Coatings for improved durability

Abstract

A coated fiber or a ceramic matrix composite material or part containing reinforcing fibers, which fibers are coated, wherein the coated fiber contains in the following order: the fiber, immediately on the fiber an inner multilayer sequence containing repeating layers of BN and C, wherein the inner multilayer sequence is represented by Cx1-(BN-C)x-(BN)x2 wherein x is 0, 1, 2, 3, 4 or 5; x1 and x2 are each independently 0 or 1; and, x + x2 ≥ 1, on the inner multilayer sequence a layer of SiN layer, on the SiN layer an outer multilayer sequence containing repeating layers of BN and C, wherein the outer multilayer sequence is represented by Cy1-(BN-C)y-(BN)y2, wherein y is 1, 2, 3, 4 or 5; y1 and y2 are each independently 0 or 1; and, y + y2 ≥ 2; and, an outermost layer of SiBN, and methods for protecting, including making, a fiber or a ceramic matrix material containing the fiber from degradation, by coating the fiber.

Description

COATINGS FOR IMPROVED DURABILITYCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of United States Provisional Patent Application No. 63 / 645,295 filed on May 10, 2024, which is hereby incorporated by reference for all purposes as if fully set forth herein.FIELD OF THE INVENTION

[0002] The subject matter disclosed herein relates to the durability of interfacial coating (IFC) systems on ceramic fibers in ceramic matrix composites (CMCs).BACKGROUND OF THE INVENTION

[0003] CMCs are ceramic materials reinforced by ceramic fibers to enhance their properties such as crack resistance. Those fibers are typically coated with various layers of inorganic material, which are beneficial for deflecting matrix cracks along the fiber-matrix interface and slowing down the propagation of cracks through the matrix.

[0004] CMCs are widely used in the aerospace industries, particularly in high temperature aircraft applications. In such applications, components made from CMCs are exposed to high temperatures, corrosive / oxidative environments, and mechanical stresses. While CMCs provide superior properties, they are susceptible to degradation. . Over time, cracks can develop into the CMC microstructure and expose the fiber and interface coating (IFC) to oxygen or other corrosive elements Interfacial coatings on fibers are susceptible to degradation over time resulting in shorter CMC life and require adequate oxidation resistance or stability at elevated temperatures.

[0005] Debonding of the fiber to enable composite behavior is often achieved with either carbon or BN coatings. These coatings are typically deposited via chemical vapor infiltration on the fibers of single tows or entire fiber preforms. The structure of these coatings vary from turbostratic to crystalline, i.e., graphitic carbon or hexagonal BN. However, these layers are susceptible to oxidation to various degrees. The Additional layers can serve as preferreddebonding location, oxidation protection for the fiber or sacrificial layers to oxidize and seal matrix cracks preventing further degradation.SUMMARY OF THE INVENTION

[0006] The present disclosure is directed, in a first aspect, to a coated fiber according to an exemplary embodiment of this disclosure comprises, a fiber; an inner multilayer sequence deposited on the fiber, the inner multilayer sequence comprising repeating layers of BN and C, wherein the inner multilayer sequence is represented by CXI-(BN-C)X-(BN)X2 wherein x is 0, 1, 2, 3, 4 or 5; xl and x2 are each independently 0 or 1; and, x + x2 > 1; a layer of SiN layer deposited on the inner multilayer sequence; an outer multilayer sequence deposited on the layer of SiN comprising repeating layers of BN and C, wherein the outer multilayer sequence is represented by Cyi-(BN-C)y-(BN)y2, wherein y is 1, 2, 3, 4 or 5; yl and y2 are each independently 0 or 1; and, y + y2 > 2; and, an outermost layer of SiBN deposited on the outer multilayer sequence. In some embodiments, the SiN layer is amorphous.

[0007] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, xl can be 0 and yl can be 1.

[0008] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, x2 can be 1 and y2 can be 0.

[0009] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the thicknesses of some or all the C layers can be < 10 nm.

[0010] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the thicknesses of some or all the BN layers can be 5 to 200 nm.

[0011] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, some or all layers on the fiber can be amorphous.

[0012] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the thickness of the SiN layer can be 50 to 400 nm.

[0013] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the composition of the SiN layer can be with a Si / N ratio of 1 to 3 / 4.

[0014] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the thickness of the SiBN layer can be 50 to 300 nm.

[0015] In another embodiment, the present disclosure is directed to a ceramic matrix composite material or part comprising reinforcing fibers according to an exemplary embodiment of this disclosure comprises, a fiber; an inner multilayer sequence deposited on the fiber, the inner multilayer sequence comprising repeating layers of BN and C, wherein the inner multilayer sequence is represented by Cxi-(BN-C)x-(BN)X2 wherein x is 0, 1, 2, 3, 4 or 5; xl and x2 are each independently 0 or 1; and, x + x2 > 1; a layer of SiN layer deposited on the inner multilayer sequence; an outer multilayer sequence deposited on the layer of SiN comprising repeating layers of BN and C, wherein the outer multilayer sequence is represented by Cyi-(BN-C)y- (BN)y2, wherein y is 1, 2, 3, 4 or 5; yl and y2 are each independently 0 or 1; and, y + y2 > 2; and, an outermost layer of SiBN deposited on the outer multilayer sequence. In some embodiments, the SiN layer is amorphous.

[0016] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, in the coated fiber, x l can be 0 and y l can be 1.

[0017] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, in the coated fiber, x2 can be 1 and y2 can be 0.

[0018] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, in the coated fiber, the thicknesses of some or all the C layerscan be < 10 nm.

[0019] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, in the coated fiber, the thicknesses of some or all the BN layers can be 5 to 200 nm.

[0020] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, in the coated fiber, some or all layers on the fiber can be amorphous.

[0021] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, in the coated fiber, the thickness of the SiN layer can be 50 to 400 nm.

[0022] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, in the coated fiber, the thickness of the SiBN layer can be 50 to 300 nm.

[0023] In yet another embodiment, the present disclosure is directed to a method making a coated fiber, the method comprising the following steps providing the fiber depositing immediately on the fiber an inner multilayer sequence containing repeating layers of BN and C, wherein the inner multilayer sequence is represented by CX1-(BN-C)X-(BN)X2 wherein x is 0, 1, 2, 3, 4 or 5; xl and x2 are each independently 0 or 1; and, x + x2 > 1, depositing on the inner multilayer sequence a layer of SiN layer, depositing on the SiN layer an outer multilayer sequence containing repeating layers of BN and C, wherein the outer multilayer sequence is represented by Cyi-(BN-C)y-(BN)y2, wherein y is 1, 2, 3, 4 or 5; yl and y2 are each independently 0 or 1; and, y + y2 > 2; and, depositing an outermost layer of SiBN.In some embodiments of making the coated fiber, the SiN layer is amorphous.

[0024] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, the coating is achieved by a chemical vapor deposition or chemical vapor infiltration process(es).

[0025] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, in the coated fiber, xl is 0 and yl is 1.

[0026] In further embodiments of the present disclosure, including further embodiments of the above exemplary embodiments, in the coated fiber, the thicknesses of the majority of the C layers are < 10 nm.BRIEF DESCRIPTION OF FIGURES

[0027] The features of the disclosure believed to be novel and the elements characteristic of the invention are set forth with particularity in the appended claims. The figures are for illustration purposes only and are not drawn to scale. The disclosure itself, however, both as to organization and method of operation, can best be understood by reference to the description of the preferred embodiment(s) which follows, taken in conjunction with the accompanying drawings in which:

[0028] Fig. 1 illustrates a coated fiber 100.DETAILED DESCRIPTION OF THE INVENTION

[0029] The embodiments of the present disclosure can comprise, consist of, and consist essentially of the features and / or steps described herein, as well as any of the additional or optional ingredients, components, steps, or limitations described herein or would otherwise be appreciated by one of skill in the art. It is to be understood that all concentrations disclosed herein are by weight percent (wt. %.) based on a total weight of the composition unless otherwise indicated.

[0030] Disclosed herein are ways to enhance the durability of ceramic matrix composites and more particularly achieving such by the provision of fiber protective layers in the form of amultilayer system or structure.

[0031] An approach to limit or to even entirely prevent tunnel oxidation has been found to be the use of thin layers of carbon, e.g., about 10 nm or less, > 0 to < 10 nm, 0.5 to 4 nm, 1 to 4 nm, 1 to 2 nm, 1 to 3 nm, 3 to 4 nm, 2 to 3 nm or 2 to 4 nm, and slightly thicker layers of BN, e.g., from tens of nm to low hundred(s) of nm, e.g., 20 to 200 nm, 30 to 180 nm, 40 to 150 nm, 50 to 120 nm, 60 to 120 nm, 80 to 100 nm, e.g., 90 nm, including any ranges that can be formed from these numbers. These BN-C layers can be provided in a repeating fashion providing a repeating structure of BN-C layers. The combined thickness of the BN-C layers can be between 40 to 500 nm.

[0032] The repeating layer structures of BN and C do not have to be exactly the same amount of layers of each of BN or C, and can be in any embodiment one more of a BN layer or a C layer, meaning the repeating structures can start with a C layer and end with a C layer or can start with a BN layer and end with a BN layer as well as starting with a BN layer and ending with a C layer and vice versa, meaning staring with a C layer and ending with a BN layer.

[0033] In an embodiment, the multilayer structure contains an outer BN-C and an inner BN-C repeating layer structure, the inner BN-C repeating layer structure being closer to the fiber.

[0034] An additional carbon layer in the outer BN-C repeating structure has been found to help promote outer debonding. Debonding is a factor for keeping the SiN layer intact. Thus, it can be desirable to add an additional carbon layer to the outer multilayer sequence to enforce outer debonding, i.e., the repeating BN-C layer structure starting and ending with C layers.

[0035] Moreover, it appears that debonding does not rely on low temperature amorphous BN morphology, but rather on an interaction with an additional C layer in the outer BN-C layer structure.

[0036] Additionally, an amorphous and smooth SiN layer can be provided in the multilayer structure, which has similar oxidation rate as SiC, but is especially beneficial in this multilayersystem as it lacks the rough crystalline nature of a SiC layer. This a-SiN layer is present between the inner and outer BN-C repeating layer structures.

[0037] Thicknesses of the SiN layer are, for example, low hundreds of nm, for example, 50-400 nm, 80-390 nm, 120-380 nm, 150-350 nm, 175-325 nm, 200-300 nm, 220-280 nm, 240-260 nm, including any ranges that can be formulated by any combination of these thickness values.

[0038] An SiBN layer can be added as the outermost layer, which helps with sealing matrix cracks and thus preventing further oxidation in the layers below.

[0039] Thicknesses of the SiBN layer are, for example, 50 to 300 nm, 80 to 200 nm, 90 nm to 180 nm, 100 nm to 150 nm, 120 to 140 nm.

[0040] In an embodiment, there are no thick layers of carbon with thicknesses above the herein provided thicknesses for the carbon layers, e.g., in the order of 10 nm or above, e.g., 40 nm.

[0041] In a further embodiment, there is no crystalline layer in the layer structures provided herein.

[0042] In an embodiment, each of the layers are amorphous and smooth, which leads to easier control of the layer system, e.g., allows for better control of achieving the correct thicknesses of the various layers within the layer system in a consistent manner.

[0043] By smooth, it is meant that deviations in the layer thicknesses are limited to the lesser of ± 10 nm or ± 10 % deviation of layer thickness away from the average layer thickness of a layer.

[0044] The provision of a layer system containing the above disclosed layers in an arrangement as disclosed herein can improve the durability of the IFC system and therefore extend the life of a component made from CMC materials.

[0045] The various layers can be deposited one step at a time by various coating methods, suchas by chemical vapor deposition (CVD) or chemical vapor infiltration (CVI), or a combination thereof. For example, each layer of the coating system can be deposited or applied in successive rounds of CVD or CVI starting from the innermost layer and working outward layer by layer until the outermost layer is provided.

[0046] Typically, the thin layers of carbon are provided by processing under low pressure, for example, < 50 torr, and relatively high temperatures, e.g., 700 to 1200°C or > 700°C to 1200°C, e.g., 800°C to 1000°C.

[0047] While providing more layers in a multilayer structure requires additional processing steps, it leads to significantly improved durability of the CMC material containing such coated fibers, and therein of the integrity of the fibers themselves.

[0048] Once all the layers of the multilayer coating system have been provided onto the fiber, a matrix material can be deposited over coated fibers using, for example, a CVI process, which leads to the formation of a CMC material. Other techniques for matrix formation are also possible, for example, slurry infiltration, melt infiltration (MI), and polymer infiltration and pyrolysis (PIP). Protective coatings for the CMC (e.g., thermal barrier coatings, environmental barrier coatings, etc.) can optionally be included on top of the CMC material.

[0049] The CMC material then can be used to form CMC components unless already formed into the desired shape when forming the CMC material, e.g., by a CVI process. Such CMC components containing the coated fibers as described herein can be incorporated into aerospace, maritime, or industrial equipment.

[0050] Figure 1 shows the fiber 110 as the substrate onto which various layers are provided to form a multilayered protective structure. The figure shows a cross sectional segment of the coating layers, but it is to be understood that the fiber is typically circular or elliptical in shape from a cross sectional perspective, but is not limited thereto, and the coating layers thereon circumscribe or envelope in the circumferential direction the fiber completely, i.e., without breaks in the layers. So, each layer is in the form a donut from a cross sectional perspective, i.e.,the layers forming concentric donuts around the fiber.

[0051] The inner multilayer structure 120, which is in contact with the fiber, contains several layers of BN and C in alternating form from each other and can be represented by the inner multilayer sequence having repeating layers of BN and C represented by CXI-(BN-C)X-(BN)X2 wherein x is 0, 1, 2, 3, 4 or 5; xl and x2 are each independently 0 or 1; and, x + x2 > 1. For example, the inner multilayer structure 120 can be in the form of BN-C-BN-C-BN in one specific embodiment as depicted in Figure 1, which can be represented by (BN-C)xwherein x is 0, 1, 2, 3, 4 or 5. Thus, in the specific embodiment illustrated in Figure 1, the inner multilayer sequence includes repeating layers of BN and C, in which the inner multilayer sequence is represented by Co-(BN-C)2-(BN)i.

[0052] An alternative structure can start with C or BN and ends with C or BN, as long as there are two alternating layers of BN and C. Thus, the overall formula for this layer is better represented by CXI-(BN-C)X-(BN)X2, wherein x is 0, 1, 2, 3, 4 or 5; xl and x2 are each independently 0 or 1; and, x + x2 > 1.

[0053] In one specific embodiment, a BN layer is in direct contact with the fiber (110).

[0054] The layer 130 immediately on top of the inner multilayer structure 120 is a SiN layer, in shorthand, a SiN layer, or an amorphous SiN layer, in shorthand, an a-SiN layer.

[0055] On top of layer 130 is the outer multilayer structure 140. Multilayer structure 140, likewise to multilayer structure 120, contains alternating BN-C layers. However, in this outer multilayer structure 140, in one specific embodiment there is an extra carbon layer as depicted in Figure 1, i.e., there are carbon layers at both top and bottom layer positions of this multilayer structure 140, e.g., C-BN-C-BN-C-BN-C, which can be represented by Cyl-(BN-C)ywherein y is 1, 2, 3, 4 or 5 and yl is 0 or 1. Alternatively, the structure can starts with C or BN and end with C or BN, as long as there are two alternating layers of BN and C. Thus, the overall formula for this layer is better represented by Cyi-(BN-C)y-(BN)y2, wherein y is 1, 2, 3, 4 or 5; yl and y2 are each independently 0 or 1; and, y + y2 > 2.

[0056] An outermost layer 150 can be provided that is an SiBN layer.

[0057] As used herein, the term "about" and "approximately" have the typical meanings in the art, however in a particular example "about" and "approximately" can mean deviations of up to 10% of the values described herein.

[0058] Although the different examples are illustrated as having specific components, the examples of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the embodiments in combination with features or components from any of the other embodiments.

[0059] The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.

[0060] While the present disclosure has been particularly described, in conjunction with specific preferred embodiments, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications and variations as falling within the true scope and spirit of the present disclosure.

Claims

CLAIMSWhat is claimed is:

1. A coated fiber, comprising a fiber; an inner multilayer sequence deposited on the fiber, the inner multilayer sequence comprising repeating layers of BN and C, wherein the inner multilayer sequence is represented by Cxi-(BN-C)x-(BN)x2 wherein x is 0, 1, 2, 3, 4 or 5; xl and x2 are each independently 0 or 1; and, x + x2 > 1, a layer of SiN layer deposited on the inner multilayer sequence, an outer multilayer sequence deposited on the layer of SiN comprising repeating layers of BN and C, wherein the outer multilayer sequence is represented by Cyi-(BN-C)y-(BN)y2, wherein y is 1 , 2, 3, 4 or 5; yl and y2 are each independently 0 or 1; and, y + y2 > 2; and, an outermost layer of SiBN deposited on the outer multilayer sequence.

2. The coated fiber according to claim 1, wherein xl is 0 and yl is 1.

3. The coated fiber according to claim 1, wherein x2 is 1 and y2 is 0.

4. The coated fiber according to claim 1, wherein the thicknesses of all the C layers are < 10 nm.

5. The coated fiber according to claim 1, wherein the thicknesses of all the BN layers are 5 to 200 nm.

6. The coated fiber according to claim 1, wherein all layers on the fiber are amorphous.

7. The coated fiber according to claim 1, wherein the thickness of the SiN layer is 50 to 400 nm.

8. The coated fiber according to claim 1 , wherein the thickness of the SiBN layer is 50 to 300 nm.

9. A ceramic matrix composite material or part comprising reinforcing fibers, which fibers are coated and comprise the a fiber immediately on the fiber an inner multilayer sequence containing repeating layers of BN and C, wherein the inner multilayer sequence is represented by CX1-(BN-C)X-(BN)X2 wherein x is 0, 1, 2, 3, 4 or 5; xl and x2 are each independently 0 or 1; and, x + x2 > 1; and, on the inner multilayer sequence a layer of amorphous SiN layer, on the amorphous SiN layer an outer multilayer sequence containing repeating layers of BN and C, wherein the outer multilayer sequence is represented by Cyi-(BN-C)y-(BN)y2, wherein y is 1 , 2, 3, 4 or 5; yl and y2 are each independently 0 or 1; and, y + y2 > 2; and, an outermost layer of SiBN.

10. The ceramic matrix composite material or part according to claim 9, wherein, in the coated fiber, xl is 0 and yl is 1.

11. The ceramic matrix composite material or part according to claim 9, wherein, in the coated fiber, x2 is 1 and y2 is 0.

12. The ceramic matrix composite material or part according to claim 9, wherein, in the coated fiber, the thicknesses of all the C layers are < 10 nm.

13. The ceramic matrix composite material or part according to claim 9, wherein, the thicknesses of all the BN layers in the coated fiber are in the range of 5 to 200 nm.

14. The ceramic matrix composite material or part according to claim 9, wherein all layers on the coated fiber are amorphous.

15. The ceramic matrix composite material or part according to claim 9, wherein the thickness of the SiN layer on the coated fiber is between 50 to 400 nm.

16. The ceramic matrix composite material or part according to claim 9, wherein the thickness of the SiBN layer on the coated fiber is between 50 to 300 nm.

17. A method for making a coated fiber, the method comprising the following steps: providing a fiber; depositing immediately on the fiber an inner multilayer sequence containing repeating layers of BN and C, wherein the inner multilayer sequence is represented by CXI-(BN-C)X-(BN)X2 wherein x is 0, 1, 2, 3, 4 or 5; xl and x2 are each independently 0 or 1; and, x + x2 > 1; depositing on the inner multilayer sequence a layer of SiN layer, depositing on the SiN layer an outer multilayer sequence containing repeating layers of BN and C, wherein the outer multilayer sequence is represented by Cyi-(BN-C)y-(BN)y2, wherein y is 1, 2, 3, 4 or 5; yl and y2 are each independently 0 or 1; and, y + y2 > 2; and, depositing an outermost layer of SiBN.

18. The method according to claim 17, wherein the deposition steps comprise at least one of the following: chemical vapor deposition or chemical vapor infiltration.

19. The method according to claim 17, wherein, in the coated fiber, xl is 0 and yl is 1.

20. The method according to claim 17, wherein the thicknesses of at least a portion of the C layers in the coated fiber are < 10 nm.

21. The method of claim 17, wherein the SiN is amorphous.

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