CMAS-resistant topcoat for environmental barrier coatings

Abstract

A top coating for an environmental barrier coating with improved resistance to calcium-magnesium-aluminum silicate (CMAS) degradation is disclosed. This CMAS-resistant composition is based on a spinel-containing material. A CMAS-resistant multilayer structure is constructed on a substrate, the multilayer structure comprising a bonding coating on the substrate; a hermetically sealed EBC layer on the bonding coating; and a CMAS-resistant top coating comprising at least one of the following: AB₂O₄ material (A = Mg, Ni, Co, Cu, Mn, Ti, Zn, Be, Fe or combinations thereof; and B = Al, Fe, Cr, Co, V or combinations thereof); or a mixture of AB₂O₄ material and AxOy (A = Mg, Ni, Co, Cu, Mn, Ti, Zn, Be). The following materials are used in the production of rare earth elements: AB2O4 material and BxOy mixtures (B = Al, Fe, Cr, Co, V); AB2O4 material and RE25i2O7 or RE2SiO5 silicates (RE = rare earth material); AB2O4 and rare earth oxide stabilized zirconium oxide mixtures; AB2O4 and rare earth oxide stabilized hafnium oxide mixtures; AB2O4 and aluminosilicate mixtures; AB2O4 and rare earth garnet mixtures; and MgO, NiO, Co2O3, Al2O3.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit and priority of U.S. Provisional Application No. 63 / 140,339, filed January 22, 2021, the disclosure of which is expressly incorporated herein by reference in its entirety.

[0003] background

[0004] 1. Public domain

[0005] Exemplary embodiments relate to coatings for protecting silicon-based ceramic matrix composites (CMCs). In particular, exemplary embodiments relate to multilayer coating structures resistant to calcium-magnesium-aluminum silicates (CMAS).

[0006] 2. Background Information

[0007] Rare earth silicates with the general formulas RE2SiO5 (monosilicate) and RE2Si2O7 (disilicate) are commonly used as candidates for environmental barrier coating (EBC) materials. However, these materials are not always able to protect EBCs from CMAS erosion, which can lead to a reduction in the thickness of the EBC, a phenomenon known as recession.

[0008] Overview

[0009] EBC is deposited onto a Si-based CMC substrate to protect the CMC from oxidation and water vapor corrosion. In high-temperature gas turbine engine environments, for example, CMAS dust infiltration or chemical reaction with EBC can cause EBC to peel off, thus failing to protect the underlying CMC substrate from CMAS corrosion.

[0010] Current EBC multilayer structures based on rare-earth silicates (RE2SiO5 or RE2Si2O7) may not be fully capable of protecting EBCs from CMAS corrosion. Therefore, new EBC materials can improve their CMAS resistance properties. Other such materials are typically based on rare-earth oxide-stabilized zirconium oxide or hafnium oxide, or rare-earth silicate systems.

[0011] Exemplary embodiments relate to CMAS-resistant coating structures for protecting silicon-based CMCs. In exemplary embodiments, multilayer ceramic coating structures comprising a spinel-containing material (e.g., magnesium aluminum oxide) as a top coating significantly improve resistance to CMAS erosion and reduce or eliminate EBC degradation due to CMAS erosion. The spinel-containing material can be deposited on top of the rare-earth silicate EBC in a multilayer structure to prevent or inhibit, for example, molten CMAS from penetrating into or reacting with the rare-earth silicates of the EBC, and thus protect the underlying EBC from CMAS damage, particularly at high temperatures. In addition to CMAS resistance, spinel-containing materials, according to various exemplary embodiments, exhibit improved steam-based recession resistance compared to rare-earth silicates that typically constitute the EBC. In exemplary embodiments, the spinel-based top coating can significantly improve the component life of ceramic matrix composites (CMCs), such as engine component life, and thus improve engine life in environments containing CMAS dust.

[0012] In an exemplary embodiment, a multilayer coating structure of a spinel-containing material in the form of a top coating is provided to protect the underlying EBC from CMAS erosion. The spinel is a type of material having the general formula AB2O4 (A may be selected from Mg, Ni, Co, Cu, Mn, Ti, Zn, Be, Fe, or combinations thereof, and B may be selected from Al, Fe, Cr, Co, V, or combinations thereof).

[0013] In an exemplary embodiment, a CMAS test at 1300°C demonstrated that the spinel-containing coating prepared by air plasma spraying (APS) successfully prevented CMAS penetration of the EBC system. The CMAS test can involve exposing the multilayer structure to a CMAS-rich environment, such as CMAS dust or materials. Examples of CMAS and CMFAS compositions are shown in Table 1 below.

[0014]

[0015] In an exemplary embodiment, the spinel-containing multilayer structure may have the following composition:

[0016] 1. AB2O4 material (A = Mg, Ni, Co, Cu, Mn, Ti, Zn, Be, Fe or combinations thereof; and B = Al, Fe, Cr, Co, V or combinations thereof)

[0017] 2. A mixture of AB2O4 material and AxOy (A = Mg, Ni, Co, Cu, Mn, Ti, Zn, Be, Fe), wherein the weight percentage of AxOy in the mixture is 5% to 95% by weight.

[0018] 3. A mixture of AB₂O₄ material and BxOy (B = Al, Fe, Cr, Co, V), wherein the weight percentage of BxOy in the mixture is 5% to 95% by weight. If the weight percentage of BxOy is greater than 95%, for example 99%, the advantage of spinel AB₂O₄ in resisting EBC degradation will be weakened or eliminated, and such a high weight percentage of BxOy (i.e., greater than 95%) is undesirable. If the weight percentage of BxOy is less than 5% by weight, the amount of BxOy is insufficient to provide the advantage of resisting EBC degradation, and such a low weight percentage of BxOy (i.e., less than 5%) is undesirable.

[0019] 4. A mixture of AB2O4 material with RE2Si2O7 or RE2SiO5 silicates (RE = Y, La, Ce, Sc, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)

[0020] 5. A mixture of AB2O4 material and zirconium oxide stabilized with rare earth oxides.

[0021] 6. A mixture of AB2O4 material and hafnium oxide stabilized with rare earth oxides.

[0022] 7. A mixture of AB2O4 material and aluminosilicate.

[0023] 8. A mixture of AB2O4 material and rare earth garnet.

[0024] 9. Materials containing only MgO, NiO, Co2O3 or Al2O3; or materials containing MgO, NiO, Co2O3 or Al2O3.

[0025] 10. The above combinations.

[0026] In an exemplary embodiment, the CMAS-resistant coating may have a multilayer configuration, with Si, silicides, ceramic oxides, or ceramic silicates as underlying bonding coatings. The EBC layer may comprise rare earth silicates (RE2Si2O7 or RE2SiO5), BSAS (BaO-SrO-Al2O3-SiO2), mullite, or mixtures thereof. A spinel top coating may be deposited on the above material system. The powder manufacturing method used to prepare the coating by thermal spraying may be a melt-and-pulverize, agglomerated, agglomerated and sintered, or blended material.

[0027] In exemplary embodiments, the CMAS-resistant topcoat may have a porosity of 2% to 40%, preferably 5% to 15%. Porosity outside this range is insufficient to effectively ensure good protection of the underlying structure. For example, if the porosity is greater than 40%, the CMAS-resistant coating does not ensure good corrosion resistance of the underlying structure. If the porosity of the CMAS-resistant coating is less than 2%, the topcoat is too dense and may peel off during thermal cycling. In exemplary embodiments, the CMAS-resistant coating or topcoat has a porous vertically fractured microstructure or a dense vertically fractured microstructure to provide a higher strain tolerance in addition to CMAS resistance. In exemplary embodiments, the CMAS-resistant coating or topcoat may also be an abrasive layer.

[0028] In an exemplary embodiment, the aforementioned multilayer structure can be deposited using any of the following methods: air plasma spraying (APS), high-velocity oxygen-enriched fuel (HVOF), low-pressure plasma spraying (LPPS), plasma spraying-physical vapor deposition (PS-PVD), chemical vapor deposition (CVD), physical vapor deposition (PVD), electron beam-physical vapor deposition (EB-PVD), suspension / solution plasma spraying (SPS), suspension / solution HVOF (S-HVOF), and slurry methods. Brief description of the attached diagram

[0030] With reference to the various figures mentioned, and as a non-limiting example of preferred embodiments of the present disclosure, the present disclosure is further described in detail below.

[0031] Figure 1 Multilayer CMAS-resistant multilayer structures according to various exemplary embodiments are shown.

[0032] Figure 2 Multilayer CMAS-resistant multilayer structures according to various exemplary embodiments are shown.

[0033] Figure 3 Various exemplary embodiments are shown. Figure 1 Scanning electron microscope (SEM) images of CMAS multilayer structures.

[0034] Figure 4 Scanning electron microscope (SEM) images of CMAS-resistant multilayer structures according to various exemplary embodiments are shown.

[0035] Figure 5 Various exemplary embodiments are shown. Figure 4 Scanning electron microscope (SEM) images of CMAS multilayer structures.

[0036] Figure 6Scanning electron microscope (SEM) images of CMAS-resistant multilayer structures according to various exemplary embodiments are shown.

[0037] Figure 7 Scanning electron microscope (SEM) images of CMFAS-resistant multilayer structures according to various exemplary embodiments are shown.

[0038] Figure 8 Scanning electron microscope (SEM) images of CMFAS-resistant multilayer structures according to various exemplary embodiments are shown.

[0039] Figure 9 Scanning electron microscope (SEM) images of CMFAS-resistant multilayer structures according to various exemplary embodiments are shown.

[0040] Detailed Explanation

[0041] Through one or more of the various aspects, embodiments and / or specific features of this disclosure, it is intended to bring out one or more advantages as particularly described above and mentioned below.

[0042] Figure 1 A multilayer structure resistant to CMAS is shown according to various exemplary embodiments. Figure 1 In this process, a CMAS-resistant multilayer structure 100 is deposited on a substrate 110. In an exemplary embodiment, the CMAS-resistant multilayer structure 100 includes a bonding coating 120 on the substrate 110. The bonding coating may be or include at least one of the following: Si; Si-oxide (oxide = Al2O3, B2O3, HfO2, TiO2, TaO2, BaO, SrO), silicide (RESi, HfSi2, TaSi2, TiSi2); RE2Si2O7-Si; RE2Si2O7-silicide; mullite-Si; and mullite-silicide, wherein RE is one of Y, La, Ce, Sc, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0043] In an exemplary embodiment, a hermetically tight EBC layer 130 is deposited on a bonding coating 120. The hermetically tight EBC layer 130 is dense and sealed such that vapors present in, for example, hot gases from a turbine engine, are not allowed to reach the substrate, which may be or comprise a Si and C-based ceramic matrix composite known to react with vapors. The hermetically tight EBC layer 130 may be or comprise at least one of the following: RE2Si2O7, RE2SiO5, mullite, and BSAS (BaO-SrO-Al2O3-SiO2), wherein RE is one of Y, La, Ce, Sc, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The EBC is deposited on the Si-based ceramic matrix composite (CMC) layer to protect the CMC from oxidation and water vapor erosion, particularly at high temperatures. However, in the case of CMAS erosion, the EBC can be penetrated.

[0044] In an exemplary embodiment, a CMAS-resistant topcoat 140 is deposited on the hermetically sealed EBC layer 130. The CMAS-resistant topcoat 140 may be or comprise at least one of the following: AB2O4 material (A = Mg, Ni, Co, Cu, Mn, Ti, Zn, Be, Fe or combinations thereof; and B = Al, Fe, Cr, Co, V or combinations thereof); a mixture of AB2O4 material and AxOy (A = Mg, Ni, Co, Cu, Mn, Ti, Zn, Be, Fe), wherein the weight percentage of AxOy in the mixture is 5% to 95% by weight; or a mixture of AB2O4 material and BxOy (B = Al, Fe, Cr, Co, V), wherein the weight percentage of BxOy in the mixture is 5% to 95% by weight. % by weight; mixtures of AB2O4 material with RE2Si2O7 or RE2SiO5 silicates (RE = Y, La, Ce, Sc, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu); mixtures of AB2O4 material with rare earth oxide-stabilized zirconium oxide; mixtures of AB2O4 material with rare earth oxide-stabilized hafnium oxide; mixtures of AB2O4 material with aluminosilicates; mixtures of AB2O4 material with rare earth garnet; and materials containing only MgO, NiO, Co2O3, and Al2O3, or containing MgO, NiO, Co2O3, and Al2O3.

[0045] In an exemplary embodiment, Table 2 illustrates the structure and composition of a CMAS-resistant multilayer structure according to various exemplary embodiments.

[0046] Table 2

[0047]

[0048]

[0049]

[0050] In exemplary embodiments, coating methods for applying CMAS-resistant topcoats, hermetic EBCs, or bonding coatings include air plasma spraying (APS), high-velocity oxygen-enriched fuel (HVOF), low-pressure plasma spraying (LPPS), plasma spraying-physical vapor deposition (PS-PVD), chemical vapor deposition (CVD), physical vapor deposition (PVD), electron beam-physical vapor deposition (EB-PVD), suspension / solution plasma spraying (SPS), suspension / solution HVOF (S-HVOF), and slurry methods. For example, as shown in Table 3 below, the APS method may include the following parameters.

[0051] Table 3

[0052]

[0053]

[0054] Figure 2 A multilayer CMAS-resistant multilayer structure 200 according to various exemplary embodiments is shown. Figure 2 In the CMAS-resistant multilayer structure 200, a bonding coating 220 is deposited on a substrate 210, an hermetically sealed EBC layer 230 is deposited on the bonding coating 220, and a CMAS-resistant top coating 240 is deposited throughout the multilayer structure. Figure 2 In the middle, except for the buffer layer 235 which is disposed between the airtight EBC layer 230 and the CMAS resistant top coating layer 240, layers 210-240 and Figure 1 Layers 110-140 shown are similar. In an exemplary embodiment, buffer layer 235 comprises a mixture of a compound similar to EBC layer 230 and a compound similar to CMAS resistant topcoat 240.

[0055] Figure 3 Scanning electron microscope (SEM) images of CMAS-resistant multilayer structures according to various exemplary embodiments are shown. Figure 3 In various exemplary embodiments, on a SiC ceramic substrate, a CMAS-resistant multilayer structure includes a spinel-Al2O3 as a top coating, a Yb2Si2O7 layer as an intermediate EBC, and Si as a bonding coating. Specifically, the CMAS-resistant layer includes a spinel-containing coating.

[0056] Figure 4 Scanning electron microscope (SEM) images of CMAS-resistant multilayer structures according to various exemplary embodiments are shown. Figure 4In this context, according to various exemplary embodiments, the CMAS-resistant multilayer structure has been subjected to a CMAS test at 1300°C for 8 hours. Figure 3 The one shown in the image. Figure 3 and Figure 4 The comparison shows that the spinel-containing top coating successfully prevents CMAS from penetrating the EBC system.

[0057] Figure 5 Scanning electron microscope (SEM) images of CMAS-resistant multilayer structures according to various exemplary embodiments are shown. Figure 5 In China, the multi-layered structure of CMAS is... Figure 3 and Figure 4 The diagram shown illustrates the area plotted for calcium (Ca). Ca plotting was performed on a cross-section using EDS (Energy Dispersive X-ray Spectroscopy) to determine the presence of elements such as Ca, which are components of CMAS in the penetrating coating system. In the case of a CMAS-resistant layer, the absence of detectable Ca within the coating indicates that external CMAS erosion has not penetrated or damaged the coating.

[0058] Figure 6 Scanning electron microscope (SEM) images of CMAS-resistant multilayer structures according to various exemplary embodiments are shown. Figure 6 In this context, according to various exemplary embodiments, the CMAS multilayer structure is... Figure 3-5 The one shown indicates that CMAS did not reach the Yb2Si2O7 layer and stopped at the spinel-Al2O3 / CMAS interface. Figure 6 In the diagram, the dark areas of the Ca plot show the absence of Ca, and CMAS is only present on the surface of the also dark protective top layer, thus demonstrating the protective effect of the CMAS-resistant layer.

[0059] Figure 7 Scanning electron microscope (SEM) images of a CMFAS-resistant multilayer structure according to various exemplary embodiments are shown. CMFAS stands for calcium-magnesium-iron-aluminum-silicate, and in this case is (CaO-6MgO-14FeO-12Al2O3-48SiO2). Figure 7 The SEM cross-section of a CMAS-resistant multilayer structure with spinel-8 wt% Al2O3 as a top coating after CMFAS erosion (alternative test) at 1300°C for 8 hours is shown, and the corresponding Ca plot indicates that Ca is absent in the CMAS-resistant coating. Figure 7On the left, according to various exemplary embodiments, on a SiC ceramic substrate, the multilayer structure includes an EBC, having a top coating containing spinel-8 wt% Al2O3, a Yb2Si2O7 layer as an intermediate EBC layer, and Si as a bonding coating. This multilayer structure was exposed to CMFAS at 1300°C for 8 hours. The right side shows a Ca element plot, indicating that CMFAS did not reach the Yb2Si2O7 EBC layer and stopped at the spinel-8 wt% Al2O3 layer / CMFAS interface. Therefore, the spinel-8 wt% Al2O3 coating successfully prevented CMFAS penetration into the EBC layer even after 8 hours at 1300°C.

[0060] Figure 8 Scanning electron microscope (SEM) images of a CMFAS-resistant multilayer structure according to various exemplary embodiments are shown. In this case, the CMFAS is (CaO-6MgO-14FeO-12Al2O3-48SiO2). Figure 8 The SEM cross-section and corresponding Ca plot of a CMAS-resistant multilayer structure with spinel-8 wt% Al2O3 as a top coating after CMFAS erosion (alternative test) at 1350 °C for 8 hours are shown. Figure 8 On the left, according to various exemplary embodiments, on a SiC ceramic substrate, this multilayer structure includes an EBC with a top coating comprising spinel-8 wt% Al2O3, a Yb2Si2O7 layer as an intermediate EBC layer, and Si as a bonding coating. This multilayer structure was exposed to CMFAS at 1350°C for 8 hours. The right side shows a Ca element plot, indicating that CMFAS did not reach the Yb2Si2O7 EBC layer and stopped at the spinel-8 wt% Al2O3 layer / CMFAS interface. Therefore, the spinel-8 wt% Al2O3 coating successfully prevented CMFAS penetration into the EBC layer even after 8 hours at 1350°C.

[0061] Figure 9 Scanning electron microscope (SEM) images of a CMFAS-resistant multilayer structure according to various exemplary embodiments are shown. In this case, the CMFAS is (CaO-6MgO-14FeO-12Al2O3-48SiO2). Figure 9 SEM cross-sections and corresponding Ca plots of a CMAS-resistant multilayer structure with spinel-20 wt% Al2O3 as a top coating after CMFAS erosion (alternative test) at 1350 °C for 8 hours are shown. Figure 9On the left, according to various exemplary embodiments, on a SiC ceramic substrate, this multilayer structure includes an EBC having a top coating comprising spinel-20 wt% Al2O3, a Yb2Si2O7 layer as an intermediate EBC layer, and Si as a bonding coating. This multilayer structure was exposed to CMFAS at 1350°C for 8 hours. The right side shows a Ca element plot, indicating that CMFAS did not reach the Yb2Si2O7 EBC layer and stopped at the spinel-20 wt% Al2O3 layer / CMFAS interface. Therefore, the spinel-20 wt% Al2O3 coating successfully prevented CMFAS penetration into the EBC layer even after 8 hours at 1350°C.

[0062] The descriptions of the embodiments described herein are intended to provide a general understanding of the various embodiments. These descriptions are not intended to constitute a complete description of all elements and features of apparatuses and systems using the structures or methods described herein. Many other embodiments may become apparent to those skilled in the art upon review of this disclosure. Other embodiments may be used and derived from this disclosure, allowing for structural and logical substitutions and changes without departing from the scope of this disclosure. Furthermore, the illustrations are representative only and may not be drawn to scale. Some scales within the illustrations may be enlarged, while others may be minimized. Therefore, this disclosure and the accompanying drawings are to be considered illustrative rather than restrictive.

[0063] One or more embodiments of this disclosure may be referred to individually and / or collectively as the term "invention" herein, for convenience only and without intention of voluntarily limiting the scope of this application to any particular invention or inventive concept. Furthermore, although specific embodiments have been illustrated and described herein, it should be understood that any subsequent arrangements designed to achieve the same or similar purpose may replace the specific embodiments shown. This disclosure is intended to cover any and all subsequent modifications or variations of the various embodiments. Combinations of the above embodiments, as well as other embodiments not specifically described herein, will be apparent to those skilled in the art upon review of this specification.

[0064] This abstract of disclosure is provided for the purpose of not construing as limiting the scope or meaning of the claims. Furthermore, in the foregoing “Detailed Description,” various features may be combined or described in a single embodiment for the purpose of brevity. This disclosure should not be construed as reflecting an intention that the claimed embodiment requires more features than are expressly listed in the individual claims. Rather, as reflected in the following claims, the inventive subject matter may relate to fewer than all features of any disclosed embodiment. Therefore, the following claims are incorporated into the “Detailed Description,” each of which stands independently when defining its individual claimed subject matter.

[0065] The subject matter disclosed above is intended to be illustrative and non-limiting, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments falling within the true spirit and scope of this disclosure. Therefore, to the fullest extent permitted by law, the scope of this disclosure depends on the broadest permissible interpretation of the following claims and their equivalents, and should not be bound or limited by the foregoing details.

Claims

1. A CMAS-resistant multilayer structure on a substrate, the multilayer structure comprising: A bonding coating on the substrate; An environmentally tight barrier coating (EBC) is applied to the bonding coating. and The CMAS-resistant top coating comprises a mixture of AB2O4 and Al2O3. in A = Mg, Ni, Co, Cu, Mn, Ti, Be, Fe or combinations thereof B = Al, Fe, Cr, Co, V or combinations thereof And the weight percentage of Al2O3 in the mixture is 5% to 20% by weight.

2. The CMAS-resistant multilayer structure of claim 1, wherein the environmentally tight barrier coating (EBC) comprises at least one of the following: RE2Si2O7, RE2SiO5, mullite, and BaO-SrO-Al2O3-SiO2; wherein RE is one of Y, La, Ce, Sc, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

3. The CMAS-resistant multilayer structure of claim 1, wherein the bonding coating comprises at least one of the following: Si; Si-oxide, wherein the oxide is selected from Al2O3, B2O3, HfO2, TiO2, TaO2, BaO and SrO; silicide, selected from RESi, HfSi2, TaSi2 and TiSi2; RE2Si2O7-Si; RE2Si2O7-silicide; mullite-Si; and mullite-silicide, wherein RE is one of Y, La, Ce, Sc, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.

4. The CMAS-resistant multilayer structure of claim 1, wherein the substrate comprises at least one of SiC and Si3N4.

5. The CMAS-resistant multilayer structure of claim 1, wherein the thickness of the CMAS-resistant top coating is in the range of 10 μm to 2000 μm.

6. The CMAS-resistant multilayer structure of claim 1, wherein the thickness of the airtight environmental barrier coating is in the range of 10 μm to 1000 μm.

7. The CMAS-resistant multilayer structure of claim 1, wherein the thickness of the bonding coating is in the range of 2 μm to 500 μm.

8. The CMAS-resistant multilayer structure of claim 1, wherein the thickness of the substrate is greater than 40 mil.

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