High temperature coating

Abstract

This invention discloses a method comprising forming a crystalline metal carbide undercoat on the surface of a carbon-carbon composite substrate. The method further comprises forming an outer coating on the surface of the undercoat. The outer coating comprises a plurality of crystalline ultra-high melting point outer coating layers. Each outer coating layer is formed sequentially by applying a mixture to the surface of an underlying layer and heating the mixture. The mixture comprises a plurality of ultra-high melting point refractory ceramic particles and a ceramic preform polymer. The mixture is heated to a heat treatment temperature in an inert atmosphere or under vacuum to pyrolyze the ceramic preform polymer and form the outer coating layer. Therefore, the outer coating layer comprises a crystalline ultra-high melting point polymer-derived ceramic matrix comprising a plurality of ultra-high melting point refractory ceramic particles.

Description

Technical Field

[0001] This disclosure relates to high-temperature coatings. Background Technology

[0002] Carbon-carbon (CC) composites can be used in high-temperature applications. For example, the aerospace industry uses CC composite components as friction materials for commercial and military aircraft, such as brake friction materials. In high-temperature applications, CC composites may be susceptible to oxidation, which can lead to a deterioration of their physical and mechanical properties. Summary of the Invention

[0003] This disclosure describes highly constructible coatings for carbon-carbon composite substrates and techniques for manufacturing such coatings, which protect the substrates from oxidation at high temperatures. In some examples, the high-temperature coating comprises a crystalline metal carbide undercoat and two or more outer coating layers. The undercoat may comprise a metal-rich metal carbide formed in situ on the substrate. The two or more outer coating layers may comprise ultra-high melting point refractory ceramic particles in a dense, crystalline, polymer-derived ceramic matrix. Each of these outer coating layers can be formed by applying a mixture of refractory ceramic particles and a ceramic preform polymer. To form a crystalline ceramic matrix, the mixture may be heated in an inert atmosphere or under vacuum to pyrolyze the ceramic preform polymer and crystallize the ceramic matrix. The composition of the ceramic particles and the ceramic preform polymer, as well as various characteristics of the distribution of the ceramic particles in the mixture, can be selected to provide corresponding outer coating layers with specific thermomechanical and thermophysical properties, such as coefficient of thermal expansion, thermal conductivity, porosity, or thermal stability. In this way, carbon-carbon composite substrates coated with the high-temperature coating described herein can be protected from oxidation, thermal degradation and / or environmental degradation.

[0004] In one example, a method includes forming a crystalline metal carbide undercoat on the surface of a carbon-carbon composite substrate. The method further includes forming an outer coating on the surface of the undercoat. The outer coating comprises a plurality of crystalline ultra-high melting point outer coating layers. Each outer coating layer is formed sequentially by applying a mixture to the surface of an underlying layer and heating the mixture. The mixture comprises a plurality of ultra-high melting point refractory ceramic particles and a ceramic preform polymer. The mixture is heated to a heat treatment temperature in an inert atmosphere or under vacuum to pyrolyze the ceramic preform polymer and form the outer coating layer. Therefore, the outer coating layer comprises a crystalline ultra-high melting point polymer-derived ceramic matrix containing the plurality of ultra-high melting point refractory ceramic particles.

[0005] In another example, an article includes a carbon-carbon composite substrate, a crystalline metal carbide undercoat on the surface of the carbon-carbon composite substrate, and an outer coating on the surface of the undercoat. The outer coating comprises a plurality of crystalline ultra-high melting point outer coating layers. Each of the plurality of outer coating layers comprises a crystalline ultra-high melting point polymer-derived ceramic matrix, the crystalline ultra-high melting point polymer-derived ceramic matrix comprising a plurality of ultra-high melting point refractory ceramic particles.

[0006] Details of one or more examples of this disclosure are set forth in the following drawings and description. Other features, objects, and advantages of this disclosure will be apparent from the description and drawings, as well as from the claims. Attached Figure Description

[0007] Figure 1A This is a perspective view showing an exemplary composite material including a high-temperature coating formed according to the technology of this disclosure.

[0008] Figure 1B This is a conceptual diagram illustrating an exemplary composite material including a high-temperature coating formed according to the technology of this disclosure.

[0009] Figure 2 This is a schematic side view of an exemplary article comprising a high-temperature coating formed according to the technology of this disclosure.

[0010] Figure 3 This is a flowchart illustrating an exemplary technique for forming a high-temperature coating according to an example of this disclosure.

[0011] Figure 4 This is a schematic diagram illustrating an exemplary aircraft brake assembly including a composite material brake disc formed according to the technology of this disclosure, the composite material brake disc including a high-temperature coating. Detailed Implementation

[0012] This disclosure describes a high-temperature coating for carbon-carbon composite articles comprising a crystalline metal carbide undercoat and a highly constructible multilayer outer coating for ultra-high temperature (e.g., greater than 1500 °C) applications. Carbon-carbon composite components can provide good mechanical properties and have a low mass density relative to other materials, such as metal alloys. However, at high temperatures, carbon-carbon composite components can be susceptible to oxidation, environmental erosion, and degradation of physical and mechanical properties. Antioxidant coatings based on refractory ceramics can improve resistance to oxidation and / or environmental erosion at high temperatures experienced in aerospace applications, such as aircraft brakes (e.g., temperatures up to 1600 °C) or rocket nozzles (e.g., temperatures up to 2400 °C). Before use in oxidizing atmospheres, a high-temperature substrate based on carbon composites can be coated with an antioxidant coating that reduces oxidation of the substrate's external surfaces and reduces the ingress of oxidizing substances (e.g., air, oxygen, and / or water vapor) into the pores of the component.

[0013] The high-temperature coatings described herein can be formed using relatively simple and inexpensive processes that enable the tailoring of high-temperature coatings for specific applications. The high-temperature coating comprises a crystalline, metal-rich metal carbide undercoat on the surface of a substrate, which adheres strongly to adjacent outer coatings and can possess self-healing capabilities through the formation of metal oxides in the microcracks of the undercoat. The antioxidant coating also comprises a crystalline, ultra-high melting point multilayer outer coating. Each outer coating layer can be formed by applying a pre-calcined mixture to the outer surface of the underlying layer, such as through relatively conventional coating processes (e.g., brushing or spraying). The pre-calcined mixture may contain ultra-high melting point refractory ceramic particles and a ceramic preform polymer. After application of the mixture, it can be heated to pyrolyze the ceramic preform polymer and crystallize it into a ceramic matrix. The resulting outer coating layer can be substantially (e.g., greater than 95% by volume) crystalline and glass-free (e.g., less than 5% by volume). In some cases, ultra-high temperature oxides can form on the outermost surface of the high-temperature coating during operation.

[0014] This application and heating process can be repeated to form one or more additional outer coating layers. The pre-calcined mixture for each layer can be customized to provide specific and tailored properties to the outer coating through individual outer coating layers and / or combinations of outer coating layers. For example, particle size and distribution, particulate composition, ceramic preform polymer composition, and the volume ratio of particles to ceramic preform polymer in the mixture used to form one or more respective outer coating layers can be selected to provide specific thermomechanical and thermophysical properties, such as coefficient of thermal expansion, porosity, thermal conductivity, or thermal stability (e.g., melting point), to the respective outer coating layer and / or the entire outer coating. Thus, a particular outer coating layer can have improved properties at a specific depth within the outer coating and / or improved properties relative to adjacent layers or coatings. For example, the outermost outer coating layer near the surface of the outer coating may have a higher melting point than the lower outer coating layer, which is less exposed to heat, while outer coating layers advancing from the outermost outer coating layer to the bottom coating layer can create a gradient of CTE to reduce mismatch of CTE between adjacent layers or a gradient of thermal conductivity to reduce heat transfer to the substrate. In this way, the high-temperature coatings described herein can allow for a high degree of customizability for specific high-temperature applications.

[0015] The high-temperature coatings described in this article can be used in a variety of high-temperature applications. Because components are subjected to high temperatures in high-speed, frictional, or combustion environments, high-temperature coatings may be particularly suitable for aerospace applications. Figure 1A and Figure 1B An example of a carbon-carbon composite article used in aerospace applications is shown, which may undergo high temperatures conducive to oxidation and includes a high-temperature coating that protects the underlying substrate from oxidation. However, the high-temperature coating described herein can be used in other applications, such as the leading edges of hypersonic vehicles or missiles.

[0016] Figure 1A This is a perspective view showing an exemplary carbon-carbon composite material 10 including a high-temperature coating formed according to the technology of this disclosure. Figure 1A In the example, the carbon-carbon composite material 10 is a brake disc (such as that used on aircraft wheels) and a brake assembly (which can experience relatively high temperatures due to friction during braking). The carbon-carbon composite material 10 includes a carbon-carbon composite substrate comprising one or more friction surfaces 12 and one or more non-friction surfaces 14. For example, unlike the non-friction surfaces 14, the friction surfaces 12 may typically correspond to surface portions of the substrate that frictionally engage with the opposing brake disc during braking operation. Figure 1AIn the example, the friction surface 12 may correspond to the outer side of the annular ring, and the non-friction surface 14 may correspond to the outer peripheral surface region and the lug region. To protect the carbon-carbon composite substrate from oxidation, the carbon-carbon composite material 10 may include a high-temperature coating on at least one non-friction surface 14 of the carbon-carbon composite substrate. Figure 1A (Not shown separately). Friction surface 12 may not include the same high-temperature coating as the non-friction surface 14.

[0017] Figure 1B This illustrates a high-temperature coating formed according to the technology of this disclosure. Figure 1B A conceptual diagram of an exemplary carbon-carbon composite material 26 (not shown separately). Figure 1B In the example, carbon-carbon composite material 26 is an extended nozzle of thrust chamber assembly 20, the extended nozzle having a tapered shape or a truncated cone. Thrust chamber assembly 20 may include an injector 22 for injecting rocket fuel and a combustion chamber 24 for burning rocket fuel to generate thrust. Due to the exhaust gases from this combustion, carbon-carbon composite material 26 can be subjected to high temperatures (e.g., 2400°C). Carbon-carbon composite material 26 includes a carbon-carbon composite substrate, the carbon-carbon composite substrate including an inner surface exposed to combustion exhaust products and an outer surface exposed to an external atmosphere. To protect the carbon-carbon composite substrate from oxidation, carbon-carbon composite material 26 may include a high-temperature coating on at least one surface of the carbon-carbon composite substrate.

[0018] Figure 2 This is a schematic side view of an article 30 including an exemplary high-temperature coating 34, according to an example of this disclosure. Article 30 includes a carbon-carbon composite substrate 32. Substrate 32 may include carbon-based reinforcing fibers and a carbon-based matrix material at least partially surrounding the carbon-based reinforcing fibers. In some examples, substrate 32 may be formed from a porous preform comprising carbon fibers or carbon precursor fibers. Examples of porous preforms that can be used to produce substrate 32 include, but are not limited to: fiber preforms such as woven fiber preforms, nonwoven fiber preforms, chopped fiber and binder preforms, binder-treated random fiber preforms, carbon fiber preforms, or ceramic fiber preforms; foam preforms; porous carbon matrix preforms; or porous ceramic matrix preforms.

[0019] In some examples, the porous preform comprises multiple mechanically bonded layers, which may be, for example, multiple fiber layers, such as multiple woven or nonwoven fabric layers, joined together, for example by an adhesive (such as a resin adhesive) or via needle punching. In some examples, the layers comprise one or more tow layers, one or more web layers, or combinations thereof. The tow layer may comprise one or more fiber tows. The fiber tows may be arranged in any suitable arrangement, including, for example, linear, radial, chordal, etc. The web layer may comprise web fibers, which may include relatively short, chopped, and entangled fibers. In other examples, the porous preform may not include predefined layers but may be formed from, for example, a bundle of fibers mechanically bonded together via needle punching. In other examples, any combination of the aforementioned types of porous preforms may be used.

[0020] The substrate 32 may also include a matrix material that at least partially encapsulates the carbon fibers. The matrix material can be introduced into the porous preform using one or more of a variety of techniques, including, for example, chemical vapor deposition / chemical vapor infiltration (CVD / CVI), resin transfer molding (RTM), vacuum / pressure infiltration (VPI), high-pressure impregnation / carbonization (PIC), etc.

[0021] The substrate 32 can withstand high temperatures during operation. As an example, a carbon-carbon composite brake disc can withstand temperatures up to about 3,000 degrees Fahrenheit (℉) (about 1,649°C) during braking events. As another example, a carbon-carbon composite rocket nozzle extension can withstand temperatures up to about 4,500℉ (about 2,482°C) during rocket engine operation. To protect the substrate 32 from oxidation, the article 30 includes a high-temperature coating 34 on one or more surfaces of the substrate 32. The coating 34 is stable at temperatures up to about 3,500℉ (about 1,649°C), such as temperatures up to about 4,500℉ (about 2,482°C). In this context, "stable" can mean that the coating 34 does not degrade into its constituent elements, does not react with carbon, and / or does not react (including but not limited to oxidation) with other elements or compounds present in the environment in which the coating 34 is used. The coating 34 can have any suitable thickness. In some examples, the thickness of the coating 34 can be between about 0.0254 mm and about 10 mm. In some examples, the thickness of coating 34 may correspond to the application or expected service life of article 30, such that a longer service life may correspond to a thicker coating 34.

[0022] Coating 34 includes an undercoat 36 on the surface of substrate 32 (e.g., directly on substrate 32 or indirectly on substrate 32 via one or more intermediate layers). Undercoat 36 includes one or more substantially crystalline (e.g., crystalline phase greater than 95% by volume) metal carbide layers. In some examples, undercoat 36 may include at least one of silicon carbide (SiC), titanium carbide (TiC), tungsten carbide (WC), zirconium carbide (ZrC), combinations thereof, or any carbide layer formed using the process principles described in U.S. Patent 6,555,173 and / or U.S. Patent 4,837,073, the entire contents of which are incorporated herein by reference.

[0023] The primer coating 36 may be configured to reduce delamination, spalling, and / or cracking of the coating 34. The primer coating 36 may be subjected to high temperatures, which could exacerbate shear forces caused by differences in the coefficients of thermal expansion between the primer coating 36 and adjacent coatings of the substrate 32 and / or coating 38. To keep these forces relatively low, the primer coating 36 may have a coefficient of thermal expansion that is relatively similar to that of the substrate 32, the outer coating 38, or both. For example, the primer coating 36 may have a coefficient of thermal expansion in the range of about 4 parts per million parts per degree Celsius (ppm / °C) to about 4.5 ppm / °C. In some examples, the primer coating 36 may be chemically compatible with the substrate 32, the outer coating 38, or both. For example, the primer coating 36 may have selected wettability relative to the substrate 32, the outer coating 38, or both.

[0024] In some examples, the base coat 36 may be configured to increase adhesion between the outer coat 38 and the substrate 32. For example, as will be further explained below, the base coat 36 may be formed by an in-situ process involving a reaction between reactive carbon and a stoichiometric excess of metal. The excess metal may form a metal oxide that can migrate into microcracks in the substrate 32, the base coat 36, and / or the outer coat 38 to provide self-healing functionality. The metal oxide may adhere more strongly to the polymer-derived ceramic matrix of the outer coat 38 and / or may at least partially impregnate into open pores in the substrate 32. Additionally or alternatively, the base coat 36 may have a relatively low thickness (e.g., less than about 20 micrometers) and / or a uniform thickness (e.g., within about 10 micrometers), controlled by the amount of reactive carbon present on the substrate 32.

[0025] Article 30 includes an outer coating 38 on the surface of a base coating 36 (e.g., directly on the base coating 36 or indirectly on the base coating 36 via one or more intermediate layers). The outer coating 38 may be configured to reduce or prevent the migration of reactive oxidizing substances into the substrate 32 at high temperatures. The outer coating 38 comprises a plurality of outer coating layers 40. Figure 2In the example, two outer coating layers 40A and 40B are shown; however, the outer coating layer 38 may comprise any number of outer coating layers 40. For example, the outer coating layer 38 may comprise three to ten outer coating layers 40, including an outermost outer coating layer providing relatively high temperature stability, and innermost and outermost coating layers 40 providing relatively high barriers to oxidizing substances, and one or more intermediate outer coating layers 40 providing a relatively progressive gradient in coefficient of thermal expansion and / or thermal conductivity. Each outer coating layer 40 comprises a ceramic matrix and a plurality of refractory ceramic particles within the ceramic matrix. For example, the ceramic matrix may form a continuous phase, and the plurality of refractory ceramic particles may form a dispersed phase within the continuous phase.

[0026] The refractory ceramic particles of the outer coating layer 40 may comprise any high-temperature refractory ceramic material. High-temperature refractory ceramic materials may include any ceramic material that maintains thermal and chemical stability at temperatures above about 1500°C. The composition of the refractory ceramic particles can be selected for various properties, including but not limited to the melting point of the ceramic material, the coefficient of thermal expansion of the ceramic material, the thermal conductivity of the ceramic material, and compatibility with a selected polymer-derived ceramic matrix. For example, during operation of the article 30, the melting point of the refractory ceramic particles in each outer coating layer 40 may be higher than the expected temperature encountered at the corresponding outer coating layer 40. In some examples, the refractory ceramic particles may have a melting point greater than about 1600°C, such as greater than about 2400°C. Exemplary ceramic materials may include, but are not limited to, hafnium carbide (HfC), hafnium nitride (HfN), hafnium diboride (HfB2), tantalum carbide (TaC), tantalum diboride (TB2), silicon carbide (SiC), zirconium diboride and silicon carbide (ZrB2-20%SiC), hafnium diboride and silicon carbide (HfB2-20%SiC), hafnium oxide (HfO2), tungsten carbide (WC), rhenium carbide (ReC), combinations thereof, and other refractory ceramic materials.

[0027] The ceramic matrix of the outer coating layer 40 may comprise any high-temperature, polymer-derived ceramic material. The polymer-derived ceramic material may comprise any ceramic material formed by the decomposition of a ceramic preform polymer and the subsequent formation of a crystalline phase. The high-temperature, polymer-derived ceramic material may comprise any polymer-derived ceramic material that, once substantially crystallized, maintains thermal and chemical stability above about 1500°C. Compositions of polymer-derived ceramic materials may be selected for various properties, including but not limited to the decomposition temperature of the polymer-derived ceramic material, the crystallization temperature of one or more crystalline phases of the polymer-derived ceramic material, the coefficient of thermal expansion of the polymer-derived ceramic material, the molecular weight of the ceramic preform polymer, the thermal conductivity of the polymer-derived ceramic material, the porosity of the polymer-derived ceramic material, the mechanical properties of the polymer-derived ceramic material, compatibility and adhesion with ceramic particles, etc. The ceramic matrix may be substantially crystalline, such that the ceramic matrix is ​​substantially free of a glassy / amorphous phase. For example, the ceramic matrix may comprise one or more crystalline phases distributed within an amorphous phase, such that the amorphous phase is less than about 5% by volume of the ceramic matrix. Exemplary polymer-derived ceramic materials may include, but are not limited to: binary ceramics, such as silicon carbide (SiC) or silicon nitride (Si3N4); ternary ceramics, such as silicon oxycarbide (SiO2). x C y ); quaternary ceramics; their combinations, and other polymer-derived ceramic materials.

[0028] The outer coating 38 comprises two or more outer coating layers 40, rather than forming the outer coating 38 as a single monolithic layer with relatively uniform properties. These two or more outer coating layers allow for variations in the properties of the outer coating 38 along its depth (or z-axis) (e.g., normal to the surface of the substrate 32). The two or more outer coating layers 40 within the outer coating 38 may have different porosities, different thermal expansion characteristics, different thermal conductivity, different thicknesses, different melting points, and / or other variations in physical or chemical properties.

[0029] In some examples, the combination of outer coating layers 40 can define one or more gradients of one or more properties within outer coating 38, or one or more differences of one or more properties between two or more outer coating layers 40 within outer coating 38. For example, based on the proximity of a portion of outer coating 38 to the surface of outer coating 38 (e.g., the innermost or outermost) or adjacent layers (e.g., base coat 36), certain properties of outer coating 38 may be more or less important at a particular depth or location within outer coating 38.

[0030] As an example, the outer coating layer 40 may form a composition gradient throughout the outer coating layer 38 or have compositional differences between two or more outer coating layers 40 within the outer coating layer 38. For example, one or more substances within the outer coating layer 40A closest to the substrate 32 and the undercoat 36 may be more likely to migrate into or interact with substances in the substrate 32 or the undercoat 36. Figure 2 In the example, compared to the composition of the outer coating layer 40B, the outer coating layer 40A, which is closest to the substrate 32 and the base coat 36, may be more chemically compatible with the substrate 32 and / or the base coat 36.

[0031] As another example, the outer coating layer 40 can form a porosity gradient throughout the outer coating layer 38 or have porosity differences between two or more outer coating layers 40 within the outer coating layer 38. For example, compared to a dense coating, oxides can migrate more easily through a porous coating, allowing one or more outer coating layers 40 within the outer coating layer 38 to have relatively low porosity to reduce oxide migration. Figure 2 In the example, the porosity of the outer coating layer 40A closest to the substrate 32 and the undercoating 36 can be lower and therefore denser compared to the porosity of the outer coating layer 40B further from the substrate 32 and / or the undercoating 36.

[0032] As another example, the outer coating layer 40 can form a thermal conductivity gradient throughout the outer coating layer 38. For instance, the high temperature of the external atmosphere in contact with the outer coating layer 38 can damage the substrate 32, allowing one or more outer coating layers 40 within the outer coating layer 38 to have a relatively low thermal conductivity to limit heat transfer to the underlying layer or substrate, such as the substrate 32. Figure 2 In the example, the thermal conductivity of the outer coating layer 40A, which is closest to the substrate 32 and the base coating layer 36, can be higher than that of the outer coating layer 40B.

[0033] As another example, the outer coating layer 40 can form a coefficient of thermal expansion (CTE) gradient throughout the outer coating layer 38. For example, the CTE of the substrate 32 and / or the undercoat 36 can be substantially different, such as substantially lower than the CTE of the outermost outer coating layer 40 (or other outer coating layer 40) of the outer coating layer 38. To reduce interlayer forces between the substrate 32, the undercoat 36, and the outer coating layer 40 of the outer coating layer 38 caused by differences in thermal expansion at high temperatures, the outer coating layer 40 can form a CTE gradient that varies incrementally between the substrate 32 or the undercoat 36 and the outermost outer coating layer 40B (or other outer coating layer 40) of the outer coating layer 38. Figure 2 In the example, the CTE of the outer coating layer 40A can be between the CTE of the base coating layer 36 and the CTE of the outer coating layer 40B.

[0034] As another example, the outer coating layer 40 can form a thermal stability gradient throughout the outer coating layer 38. For instance, one or more outer coating layers 40 of the outer coating layer 38 can experience temperatures higher than other inner coating layers 40, such that one or more outer coating layers 40 can have a higher degradation or melting temperature than the inner coating layers 40. Figure 2 In the example, the degradation or melting point of the outer coating layer 40A (e.g., the components within the outer coating layer 40A) may be lower than the degradation or melting point of the outer coating layer 40B, which is closest to the outer surface of the outer coating layer 38.

[0035] Multiple refractory ceramic particles and / or the parameters and composition of the ceramic matrix for each layer can be selected to provide an outer coating 38 having the various properties described above. By configuring the outer coating layers 40 with different compositions or parameters, the outer coating 38 can be configured to reduce the thermal conductivity through the outer coating 38 to the substrate 32, improve the resistance of the outer coating 38 to oxidation and / or environmental erosion, and / or improve the mechanical properties of the article 30 compared to an outer coating that does not include multiple outer coating layers.

[0036] In some examples, at least two of the outer coating layers 40 comprise different average particle sizes or shapes and / or different particle size distributions of multiple ultra-high melting point refractory ceramic particles within a ceramic matrix. For example, outer coating layer 40A may comprise multiple ultra-high melting point refractory ceramic particles with different average particle sizes or shapes and / or differential particle size distributions than outer coating layer 40B. The density of the outer coating layer 40 may be related to the compaction or filling density of the multiple refractory ceramic particles. To produce an outer coating layer 40 that resists shrinkage during heat treatment (e.g., pyrolysis and crystallization), the mixture used to form the respective outer coating layer 40 may comprise a bimodal particle size distribution. This particle size distribution may be configured to form a highly filled outer coating layer 40 during heat treatment, which resists cracking during and after formation. The particle size distribution may vary based on the composition of the refractory ceramic particles, the composition of the ceramic matrix, and the volume ratio of the refractory ceramic particles to the ceramic matrix, such that different outer coating layers 40 with different compositions and volume ratios of refractory ceramic particles to the ceramic matrix may have different particle size distributions. In some examples, the difference between the average (e.g., median) particle size (e.g., diameter) of the refractory ceramic particles between the two outer coating layers is at least about 50%.

[0037] In some examples, at least two outer coating layers 40 may comprise different particulate compositions of multiple ultra-high melting point refractory ceramic particles. For example, outer coating layer 40A may comprise a particulate composition or combination / mixture of multiple ultra-high melting point refractory ceramic particles different from outer coating layer 40B. A particular composition of refractory ceramic particles may have specific chemical and thermal properties, such as melting point and coefficient of thermal expansion, which may be more suitable for a specific depth within outer coating layer 38. As an example, the refractory ceramic particles of outer coating layer 40B closest to the outer surface of outer coating layer 38 may have a higher melting point than those of outer coating layer 40A because outer coating layer 40B can be exposed to higher temperatures than outer coating layer 40A. For example, the refractory ceramic particles of outer coating layer 40B may be selected such that the outermost layer of outer coating layer 38 forms ultra-high temperature oxides, such as HfO2, during operation. As another example, the refractory ceramic particles of the outer coating layer 40A may have a thermal expansion coefficient that matches the base coating layer 36 more closely than that of the refractory ceramic particles of the outer coating layer 40B, thereby reducing the forces at the interface between the base coating layer 36 and the outer coating layer 38.

[0038] In some examples, at least two of the outer coating layers 40 comprise a mixture of different particle compositions of multiple ultra-high melting point refractory ceramic particles. The multiple refractory ceramic particles may comprise a mixture of more than one substance, such that the corresponding outer coating layer 40 may have properties produced by the blend of refractory ceramic particles.

[0039] In some examples, at least two outer coating layers 40 may contain different matrix compositions of ceramic substrates. For example, outer coating layer 40A may contain a different ceramic substrate composition than outer coating layer 40B. A particular composition of the ceramic substrate may have specific chemical and thermal properties, such as melting point and coefficient of thermal expansion, which may be more suitable for a specific depth within the outer coating layer 38. As an example, the ceramic substrate of outer coating layer 40B, which is closest to the outer surface of outer coating layer 38, may have a higher melting point than the ceramic substrate of outer coating layer 40A because outer coating layer 40B can be exposed to higher temperatures than outer coating layer 40A. As another example, the ceramic substrate of outer coating layer 40A may have a coefficient of thermal expansion that more closely matches that of the undercoat layer 36 than that of outer coating layer 40B, thereby reducing forces at the interface between the undercoat layer 36 and the outer coating layer 38.

[0040] In some examples, at least two of the outer coating layers 40 comprise different volume ratios of ceramic matrix to multiple ultra-high melting point refractory ceramic particles. For example, various properties of each outer coating layer 40 (such as the effective coefficient of thermal expansion) can be generated by a combination of the properties of the refractory ceramic particles and the ceramic matrix. As an example, the intermediate outer coating layer 40A may have a volume ratio of ceramic matrix to multiple refractory ceramic particles corresponding to a lower CTE than that of the ceramic matrix to refractory ceramic particles in outer coating layer 40A, such that the difference in CTE between the base coat 36 and the outer coating layer 40B can increase throughout outer coating layer 40A.

[0041] In some examples, the high-temperature coating 34 includes an oxide layer 42 on the surface of the outer coating 38. For example, ultra-high temperature applications may exceed the capabilities of metal carbides for thermal protection. The oxide layer 42 comprises a high-temperature metal oxide formed from a metal carbide, as will be further described below. Exemplary metal oxide materials that can be used include, but are not limited to, hafnium oxide (HfO2), zirconium oxide (ZrO2), etc.

[0042] Figure 3 This is a flowchart illustrating an exemplary technique for forming a high-temperature coating according to an example of this disclosure. (The term "relative to..." is unclear and likely a typo.) Figure 2 Product 30 Description Figure 3 The technology; however Figure 3 The technology can be used to form other products including high-temperature coatings, such as products with a larger number of layers.

[0043] Figure 3 The technique includes forming a crystalline metal carbide undercoat 36 (50) on the surface of a carbon-carbon composite substrate 32. In some examples, a metal-rich combination of one or more carbon coatings and one or more metal coatings can be used to form the undercoat 36 in situ. Forming the undercoat 36 may include cleaning the surface of the substrate 32, applying a reactive carbon coating (e.g., by brushing) to the surface of the substrate 32, and drying the carbon coating. Forming the undercoat 36 may also include applying a metal coating over the carbon coating and drying the metal coating. The metal coating may be metal-rich and applied in stoichiometric excess. Forming the undercoat 36 may also include heating the carbon coating and the metal coating to a heat treatment temperature. The heat treatment temperature may be high enough to allow the metal in the metal coating to move, such as by melting, and to allow the metal to react with the carbon in the carbon coating to form a crystalline metal carbide. The metal carbide may be further heated to further alter the microstructure, phase composition, or other properties or characteristics of the metal carbide. Excess metal from the metal coating may migrate into the pores of the substrate 32. The resulting base coating 36 may include a metal carbide portion on the surface of the substrate 32 and a metal portion extending into the substrate 32.

[0044] Figure 3The technique involves forming an outer coating 38 (52) on the surface of the base coating 36. The outer coating comprises multiple crystalline ultra-high melting point outer coating layers 40.

[0045] Each outer coating layer is formed sequentially by applying a mixture to the surface of the underlying layer (54). The mixture comprises multiple ultra-high melting point refractory ceramic particles and a ceramic preform polymer. The ceramic preform polymer of each mixture can be selected for the desired properties of the resulting pyrolytic, crystallized ceramic matrix. A variety of ceramic preform polymers can be used, including but not limited to polysilanes, polycarbosilanes, polysiloxanes, polycarbosiloxanes, polysilazanes, polycarbosilazanes, etc. A variety of methods can be used to apply the mixture to the underlying layer. In some examples, at least one of brushing or spraying is used to apply the mixture. For example, brushing or spraying may be relatively inexpensive and can form relatively thin layers, such that the outer coating 38 can contain a large number of layers while remaining relatively thin.

[0046] In some examples, the composition, particle size or shape, and / or particle size distribution of each mixture can be selected to produce the resulting ceramic matrix, which is relatively free of thermal defects, such as cracking caused by temperature changes during pyrolysis or crystallization. For example, during the pyrolysis of the ceramic preform polymer, the ceramic preform polymer can change size due to shrinkage, thermal expansion, or other temperature-induced dimensional changes resulting from the release of various volatiles. This dimensional change can differ from the dimensional changes of multiple refractory ceramic particles or adjacent underlying coatings, such as dimensional changes caused by different coefficients of thermal expansion or relatively low chemical stability of the ceramic preform polymer. Therefore, the respective mixtures used to form each corresponding outer coating layer can be different in one or more respects. For example, the composition, particle size or shape, and / or particle size distribution of the first mixture applied to form layer 40A differs from the composition, particle size or shape, and / or particle size distribution of the second mixture applied to form layer 40B.

[0047] Each outer coating layer can be formed sequentially by heating the mixture to a heat treatment temperature in an inert atmosphere or under vacuum (56). The heat treatment temperature is high enough to pyrolyze the ceramic preform polymer and form a ceramic matrix. The heat treatment temperature can also be high enough to crystallize the ceramic matrix. For example, the heat treatment temperature can be high enough to convert most or all of the glass phase into one or more crystalline phases. In some examples, the heat treatment temperature can be greater than about 1800℉ for several hours, such as about 2600℉. The resulting outer coating layer 40 comprises a crystalline ultra-high melting point polymer-derived ceramic matrix containing a plurality of ultra-high melting point refractory ceramic particles.

[0048] Forming the outer coating 38 may include forming two or more outer coating layers 40. As an example, in order to form... Figure 2The two outer coating layers 40A and 40B shown can be formed by applying a first mixture to the surface of a base coat 36 and subsequently heating the first mixture to pyrolyze the first ceramic preform polymer of the first mixture to form a first outer coating layer 40A. To form subsequent layers, the technique can include applying a second mixture to the surface of the first outer coating layer 40A and subsequently heating the second mixture to pyrolyze the second ceramic preform polymer of the second mixture to form a second outer coating layer 40B. This process of applying and heating the mixture to form the outer coating layers 40 can be repeated until a desired number of outer coating layers 40 are formed.

[0049] As described above, the composition of the ceramic preform mixture used to form a particular outer coating layer 40 can be selected based on various characteristics of the resulting outer coating layer 40. Therefore, various parameters of the ceramic preform mixture can be varied between applying two or more outer coating layers 40.

[0050] As an example, the average particle size or shape and / or particle size distribution of the first plurality of refractory ceramic particles in the first mixture used to form the first outer coating layer 40A may differ from the average particle size or shape of the second plurality of refractory ceramic particles in the second mixture used to form the second outer coating layer 40B, such that the first outer coating layer 40A and the second outer coating layer 40B comprise different average particle sizes or shapes of the respective first and second plurality of refractory ceramic particles. As another example, the particulate composition of the first plurality of refractory ceramic particles in the first mixture used to form the first outer coating layer 40A and / or the composition of the first ceramic preform polymer may differ from the particulate composition of the second plurality of refractory ceramic particles in the second mixture used to form the second outer coating layer 40B or the composition of the second ceramic preform polymer, such that the first outer coating layer 40A and the second outer coating layer 40B comprise different particulate compositions of the respective first and second plurality of refractory ceramic particles.

[0051] As another example, the volume ratio of the first ceramic preform polymer composition or the first ceramic preform polymer to the first plurality of refractory ceramic particles may differ from the volume ratio of the second ceramic preform polymer composition or the second ceramic preform polymer to the second plurality of refractory ceramic particles, such that the first outer coating layer 40A and the second outer coating layer 40B may include different volume ratios of the first ceramic matrix to the first plurality of refractory ceramic particles and the second ceramic matrix to the second plurality of refractory ceramic particles. For example, from the surface of the base coating layer 36 to the surface of the outer coating layer 38, each of the plurality of outer coating layers includes a varying volume ratio of ceramic matrix to the plurality of ultra-high melting point refractory ceramic particles. In some examples, the volume ratio of the plurality of ultra-high melting point refractory ceramic particles to the ceramic preform polymer is between about 30:70 and about 70:30.

[0052] In some examples, Figure 3 The technique may include forming an oxide layer 42 on the surface of an outer coating 38. Forming the oxide layer may include applying a metal carbide coating to the surface of a plurality of outer coating layers and heating the metal carbide coating. When the metal carbide is heated, the metal from the metal carbide may react with oxygen to form a metal oxide having higher thermal stability (e.g., degradation or melting temperature) than the metal carbide.

[0053] As mentioned above, Figure 3 The technology can be used to form high-temperature coatings tailored for specific high-temperature applications. As an example of how such selection and customization can be performed, the outermost coating layer 40 of the outer coating 38 can be determined based on the expected temperature encountered at the outer surface of the outer coating 38, which can be exposed to the highest temperature. For the outermost coating layer 40, a composition of multiple refractory ceramic particles and a ceramic preform polymer corresponding to the ceramic matrix can be selected, each having a melting point above the expected temperature.

[0054] The combination of refractory ceramic particles and ceramic matrix in the outermost coating layer 40 can have the desired CTE and thermal conductivity. In some examples, the various outer coating layers 40 between the outermost coating layer 40 and the base layer 36 can be configured to create a CTE gradient. For example, the CTE of the outermost coating layer 40 can be substantially different from the CTE of the substrate 32. The composition of the metal carbide of the base layer 36 and / or the composition, particle size, particle size distribution, or volume ratio of the refractory ceramic particles and / or the ceramic preform polymer corresponding to the ceramic matrix of the outer coating layer 40 can be selected to incrementally increase or decrease the CTE, such that the difference in CTE between adjacent layers can be reduced. In some examples, the various outer coating layers 40 between the outermost coating layer 40 and the base layer 36 can be configured to create a thermal conductivity gradient. For example, the desired temperature experienced by the outermost layer can be substantially higher than the desired temperature experienced by the substrate 32. A composition or volume ratio of refractory ceramic particles and / or ceramic preform polymers corresponding to the ceramic matrix of the outer coating layer 40 can be selected to reduce thermal conductivity, so that the heat flux (and temperature) that can be passed through each subsequent outer coating layer 40 can be reduced.

[0055] like Figure 1A The high-temperature coating described herein can be used in aircraft brakes. Figure 4 This is a schematic diagram illustrating an exemplary aircraft brake assembly including a composite material brake disc formed according to the technology of this disclosure, the composite material brake disc comprising a high-temperature coating. For ease of description, examples of this disclosure will be described primarily with respect to aircraft brake assemblies. However, the articles of this disclosure can be used to form brake components other than aircraft brake discs. For example, brake components can be used as friction materials in other types of braking applications and vehicles.

[0056] exist Figure 4 In the example, the wheel and brake assembly 60 includes a wheel 62, an actuator assembly 64, a brake stack 66, and an axle 68. The wheel 62 includes a hub 70, wheel support flanges 72, flange seals 74A and 74B, lug bolts 76, and lug nuts 78. The actuator assembly 64 includes an actuator housing 80, actuator housing bolts 82, and a plunger 84. The brake stack 66 includes alternating rotor brake discs 86 and stator brake discs 88; the rotor brake discs 86 are configured to move relative to the stator brake discs 88. The rotor brake discs 86 are mounted on the wheel 62 via beam keys 90, and specifically on the hub 70. The stator brake discs 88 are mounted to the axle 68 via key teeth 94, and specifically on torque tubes 92. The wheel and brake assembly 60 can support any kind of private, commercial, or military aircraft or other types of vehicles.

[0057] Wheel and brake assembly 60 includes wheel 62, in Figure 4 In the example, wheel 12 is defined by a hub 70 and a wheel support flange 72. The wheel support flange 72 is mechanically attached to the hub 70 by lug bolts 76 and lug nuts 78. Wheel 62 defines flange seals 74A and 74B. During assembly, an inflatable tire (not shown) can be placed above the hub 70 and secured to the opposite side by the wheel support flange 72. Thereafter, the lug nuts 78 can be fastened to the lug bolts 76, and the inflatable tire can be inflated using the flange seals 74A and 74B, thereby providing an airtight seal for the inflatable tire.

[0058] The wheel and brake assembly 60 can be mounted to the vehicle via torque tube 92 and axle 68. Figure 4 In the example, torque tube 92 is attached to shaft 68 by multiple bolts 96. Torque tube 92 supports actuator assembly 64 and stator brake disc 88. Shaft 68 may be mounted on struts of landing gear (not shown) or other suitable parts of the vehicle to connect wheels and brake assembly 60 to the vehicle.

[0059] During vehicle operation, braking may be required periodically, such as during the landing and taxiing of an aircraft. The wheel and brake assembly 60 is configured to provide braking functionality to the vehicle via actuator assembly 64 and brake stack 66. Actuator assembly 64 includes actuator housing 80 and plunger 84. Actuator assembly 64 may include one or more of different types of actuators, such as, for example, electromechanical actuators, hydraulic actuators, pneumatic actuators, etc. During operation, plunger 84 may extend away from actuator housing 80 to axially compress brake stack 66 against a compression point for braking.

[0060] The brake stack 66 comprises alternating rotor brake discs 86 and stator brake discs 88. The rotor brake discs 86 are mounted on the hub 70 for common rotation via a beam key 90. The stator brake discs 88 are mounted to the torque tube 92 via key teeth 94. Figure 4 In the example, the brake stack 66 includes four rotors and five stators. However, in other examples, the brake stack 66 may include a different number of rotors and / or stators.

[0061] In some examples, the rotor brake disc 86 and stator brake disc 88 may be mounted in the wheel and brake assembly 60 via beam keys 90 and key teeth 94, respectively. In some examples, the beam keys 90 may be circumferentially spaced around an inner portion of the hub 70. For example, the beam keys 90 may be shaped to have opposing ends (e.g., opposite sides of a rectangle) and may have one end mechanically attached to an inner portion of the hub 70 and an opposing end mechanically attached to an outer portion of the hub 70. The beam keys 90 may be integrally formed with the hub 70, or may be separate from and mechanically attached to the hub 70, for example, to provide a thermal barrier between the rotor brake disc 86 and the hub 70. For this purpose, in various examples, the wheel and brake assembly 60 may include a heat shield (not shown) extending radially outward and surrounding the brake stack 66, for example, to limit heat transfer between the brake stack 66 and the wheel 62.

[0062] In some examples, the key teeth 94 may be circumferentially spaced around the outer portion of the torque tube 92. Accordingly, the stator brake disc 88 may include a plurality of radially inwardly disposed lugs along the inner diameter of the brake disc, the lugs being configured to engage with the key teeth 94. Similarly, the rotor brake disc 86 may include a plurality of radially inwardly disposed lugs along the outer diameter of the brake disc, the lugs being configured to engage with the beam key 90. Thus, the rotor brake disc 86 will rotate with the movement of the wheel, while the stator brake disc 88 remains stationary, allowing the friction surfaces of adjacent stator brake discs 88 and rotor brake discs 86 to engage with each other, thereby slowing the rotation of the wheel 62.

[0063] Rotor brake disc 86 and stator brake disc 88 provide relative friction surfaces for braking an aircraft. As the kinetic energy of a moving aircraft is converted into heat energy in the brake stack 66, the temperature in the brake stack 66 can rise rapidly. Accordingly, the rotor brake disc 86 and stator brake disc 88 forming the brake stack 66 may include coatings capable of operating at very high temperatures and blocking various oxidizing substances.

[0064] Example 1: A method comprising: forming a crystalline metal carbide undercoat on a surface of a carbon-carbon composite substrate; and forming an outer coating on a surface of the undercoat, wherein the outer coating comprises a plurality of crystalline ultra-high melting point outer coating layers, and wherein each outer coating layer is formed sequentially by at least the following: applying a mixture to a surface of an underlying layer, wherein the mixture comprises a plurality of ultra-high melting point refractory ceramic particles and a ceramic preform polymer; and heating the mixture to a heat treatment temperature in an inert atmosphere or under vacuum to pyrolyze the ceramic preform polymer and form the outer coating layer, wherein the outer coating layer comprises a ceramic matrix derived from the crystalline ultra-high melting point polymer, the ceramic matrix comprising the plurality of ultra-high melting point refractory ceramic particles.

[0065] Example 2: According to the method of Example 1, each of the plurality of ultra-high melting point refractory ceramic particles and the ultra-high melting point polymer-derived ceramic matrix has a melting point greater than about 1500 degrees Celsius (°C).

[0066] Example 3: According to the method of any one of Examples 1 and 2, at least two of the plurality of outer coating layers comprise a ceramic matrix having at least one of different coefficients of thermal expansion or different thermal conductivity.

[0067] Example 4: According to any one of Examples 1 to 3, the melting point of the ceramic substrate of the outermost outer coating layer of the plurality of outer coating layers is higher than the melting point of the ceramic substrate of the lower outer coating layer of the plurality of outer coating layers.

[0068] Example 5: The method according to any one of Examples 1 to 4, wherein at least one of the following: the first mixture for forming the first layer of the plurality of outer coating layers comprises a plurality of ultra-high melting point refractory ceramic particles with an average particle size or shape different from the second mixture for forming the second layer of the plurality of outer coating layers, or the first mixture for forming the first layer of the plurality of outer coating layers comprises a plurality of ultra-high melting point refractory ceramic particles with a particle size distribution different from the second mixture for forming the second layer of the plurality of outer coating layers.

[0069] Example 6: The method according to any one of Examples 1 to 5, wherein at least one of the following: the first mixture for forming the first layer of the plurality of outer coating layers comprises a particle composition of a plurality of ultra-high melting point refractory ceramic particles different from the second mixture for forming the second layer of the plurality of outer coating layers; the first mixture for forming the first layer of the plurality of outer coating layers comprises a particle composition mixture of a plurality of ultra-high melting point refractory ceramic particles different from the second mixture for forming the second layer of the plurality of outer coating layers; or the first mixture for forming the first layer of the plurality of outer coating layers comprises a ceramic preform polymer composition different from the second mixture for forming the second layer of the plurality of outer coating layers.

[0070] Example 7: According to any one of Examples 1 to 6, the first layer of the plurality of outer coating layers includes a ceramic matrix and a plurality of ultra-high melting point refractory ceramic particles with a volume ratio that is different from that of the second layer of the plurality of outer coating layers.

[0071] Example 8: According to the method of Example 7, each of the plurality of outer coating layers comprises a varying volume ratio of a ceramic matrix to a plurality of ultra-high melting point refractory ceramic particles from the surface of the base coating layer to the surface of the outer coating layer.

[0072] Example 9: The method according to any one of Examples 1 to 8, wherein applying the mixture to the surface comprises at least one of: brushing the mixture onto the surface, or spraying the mixture onto the surface.

[0073] Example 10: The method according to any one of Examples 1 to 9 further includes: applying a metal carbide coating to the surface of the plurality of outer coating layers; and heating the metal carbide coating to form a metal oxide coating.

[0074] Example 11: An article comprising: a carbon-carbon composite substrate; a crystalline metal carbide undercoat on a surface of the carbon-carbon composite substrate; and an outer coating on a surface of the undercoat, wherein the outer coating comprises a plurality of crystalline ultra-high melting point outer coating layers, and wherein each of the plurality of outer coating layers comprises a crystalline ultra-high melting point polymer-derived ceramic matrix, the crystalline ultra-high melting point polymer-derived ceramic matrix comprising a plurality of ultra-high melting point refractory ceramic particles.

[0075] Example 12: The article according to Example 11, wherein each of the plurality of ultra-high melting point refractory ceramic particles and the ultra-high melting point polymer-derived ceramic matrix has a melting point greater than about 1500 degrees Celsius (°C).

[0076] Example 13: The article according to any one of Examples 11 and 12, wherein at least two of the plurality of outer coating layers comprise a ceramic matrix having at least one of having a different coefficient of thermal expansion or a different thermal conductivity.

[0077] Example 14: The article according to any one of Examples 11 to 13, wherein the melting point of the ceramic substrate of the outermost of the plurality of outer coating layers is higher than the melting point of the ceramic substrate of the lower outer coating layer of the plurality of outer coating layers.

[0078] Example 15: An article according to any one of Examples 11 to 14, wherein at least one of the following: the first layer of the plurality of outer coating layers comprises an average particle size or shape of a plurality of ultra-high melting point refractory ceramic particles that is different from the second layer of the plurality of outer coating layers, or the first layer of the plurality of outer coating layers comprises a particle size distribution of a plurality of ultra-high melting point refractory ceramic particles that is different from the second layer of the plurality of outer coating layers.

[0079] Example 16: An article according to any one of Examples 11 to 15, wherein at least one of the following: the first layer of the plurality of outer coating layers comprises a particulate composition of a plurality of ultra-high melting point refractory ceramic particles different from the second layer of the plurality of outer coating layers; the first layer of the plurality of outer coating layers comprises a mixture of particulate compositions of a plurality of ultra-high melting point refractory ceramic particles different from the second layer of the plurality of outer coating layers; or the first layer of the plurality of outer coating layers comprises a ceramic matrix composition different from the second layer of the plurality of outer coating layers.

[0080] Example 17: The article according to any one of Examples 11 to 16, wherein the first layer of the plurality of outer coating layers comprises a ceramic matrix and a plurality of ultra-high melting point refractory ceramic particles in a volume ratio different from that of the second layer of the plurality of outer coating layers.

[0081] Example 18: The article according to Example 17, wherein each of the plurality of outer coating layers comprises a varying volume ratio of a ceramic matrix to a plurality of ultra-high melting point refractory ceramic particles from the surface of the base coating layer to the surface of the outer coating layer.

[0082] Example 19: The article of any one of Examples 11 to 18 further includes a metal oxide coating on the surface of the outer coating.

[0083] Example 20: The article of any one of Examples 11 to 19, wherein the carbon-carbon composite substrate comprises a component of an aircraft.

[0084] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method comprising: A crystalline metal carbide undercoat is formed on the surface of a carbon-carbon composite substrate; as well as An outer coating is formed on the surface of the crystalline metal carbide base coating, wherein the outer coating comprises a plurality of crystalline ultra-high melting point outer coating layers, and wherein each outer coating layer is formed sequentially on the underlying layer by at least the following steps: A mixture is applied to the surface of the lower layer, wherein the mixture comprises a plurality of ultra-high melting point refractory ceramic particles and a ceramic preform polymer, and wherein the ultra-high melting point refractory ceramic particles have a melting point of at least 2400°C; and In an inert atmosphere or under vacuum, the mixture is heated to a heat treatment temperature to pyrolyze the ceramic preform polymer and form the outer coating layer, wherein the outer coating layer comprises a ceramic matrix derived from a crystalline ultra-high melting point polymer, the ceramic matrix comprising the plurality of ultra-high melting point refractory ceramic particles. Each outer coating layer comprises a ceramic matrix derived from a crystalline ultra-high melting point polymer, wherein the crystalline ultra-high melting point polymer-derived ceramic matrix comprises the plurality of ultra-high melting point refractory ceramic particles, and The outermost layer of the outer coating comprises the outermost outermost coating layer of a plurality of outer coating layers.

2. The method according to claim 1, wherein the melting point of the ultra-high melting point polymer-derived ceramic matrix is ​​greater than 1500 degrees Celsius (°C).

3. The method according to claim 1 or 2, wherein at least two of the plurality of outer coating layers comprise a ceramic matrix having at least one of different coefficients of thermal expansion or different thermal conductivity.

4. The method according to claim 1 or 2, wherein at least two of the plurality of outer coating layers have at least one of a different coefficient of thermal expansion, thermal conductivity, porosity, or thermal stability.

5. The method according to claim 1 or 2, further comprising: Apply a metal carbide coating to the surface of the plurality of outer coating layers; as well as The metal carbide coating is heated to form a metal oxide coating.

6. An article comprising: Carbon-carbon composite substrate; A crystalline metal carbide undercoat is applied to the surface of the carbon-carbon composite substrate; and An outer coating layer is provided on the surface of the crystalline metal carbide base coating layer. The outer coating layer comprises multiple crystalline ultra-high melting point outer coating layers, each of which comprises a crystalline ultra-high melting point polymer-derived ceramic matrix containing multiple ultra-high melting point refractory ceramic particles. The ultra-high melting point refractory ceramic particles mentioned above have a melting point of at least 2400°C, and The outermost layer of the outer coating comprises the outermost outermost coating layer of a plurality of outer coating layers.

7. The article of claim 6, wherein the melting point of the ultra-high melting point polymer-derived ceramic matrix is ​​greater than 1500 degrees Celsius (°C).

8. The article of claim 6 or 7, wherein at least two of the plurality of outer coating layers comprise a ceramic matrix having at least one of a different coefficient of thermal expansion or a different thermal conductivity.

9. The article according to claim 6 or 7, wherein at least two of the plurality of outer coating layers have at least one of a different coefficient of thermal expansion, thermal conductivity, porosity or thermal stability.

10. The article of claim 6 or 7 further comprises a metal oxide coating on the surface of the outer coating.

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