Environmental Barrier Coating

Abstract

An article according to an exemplary embodiment of the present disclosure includes, among other possibilities, a substrate and a barrier layer on the substrate. The barrier layer includes a bond coat including a matrix, diffusing particles disposed within the matrix, and gettering particles disposed within the matrix, and a top coat including a component reactive with calcium-magnesium-aluminosilicate (CMAS). Articles and methods for applying the calcium-magnesium-aluminosilicate (CMAS)-resistant top coat are also disclosed.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority to U.S. Patent Application No. 17 / 849,227, filed June 24, 2022, which is incorporated herein by reference in its entirety. [Background technology]

[0002] A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air entering the compressor section is compressed and sent to the combustion section, where it is mixed with fuel and ignited to generate a high-energy exhaust gas stream. The high-energy exhaust gas stream expands through the turbine section, powering the compressor and fan sections. The compressor section typically includes low-pressure and high-pressure compressors, and the turbine section includes low-pressure and high-pressure turbines.

[0003] The present disclosure relates to composite articles, such as those used in gas turbine engines, and methods of coating those articles. Components, such as gas turbine engine components, may be subjected to high temperatures, corrosive and oxidative conditions, and high stress levels. To improve thermal and / or oxidative stability, the components may include a protective barrier coating. Summary of the Invention [Means for solving the problem]

[0004] An article according to an exemplary embodiment of the present disclosure includes, among other possibilities, a substrate and a barrier layer on the substrate, the barrier layer including a bond coat including a matrix, diffusing particles disposed within the matrix, and gettering particles disposed within the matrix, and a top coat including a component reactive with calcium-magnesium-aluminosilicate (CMAS).

[0005] In a further example of the foregoing, the bond coat includes a first bond coat layer adjacent to the substrate and a second bond coat layer adjacent to the top coat.

[0006] In a further example of any of the foregoing, the first layer and the second layer each comprise from about 5 to about 40 volume percent matrix.

[0007] In a further example of any of the foregoing, the second layer includes between about 55 and 94 volume percent gettering particles.

[0008] In a further example of any of the foregoing, the first layer may include between about 60 and about 95 volume percent gettering particles.

[0009] In a further example of any of the foregoing, the second layer includes gettering particles having an average largest dimension of from about 1 to about 75 microns.

[0010] In a further example of any of the foregoing, the average diameter of the gettering particles of the second layer is greater than the average diameter of the gettering particles of the first layer.

[0011] In a further example of any of the foregoing, the gettering particles are silicon carbide particles or silicon oxycarbide particles.

[0012] In a further example of any of the foregoing, the topcoat includes an intermediate layer adjacent to the bondcoat that does not include a component that reacts with calcium-magnesium-aluminosilicate (CMAS).

[0013] In a further example of any of the foregoing, the component that reacts with calcium-magnesium-aluminosilicate (CMAS) includes titanium or cerium.

[0014] In a further example of any of the foregoing, the bond coat includes a sintering aid.

[0015] In a further example of any of the foregoing, the topcoat includes about 2 to about 30 weight ratio components reactive with calcium-magnesium-aluminosilicate (CMAS).

[0016] An article according to an exemplary embodiment of the present disclosure includes, among other possibilities, a ceramic matrix composite substrate and a barrier layer on the substrate, the barrier layer including a bond coat including a silicon dioxide matrix, diffusing particles disposed within the matrix, and silicon carbide or silicon oxycarbide gettering particles disposed within the matrix; and a top coat including a component reactive with calcium-magnesium-aluminosilicate (CMAS).

[0017] In a further example of the foregoing, the bond coat includes a first bond coat layer adjacent to the substrate and a second bond coat layer adjacent to the top coat.

[0018] In a further example of any of the foregoing, the second layer includes gettering particles having an average largest dimension of about 1 to about 75 microns, and the average diameter of the gettering particles of the second layer is greater than the average diameter of the gettering particles of the first layer.

[0019] In a further example of any of the foregoing, the component that reacts with calcium-magnesium-aluminosilicate (CMAS) includes titanium or cerium.

[0020] In a further example of any of the foregoing, the bond coat includes a sintering aid.

[0021] In a further example of any of the foregoing, the topcoat includes about 2 to about 30 weight ratio components reactive with calcium-magnesium-aluminosilicate (CMAS).

[0022] According to an exemplary embodiment of the present disclosure, a method for applying a calcium-magnesium-aluminosilicate (CMAS)-resistant topcoat includes, among other possibilities, depositing the topcoat onto a bond coat by thermal spraying. The thermal spray feedstock powder includes, by weight, about 70-98% topcoat material powder, and the balance a CMAS reactive component or a precursor to a CMAS reactive component.

[0023] In a further example of the foregoing, the precursor to the CMAS reactive component is HfTiO4 or HfO2-CeO2. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram of an exemplary gas turbine engine. [Figure 2] 10. The gas turbine engine article of claim 1 having a coating. [Figure 3] 2A and 2B schematically illustrate other articles for gas turbine engines with other exemplary coatings. [Figure 4] 2A and 2B schematically illustrate other articles for gas turbine engines with other exemplary coatings. DETAILED DESCRIPTION OF THE INVENTION

[0025] 1 illustrates a schematic representation of a gas turbine engine 20. The gas turbine engine 20 is generally disclosed herein as a two-spool turbofan incorporating a fan section 22, a compressor section 24, a combustor section 26, and a turbine section 28. The fan section 22 drives air along a bypass flowpath B within a bypass duct defined within a housing 15, such as a fan case or nacelle, and along a core flowpath C for compression and communication with the combustor section 26 and subsequent expansion through the turbine section 28. While the disclosed, non-limiting embodiment is shown as a two-spool turbofan gas turbine engine, it should be understood that the concepts described herein are not limited to use with two-spool turbofans, as the present teachings may also be applied to other types of turbine engines, including three-spool configurations.

[0026] The exemplary engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about the engine's central longitudinal axis A relative to an engine static structure 36 via a number of bearing systems 38. It should be understood that different bearing systems 38 may alternatively or additionally be provided in different locations, and the locations of the bearing systems 38 may be varied as appropriate depending on the application.

[0027] The low-speed spool 30 typically includes an inner shaft 40 that interconnects a first (or low-pressure) compressor 44 and a first (or low-pressure) turbine 46. The inner shaft 40 is connected to the fan 42 via a speed-changing mechanism, shown in the exemplary gas turbine engine 20 as a gear structure 48, for driving the fan 42 at a lower speed than the low-speed spool 30. The high-speed spool 32 includes an outer shaft 50 that interconnects a second (or high-pressure) compressor 52 and a second (or high-pressure) turbine 54. A combustor 56 is located in the exemplary gas turbine 20 between the high-pressure compressor 52 and the high-pressure turbine 54. A mid-turbine frame 57 of the engine static structure 36 may typically be located between the high-pressure turbine 54 and the low-pressure turbine 46. The mid-turbine frame 57 further supports a bearing system 38 within the turbine section 28. The inner shaft 40 and the outer shaft 50 are concentric and rotate via the bearing system 38 about a central longitudinal axis A of the engine that is collinear with the longitudinal axis A of the inner shaft 40 and the outer shaft 50.

[0028] The core airflow is compressed by the low-pressure compressor 44 and then the high-pressure compressor 52, mixed with fuel and combusted in the combustor 56, and then expanded through the high-pressure turbine 54 and the low-pressure turbine 46. A mid-turbine frame 57 includes airfoils 59 located within the core airflowpath C. The turbines 46, 54 rotate the low-speed spool 30 and the high-speed spool 32, respectively, in response to the expansion. It will be appreciated that the locations of the fan section 22, compressor section 24, combustor section 26, turbine section 28, and fan drive gear system 48 may each be varied. For example, the gear system 48 may be located aft of the low-pressure compressor, or aft of the combustor section 26, or even aft of the turbine section 28, and the fan 42 may be located forward or aft of the gear system 48.

[0029] In one example, engine 20 is a high-bypass gear aircraft engine. As a further example, the bypass ratio of engine 20 may be greater than about 6, and in exemplary embodiments, greater than about 10, and may be less than or equal to about 18.0, or more narrowly, less than or equal to 16.0. Gear structure 48 is a planetary gear train, such as a planetary gear system or other gear system, having a gear reduction ratio greater than about 2.3. The gear reduction ratio may be less than or equal to 4.0. Low-pressure turbine 46 has a pressure ratio greater than about 5. The low-pressure turbine pressure ratio may be less than or equal to 13.0, or more narrowly, less than or equal to 12.0. In one disclosed embodiment, engine 20 has a bypass ratio greater than about 10 (10:1), the fan diameter is significantly larger than the diameter of low-pressure compressor 44, and the low-pressure turbine 46 pressure ratio is greater than about 5 (5:1). The pressure ratio of low-pressure turbine 46 is the pressure measured before the inlet of low-pressure turbine 46 relative to the pressure at the outlet of low-pressure turbine 46 before the exhaust nozzle. The gear structure 48 may be a planetary gear train, such as an epicyclic gear system or other gear system, having a gear reduction ratio greater than about 2.3:1 and less than about 5:1. However, it should be understood that the above parameters are merely exemplary of one embodiment of a gear structure engine, and that the present invention is applicable to other gas turbine engines, including direct drive turbofans.

[0030] Due to the high bypass ratio, a significant amount of thrust is provided by the bypass flow B. The fan section 22 of the engine 20 is designed to cruise at specific flight conditions, typically about Mach 0.8 and about 35,000 feet (10,668 meters). At Mach 0.8 and 35,000 feet (10,668 meters), when the engine is at its highest fuel consumption (also referred to as "bucket cruise thrust specific fuel consumption ('TSFC')"), is an industry standard parameter of lbm of fuel burned divided by the lbf of thrust the engine produces at its minimum point. The engine parameters described above and in this paragraph are measured at this condition unless otherwise specified. The "low fan pressure ratio" is the overall pressure ratio of the fan blades alone, without the use of a fan exit guide vane ("FEGV") system. According to one non-limiting embodiment, the low fan pressure ratio disclosed herein is less than about 1.45, or more specifically, greater than or equal to 1.25. "Low corrected fan tip speed" is [(Tram°R) / (518.7°R)] 0.5 The "low corrected fan tip speed" is the actual fan tip speed in feet per second divided by an industry standard temperature correction value of 1150.0 feet per second (350.5 meters per second). According to one non-limiting embodiment, the "low corrected fan tip speed" disclosed herein may be less than about 1150.0 feet per second (350.5 meters per second) and greater than or equal to 1000.0 feet per second (304.8 meters per second).

[0031] 2 schematically illustrates a representative portion of an exemplary article 100 for a gas turbine engine 20, including a composite bond coat 102 that functions as a barrier layer. The article 100 may be, for example, an airfoil in the compressor section 24 or turbine section 28, a combustor liner panel in the combustor section 26, a blade outer air seal, or other component that would benefit from the examples herein. In this example, the bond coat 102 is used as an environmental barrier layer to protect an underlying substrate 104 from environmental and thermal conditions. As will be appreciated, the bond coat 102 may be used as a stand-alone barrier layer, as an outermost / top coat with additional underlayers, or in combination with other coating underlayers or overlayers, such as, but not limited to, ceramic-based top coats.

[0032] The bond coat 102 includes a matrix 106, a dispersion of "gettering" particles 108, and a dispersion of diffusing particles 110. In one example, the matrix 106 may be silicon dioxide (SiO2). In one example, the gettering particles 108 are silicide particles, such as silicon oxycarbide particles (SiOC) or molybdenum disilicide (MoSi2) particles 108, although other examples are contemplated. The gettering particles 108 may be, for example, molybdenum disilicide particles, tungsten disilicide particles, vanadium disilicide particles, niobium disilicide particles, silicon oxycarbide particles, silicon carbide (SiC) particles, silicon nitride (Si3N4) particles, silicon oxycarbonitride (SiOCN) particles, silicon nitride (SiAlON) particles, boron silicon oxycarbide (SiBOCN) particles, or a combination thereof. The diffusing particles 110 can be, for example, barium magnesium aluminosilicate (BMAS) particles, barium strontium aluminum silicate particles, magnesium silicate particles, calcium aluminosilicate particles (CAS), alkaline earth aluminum silicate particles, yttrium aluminum silicate particles, ytterbium aluminum silicate particles, other rare earth metal aluminum silicate particles, or combinations thereof.

[0033] The bond coat 102 protects the underlying substrate 104 from oxygen and moisture. For example, the substrate 104 can be a ceramic-based substrate, such as a silicon-containing ceramic material. One example is silicon carbide. Another non-limiting example is silicon nitride. Ceramic matrix composite (CMC) substrates 104, such as silicon carbide fibers in a silicon carbide matrix, are also contemplated. These CMC substrates may be formed by melt infiltration, chemical vapor infiltration (CVI), polymer infiltration and pyrolysis (PIP), particle infiltration, or other known methods. The gettering particles 108 and diffusing particles 110 function as oxygen and moisture diffusion barriers that limit exposure of the underlying substrate 104 to oxygen and / or moisture from the ambient environment. Without being bound by theory, the diffusing particles 110, such as the BMAS particles 110, enhance oxidation and moisture protection by diffusing to the outer surface of the barrier layer opposite the substrate 104 and forming a sealing layer that seals the underlying substrate 104 from oxygen / moisture exposure. Additionally, the cationic metal species of the diffusing particles 110 (e.g., BMAS particles, barium, magnesium, and aluminum) can diffuse into the gettering particles 108, enhancing the oxidation stability of the gettering material. Furthermore, the diffusion behavior of the diffusing particles 110 can act to seal any microcracks that may form in the barrier layer. Sealing the microcracks can prevent oxygen from penetrating the barrier layer, further improving the oxidation resistance of the barrier layer. The gettering particles 108 can react with oxidant species, such as oxygen and water, that may diffuse into the bond coat 102. In this way, the gettering particles 108 can reduce the likelihood that these oxidant species will reach and oxidize the substrate 104 .

[0034] The bond coat 102 may be applied by known methods, such as slurry coating.

[0035] The bond coat 102 may include a sintering aid such as silica, alkaline earth aluminosilicate, rare earth aluminosilicate, borosilicate, or a combination thereof.

[0036] The ceramic-based topcoat 114 is in direct contact with the bond coat 102. By way of example, the ceramic-based topcoat 114 can include one or more layers of an oxide-based material. The oxide-based material can be, for example, but not limited to, a hafnium-based oxide, a zirconium-based oxide, or a yttrium-based oxide (such as hafnia, hafnium silicate, yttrium silicate, yttria-stabilized zirconia, or gadolinia-stabilized zirconia), calcium aluminosilicate, mullite, barium strontium aluminosilicate, or a combination thereof. The topcoat 114 can be applied by known methods, such as thermal spraying (e.g., air plasma spraying) or slurry application. In some examples, the thickness of the topcoat 114 is about 2 to about 8 mils (50.8 to 203.2 microns).

[0037] Together, the topcoat 114 and the bond coat 102 form a barrier coating 116 for the substrate 104. The topcoat 114 is the outermost layer of the barrier coating 116 and is exposed to the elements when the article 100 is in use.

[0038] Engine 20 components, such as article 100, are susceptible to attack by silicate-based deposits, such as calcium-magnesium-aluminosilicate (CMAS), which may accumulate on the surface of article 100. During operation of engine 20, silicate-based debris (such as sand, ash, or dirt) may melt onto the surface of the component, subsequently forming CMAS. CMAS deposits can sometimes melt and react with and / or penetrate article 100 or the component's coating, damaging the article / coating. As described below, the durability of these engine 20 components may be enhanced by including a coating containing a CMAS-resistant component that can reduce the activity of CMAS. For example, a CMAS-resistant component may include one or more components that are reactive to CMAS and form a compound that seals the surface of the article / coating in a process known as "reactive crystallization."

[0039] Thus, the topcoat 114 is provided with a component that reacts with CMAS to induce reactive crystallization, thereby providing a CMAS-resistant topcoat 114. Cerium (Ce)-containing oxides, such as ceria (CeO), and titanium (Ti)-containing oxides, such as titania (TiO), are two examples of components that react with CMAS. Any of the example topcoat 114 materials described above may be co-deposited with a component that reacts with CMAS or a precursor to a component that reacts with CMAS. Co-deposition may be achieved by any known method. For example, if the topcoat 114 is applied by a thermal spray process, such as air plasma spraying, the desired components of the topcoat 114 may be co-sprayed. If the topcoat 114 is applied by a slurry process, the desired components may be added to the slurry and deposited by any known method.

[0040] In a particular example, titania (TiO2) and / or ceria (CeO2) are co-deposited with the topcoat 114 material. During or after deposition, the titania and / or ceria react with the topcoat 114 material to form titanate silicates and / or cerate silicates. For example, if the topcoat 114 material is hafnium silicate (HfSiO4), the hafnium silicate is co-deposited with TiO2 and / or CeO2 and reacts to form HfTiO2 and / or CeO2, respectively, in the topcoat 114 during or after deposition. x Si y O4 / HfCe x Si y Provide O4, where x = 0 to 4, y = 0 to 4, and the sum of y and x is 4.

[0041] In another example, hafnium titanate (HfTiO4) and / or hafnium cerate (HfCeO4) are deposited along with the topcoat 114 material. During or after deposition, titania and / or ceria react with the topcoat 114 material to form titanate silicates and / or cerate silicates. For example, if the topcoat 114 material is hafnium silicate (HfSiO4), the hafnium silicate is co-deposited with TiO4 and / or HfCeO4, which react to form HfTiO4 and / or HfCeO4, respectively, in the topcoat 114 during or after deposition. x Si y O4 / HfCe x Si y Provide O4, where x = 0 to 4, y = 0 to 4, and the sum of y and x is 4.

[0042] Another example is hafnium titanate silicate (HfTi x Si y O4) and / or hafnium cerate silicate (HfCe x Si y O4) (x=0-4, y=0-4, the sum of y and x is 4) is deposited along with the topcoat 114 material. During or after deposition, titania and / or ceria react with the topcoat 114 material to form different titanate silicates and / or cerate silicates. For example, if the topcoat 114 material is hafnium silicate (HfSiO4), the hafnium silicate is co-deposited with HfTiO4 and / or HFCeO4, which react and form HfTiO4 and / or HFCeO4, respectively, in the topcoat 114 during or after deposition. x Si z O4 / HfCe w Si z Provide O4, where w = 0 to 4, z = 0 to 4, and the sum of w and z is 4.

[0043] In one particular example of a barrier layer 116 shown in FIG. 3, the bond coat 102 includes two layers 102a / 102b. The first layer 102a is disposed on the substrate 104, and the second layer 102b is disposed on the first layer. The top coat 114 is disposed on the second layer 102b. In this example, both layers 102a / 102b include a matrix 106, such as silicon dioxide, in an amount of about 5 to about 40 volume percent. The first layer 102a includes gettering particles 108, such as silicon carbide or silicon oxycarbide, having an average diameter of about 1 to 75 microns (0.04 to 2.9 mils), in an amount of about 60 to about 95 volume percent. The second layer 102b includes gettering particles 108, such as silicon carbide or silicon oxycarbide, having an average diameter of about 1-45 microns (0.04-1.77 mils), and the balance diffusing particles 110 in an amount of about 55-94 volume percent.

[0044] In a particular example, the average diameter of the gettering particles 108 in the second layer 102b is larger than the average diameter of the gettering particles 108 in the first layer 102a. Generally, smaller particles conform better to adjacent surfaces, increasing the adhesion of the particles to the surfaces. Smaller particles also improve packing and reduce the porosity of the coating layer. Furthermore, smaller particles have a higher surface area-to-volume ratio, which increases the likelihood that oxidant particles in the barrier coating 116 will react with the gettering particles 108 rather than with the substrate 104, providing an additional protective layer near the substrate 104. On the other hand, larger gettering particles 108 have a longer lifespan within the barrier coating 116 because they have more material available to react with oxidants and provide environmental protection, as discussed above. Thus, providing small gettering particles 108 in the first layer 102a improves adhesion of the first layer 102a to the substrate 104 and provides a relatively less porous layer 102a, while providing large gettering particles 108 in the second layer 102b improves the environmental protection and lifespan of layer 102b, which is outside of the first layer 102a and therefore more likely to encounter oxidant particles.

[0045] Topcoat 114 includes about 2 to about 30% by weight of a CMAS reactive component, such as titania, ceria, hafnium titanate, hafnium cerate, hafnium titanate silicate, and / or hafnium cerate silicate.

[0046] 4, the topcoat 114 includes a thin intermediate layer 120 of topcoat 114 material that does not contain the CMAS-reactive component adjacent to the bond coat 102. CMAS may have similar chemical properties to the diffusing particles 110, and therefore the CMAS-reactive component may react with the diffusing particles 110. The intermediate layer 120 serves to minimize or prevent such reaction. In other examples, the topcoat 114 has a graded composition throughout its depth, with the CMAS-reactive component concentrated at the outer surface of the topcoat 114.

[0047] In a particular example, the topcoat 114 is applied by thermal spraying, such as air plasma spraying, using a feedstock powder that includes about 70 to about 98% by weight of a topcoat 114 material powder, such as hafnium silicate powder, with the balance also including a CMAS reactive component or a precursor to the CMAS reactive component, such as HfTiO4 and / or HfO2-CeO2.

[0048] As used herein, the term "about" has its typical meaning in the art, although in certain instances, "about" can mean a deviation of up to 10% of the values set forth herein.

[0049] Although different examples are described as having particular components, the examples of the present disclosure are not limited to those particular combinations. Some of the components or features from any of the embodiments can be used in combination with features or components from any of the other embodiments.

[0050] The foregoing description should be construed as illustrative and not in any limiting sense. Those skilled in the art will recognize that certain modifications may fall within the scope of the present disclosure. For these reasons, the following claims should be studied to determine the true scope and content of the present disclosure.

Claims

1. a substrate; a barrier layer on the substrate; An article comprising: The barrier layer is a bond coat comprising a matrix, diffusing particles disposed within the matrix, and gettering particles disposed within the matrix; a topcoat including a component reactive with calcium-magnesium-aluminosilicate (CMAS); An item, including:

2. The article of claim 1 , wherein the bond coat comprises a first bond coat layer adjacent the substrate and a second bond coat layer adjacent the top coat.

3. The article of claim 2 , wherein the first and second layers each comprise from about 5 to about 40 volume percent matrix.

4. The article of claim 3 , wherein the second layer comprises about 55 to 94 volume percent gettering particles.

5. The article of claim 3 , wherein the first layer comprises from about 60 to about 95 volume percent gettering particles.

6. The article of claim 2, wherein the second layer comprises gettering particles having an average largest dimension of from about 1 to about 75 microns.

7. The article of claim 6 , wherein the average diameter of the gettering particles of the second layer is greater than the average diameter of the gettering particles of the first layer.

8. The article of claim 1 , wherein the gettering particles are silicon carbide or silicon oxycarbide.

9. The article of claim 1 , wherein the topcoat comprises an intermediate layer adjacent to the bond coat that is free of components that react with calcium-magnesium-aluminosilicate (CMAS).

10. The article of claim 1 , wherein the component that reacts with calcium-magnesium-aluminosilicate (CMAS) comprises titanium or cerium.

11. The article of claim 1 , wherein the bond coat comprises a sintering aid.

12. The article of claim 1 , wherein the topcoat comprises from about 2 to about 30% by weight of a component that reacts with calcium-magnesium-aluminosilicate (CMAS).

13. a ceramic matrix composite substrate; a barrier layer on the substrate; An article comprising: The barrier layer is a bond coat comprising a silicon dioxide matrix, diffusion particles disposed within the matrix, and silicon carbide or silicon oxycarbide gettering particles disposed within the matrix; a topcoat including a component reactive with calcium-magnesium-aluminosilicate (CMAS); An item, including:

14. The article of claim 13 , wherein the bond coat comprises a first bond coat layer adjacent the substrate and a second bond coat layer adjacent the top coat.

15. 15. The article of claim 14, wherein the second layer comprises gettering particles having an average largest dimension of from about 1 to about 75 microns, the average diameter of the gettering particles of the second layer being greater than the average diameter of the gettering particles of the first layer.

16. The article of claim 13, wherein the component that reacts with calcium-magnesium-aluminosilicate (CMAS) comprises titanium or cerium.

17. The article of claim 13 , wherein the bond coat comprises a sintering aid.

18. The article of claim 13, wherein the topcoat comprises from about 2 to about 30% by weight of a component that reacts with calcium-magnesium-aluminosilicate (CMAS).

19. 1. A method for applying a calcium-magnesium-aluminosilicate (CMAS) resistant topcoat, comprising: The method includes depositing a topcoat onto the bond coat by thermal spraying, wherein the thermal spray feedstock powder comprises about 70-98% by weight of the topcoat material powder, and the balance is a CMAS-reactive component or a precursor to a CMAS-reactive component.

20. The precursor of the CMAS reactive component is HfTiO ４ or HfO ２ -CeO ２ 20. The method of claim 19, wherein:

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