermal expansion behavior of the matrix or adjacent layers, reducing the interfacial stress under thermal cycling and preventing the coating from cracking and falling off.

[0086] Secondly, ternary doping can form a stable solid solution structure (such as pyrochlore phase or fluorite phase), inhibit grain boundary migration and phase decomposition at high temperatures, significantly improve the corrosion resistance of CMAS, molten salt, water vapor and other corrosion media, and prolong the service life of the coating. Among them, Sc 3+ can enhance the sintering resistance, Y 3+ helps to inhibit thermal conductivity and improve oxidation stability.

[0087] In addition, the synergistic effect of the doped layer and Ir element can improve the interfacial bonding and overall mechanical stability. The ceramic phase adjusted by ternary doping is more consistent with the embedded structure of Ir at the lattice level, which helps to relieve stress concentration caused by composition gradient or thermal mismatch, and strengthens the overall thermal shock and wear resistance of the coating.

[0088] Therefore, the ternary doping design provides a better thermophysical matching, chemical stability and interface synergy for the gradient intermediate layer, and is one of the key strategies to improve the reliability of the seal coating.

[0089] It should be noted that the Yb2Si2O7-Ir gradient interlayer and the ternary doped environmental barrier layer form a good synergistic effect. In terms of thermophysical properties, Yb2Si2O7 serves as a ceramic matrix material to provide excellent low thermal conductivity, achieving the basic thermal barrier function; the Ir metal phase gives the coating good interlayer toughness and thermal shock resistance, effectively inhibiting crack propagation; and the introduction of Y / Sc ternary doping further reduces the thermal conductivity of the ceramic phase, and can optimize the thermal expansion coefficient by adjusting the lattice parameter, so that the gradient interlayer realizes the gradual transition of thermophysical properties from ceramic to metal in the thickness direction, reducing the risk of accumulation of thermal mismatch stress.

[0090] In terms of environmental adaptability, the (Yb,Y,Sc)2SiO solid solution phase formed by ternary doping helps to generate a dense SiO2 passivation layer on the surface at high temperatures, improving the erosion resistance of the coating to environmental factors such as water vapor, acidic gases (such as SO x ) and the like; the introduction of Ir can compensate for the brittleness of the ceramic phase at grain boundaries or defects, limit the penetration and diffusion of oxygen ions, and delay the oxidation of the matrix, thereby forming a composite protection mechanism of "ceramic chemical corrosion resistance + metal oxidation barrier".

[0091] In addition, in terms of mechanical properties, Yb2Si2O7 ceramic itself has high hardness but is brittle, and Ir has good ductility and buffering capacity; ternary doping improves the toughness of the ceramic phase through grain refinement and solid solution strengthening, while Ir provides a local plastic deformation space, effectively relieving thermal stress concentration. The combined action of the two makes the coating have strong crack resistance and self-adaptability during multiple thermal cycles and external force loading, and the overall structure is more reliable and stable.

[0092] Further, when x-y≥0.1, the CMAS (CaO-MgO-Al2O3-SiO2) corrosion penetration resistance of the gradient interlayer under the condition of 1350°C and 240 hours is ≤5μm.

[0093] Further, when y-x≥0.1, the molten salt corrosion rate of the gradient interlayer under the condition of 1200°C and 300 hours is ≤0.02% / h.

[0094] When the proportion of Y element in the ternary doping is high (0.1 or more than Sc), the structure exhibits good penetration resistance in the high-temperature long-time CMAS corrosion test (1350°C / 240 hours), with a corrosion depth of less than or equal to 5 microns. When the proportion of Sc doping is significantly higher than that of Y, the mass loss rate of the structure is very small (≤0.02% / h) when continuously exposed to 1200°C for 300 hours, showing strong molten salt corrosion resistance.

[0095] In some embodiments, a first composite layer is further provided between the bonding layer and the gradient intermediate layer. The first composite layer comprises HfO2-Yb2O3. The thickness of the first composite layer is 30-60 μm (e.g., 30 μm, 40 μm, 50 μm, 60 μm, etc., and in one embodiment, 50 μm). The coefficient of thermal expansion of the first composite layer varies by no more than 2 x 10 -6 / °C.

[0096] The first composite layer is composed of HfO2 and Yb2O3, and the core purpose of the provision thereof is to achieve smooth transition of thermal physical properties and optimization of interface chemical compatibility through gradient design of components, thereby improving overall structural stability.

[0097] In terms of thermal physical matching, the coefficient of thermal expansion of the HfSiO4 bonding layer is about (8-9) x 10 -6 / K, while the coefficient of thermal expansion of the Yb2Si2O7-Ir intermediate layer is about (7-8) x 10 -6 / K, and there is a risk of thermal expansion mismatch. By introducing the HfO2-Yb2O3 gradient transition region between the two, the variation of the coefficient of thermal expansion can be controlled within the range of ≤2 x 10 -6 / °C, effectively relieving the thermal stress concentration at the interface during thermal cycling and reducing the risk of cracking.

[0098] In terms of chemical stability, HfO2 (melting point 2825 °C) and Yb2O3 (melting point 2250 °C) are both high-melting-point oxides with excellent thermal stability, can form a solid solution structure between them, have good high-temperature grain boundary diffusion resistance, can prevent the migration of Si elements in HfSiO4 to the Yb2Si2O7 layer at high temperatures, thereby inhibiting the occurrence of phase decomposition and enhancing the long-term service reliability of the coating.

[0099] In addition, the first composite layer adopts a gradient design with continuous variation of components, and the specific proportion can gradually transition from 100% HfO2 on the HfSiO4 side to 100% Yb2O3 on the Yb2Si2O7-Ir side. This design not only regulates the transition of the coefficient of thermal expansion layer by layer, but also balances the mechanical properties: HfO2 provides higher hardness (high-temperature Rockwell hardness HR15Y is 85-90), while Yb2O3 imparts certain toughness to the material, and the two can synergistically improve the structural integrity and reduce the brittleness of the coating. In addition, the Hf-Yb-O solid solution formed in the gradient layer has good interface chemical bonding capacity, can enhance the bonding strength with the upper and lower layers through Hf-O-Si or Yb-O-Si bridge bonds, and stabilize the interface bonding strength at more than 35 MPa.

[0100] In summary, the first composite layer helps to achieve the comprehensive optimization of thermal performance, mechanical strength and interface stability, and is one of the key technical measures to realize high reliability of the gradient self-repairing seal coating.

[0101] In some embodiments, a second composite layer is further provided between the gradient intermediate layer and the transition layer; the second composite layer comprises Al2O3-TiC. The second composite layer is of a gradient structure; and in the gradient structure, the content of Al2O3 transitions from 100% to 0% along the thickness direction; the content of TiC transitions from 0% to 100%; and / or the interfacial bonding strength between the gradient intermediate layer and the transition layer is not less than 35 MPa.

[0102] In the above-mentioned second composite layer, the gradient structure composed of Al2O3-TiC aims to optimize the mechanical properties and thermal expansion matching of the interface region, thereby improving the structural stability and service reliability of the overall coating.

[0103] The main purpose of providing the second composite layer is to optimize the structural stability and environmental adaptability of the interface region. First, the composite layer realizes the complementation of mechanical properties through the gradient combination of Al2O3 and TiC: Al2O3 has extremely high hardness (HV2000~2200) but is relatively brittle, TiC has higher hardness (HV2800~3200) and good toughness, and the gradient transition of the two can effectively relieve stress concentration and prevent the peeling or cracking of the 8YSZ layer; second, in terms of thermal expansion performance, Al2O3 (~8×10 -6 / K) matches well with 8YSZ, and TiC (~7.4×10 -6 / K) is closer to the intermediate layer, and the gradient change helps to realize the smooth transition of the thermal expansion coefficient and reduce the interfacial stress in thermal cycling; in addition, TiC can form a stable TiO2 passivation film at high temperature, enhance the corrosion resistance of the interface, resist the corrosion of water vapor and acid gas, and further improve the service reliability of the overall seal structure.

[0104] The second composite layer is designed as a composition gradient structure along the thickness direction: (1) The side close to the transition layer (8YSZ) is 100% Al2O3 with a thickness of about 10~20 μm, mainly providing high hardness support; the middle region is a buffer layer with Al2O3 and TiC mixed at a volume ratio of 70:30, with a thickness of 20~30 μm, taking into account hardness and toughness; (2) Near the middle layer of the gradient (Yb2Si2O7-Ir) side is TiC content of 100%, thickness of 20-30 pm, to enhance the thermal shock resistance and oxidation resistance. The gradient transition strategy not only achieves synergistic regulation between hardness and toughness, but also effectively alleviates thermal stress by strengthening the wear resistance of the upper Al2O3 region and the TiC region, and can inhibit the brittle phase (such as Al4C3) that may be generated between Al2O3 and TiC at high temperature by continuous change of composition, thereby improving the chemical stability and service reliability of the interface.

[0105] Reference Figure 2 In the embodiments of the present application, a preparation method of the gradient self-repairing seal coating as described in any of the preceding embodiments is provided, comprising: Step S1, a silicate-containing bonding layer is prepared on the surface of the substrate by using high-velocity oxy-fuel spraying.

[0106] The above-mentioned high-velocity oxy-fuel spraying (HVOF) is a thermal spraying technology. This method can achieve a high particle velocity (>600 m / s) and a moderate temperature (<3000 K) environment, which is helpful for preparing a coating with high density and low oxidation. It is suitable for silicate materials (such as HfSiO4), forming a structural layer with high bonding strength (≥40 MPa), porosity ≤5%, thickness 300-500 pm, and temperature resistance ≥1400°C, which provides a stable substrate for the subsequent gradient layer.

[0107] Step S2, a gradient intermediate layer containing rare earth silicate and Ir is deposited on the bonding layer by using a pulsed plasma spraying process.

[0108] The above-mentioned pulsed plasma spraying (PS-PVD or pulsed plasma spray) has good energy control ability and multi-layer structure adjustment ability, and can realize continuous gradient transition of composition, such as linear change of Ir from 0wt% to 15wt%. This process helps to regulate the porosity (15-25%) and hardness gradient (HR75→HR60), and construct a gradient intermediate layer with thermal expansion gradient regulation and crack buffering ability.

[0109] Further, in some embodiments, (Yb 1-x- y Y x Sc y )2SiO5 ternary doping structure (ternary doping region) can be introduced in part or all of the layer, further improving the CMAS corrosion resistance and molten salt resistance (≤5 pm, ≤0.02% / h, respectively).

[0110] Step S3, a transition layer containing zirconia material and graphene is formed on the gradient intermediate layer by plasma spraying method.

[0111] The above-mentioned plasma spraying method (APS or SPS) can be applied to the deposition of nano-structured material (such as 8YSZ+graphene) composite system, which is beneficial to retain the graphene structure and ensure the "nano spring" strengthening and lubrication self-repairing function. By controlling the spraying parameters, the performance indicators of porosity 20-30%, HR15Y 80-90, and 8YSZ content 80-90vol% and graphene 3vol% can be achieved.

[0112] The partial decomposition of graphene in the high-temperature spraying process can introduce nanopores, which can improve the thermal insulation and lubrication performance.

[0113] Step S4, an abradable surface layer containing rare earth silicate and graphite material is formed on the transition layer by cold spraying process.

[0114] The above-mentioned abradable surface layer is formed by cold spraying (Cold Spray) method, which has low-temperature deposition characteristics and can avoid oxidation of the graphite material and retain its sheet structure, achieving excellent performance of friction coefficient ≤0.12, porosity 30-40%, and HR15Y 70-80. The graphite material content is controlled at 10-20vol%, and the spraying structure is designed as a connected honeycomb shape, which helps to improve the energy absorption capacity and scraping self-repairing performance.

[0115] The preparation processes of the functional layers in the embodiment successively adopt HVOF (high-velocity oxy-fuel spraying), PS-PVD (plasma deposition evaporation), APS (conventional plasma spraying), and cold spraying (Cold Spray) processes, which respectively match the thermal physical properties and functional requirements of the materials of the layers, ensure that the overall structure has high bonding strength and interface stability (>35MPa), the gradient transition structure effectively relieves thermal mismatch stress, the interlayer thermal expansion coefficient smoothly changes (≤2×10 -6 / ℃), and finally constructs a high-performance self-repairing gradient seal coating system integrating heat shielding, wear resistance, corrosion resistance, and self-lubrication performance.

[0116] In some embodiments, the gradient intermediate layer is a gradient structure formed by depositing Yb2Si2O7-Ir nano-powder by pulse plasma spraying process; wherein the Yb2Si2O7-Ir nano-powder is prepared by sol-gel method; and / or, the particle size of the Yb2Si2O7-Ir nano-powder is 50nm-100nm; and / or, the Yb2Si2O7-Ir nano-powder is doped with at least 1vol% of carbon nanotubes; and / or, In some embodiments, the main arc power of the pulsed plasma spraying process is 40 kW to 65 kW. For example, it can be 40 kW, 45 kW, 50 kW, 55 kW, 60 kW, 65 kW, and the like.

[0117] In some embodiments, the pulse frequency of the pulsed plasma spraying process is 100 Hz.

[0118] In some embodiments, the gas pressure of the cold spraying process is 2 MPa.

[0119] In some embodiments, the temperature of the cold spraying process is not greater than 100°C.

[0120] In some embodiments, the porosity of the abradable coating is 30% to 40%. For example, it can be 30%, 32%, 34%, 36%, 38%, 40%, and the like.

[0121] In some embodiments, the plasma spraying method is a three-electrode plasma spraying process.

[0122] In some embodiments, after forming the abradable coating containing rare earth silicate and graphite material, further comprising: performing vacuum annealing treatment.

[0123] In order to improve the interface bonding quality and service stability between the Yb2Si2O7-Ir gradient intermediate layer and the 8YSZ transition layer, an Al2O3-TiC gradient composite layer is introduced therebetween, and microstructure regulation is performed through vacuum annealing after preparation is completed.

[0124] In terms of mechanical properties, Al2O3 has a higher hardness (HV2000-2200) but poor toughness, while TiC has a higher hardness (HV2800-3200) and good wear resistance and certain toughness. Through the composition gradient design of Al2O3→TiC, the interlayer toughness can be enhanced on the basis of ensuring high hardness, the anti-cracking and anti-peeling performance of the composite zone can be improved, and the risk of brittle failure of the 8YSZ transition layer due to thermal fatigue can be effectively alleviated.

[0125] In terms of thermal expansion matching, the thermal expansion coefficient of Al2O3 (~8×10 -6 / K) is closer to that of 8YSZ (~10×10 -6 / K), while TiC (~7.4×10 -6 / K) is more matched with Yb2Si2O7-Ir. The gradient transition can realize the continuous change of the thermal expansion coefficient from top to bottom, avoid the sudden change of interface stress, and inhibit the interlayer cracking or peeling caused by thermal cycling.

[0126] In addition, TiC can generate a dense and stable TiO2 passivation layer in situ under high temperature conditions, enhancing the interface's ability to resist water vapor and acid gas corrosion. The ceramic phase Ti3AlC2 may be formed between Al2O3 and TiC under high temperature, and appropriate control of the gradient ratio can avoid the excessive generation of brittle phases (such as Al4C3), maintaining the structural integrity of the interface.

[0127] To further stabilize the microstructure and enhance the interface bonding strength, vacuum annealing treatment (recommended temperature range: 1000°C~1200°C, time: 1~3 hours) is adopted after the formation of the layer structure, which can achieve the following effects: promoting element diffusion to form a stable interface transition zone; releasing residual stress formed during the spraying process; improving the density and overall bonding performance of the gradient composite layer. Ultimately, the composite layer exhibits excellent mechanical matching, thermal stability, and environmental adaptability under service conditions.

[0128] In the embodiments of the present application, a product is provided, which comprises a thermal protection member; At least a part of the thermal protection member is coated with a gradient self-repairing seal coating as described in any of the preceding embodiments.

[0129] In the embodiments, the product can include but is not limited to an aerospace vehicle, a hypersonic aircraft, a gas turbine, a thermal barrier ceramic member, an engine nozzle, a hot-end seal part, a heat shield, or other high-temperature structural parts; the thermal protection member can include but is not limited to a nozzle liner, a combustion chamber inner wall, a tail nozzle guide vane, a leading edge bluff body, a hot-end turbine blade, a vortex ring, a sealing gasket, a shell surface layer, and other key areas exposed to high-temperature and highly corrosive environments, which are used to withstand the combined effects of high-speed airflow, thermal shock, wear, and various corrosive media, ensuring the structural stability and service life of the product under extreme working conditions.

[0130] The application will be further described in the following specific examples. It should be understood that these examples are only used to illustrate the application in more detail, and should not be understood as limiting the application in any form.

[0131] Table 1: Different layer components and key parameters in examples and comparative examples

[0132] In Table 1, "Example" represents an example, such as "Example 1" representing Example 1; "Comparative Example" represents a comparative example, such as "Comparative Example 1" representing Comparative Example 1; and "Surface Layer Process" represents the process of the abradable surface layer.

[0133] Example 1 In the embodiments, the preparation of a gradient self-repairing seal coating on the surface of a thermal protection member is carried out.

[0134] Experimental method: (1) A bond coat layer containing silicate is prepared on the surface of the substrate by supersonic flame spraying; the bond coat layer is HfSiO4, the thickness is 400 μm, the porosity is 3%, the Rockwell hardness HR45Y is 70, the bonding strength is 45 MPa, and the temperature resistance is 1450 °C.

[0135] (2) A first composite layer is provided; the first composite layer is HfO2-Yb2O3, the thickness is 50 μm, and the thermal expansion coefficient gradient change is 1.5×10 -6 / ℃.

[0136] (3) Yb2Si2O7-Ir nano-powder is deposited on the bond coat layer by using a pulse plasma spraying process to form a gradient intermediate layer; the particle size of the Yb2Si2O7-Ir nano-powder is 50 nm to 100 nm and D 50 is 60 nm; 1% of carbon nanotubes are doped in the Yb2Si2O7-Ir nano-powder. The pulse plasma spraying (main arc power 50 kW, pulse frequency 100 Hz) is performed, the gradient intermediate layer is Yb2Si2O7-Ir (the molar ratio of Ir to Si is 0.3), the porosity is 20%, the Ir content linearly increases from 0 wt% to 15 wt% along the thickness, and the Rockwell hardness decreases from 75 to 60.

[0137] (4) A second composite layer is provided, which is an Al2O3-TiC gradient structure (Al2O3 transitions from 100% to 0% and TiC transitions from 0% to 100%), and the interface bonding strength is 38 MPa.

[0138] (5) A transition layer containing zirconia material and graphene is formed on the gradient intermediate layer by using a three-electrode plasma spraying process; the transition layer is 8YSZ (85 vol%) + graphene (3 vol%), the porosity is 25%, and the high-temperature Rockwell hardness HR15Y is 85.

[0139] (6) A abradable surface layer containing rare earth silicate and graphite material is formed on the transition layer by using a cold spraying process. The composition is Yb2Si2O7 + 15 vol% graphite, the cold spraying is performed (gas pressure 2 MPa, temperature 80 °C), a connected honeycomb structure is formed, the porosity is 35%, the high-temperature Rockwell hardness HR15Y is 75, and the friction coefficient is 0.10.

[0140] (7) Post-processing: vacuum annealing (1100 °C, 2 h) after cold spraying.

[0141] Example 2 In this embodiment, the preparation of a gradient self-repairing seal coating on the surface of a thermal protection member is carried out. In this embodiment, the method is basically the same as that in Example 1, and the difference lies in that a ternary doped region is provided in the gradient intermediate layer, and the composition is (Yb 0.6 Y 0.3 Sc 0.1)2SiO5, (x = 0.3, y = 0.1, x-y = 0.2 > 0.1), other parameters same as example 1. Refer to table 1 for details.

[0142] Example 3 In this example, a gradient self-healing seal coating on the surface of a thermal protection component was prepared. The method used in this example was basically the same as example 1, the difference was that the first composite layer and the second composite layer were omitted, and the gradient intermediate layer was directly prepared on the bonding layer, the interface bonding strength of the gradient intermediate layer and the transition layer was 36 MPa, and other parameters were the same as example 1. Refer to table 1 for details.

[0143] Comparative example 1 In this comparative example, a coating on the surface of a thermal protection component was prepared (lacking a gradient intermediate layer). The method used in this comparative example was basically the same as example 1, the difference was that the gradient intermediate layer was not prepared. Refer to table 1 for details.

[0144] Comparative example 2 In this comparative example, a coating on the surface of a thermal protection component was prepared. The method used in this comparative example was basically the same as example 1, the difference was that the bonding layer: Al2O3 (non-silicate), plasma spraying (non-supersonic flame), thickness 400 μm, porosity 8%, bonding strength 25 MPa. Refer to table 1 for details.

[0145] Comparative example 3: In this comparative example, a coating on the surface of a thermal protection component was prepared. The method used in this comparative example was basically the same as example 1, the difference was that the molar ratio of Ir to Si in the gradient intermediate layer = 0.6. Refer to table 1 for details.

[0146] Comparative example 4: In this comparative example, a coating on the surface of a thermal protection component was prepared. The method used in this comparative example was basically the same as example 1, the difference was that the abradable surface layer was flame sprayed (non-cold sprayed), graphite content 25 vol%, porosity 25%. Refer to table 1 for details.

[0147] Test experiment 1. Test method: (1) Thermal cycle stability: 1400℃ (1h holding) → room temperature (water cooling) for 100 cycles, calculate the area ratio of coating peeling.

[0148] (2) Anti-CMAS corrosion: immerse in CMAS slag at 1350℃ for 240h, measure the corrosion penetration rate (μm).

[0149] (3) Anti-molten salt corrosion: place in Na2SO4-NaVO3 molten salt at 1200℃ for 300h, calculate the mass loss rate (% / h).

[0150] (4) Bonding strength: The bonding strength between the coating and the substrate was tested according to GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1 : Method of test at room temperature" (MPa).

[0151] 2. Test results: Table 2. Test results of each test item

[0152] 3. Analysis: (1) In terms of thermal cycle stability, the spalling area of the coatings of Examples 1, 2 and 3 was less than 8% after 100 cycles from 1400°C to room temperature with water cooling. This is mainly due to the gradient structure (such as the gradient intermediate layer) and the first and second composite layers (in Examples 1 and 2) effectively relieving the thermal stress caused by the mismatch of the thermal expansion coefficients of the materials. In contrast, Comparative Example 1 lacks a gradient intermediate layer, and the thermal stress cannot be effectively transferred, resulting in a spalling area of more than 60%. The bonding layer material (Al2O3) of Comparative Example 2 is not properly processed, resulting in a mismatch between its thermodynamic properties and the substrate, also causing severe thermal stress concentration, with a spalling area of more than 40%. Comparative Examples 3 and 4 also have poor thermal cycle stability due to excessive Ir content and process problems in the abradable surface layer, with spalling areas of more than 30% and 25%, respectively.

[0153] (2) In terms of CMAS corrosion resistance, after 240 hours of corrosion at 1350°C, the corrosion penetration rate of Example 2 was only 4 μm, showing the best performance. This is because its gradient intermediate layer sets a (Yb 0.6 Y 0.3 Sc 0.1 )2SiO5 ternary doped region, which can effectively resist the penetration of CMAS (molten silicate) when the Y element content is high (x-y≥0.1). The penetration rate of Example 1 is 8 μm, also showing good corrosion resistance. Comparative Example 1 lacks a gradient intermediate layer containing rare earth silicate for protection, with a corrosion penetration rate of more than 50 μm, and poor corrosion resistance.

[0154] (3) Molten salt corrosion resistance: After 300 hours of testing in a molten salt at 1200°C, the mass loss rate of Examples 1, 2 and 3 was less than 0.04% / h. This is due to the synergistic effect of Ir and rare earth silicate in the gradient intermediate layer, effectively resisting the erosion of the molten salt. In Comparative Example 3, the molar ratio of Ir to Si is increased to 0.6, which is outside the preferred range (0.2-0.5), which may cause the coating structure to be loose, thereby reducing its molten salt corrosion resistance and increasing the rate to 0.07% / h. Other comparative examples also show poor molten salt corrosion resistance due to structural or compositional defects.

[0155] (4) Bonding strength: the bonding strength of the coating of examples 1, 2 and 3 all reached above 40 MPa. This is due to the use of supersonic flame spraying process to prepare the HfSiO4 bonding layer, and the design of the gradient transition layer, which ensures the high bonding force between the coating and the substrate. Comparative example 2 uses plasma sprayed Al2O3 as the bonding layer, and the material and preparation process do not meet the core design of the present application, resulting in a bonding strength of only 25 MPa, which is much lower than the examples. The bonding strength of comparative examples 1, 3 and 4 is also significantly lower than the examples.

[0156] In summary, the present application significantly improves the thermal cycle stability, CMAS and molten salt corrosion resistance and bonding strength with the substrate of the sealing coating through precise gradient structure design (such as gradient intermediate layer and composite layer), specific material combination (such as HfSiO4 bonding layer, Yb2Si2O7-Ir intermediate layer, 8YSZ-graphene transition layer, etc.) and optimized process control (such as supersonic flame spraying, pulsed plasma spraying, cold spraying, etc.). The comparative examples lack key functional layers, use improper materials or processes, or the proportion of key components is out of balance, which destroys the core technical features of the present application, resulting in a significant decline in the performance of the coating in various performance tests.

[0157] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A gradient self-healing seal coating, characterized in that, The coating comprises, in sequence from the substrate to the surface, a bonding layer comprising silicate, a gradient intermediate layer comprising rare earth silicate and Ir element, a transition layer comprising zirconia material and graphene, and an abradable surface layer comprising rare earth silicate and graphite material.

2. The gradient self-repairing seal coating of claim 1, wherein, The molar ratio of Ir element to Si element in the rare earth silicate is 0.2-0.5; and / or, The rare earth silicate material comprises Yb2Si2O7.

3. The gradient self-repairing seal coating of claim 1, wherein, The gradient intermediate layer is a gradient structure formed by a pulsed plasma spraying method based on the bonding layer; wherein the gradient structure satisfies at least one of the following conditions: A. The porosity of the gradient structure is 15%-25%; B. The content of Ir element in the gradient structure linearly increases from 0wt% to 15wt% along the thickness direction; C. The Rockwell hardness of the gradient structure decreases from 75 to 60 along the thickness direction.

4. The gradient self-repairing seal coating of claim 1, wherein, The zirconia material comprises 8YSZ; and / or, The volume ratio of the zirconia material in the transition layer is 80%-90%; and / or, The volume ratio of graphene in the transition layer is 3vol%; and / or, The porosity of the transition layer is 20%-30%; and / or, The high-temperature Rockwell hardness HR15Y of the transition layer is 80-90; and / or, The silicate in the bonding layer comprises HfSiO4; and / or, The bonding layer is formed by high-velocity oxy-fuel spraying; and / or, The thickness of the bonding layer is 300-500μm; and / or, The porosity of the bonding layer is not more than 5%; and / or, The Rockwell hardness HR45Y of the bonding layer is 65-75; and / or, The bonding strength of the bonding layer is not less than 40MPa; and / or, The temperature resistance of the bonding layer is not less than 1400℃; and / or, The graphite material in the abradable surface layer accounts for 10vol%-20vol%; and / or, The abradable surface layer is a connected honeycomb structure formed by cold spraying; and / or, The porosity of the abradable surface layer is 30%-40%; and / or, The high-temperature Rockwell hardness HR15Y of the abradable surface layer is 70-80; and / or, The friction coefficient of the abradable surface layer is not more than 0.

12.

5. The gradient self-repairing seal coating of claim 1, wherein, At least part of the gradient intermediate layer is provided with a ternary doped region; The ternary doped region includes (Yb 1-x-y Y x Sc y )2SiO5; Wherein, x+y≤0.5; Preferably, when x-y≥0.1, the CMAS corrosion penetration rate of the gradient intermediate layer under the condition of 1350℃ and 240 hours is ≤5μm; Preferably, when y-x≥0.1, the molten salt corrosion rate of the gradient intermediate layer under the condition of 1200℃ and 300 hours is ≤0.02% / h.

6. The gradient self-repairing seal coating of claim 1, wherein, A first composite layer is further provided between the bonding layer and the gradient intermediate layer; The first composite layer comprises HfO2-Yb2O3; and / or, the thickness of the first composite layer is 30-60 μm; and / or, the gradient change of the thermal expansion coefficient of the first composite layer is not greater than 2x10-5 / ℃. -6 / ℃.

7. The gradient self-repairing seal coating of claim 1, wherein, A second composite layer is further provided between the gradient intermediate layer and the transition layer; the second composite layer comprises Al2O3-TiC; The second composite layer is a gradient structure; and in the gradient structure, the content of Al2O3 transitions from 100% to 0% along the thickness direction; the content of TiC transitions from 0% to 100%; and / or, the interface bonding strength between the gradient intermediate layer and the transition layer is not less than 35MPa.

8. A method of producing a gradient self-healing seal coating according to any one of claims 1 to 7, characterized in that Comprise: A bond coat layer containing silicate is prepared on a substrate surface by using high velocity oxygen fuel spraying; A gradient intermediate layer containing rare earth silicate and Ir is deposited on the bond coat layer by using a pulsed plasma spraying process; A transition layer containing zirconia material and graphene is formed on the gradient intermediate layer by using a plasma spraying method; An abradable surface layer containing rare earth silicate and graphite material is formed on the transition layer by using a cold spraying process.

9. The method of claim 8, wherein the gradient self-healing seal coating is prepared by, The gradient intermediate layer is a gradient structure formed by depositing Yb2Si2O7-Ir nanopowder by using a pulsed plasma spraying process; wherein the Yb2Si2O7-Ir nanopowder is prepared by using a sol-gel method; and / or, the particle size of the Yb2Si2O7-Ir nanopowder is 50nm-100nm; and / or, the Yb2Si2O7-Ir nanopowder is doped with at least 1vol% of carbon nanotubes; and / or, The main arc power of the pulsed plasma spraying process is 40kW-65kW; and / or, The pulse frequency of the pulsed plasma spraying process is 100Hz; and / or, The gas pressure of the cold spraying process is 2MPa; and / or, The temperature of the cold spraying process is not more than 100℃; and / or, The porosity of the abradable surface layer is 30%-40%; and / or, The plasma spraying method is a three-electrode plasma spraying process; and / or, After forming the abradable surface layer containing rare earth silicate and graphite material, the method further comprises: performing vacuum annealing treatment.

10. A product characterized by, The product comprises a thermal protection member; The thermal protection member is at least partially coated with the gradient self-repairing seal coating as claimed in any one of claims 1-8.

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