Barrier layer for an article, and article

Abstract

To provide a barrier layer for a product used in a gas-turbine engine, etc.SOLUTION: A barrier layer for a product in an exemplary embodiment includes especially a matrix, diffusive particles disposed in the matrix, and a bond coat including gettering particles disposed in the matrix. The composition of the gettering particles is a reaction product of the chemical reaction defined below.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to composite articles such as those used in gas turbine engines. [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 to drive the compressor section and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines. Summary of the Invention [Problem to be solved by the invention]

[0003] Components, such as gas turbine engine components, may be exposed 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. [Means for solving the problem]

[0004] A barrier layer for an article according to an exemplary embodiment of the present disclosure includes a bond coat including, among other things, a matrix, diffusion particles disposed in the matrix, and gettering particles disposed in the matrix, the composition of the gettering particles being a reaction product of the chemical reaction of (Chemical Formula 1) defined by (Chemical Formula 2).

[0005] [ka]

[0006] [ka]

[0007] In a further example of the above, z is zero and at least two of w, x, and y are greater than zero.

[0008] In a further example of any of the foregoing, each of w, x, and y is greater than zero.

[0009] In a further example of any of the foregoing, x is zero and at least two of w, y, and z are greater than zero.

[0010] In a further example of any of the foregoing, each of w, y, and z is greater than zero.

[0011] In a further example of any of the foregoing, y is zero and at least two of w, x, and z are greater than zero.

[0012] In a further example of any of the foregoing, each of w, x, and z is greater than zero.

[0013] In a further example of any of the foregoing, w is greater than zero and at least two of x, y, and z are greater than zero.

[0014] In a further example of any of the foregoing, Ω=ξ / (y+z / 2), where Ω is greater than or equal to 1.

[0015] In further examples of any of the foregoing, the ratio of silicon to carbon (Si:C) is greater than 0.75.

[0016] In further examples of any of the foregoing, the ratio of silicon to nitrogen (Si:N) is greater than 0.75.

[0017] In further examples of any of the foregoing, the ratio of silicon to oxygen (Si:O) is greater than 1.

[0018] In a further example of any of the foregoing, the matrix is ​​substantially pure silicon dioxide.

[0019] An article according to an exemplary embodiment of the present disclosure includes, among other things, a substrate and a barrier layer disposed on the substrate. The barrier layer includes a matrix of substantially pure silicon dioxide, diffusion particles disposed in the matrix, and gettering particles disposed in the matrix. The composition of the gettering particles is a reaction product of the chemical reaction of (Chemical Formula 1) defined by (Chemical Formula 2).

[0020] [ka]

[0021] [ka]

[0022] In a further example of any of the foregoing, w is greater than zero and at least two of x, y, and z are greater than zero.

[0023] In a further example of any of the foregoing, Ω=ξ / (y+z / 2), where Ω is greater than or equal to 1.

[0024] In further examples of any of the foregoing, the ratio of silicon to carbon (Si:C) is greater than 0.75.

[0025] In further examples of any of the foregoing, the ratio of silicon to nitrogen (Si:N) is greater than 0.75.

[0026] In further examples of any of the foregoing, the ratio of silicon to oxygen (Si:O) is greater than 1.

[0027] In a further example of any of the foregoing, the substrate is a ceramic matrix composite substrate. [Brief description of the drawings]

[0028] [Figure 1] 1 is a schematic diagram of an exemplary gas turbine engine. [Diagram 2]2 illustrates the gas turbine engine article of claim 1 having a coating. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] FIG. 1 illustrates a schematic of a gas turbine engine 20. The gas turbine engine 20 is disclosed herein generally 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 in a bypass duct defined in a housing 15, such as a fan case or nacelle, and drives air along a core flowpath C for compression and communication to the combustor section 26 and then expansion through the turbine section 28. Although shown in the disclosed non-limiting embodiment as a two-spool turbofan gas turbine engine, it should be understood that the concepts described herein are not limited to use with a two-spool turbofan, as the present teachings may also be applied to other types of turbine engines, including three-spool configurations.

[0030] The exemplary engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about a central longitudinal axis A of the engine relative to an engine static structure 36 via a number of bearing systems 38. It will be appreciated that different bearing systems 38 may alternatively or additionally be provided at different locations and the locations of the bearing systems 38 may vary as appropriate depending on the application.

[0031] The low speed spool 30 generally 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 change mechanism, shown in the exemplary gas turbine engine 20 as a gear arrangement 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 disposed 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 generally be disposed 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 about a central longitudinal axis A of the engine, collinear with its longitudinal axis, via the bearing system 38.

[0032] The core airflow is compressed by the low pressure compressor 44, 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 an airfoil 59 located within the core airflowpath C. The turbines 46, 54 rotate the respective low speed spool 30 and high speed spool 32 in response to the expansion. It will be appreciated that the locations of each of the fan section 22, compressor section 24, combustor section 26, turbine section 28, and fan drive gear system 48 may 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 location of the gear system 48.

[0033] In one example, the engine 20 is a high bypass gear aircraft engine. In a further example, the bypass ratio of the engine 20 can be greater than about 6, and in an exemplary embodiment, greater than about 10, and can be less than or equal to about 18.0, or more specifically, less than or equal to 16.0. The 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 can be less than or equal to 4.0. The low pressure turbine 46 has a pressure ratio greater than about 5. The low pressure turbine pressure ratio can be less than or equal to 13.0, or more specifically, less than or equal to 12.0. In one disclosed embodiment, the bypass ratio of the engine 20 is greater than about 10 (10:1), the diameter of the fan is significantly larger than the diameter of the low pressure compressor 44, and the pressure ratio of the low pressure turbine 46 is greater than about 5 (5:1). The pressure ratio of the low pressure turbine 46 is the pressure measured in front of the inlet of the low pressure turbine 46 relative to the pressure at the outlet of the low pressure turbine 46 in front of 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.

[0034] 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 certain flight conditions, typically at about Mach 0.8 and about 35,000 feet (10,668 meters). At flight conditions of 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 the 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 According to one non-limiting embodiment, a "low corrected fan tip speed" disclosed herein is less than about 1150.0 ft / sec (350.5 m / sec) and may be greater than or equal to 1000.0 ft / sec (304.8 m / sec).

[0035] 2 is a schematic diagram illustrating a representative portion of an exemplary article 100 for use in a gas turbine engine 20 that includes 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, an outer wing air seal, or other component that would benefit from embodiments herein. In this example, the bond coat 102 is used as an environmental barrier layer that protects an underlying substrate 104 from environmental and thermal conditions. As will be appreciated, the bond coat 102 may be used as the sole barrier layer, as an outermost layer / topcoat with additional underlayers, or in combination with other coating underlayers or overlayers, such as a ceramic-based topcoat.

[0036] The bond coat 102 includes a matrix 106 and a dispersion of "gettering" particles 108 in the matrix 106. The bond coat 102 may also include a dispersion of diffusing particles 110 in the matrix 106. The matrix 106 is an amorphous oxide material based on silicon dioxide (SiO2). In a particular example, the matrix 106 is substantially pure silicon dioxide, e.g., comprises greater than 95% silicon dioxide. The diffusing particles 110 may 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.

[0037] The article 100 may be exposed to high temperatures, for example, when used in the engine 20. The high temperatures may cause the composition of the bond coat 102 to change over time. For example, the diffusion particles 110 may concentrate silicon from the silicon dioxide matrix 106. Eventually, a chemical equilibrium may be reached, after which the composition of the bond coat 102 remains substantially unchanged.

[0038] 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 are also contemplated, such as silicon carbide fibers in a silicon carbide matrix. These CMC substrates can be formed by melt infiltration, chemical vapor infiltration (CVI), polymer infiltration and pyrolysis (PIP), particle infiltration, or other known methods. In another example, the substrate 104 can be a metal substrate.

[0039] The gettering particles 108 and optional diffusing particles 110 act as oxygen and moisture diffusion barriers to limit exposure of the underlying substrate 104 to oxygen and / or moisture from the surrounding environment. The gettering particles 108 can react with oxidant species, such as oxygen and water, that may diffuse into the bond coat 102. In this manner, the gettering particles 108 can reduce the likelihood of those oxidant species reaching and oxidizing the substrate 104. Without being bound to a particular theory, the diffusing particles 110, such as the BMAS particles 110, can diffuse to the outer surface of the barrier layer opposite the substrate 104, enhancing oxidation and moisture protection by forming a sealing layer that seals the underlying substrate 104 from exposure to oxygen / moisture. 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 to increase the oxidative stability of the gettering material. Additionally, the diffusion behavior of the diffusing particles 110 can act to seal any microcracks that may form in the barrier layer. By sealing the microcracks, it is possible to prevent oxygen from penetrating into the barrier layer, and the oxidation resistance of the barrier layer is further improved.

[0040] The bond coat 102 may be applied by any known method, such as a slurry coating method or a spraying method, as are commonly known in the art.

[0041] In some examples, the ceramic-based topcoat 114 is directly bonded to 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, a hafnium-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 combinations thereof, but is not limited to such oxides.

[0042] The topcoat 114 and the bond coat 102 together 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 exterior environment when the article 100 is in use.

[0043] In addition to providing environmental protection to the underlying substrate 104, the barrier coating 116 has the advantage of also providing thermal protection to the substrate 104. The substrate 104 / article 100 may be exposed to very high temperature operating conditions within the engine 20. Providing thermal protection to the article 100 extends its useful life and allows for increased thermal efficiency of the engine 20 by allowing higher operating temperatures or less cooling air.

[0044] The gettering particles 108 constitute a majority (e.g., greater than about 50%) of the bond coat 102. Thus, by selecting gettering particles 108 that have low thermal conductivity and therefore provide good thermal protection to the substrate 104, the overall thermal protection provided to the substrate 104 by the barrier coating 116 can be improved. In one example, the gettering particles 108 have a thermal conductivity of less than about 10 W / mK. In a further example, the gettering particles 108 have a thermal conductivity of less than about 5 W / mK.

[0045] Silicon and carbon containing particles are good candidates for gettering particles 108 due to their mechanical properties and reactivity with oxidizing agents. However, silicon and carbon containing materials do not necessarily have good thermal properties (e.g., relatively poor thermal conductivity). For example, crystalline silicon carbide has desirable properties with respect to oxidation resistance, but has high thermal conductivity. The high thermal conductivity is related to the high strength of the chemical bonds in crystalline silicon carbide. Amorphous silicon carbide has poor thermal conductivity due to its relatively weak chemical bonds.

[0046] Silicon- and carbon-containing materials tend to crystallize over time when exposed to very high temperatures (e.g., some of the operating temperatures of engine 20), which can also increase the thermal conductivity of the material. However, the addition of oxygen and / or nitrogen to silicon- and carbon-containing materials tends to prevent crystallization, even at very high temperatures.

[0047] To this end, the gettering particles 108 have the chemical formula Si w O x C y N z where each of w, x, y, and z is equal to or greater than zero. In a particular example, w is greater than zero and each of x, y, and z is equal to or greater than zero. In a further example, w is greater than zero and at least two of x, y, and z, or each of x, y, and z, are greater than zero. The particular composition of the gettering particles 108 is selected so that the gettering particles 108 exhibit good reactivity with oxidizing agents, do not oxidize to undesirable reaction products such as large amounts of gas that may accumulate in the barrier coating 116, and exhibit slow crystallization rates.

[0048] In particular, it has been discovered that gettering particles 108 selected according to the reaction product of the reaction shown in (Chemical Formula 1), as defined in (Chemical Formula 2), balance the desired properties and exhibit excellent thermal and environmental properties.

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[0051] ξ represents the molar ratio of oxygen as a reactant in the reaction of (Chemical formula 1). The ratio of ξ to the sum of the number of moles of carbon monoxide (y) and the number of moles of nitrogen (z / 2) as reaction products in the reaction of (Chemical formula 1) is expressed as Ω=ξ / (y+z / 2). In a specific example, Ω≧1. Further examples are silicon to carbon ratio (Si:C)>0.75, silicon to nitrogen ratio (Si:N)>0.75, silicon to oxygen ratio (Si:O)>1.

[0052] In certain applications of (Chemical Formula 1) and (Chemical Formula 2), z=0 (e.g., starting compound Si w O x C y N z does not contain nitrogen), w = 0.5, x = 0, y = 0.5, which gives the following reaction corresponding to silicon oxycarbide (SiOC):

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[0054] In another example where z=0 as in the example above, w=0.33, x=0.33, and y=0.5, resulting in silicon carbide (SiC).

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[0056] In another specific application of (Chemical Formula 1) and (Chemical Formula 2), y=0 (e.g., starting compound Si w O x C y N z contains no carbon), w=3 / 7, x=0, z=4 / 7, resulting in silicon nitride (Si3N4).

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[0058] In another specific application of (Chemical Formula 1) and (Chemical Formula 2), as in the above-described example, y=0, w=0.33, x=0.33, and z=0.33, resulting in silicon oxynitride (SiON).

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[0060] In another specific application of (Chemical Formula 1) and (Chemical Formula 2), x=0 (e.g., starting compound Si w O x C y N z contains no oxygen), w=0.5, y=0.5, and z=0, which gives silicon carbide (SiC), as shown below, which is the same as the above example where z=0, w=0.33, x=0.33, and y=0.5.

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[0062] In another specific application of (Chemical Formula 1) and (Chemical Formula 2), we set x=0 as in the above example, w=3 / 7, y=3 / 7, z=0, and obtain silicon nitride (Si3N4) as shown below, which is the same as the result above of y=0, w=3 / 7, x=0, z=4 / 7.

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[0064] In another specific application example of (Chemical formula 1) and (Chemical formula 2), x=0 as in the above-described example, w=3 / 7, y=3 / 7, z=0, and silicon carbide and silicon nitride (1 / 2Si 0.5 C 0.5 and 1 / 2Si 3 / 7 N 4 / 7 ) is obtained.

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[0066] Table 1 summarizes exemplary values ​​of w, x, y, and z in the above formulas (1) and (2).

[0067] [Table 1]

[0068] The term "about" as used herein has its typical meaning in the art, however, in certain instances, "about" can mean a deviation of up to 10% of the values ​​set forth herein.

[0069] Although different examples are described as having particular components, the examples of the disclosure are not limited to those particular combinations, and 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.

[0070] The foregoing description should be interpreted as illustrative and not in any limiting sense. Those skilled in the art will appreciate 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 method for applying a barrier layer to an article, comprising the steps of: coating a barrier layer on a substrate; The barrier layer includes a bond coat including a matrix, diffusion particles disposed in the matrix, and gettering particles disposed in the matrix, the composition of the gettering particles having a formula SiWOxCyNz, where w is greater than zero and at least two of x, y, and z are greater than zero; The gettering particles include a reaction product with oxygen by a chemical reaction defined by (Chemical Formula 1) and (Chemical Formula 2). 【Chemistry 1】 【Chemistry 2】

2. 2. The method of applying a barrier layer for an article according to claim 1, wherein Ω=ξ / (y+z / 2), Ω being 1 or greater.

3. The method of applying a barrier layer for an article according to claim 2, wherein the silicon to carbon ratio (Si:C) is greater than 0.

75.

4. 4. The method of applying a barrier layer for an article according to claim 3, wherein the silicon to nitrogen ratio (Si:N) is greater than 0.

75.

5. 5. The method of applying a barrier layer for an article according to claim 4, wherein the ratio of silicon to oxygen (Si:O) is greater than 1.

6. 10. The method of applying a barrier layer for an article according to claim 1, wherein said matrix is ​​substantially pure silicon dioxide.

7. A method for applying a barrier layer to an article, comprising the steps of: coating a barrier layer on a substrate; The barrier layer is a matrix of substantially pure silicon dioxide; diffusing particles disposed in the matrix; and gettering particles disposed in the matrix, the composition of the gettering particles having the formula SiWOxCyNz, where w is greater than zero and at least two of x, y, and z are greater than zero; The gettering particles include a reaction product with oxygen by a chemical reaction defined by (Chemical Formula 1) and (Chemical Formula 2). 【Chemistry 1】 【Chemistry 2】

8. 8. The method of applying a barrier layer for an article according to claim 7, wherein Ω=ξ / (y+z / 2), Ω being 1 or greater.

9. The method of applying a barrier layer for an article according to claim 8, wherein the silicon to carbon ratio (Si:C) is greater than 0.

75.

10. 10. The method of applying a barrier layer for an article according to claim 9, wherein the silicon to nitrogen ratio (Si:N) is greater than 0.

75.

11. The method of applying a barrier layer for an article according to claim 10, wherein the ratio of silicon to oxygen (Si:O) is greater than 1.

12. The method of applying a barrier layer for an article according to claim 7, wherein the substrate is a ceramic matrix composite substrate.

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