Hybrid coating for enhanced CMAS resistance of thermal barrier coating

Abstract

A method for coating a substrate (22) includes: applying a columnar ceramic coating (26); infiltrating the ceramic coating; and sealing the infiltrated ceramic coating. The infiltrating is via melt infiltration or sol-gel infiltration and the sealing is via ALD, PVD, CVD, or thin film deposition. The coated substrate may be a gas turbine engine component.

Description

HYBRID COATING FOR ENHANCED CMAS RESISTANCE OF THERMAL BARRIER COATING CROSS-REFERENCE TO RELATED APPLICATION

[0001] Benefit is claimed of U.S. Patent Application No. 63 / 679,868, filed August 6, 2024, and entitled “Hybrid Coating for Enhanced CMAS Resistance of Thermal Barrier Coating”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length. BACKGROUND

[0002] The disclosure relates to gas turbine engines. More particularly, the disclosure relates to addressing calcium magnesium aluminosilicate (CMAS).

[0003] Gas turbine engines (used in propulsion and power applications and broadly inclusive of turbojets, turboprops, turbofans, turboshafts, industrial gas turbines, and the like) have combustor and turbine sections that operate at high temperature (the “hot section” of the engine).

[0004] Extremely fine dust, including calcium, magnesium, aluminum, and silicon oxides (CMAS), is a major problem for modern jet engines. It is mostly found in and above desert areas but can drift into other areas as well. CMAS is a problem because it is ingested by the engine and melts in the combustion chamber. The liquid CMAS deposits on the airfoils and walls (e.g., gaspath inner diameter (ID) and outer diameter (OD) surfaces) of the hot section of the engine and infiltrates the ceramic thermal barrier coatings (TBC) that protect them. The ceramic coatings have either a columnar structure or controlled porosity that gives them strain tolerance to compensate for the different thermal expansion rates between the coating and the metallic substrate. The CMAS seeps into the gaps and porosity. When the engine is shut down, it cools, the CMAS can freeze, reducing or eliminating the strain tolerance of the coating. The resulting build-up of stresses as the metallic substate cools and contracts can cause the ceramic coating to spall after multiple cycles. CMAS is not merely relevant to engines producing thrust for aircraft but also helicopter engines, armored land vehicle (wheeled or tracked) engines, ships, and the like.

[0005] There have been various proposals to apply supplemental coating(s) to as-applied pre-service TBC on components or post-service to spalled regions of the components so as to extend service life.

[0006] Examples of pre-service coatings are found in US Patent 11795829B2, (the ‘829 patent), October 24, 2023, “Reactive Thermal Barrier Coating”, of Hazel et al, the disclosureof which is incorporated in its entirety herein as if set forth at length and US Patent Publication 2023 / 0139765A1 (the ‘765 publication), May 4, 2023, “Reactive Thermal Barrier Coating”, the disclosure of which is incorporated in its entirety herein as if set forth at length.

[0007] Examples of post-service coatings are found in US Patent Publication 2022 / 0136095A1 (the ‘095 publication), May 5, 2022, “Reactive Phase Spray Formulation Coatings”, US Patent Publication 2021 / 0324201A1 (the ‘201 publication), October 21, 2021, “Consumable Coatings and Methods of Protecting a High Temperature Component from Dust Deposits”, and US Patent Publication 2021 / 0277523A1 (the ‘523 publication), September 9, 2021, “Coating Systems Including Infiltration Coatings and Reactive Phase Spray Formulation Coatings”. SUMMARY

[0008] One aspect of the disclosure involves a method for coating a substrate. The method includes: applying a columnar ceramic coating; infiltrating the ceramic coating; and sealing the infiltrated ceramic coating. The infiltrating is via melt infiltration or sol-gel infiltration and the sealing is via atomic layer deposition (ALD), physical vapor deposition (PVD), chemical vapor deposition (CVD), or thin film deposition.

[0009] In a further embodiment of any of the foregoing embodiments, additionally or alternatively, the substrate is metallic.

[0010] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the applying the ceramic coating comprises PVD.

[0011] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the sealing comprises ALD.

[0012] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the infiltrating is by melt infiltration.

[0013] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively, the infiltrating comprises an infiltration by a nitrate or acetate.

[0014] A further embodiment of any of the foregoing embodiments may additionally and / or alternatively include calcining after the infiltrating.

[0015] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the calcining leaves an oxide infiltrate between and atop columns of the ceramic; and the sealing forms a layer of an oxide sealant atop the infiltrate atop the columns and infiltrating into the infiltrate.

[0016] In a further embodiment of any of the foregoing embodiments, additionally or alternatively, the substrate is shaped to form a gas turbine engine component having a gaspath surface and the applying, infiltrating and sealing is along said gaspath surface.

[0017] Other embodiments may include variations as discussed for aspects or embodiments above or below.

[0018] A further aspect of the disclosure involves a coated substrate comprising: a substrate; a columnar ceramic coating; first means for sealing openings of intercolumnar gaps to hinder infiltration of the intercolumnar gaps by CMAS; and second means for lining the intercolumnar gaps to react with CMAS.

[0019] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the first means comprises hafnia; and the second means comprises lanthana.

[0020] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the first means comprises an ALD coating; and the second means comprises a melt or sol-gel coating.

[0021] In a further embodiment of any of the foregoing embodiments, additionally or alternatively, the coated substrate is a gas turbine engine component having a gaspath surface and the applying, infiltrating and sealing is along said gaspath surface.

[0022] A further embodiment of any of the foregoing embodiments may additionally and / or alternatively include a method for using the coated substrate. The method comprises: exposing the coated substrate to CMAS; the first means hindering infiltration of the intercolumnar gaps by CMAS; and the second means reacting with CMAS.

[0023] Other embodiments may include variations as discussed for aspects or embodiments above or below.

[0024] A further aspect of the disclosure involves a method for coating a substrate. The method comprises: applying a columnar ceramic coating; melt infiltrating the ceramic coating; and sealing the infiltrated ceramic coating via ALD.

[0025] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the melt infiltrating is of at least 50% by weight one or more of nitrates and acetates; the ALD is of at least 50% by weight one or more oxides; and the applying the ceramic coating is via PVD.

[0026] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the melt infiltrating is of at least 50% by weight one or a combination of lanthanum nitrate and yttrium nitrate; and the ALD is of at least 50% by weight one or more of La2O3, Y2O3, and HfO2.

[0027] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the melt infiltrating is of at least 50% by weight La2O3; and the ALD is of at least 50% by weight one of La2O3, Y2O3, and HfO2.

[0028] In a further embodiment of any of the foregoing embodiments, additionally or alternatively, the substrate is shaped to form a gas turbine engine component having a gaspath surface and the applying, infiltrating and sealing is along said gaspath surface.

[0029] Other embodiments may include variations as discussed for aspects or embodiments above or below.

[0030] A further aspect of the disclosure involves a method for coating a substrate, the method comprising: applying a columnar ceramic coating; a first ALD stage for infiltrating the ceramic coating; and a second ALD stage for sealing the infiltrated ceramic coating.

[0031] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the first ALD is of at least 50% by weight one or more of TiO2and Al2O3; the second ALD stage is of at least 50% by weight one or more of La2O3, Y2O3, and HfO2; and the applying the ceramic coating is via PVD.

[0032] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the first ALD is of at least 90% by weight one or a combination of TiO2and Al2O3; the second ALD stage is of at least 90% by weight one or more of La2O3, Y2O3, and HfO2; and the applying the ceramic coating is via PVD.

[0033] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the first ALD is of at least 50% by weight one of TiO2 and Al2O3; the second ALD stage is of at least 50% by weight one of La2O3, Y2O3, and HfO2; and the applying the ceramic coating is via PVD.

[0034] In a further embodiment of any of the foregoing embodiments, additionally or alternatively, the substrate is shaped to form a gas turbine engine component having a gaspath surface and the applying, infiltrating and sealing is along said gaspath surface.

[0035] Other embodiments may include variations as discussed for aspects or embodiments above or below.

[0036] A further aspect of the disclosure involves a coated substrate comprising: a substrate; a columnar ceramic coating; an inter-columnar ceramic coating; and a sealant atop the columnar ceramic coating and inter-columnar ceramic coating.

[0037] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the columnar ceramic coating comprises at least one of YSZ and GdZ; the inter- columnar ceramic coating comprises at least 50% by weight one or more of La2O3, TiO2, andAl2O3; the sealant comprises at least 50% by weight one or more of La2O3, Y2O3, and HfO2; and if the inter-columnar ceramic coating and the sealant each comprise at least 50% by weight La2O3, then the inter-columnar ceramic coating has greater porosity than the sealant.

[0038] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the inter-columnar ceramic coating comprises at least 90% by weight one or more of La2O3, TiO2, and Al2O3; the sealant comprises at least 90% by weight one or more of La2O3, Y2O3, and HfO2; and if the inter-columnar ceramic coating and the sealant each comprise at least 50% by weight La2O3, then the inter-columnar ceramic coating has greater porosity than the sealant.

[0039] In a further embodiment of any of the foregoing embodiments, additionally and / or alternatively: the inter-columnar ceramic coating is more reactive with CMAS than is the sealant; and / or the inter-columnar ceramic coating is more porous than is the sealant.

[0040] In a further embodiment of any of the foregoing embodiments, additionally or alternatively, the coated substrate is a gas turbine engine component having a gaspath surface and the applying, infiltrating and sealing is along said gaspath surface.

[0041] Other embodiments may include variations as discussed for aspects or embodiments above.

[0042] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 is a partially schematic sectional view of a baseline columnar thermal / environmental barrier coating system on a substrate.

[0044] FIG. 2 is a schematic view of the coated substrate after an inter-columnar infiltration.

[0045] FIG. 3 is a view of the coated substrate of FIG. 2 after a surface sealing.

[0046] FIG. 3A is an enlarged view of a column lateral surface.

[0047] FIG. 3B is an enlarged view of a column tip.

[0048] FIG. 3C is an enlarged view of an opening in an initial inter-column gap bridged by infiltrate.

[0049] FIG. 4 is an enlarged view of an opening in an initial inter-column gap bridged by sealant.

[0050] FIG. 5 is a schematic view of a blade.

[0051] FIG. 6 is a schematic view of a vane.

[0052] FIG. 7 is a schematic view of a combustor panel.

[0053] FIG. 8 is a schematic view of a blade outer airseal.

[0054] Like reference numbers and designations in the various drawings indicate like elements.DETAILED DESCRIPTION

[0055] After applying a columnar ceramic barrier coating layer, a two-stage process involves infiltrating the columns with an infiltrate / infiltrant and then sealing the columns with a sealant / barrier. Relative to the infiltration, the sealing may be more depthwise limited and confined to a region near the outer surface (away from the substrate) of the coating as a whole. Both infiltrate and sealant / barrier may comprise one or more metal oxides (e.g., transition metal oxides and / or rare earth oxides (REO)).

[0056] As is discussed further below, the infiltrate may represent an initial infiltrate or a reacted infiltrate. For example, to obtain a metal oxide infiltrate, some implementations may involve an initial infiltration (e.g., a melt infiltration) of a salt (e.g., nitrate or acetate) of such metal. A reaction (e.g., reaction with oxygen when heated in air) may liberate nitrogen and carbon from the nitrate or acetate, in the form of NOX and carbon dioxide, respectively, leaving the metal oxide as the ultimate / reacted infiltrate. The vapor (e.g., NOXor carbon dioxide) liberated by such reaction leaves the infiltrate with greater porosity than non-reactive vapor deposition techniques. The porosity may facilitate reaction with CMAS and gives rise to the possibility of using a chemically similar infiltrate and sealant barrier differing in greater porosity of the infiltrate. Example salt comprises at least 90% (or consists of or consists essentially of) by weight material selected from the group consisting of: cerium acetate; cerium nitrate; hafnium acetate; hafnium nitrate; zirconium acetate; zirconium nitrate; lanthanum acetate; lanthanum nitrate; gadolinium acetate; gadolinium nitrate; yttrium acetate; yttrium nitrate; and combinations thereof.

[0057] The infiltrate may be selected to be more reactive with CMAS than is the column material. The reactivity has the effect of limiting CMAS penetration via driving intrinsic crystallization of the CMAS by reacting with molten CMAS and forming a crystalline precipitate. The reactivity has the effect of pulling constituents from the liquid CMAS via crystallization. The crystalline phases may contain elements from the infiltrate material and the CMAS (e.g. La from the infiltrate and Ca and Si from the CMAS for apatite Ca2La8Si6O26). The formation of crystalline products limits the penetration of CMAS into the TBC by: 1) reducing the volume of CMAS material available for penetration of the columns; 2) blocking the flow path of the molten CMAS; and 3) changing the composition of the molten CMAS to induce secondary crystallization of the melt.

[0058] The reactivity may be measured as / by the tendency to form stabile crystalline phases such as apatite phase with rare earths. See, Lei GUO, et al., “Interaction laws of RE2O3 and CMAS and rare earth selection criterions for RE-containing thermal barriercoatings against CMAS attack”, Corrosion Science, November 19, 2023, Volume 226, Elsevier Ltd., Amsterdam, Netherlands.

[0059] The sealant / barrier may be selected to be less reactive with CMAS than is the infiltrate or even the column material. Such lower reactivity serves to prevent or delay the CMAS penetration into the gap of TBC columns via acting as a dense barrier.

[0060] FIG. 1 shows a baseline coated substrate 20 comprising, in main, a substrate 22, a metallic bondcoat 24, and a columnar ceramic coating 26 atop the bondcoat. Example bondcoats include MCrAlY (where M is Ni, Co, and / or Fe, e.g., a NiCoCrAlY) overlays and / or diffusion aluminides. A thickness of the bondcoat is shown as TB and a thickness of the columnar ceramic is shown as TC. The columnar ceramic has individual columns 30 with intercolumnar gaps 32. The gaps are known to render the coating particularly susceptible to infiltration by CMAS. Example coated surfaces are gaspath-facing turbine engine component surfaces. Example surfaces are airfoils (e.g., of blades and vanes), blade inner diameter platform outer diameter surfaces, vane outer diameter shroud inner diameter surfaces and inner diameter shroud outer diameter surfaces, combustor panels, nozzles, and the like. Example substrates are nickel-based alloys / superalloys.

[0061] The columnar ceramic may be applied by any appropriate known or yet-developed technique and with any known or yet-developed material. Example materials are yttria-stabilized zirconia (e.g., 7YSZ) and gadolinium zirconate (e.g., 59GZO). Example application techniques are physical vapor deposition (PVD) (e.g., electron beam PVD (EB- PVD)) and plasma spray (e.g., suspension plasma spray or solution plasma spray).

[0062] FIG. 2 shows the article after application of an infiltrate 40 to coat the columns 30. The infiltrate extends well down into the gaps 32 to coat lateral sides of the columns. Infiltration depth is shown as DI. This may be measured as an average based on EDS of a cross-section. Example average DI is at least about 50% of TC. More particularly, it may be at least 60% or an example 60% to 80%. Depending upon implementation, the infiltrate may fill varying amounts of the gaps 32 and with different characteristics. Column surfaces (sides) may be characterized by feathering (not shown). The feathering creates porosity between feathers and open to the main portion of the intercolumn gap. Melt infiltration will have little tendency to be drawn in to the feather gaps / open intracolumnar porosity (as opposed to more internal close intracolumnar porosity). However, atomic layer deposition (ALD) will enter the feather gaps due to gas phase permeability of the feather gaps.

[0063] For example, melt phase infiltration may fill an example 30% to 70% of inter- columnar gap volume. In terms of infiltration into the column feather porosity, this may berelatively low if at all. For example, not more than 20% of the feather porosity may be filled in a typical melt infiltration. For example ALD of the infiltrate, an example at least 80% of the feather porosity may be filled.

[0064] Post-infiltration, a sealant / barrier layer may be applied. FIG. 3 shows sealant / barrier 50 atop the columns. It may bridge surface openings of rump gaps 32 (not shown) to largely close off the gaps (if not already closed by the infiltrate as shown). By bridging at the outer surface, infiltration of CMAS is resisted. By leaving substantial porosity in terms of the vestigial gaps 32, coating compliance is preserved (accommodating, inter alia, differential thermal expansion and expansion due to infiltration of chemical species into the coating). Example sealant / barrier depth is shown as DS. This may reflect column tip geometry.

[0065] FIG. 3A shows an infiltrate 40 thickness TI along the column sides within the gaps 32. As noted above, the example gaps are not fully filled but are narrowed by the infiltrate Example infiltration leaves the gaps with approximately 30% to 90% of their original volume as noted above (with narrower ranges of 30% to 70% particularly for melt infiltration or other liquid infiltration and 50% to 90% particularly for ALD and other vapor infiltrations). FIG. 3B shows infiltrate thickness TI2along the tops of the columns and shows local sealant thickness TS. There is substantial porosity in the illustrated melt infiltrate, with the sealant itself infiltrating porosity of adjacent infiltrate. Such infiltration of the sealant 50 into the infiltrate 40 may be associated with the porosity due to reaction of a melt infiltrate 40. In the case of an ALD infiltrate 40 there may be little or no porosity to be infiltrated by the sealant.

[0066] FIG. 3C shows bridging by the infiltrate 40 adjacent the column tips. FIG. 4 shows bridging by the sealant 50 atop the infiltrate 40 (which alone did not close the gap 32) adjacent the column tips. The FIG. 3C illustration may be more associated with melt infiltration due to surface tension assisting in initial infiltrate bridging prior to solidification. The FIG. 4 illustration may be more representative of ALD sealant bridging residual gap openings in ALD infiltrate.

[0067] As is discussed further below, candidate infiltrates 40 include La2O3, TiO2, Y2O3, CeO2, Gd2O3, Al2O3, Sm2O3, combinations thereof, and nanolaminates thereof. More broadly, example infiltrate 40 materials are La2O3, TiO2, Y2O3, CeO2, Gd2O3, Al2O3, Sm2O3, other lanthanum series oxides, combinations thereof, and nanolaminates thereof. Further additives and impurities are possible, but key examples are at least 50 percent by weight and / or volume a combination of said compounds, more particularly, at least 70 percent. A nanolaminate has nano-thick alternating sublayers of different materials. As an examplenanolaminate of CeO2 and Al2O3 can be one nm of CeO2 followed by one nm of Al2O3, and this alternating sublayer structure is repeated until the desired thickness is reached. An example nanolaminate has at least ten sublayers of each of two or more components with individual sublayer thicknesses of 0.50 nm to 10 nm as an example.

[0068] Example sealant / barrier 50 materials are Al2O3, ZrO2, Y2O3, La2O3, HfO2, TiO2, combinations thereof, and nanolaminates thereof. More broadly, example sealant / barrier 50 materials are Al2O3, ZrO2, Y2O3, La2O3, HfO2, TiO2, CeO2, Sm2O3, Yb2O3Gd2O3, other lanthanum series oxides, combinations thereof, and nanolaminates thereof. Further additives and impurities are possible, but key examples are at least 50 percent by weight and / or volume a combination of said compounds, more particularly, at least 70 percent.

[0069] In general, the infiltrate 40 may be selected with a bias toward reactivity. Reactivity involves forming favorable reaction product types and strong protective phase formation kinetics. One key factor is forming apatite phase as discussed above for rare earths. In many cases interaction between the infiltrate and CMAS follows the sequence: 1) infiltrate dissolves into the molten CMAS; 2) when the concentration of infiltrate is sufficiently high, nucleation of a crystalline phase occurs; 3) the crystalline phase grows consuming elements of the molten CMAS and infiltrate; and 4) the CMAS melt composition shifts as a result of the crystal growth and the growth continues until the composition of the melt is no longer favorable to further crystallization.

[0070] In contrast, the barrier material 50 may be selected for acting as a physical barrier. For example, ZrO2 and HfO2 have lower solubility in silicate melts than do the rare earth oxides. Thus, it may be desirable to have a greater concentration of one or a combination of ZrO2and HfO2in the barrier material 50 than in the infiltrate 40. Example difference is such that the combined ZrO2 and HfO2 contents differ by at least 20% or at least 40% by volume (e.g., an 80% content in the sealant / barrier with a 40% content in the infiltrate 40 representing such a 40% difference). Example infiltration techniques include melt infiltration, sol-gel coating, atomic layer deposition (ALD), and solution coating. Melt infiltration may have advantages of deeper infiltration and filling more coating materials between columns. ALD may have advantages of producing conformal, dense coating as well as penetrating into open intracolumn porosities. For all but ALD, after initial infiltration of a precursor, a calcining process may be used to produce a final oxide.

[0071] Example sealant application techniques include thin film technologies such as ALD, CVD, PVD, and PLD (pulse laser deposition). These tend to result in a thin dense layer. However, other technologies such as sol-gel, thermal spray, solution coating, and slurrycoating are possible. ALD may have a particular advantage of producing conformal and thin dense layers.

[0072] In key examples, if the inter-columnar ceramic coating and the sealant each comprise at least 50% by weight the same oxide, then different application techniques for the two layers would be used. For non-ALD application of the infiltrate, the infiltrate would be expected to have greater porosity than the sealant / barrier. Example porosity difference is a porosity delta of at least 20% or at least 25% or at least 30%. For example, the sealant (away from any overlap zone where sealant has infiltrated into porosity of the infiltrate) may have porosity of 5% or less. The infiltrate (away from such overlap) may have porosity of at least 25% or at least 30%. (e.g. 30% to 70%) with those 5% and 30% values the delta is 25%.

[0073] Key combinations of infiltrates and application techniques and sealants / barriers and application techniques are discussed below.

[0074] A first example of the infiltrate and application technique (designated I1 in the table below) is TiO2 and ALD. TiO2 can densely infiltrate and is reactive with CMAS. TiO2 is most reactive with CaO relative to its reactivity with other CMAS components. (e.g., relative to reactivity with SiO2or Al2O3) forming CaTiO3. TiO2may also form additional crystalline phases including melilite, paqueite, and diopside. Specifically, it drives intrinsic crystallization of the residual Al, Mg, and Fe from CMAS so as to limit their further infiltration. An example deposition process involves approximately 200 nanometers of thickness (more broadly 100 nanometers to 1000 nanometers) and 100 micrometers of penetration depth. Such penetration may represent at least 30% of the intercolumn gap depth or at least 50%. Example ALD involves TDMAT (tetrakis(dimethylamino)titanium(IV)) precursor / titanium source and water as an oxidant (see further discussion below).

[0075] A second example of the infiltrate and application technique (designated I2 in the table below) is La2O3 and melt infiltration. La2O3 infiltrate with low density and is reactive with CMAS (particularly Ca and SiO2). Specifically, it crystalizes to form the crystalline phase apatite so as to prevent further infiltration. An example infiltration process involves penetration depth of at least 50% of the intercolumn gap depth or at least 80%. The melt infiltration involves of a lanthanum salt (e.g., lanthanum nitrate) followed by oxidation to form La2O3.

[0076] A third example of the infiltrate and application technique (designated I3 in the table below) is Al2O3 and ALD. Al2O3 can densely infiltrate and is reactive with CMAS. It may drive intrinsic crystallization of the CMAS so as to avoid reaction of the CMAS with the ceramic 26. Al2O3 may be the best infiltrate because it can form MgAl2O4, Ca(Al,Fe)12O19,CaAl2Si2O8, and also a crystalline spinel (MgAl2-xFexO4) phase. An example deposition process involves approximately 200 nanometers of coating thickness (more broadly 100 nanometers to 800 nanometers) and 200 micron of penetration depth. Such penetration may represent at least 80% of the intercolumn gap depth or at least 95%. Example ALD involves TMA (trimethylaluminum) as a precursor / aluminum source and water as an oxidant.

[0077] A fourth example of the infiltrate and application technique (designated I4 in the table below) is Al2O3and sol-gel via immersion in an Al2O3sol solution in water. The solution with the part immersed may be placed into a vacuum chamber, and the pressure reduced to at least (e.g., to -20 inches (-508 mm) Hg of vacuum for 10 minutes). The solution may be brought back to ambient atmospheric pressure, and the part removed from the solution. The part may be air dried and then calcined (e.g., at 650°C for 2 hours). The calcining converts any residual aluminum hydroxide into aluminum oxide.

[0078] A fifth example of the infiltrate and application technique (designated I5 in the table below) is Y2O3 and melt infiltration. An example infiltration process involves penetration depth of at least 50% of the intercolumn gap depth or at least 80%. The melt infiltration involves of a yttrium salt (e.g., yttrium nitrate) followed by oxidation to form Y2O3.

[0079] A first example of the sealant / barrier material and application technique (designated S1 in the table below) is La2O3 and ALD. Example ALD is about 400 nanometers, more broadly 100 nanometers to 1000 nanometers. Example ALD involves one or more of tris (i-propylcyclopentadienyl) lanthanum (La(iPrCp)3), tris (2,2,6,6-tetramethyl- 3,5-heptanedionato) lanthanum (LaTHD), tris (N,N-bis(trimethylsilyl)amide) lanthanum (La[N(SiMe3)2]3), and tris (N,N'-di-i-propylformamidinato) lanthanum (La-FMD) as a precursor / lanthanum source and water as an oxidant. Ozone may be used as an oxidant additionally or alternatively to water here and in other examples.

[0080] A second example of the sealant / barrier material and application technique (designated S2 in the table below) is Y2O3and ALD. Example ALD is about 500 nanometers, more broadly 100 nanometers to 1000 nanometers. Example ALD involves tris (methylcyclopentadienyl) yttrium as a precursor / yttrium source and water as an oxidant. Yttrium sources also include tris (N,N′-di-i-propylacetamidinate) yttrium (Y-AMD), tris (N,N'-di-i-propylformamidinato) yttrium (Y-FMD), and tris (butylcyclopentadienyl) yttrium (Y(BuCp)3)).

[0081] A third example of the sealant / barrier material and application technique (designated S3 in the table below) is HfO2 and ALD. Example ALD is about 500 nanometers,more broadly 100 nanometers to 1000 nanometers. Example ALD involves one or more of hafnium chloride, tetrakis(dimethylamino) hafnium, and hafnium t-butoxide as a precursor / hafnium source and water as an oxidant.

[0082] A fourth example of the sealant / barrier material and application technique (designated S4 in the table below) is Y2O3 and CVD. Example CVD is about 500 nanometers, more broadly 100 nanometers to 1000 nanometers. Example CVD involves tris (methylcyclopentadienyl) yttrium as a precursor / yttrium source and water as an oxidant. Yttrium sources also include tris (N,N′-di-i-propylacetamidinate) yttrium (Y-AMD), tris (N,N'-di-i-propylformamidinato) yttrium (Y-FMD), and tris (butylcyclopentadienyl) yttrium (Y(BuCp)3).Table I Example Combinations

[0083] One example (Ex. 2 in Table I) of melt infiltration of La2O3followed by ALD Y2O3 starts with a TBC-coated substrate. An example substrate is cast SX IN-718 with an air plasma spray MCrAlY bondcoat and an EB-PVD 7YSZ barrier coat.

[0084] The TBC coated part was cleaned with ultrasonic immersion in isopropanol and dried at 600°C.

[0085] A salt bath of lanthanum nitrate was preheated to 120°C to a molten state. The part was placed in the molten salt bath for 30 min. The part was removed from the salt bath, and excess material on the part was gently scrapped off. The top of the part surface was cleaned off with deionized (DI) water. The part was air dried and then calcined at 650°C for 2 hours. The calcining converts the rare earth (La) nitrate into a rare earth oxide, releasing various NOX. This creates porosity in the infiltrate. After cooling, the part was dusted off with a stream of pressurized nitrogen gas.

[0086] The part was loaded into an ALD reactor and brought under vacuum (<200 Pa). The ALD reactor was heated to 250°C and stabilized for one hour before ALD Y2O3 deposition The organometallic yttrium precursor (e.g., tris(methylcyclopentadienyl)yttrium) and water were loaded onto the ALD. Alternating pulses of yttrium and water (to act as an oxidant) were injected into the ALD reactor chamber (separated by purges / evacuations), until an Y2O3 coating of 500 nm was achieved on the part surface. The reaction may liberate carbon-containing species including hydrocarbons. Once the deposition was done, the reactor was cooled down, and the completed part was removed from reactor. More general reactor temperatures for this precursor are 200°C to 400°C.

[0087] As an alternative to ALD, for a CVD application of the sealant / barrier material, the metal precursor (e.g., organometallic precursor) and oxidant are fed simultaneously rather than in the sequential pulses of ALD. As a further alternative, a PVD application (e.g., EB- PVD) may, on the one hand, involve direct deposition from a source of the metal oxide. On the other hand, it may involve deposition from a source of the metal (e.g., a source of the pure metal) in an oxygen-containing environment (e.g., air) with simultaneous deposition and oxidation.

[0088] FIG. 5 shows a blade 900 having an airfoil 902 extending outward from a platform 904. The blade includes an attachment root 906 inboard of the platform. The platform 904 has an outboard gaspath surface 908. The airfoil has a surface comprising a leading edge 910, a trailing edge 911, a pressure side 912, and a suction side 913. The airfoil extends from an inboard end at the platform to an outboard end and an outboard end at a tip 914. The relevant gaspath surface of the blade for ceramic coating is thus the pressure and suction sides and the platform gaspath surface. Alternate blades may have features such as shrouded tips (not shown) and internal cooling passageway networks (not shown).

[0089] FIG. 6 shows a vane 930 which may have a similar airfoil to the blade 900. The airfoil extends from an inboard end at an inner diameter shroud or platform or band segment 932 to an outboard end at an outer diameter / outboard shroud or band segment 933. The segments 922, 933 have respective outer diameter and inner diameter gaspath surfaces 934 and 935.

[0090] FIG. 7 shows a component as a combustor panel (e.g., a floatwall panel) 950. The panel 950 may be formed having a body 951 shaped as a generally frustoconical segment having respective inboard and outboard surfaces 952 and 953. The example inboard surface is thus a gaspath-facing surface formed as a frustoconical segment.

[0091] The example panel is configured for use in an annular combustor circumscribing the engine centerline. In the example panel, the inboard surface 952 forms an interior surface (i.e., facing the combustor interior) so that the panel is an outboard panel. For an inboard panel, the inboard surface would be the exterior surface. Accordingly, mounting features such as studs 955 extend from the outboard surface for securing the panel relative to the engine. The ceramic coating may be at least on the interior surface.

[0092] An example annular combustor is formed by a number of concentric inner rings and outer rings of such panels. A plurality of such rings are arrayed end-to-end at both inner diameter (ID) and outer diameter (OD) boundaries. These rings may extend downstream from a bulkhead (also a ring of panels) mounting fuel injector nozzles, air swirlers, and the like. The panel rings may extend downstream to a guide vane ring at the inlet to the turbine section.

[0093] The example panel body 951 further includes an upstream / leading edge 956, a downstream / trailing edge 957 and lateral (circumferential end) edges 958 and 959. A flow direction along each such panel may be generally from the upstream / leading edge to the downstream / trailing edge. Along one or more of the edges or elsewhere, the panel may include rails or standoffs 960 extending from the exterior surface 953 for engaging a combustor shell (not shown). The example panel includes a circumferential array of large apertures 961 for the introduction of process air (these are typically cast in the substrate). Smaller apertures (not shown) may be provided for film cooling (these are typically machined post-casting). Moreover, select panels may accommodate other openings (these are typically cast in the substrate) for spark plug or igniter or sensor placement.

[0094] FIG. 8 shows a blade outer air seal (BOAS) segment 970. The BOAS has a main body portion 971 having a leading / upstream / forward end 972 and a trailing / downstream / aft end 973. The body has first and second circumferential ends or matefaces 974 and 975. Thebody has an ID face 976 (which may be the most relevant surface portion for the ceramic coating) and an OD face 977. To mount the BOAS to environmental structure (e.g., a main portion of the case), the exemplary BOAS has a plurality of mounting hooks. The exemplary BOAS has a forward mounting hook 978 and an aft hook 979.

[0095] The assembled ID faces of the circumferential array of BOAS segments thus locally bound an outboard extreme of the core flowpath through the engine. The BOAS may have features (not shown) for interlocking the array. Exemplary features include finger and shiplap joints. The example BOAS also has an apertured plate 980 mounted to the body OD face to enclose a cooling plenum of the body having outlets along the matefaces and optionally elsewhere.

[0096] The use of “first”, “second”, and the like in the following claims is for differentiation within the claim only and does not necessarily indicate relative or absolute importance or temporal order. Similarly, the identification in a claim of one element as “first” (or the like) does not preclude such “first” element from identifying an element that is referred to as “second” (or the like) in another claim or in the description.

[0097] One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when applied to an existing baseline configuration, details of such baseline may influence details of particular implementations. Accordingly, other embodiments are within the scope of the following claims.

Claims

CLAIMS What is claimed is:

1. A method for coating a substrate (22), the method comprising: applying a columnar ceramic coating (26); infiltrating the ceramic coating; and sealing the infiltrated ceramic coating, wherein: the infiltrating is via melt infiltration or sol-gel infiltration; and the sealing is via ALD, PVD, CVD, or thin film deposition.

2. The method of claim 1 wherein: the substrate is metallic.

3. The method of claim 1 wherein: the applying the ceramic coating comprises PVD.

4. The method of claim 1 wherein: the sealing comprises ALD.

5. The method of claim 1 wherein: the infiltrating is by said melt infiltration.

6. The method of any previous claim wherein: the infiltrating comprises an infiltration by a nitrate or acetate.

7. The method of claim 6 further comprising: calcining after the infiltrating.

8. The method of claim 7 wherein: the calcining leaves an oxide infiltrate between and atop columns of the ceramic; and the sealing forms a layer of an oxide sealant atop the infiltrate atop the columns and infiltrating into the infiltrate.

9. The method of claim 1 wherein:the substrate is shaped to form a gas turbine engine component having a gaspath surface and the applying, infiltrating and sealing is along said gaspath surface.

10. A coated substrate (20) comprising: a substrate (22); a columnar ceramic coating (26); first means (50) for sealing openings of intercolumnar gaps (32) to hinder infiltration of the intercolumnar gaps by CMAS; and second means (40) for lining the intercolumnar gaps to react with CMAS.

11. The coated substrate of claim 10 wherein: the first means comprises hafnia; and the second means comprises lanthana.

12. The coated substrate of claim 10 wherein: the first means comprises an ALD coating; and the second means comprises a melt or sol-gel coating.

13. The coated substrate of claim 10 wherein: the coated substrate is a gas turbine engine component having a gaspath surface and the applying, infiltrating and sealing is along said gaspath surface.

14. A method for using the coated substrate of claim 10, the method comprising: exposing the coated substrate to CMAS; the first means hindering infiltration of the intercolumnar gaps by CMAS; and the second means reacting with CMAS.

15. A method for coating a substrate, the method comprising: applying a columnar ceramic coating; melt infiltrating the ceramic coating; and sealing the infiltrated ceramic coating via ALD.

16. The method of claim 15 wherein: the melt infiltrating is of at least 50% by weight one or more of nitrates and acetates;the ALD is of at least 50% by weight one or more oxides; and the applying the ceramic coating is via PVD.

17. The method of claim 16 wherein: the melt infiltrating is of at least 50% by weight one or a combination of lanthanum nitrate and yttrium nitrate; and the ALD is of at least 50% by weight one or more of La2O3, Y2O3, and HfO2.

18. The method of claim 16 wherein: the melt infiltrating is of at least 50% by weight La2O3; and the ALD is of at least 50% by weight one of La2O3, Y2O3, and HfO2.

19. The method of any of claim 15 to claim 18 wherein: the substrate is shaped to form a gas turbine engine component having a gaspath surface and the applying, infiltrating and sealing is along said gaspath surface.

20. A method for coating a substrate, the method comprising: applying a columnar ceramic coating; a first ALD stage for infiltrating the ceramic coating; and a second ALD stage for sealing the infiltrated ceramic coating.

21. The method of claim 20 wherein: the first ALD is of at least 50% by weight one or more of TiO2and Al2O3; the second ALD stage is of at least 50% by weight one or more of La2O3, Y2O3, and HfO2; and the applying the ceramic coating is via PVD.

22. The method of claim 20 wherein: the first ALD is of at least 90% by weight one or a combination of TiO2 and Al2O3; the second ALD stage is of at least 90% by weight one or more of La2O3, Y2O3, and HfO2; and the applying the ceramic coating is via PVD.

23. The method of claim 20 wherein:the first ALD is of at least 50% by weight one of TiO2 and Al2O3; the second ALD stage is of at least 50% by weight one of La2O3, Y2O3, and HfO2; and the applying the ceramic coating is via PVD.

24. The method of any of claim 20 to claim 23 wherein: the substrate is shaped to form a gas turbine engine component having a gaspath surface and the applying, infiltrating and sealing is along said gaspath surface.

25. A coated substrate (20) comprising: a substrate (22); a columnar ceramic coating (26); an inter-columnar ceramic coating (40); and a sealant (50) atop the columnar ceramic coating and inter-columnar ceramic coating.

26. The coated substrate of claim 25 wherein: the columnar ceramic coating comprises at least one of YSZ and GdZ; the inter-columnar ceramic coating comprises at least 50% by weight one or more of La2O3, TiO2, and Al2O3; the sealant comprises at least 50% by weight one or more of La2O3, Y2O3, and HfO2; and if the inter-columnar ceramic coating and the sealant each comprise at least 50% by weight La2O3, then the inter-columnar ceramic coating has greater porosity than the sealant.

27. The coated substrate of claim 25 wherein: the inter-columnar ceramic coating comprises at least 90% by weight one or more of La2O3, TiO2, and Al2O3; the sealant comprises at least 90% by weight one or more of La2O3, Y2O3, and HfO2; and if the inter-columnar ceramic coating and the sealant each comprise at least 50% by weight La2O3, then the inter-columnar ceramic coating has greater porosity than the sealant.

28. The coated substrate of claim 25 wherein: the inter-columnar ceramic coating is more reactive with CMAS than is the sealant.

29. The coated substrate of any of claim 25 to claim 28 wherein: the inter-columnar ceramic coating is more porous than is the sealant.

30. The coated substrate of any of claim 25 to claim 28 wherein: the coated substrate is a gas turbine engine component having a gaspath surface and the applying, infiltrating and sealing is along said gaspath surface.

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