WO2008109214A2 - Environmental barrier coating - Google Patents
Environmental barrier coating Download PDFInfo
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- WO2008109214A2 WO2008109214A2 PCT/US2008/052783 US2008052783W WO2008109214A2 WO 2008109214 A2 WO2008109214 A2 WO 2008109214A2 US 2008052783 W US2008052783 W US 2008052783W WO 2008109214 A2 WO2008109214 A2 WO 2008109214A2
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- WO
- WIPO (PCT)
- Prior art keywords
- article
- rare earth
- percent
- weight
- layer
- Prior art date
Links
- 238000000576 coating method Methods 0.000 title claims description 20
- 239000011248 coating agent Substances 0.000 title claims description 19
- 230000007613 environmental effect Effects 0.000 title description 9
- 230000004888 barrier function Effects 0.000 title description 4
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 94
- -1 rare earth silicate Chemical class 0.000 claims abstract description 78
- 229910052878 cordierite Inorganic materials 0.000 claims abstract description 76
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 claims abstract description 76
- 239000000758 substrate Substances 0.000 claims abstract description 60
- 229910052581 Si3N4 Inorganic materials 0.000 claims abstract description 13
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims abstract description 13
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910010271 silicon carbide Inorganic materials 0.000 claims abstract description 11
- 229910052727 yttrium Inorganic materials 0.000 claims description 13
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 13
- 239000000919 ceramic Substances 0.000 claims description 11
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 10
- 229910052710 silicon Inorganic materials 0.000 claims description 10
- 239000010703 silicon Substances 0.000 claims description 10
- 229910052769 Ytterbium Inorganic materials 0.000 claims description 9
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 claims description 9
- 229910052684 Cerium Inorganic materials 0.000 claims description 8
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 8
- 229910052691 Erbium Inorganic materials 0.000 claims description 8
- 229910052765 Lutetium Inorganic materials 0.000 claims description 8
- 229910052772 Samarium Inorganic materials 0.000 claims description 8
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 8
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 claims description 8
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 claims description 8
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 claims description 8
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 claims description 8
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims description 7
- 239000000203 mixture Substances 0.000 abstract description 24
- 239000010410 layer Substances 0.000 description 99
- 239000000843 powder Substances 0.000 description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 9
- 239000002002 slurry Substances 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 230000004580 weight loss Effects 0.000 description 7
- 239000007789 gas Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 5
- 238000005245 sintering Methods 0.000 description 5
- 238000005229 chemical vapour deposition Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000002485 combustion reaction Methods 0.000 description 3
- 238000003618 dip coating Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000002202 Polyethylene glycol Substances 0.000 description 2
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 2
- 239000003570 air Substances 0.000 description 2
- 230000004075 alteration Effects 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000008199 coating composition Substances 0.000 description 2
- 238000000280 densification Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000011229 interlayer Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 229920000553 poly(phenylenevinylene) Polymers 0.000 description 2
- 229920001223 polyethylene glycol Polymers 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000006057 Non-nutritive feed additive Substances 0.000 description 1
- 229910007217 Si(OH)x Inorganic materials 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 1
- SNAAJJQQZSMGQD-UHFFFAOYSA-N aluminum magnesium Chemical group [Mg].[Al] SNAAJJQQZSMGQD-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- LRCFXGAMWKDGLA-UHFFFAOYSA-N dioxosilane;hydrate Chemical compound O.O=[Si]=O LRCFXGAMWKDGLA-UHFFFAOYSA-N 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000007580 dry-mixing Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000013213 extrapolation Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000001513 hot isostatic pressing Methods 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- 238000009768 microwave sintering Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- 229960004029 silicic acid Drugs 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
- C04B41/52—Multiple coating or impregnating multiple coating or impregnating with the same composition or with compositions only differing in the concentration of the constituents, is classified as single coating or impregnation
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
- C04B41/81—Coating or impregnation
- C04B41/89—Coating or impregnation for obtaining at least two superposed coatings having different compositions
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- F05B2230/00—Manufacture
- F05B2230/90—Coating; Surface treatment
Definitions
- the present invention is directed to a multilayer system for protecting components exposed to environmental and thermal conditions and, particularly, barrier coating for components for heat engines, such as gas turbine engines.
- Ceramics are commonly used in high temperature structural applications such as gas turbine engines, internal combustion engines, and heat exchangers. In particular, silicon containing ceramics are often used in such extreme conditions, but are prone to rapid recession in combustion environments in which water vapor is typically produced. Temperature capability of structural components exposed to environmental and thermal conditions limit efficiency and emissions of gas turbine engines. Components used in gas turbine engines, which may be exposed to temperatures in excess of 1000 0 C, should be strong and resist corrosion due to exposure to air streams as well as abrasion and shock resistance against collision with fine particles.
- components such as turbine rotors, turbine blades, nozzles, combustors, scrolls, nozzle supports, seal rings, spring rings, diffiisers, ducts and shrouds in the engine hot section are susceptible to coating loss from spallation or erosion.
- Silicon containing ceramics typically form a slow forming silica (SiO 2 ) scale in clean oxidizing environments. However, water vapor, molten salts, or a reducing atmosphere present in the environment may react with the silica scale to form liquid silicates. Oxygen may then diffuse through the liquid silicate and oxidize the ceramic substrate. High water vapor levels result in the formation of hydrated silica species (Si(OH)x) and subsequent evaporation of the silica scale. Oxidizing and reducing gases in complex combustion atmospheres generate SiO(g) directly or SiO 2 which is reduced to SiO(g). To reduce the rate of recession, ceramics may be coated as, for example, disclosed in U.S. Patent No. 6,759,151 issued to Lee; U.S. Patent No. 6,682,821 issued to Fukudome et al.; and U.S. Patent No. 6,645,649 issued to Tanaka et al.
- the present invention generally relates to a multilayer system for protecting components.
- the present invention provides, in one embodiment a multilayer article comprising a substrate, a first layer overlying at least one surface of the substrate, and a second layer overlying the first layer.
- the first layer comprises a first rare earth silicate and cordierite
- the second layer comprises a second rare earth silicate and up to about 12 percent, by weight, of cordierite.
- the present invention provides a multilayer article comprising a substrate, a first coating adjacent at least one surface of the substrate, and a second coating adjacent the first coating.
- the first coating consists essentially of a first rare earth silicate and cordierite, and the second coating comprises a second rare earth silicate.
- FIG. Ia is a micrograph of one sample of the present invention.
- FIG. Ib is a micrograph of another sample of the present invention.
- FIG. 2 is a graph showing recession rates of various compositions of the present invention.
- the present invention relates generally to a multilayer article suitable for service in environmental and thermal conditions.
- the article may be exposed to humid conditions.
- the article may be exposed to high temperature conditions, such as 1000 0 C or higher.
- the article may be exposed to high velocity conditions of 5 m/sec to 50 m/sec.
- the article may be exposed to any two or more conditions of humidity, high temperature, and high velocity.
- severe environmental conditions includes a gas jet turbine environment with humid, high velocity (5 m/sec to 50 m/sec), and high temperature (greater than about 1000 0 C) conditions.
- Embodiments of the present invention may generally comprise an article formed of a substrate.
- the substrate may by any material suitable for a particular purpose.
- the material may be suitable for high temperature and/or high pressure structural applications.
- the substrate may be a ceramic or a silicon- containing metal alloy.
- the substrate is a silicon containing ceramic, such as silicon nitride, silicon carbide, silicon oxynitride including silicon aluminum oxynitride, and combinations thereof.
- the substrate may be silicon carbide having a coefficient of thermal expansion (CTE) of about 4.5 x 10" 6 /°C.
- the substrate may be silicon nitride having a CTE of about 3.3 x 10" 6 /°C.
- the substrate may comprise at least about 50 percent, by weight, of silicon nitride.
- the substrate consists essentially of silicon nitride.
- the substrate may be partially or entirely overlaid with two or more layers of a mixture comprising cordierite and a rare earth silicate.
- the mineral cordierite is magnesium aluminum silicate or Mg 2 Al 4 Si 5 O j 8 and has a CTE of about 2.48 x 10" 6 /°C.
- references to cordierite or any other material such as a rare earth silicate is meant to include the pure form of the material as well as forms including impurities.
- An amount of cordierite in each layer may decrease as that layer is further removed from the substrate. Accordingly, the amount of the rare earth silicate may increase in each layer as that layer is further removed from the substrate.
- the final outer layer may, but need not, comprise cordierite.
- the amount of cordierite in each layer may increase as that layer is further removed from the substrate. Accordingly, the amount of the rare earth silicate may decrease in each layer as that layer is further removed from the substrate.
- cordierite may be layered on one or more surfaces of the substrate forming a first layer.
- the first layer may cover all surfaces of the substrate.
- the first layer may be a coating disposed on the surface of the substrate.
- the first layer of cordierite overlaying the substrate may be a mixture of cordierite and a rare earth silicate.
- the mixture of rare earth silicate and the ratio of the rare earth silicate to cordierite may be selected to provide a composition having a CTE similar to that of the substrate.
- the mixture of rare earth silicate and the ratio of the rare earth silicate to cordierite may be selected to provide an intermediate CTE, between that of the substrate and that of any additional layers.
- the rare earth silicate may be any OfRE 2 Si 2 O 7 , RE 2 SiO 5 , and combinations thereof, where RE is a rare earth element.
- the rare earth element may be selected from any rare earth element suitable for a particular purpose. In one embodiment, the rare earth element may be any one of yttrium (Y), ytterbium (Yb), erbium (Er), samarium (Sm), dysprosium (Dy), lutetium (Lu), and cerium (Ce).
- the rare earth element is Yttrium.
- the first layer consists essentially of cordierite and the rare earth silicate.
- the phrase "consisting essentially of is used to list major components of a mixture, and is not meant to exclude impurities or trace levels of components which do not affect one or more characteristics of the mixture.
- the first layer adjacent the substrate may have a CTE similar to that of a CTE of the substrate. In one embodiment, the first layer may have a CTE ranging between and including about 3.2 x 10" 6 / o C to about 4.0 x 10- 6 /°C.
- the first layer may have a CTE ranging between and including about 3.6 x 10" 6 /°C to about 4.0 x 10" 6 /°C. In yet another embodiment, the CTE of the first layer may range between and including about 3.8 x 10" 6 / o C.
- the first layer may comprise at least about 6 percent, by weight of cordierite. In another embodiment, the first layer may comprise between and including about 6 percent, by weight, and about 43 percent, by weight, of cordierite. In yet another embodiment, the first layer may comprise between and including about 12 percent, by weight of cordierite and about 25 percent, by weight, of cordierite. In one embodiment, the first layer may comprise about 12 percent, by weight, of cordierite. In another embodiment, the first layer may comprise about 25 percent, by weight, of cordierite.
- the first layer may comprise at least about 50 percent, by weight, of the rare earth silicate. In another embodiment, the first layer may comprise between and including about 57 percent, by weight, and about 94 percent, by weight, of the rare earth silicate. In yet another embodiment, the first layer may comprise between and including about 57 percent, by weight, and about 88 percent, by weight, of the rare earth silicate. In another embodiment, the first layer may comprise about 75 percent, by weight, of the rare earth silicate. In yet another embodiment, the first layer may consist essentially of the rare earth silicate and cordierite. A second layer comprising a rare earth silicate may overlay a portion or the entire first layer and may form a coating disposed on the first layer. The second layer may, but need not, comprise cordierite.
- the rare earth silicate in the second layer may be any rare earth silicate suitable to withstand a severe environment.
- the rare earth silicate may be any OfRE 2 Si 2 O 7 , RE 2 SiO 5 , and combinations thereof, where RE is a rare earth element.
- the rare earth element may be selected from any rare earth element suitable for a particular purpose, In one embodiment, the rare earth element may be any one of Yttrium (Y), ytterbium (YB), Erbium (Er), Samarium (Sm), Dysprosium (Dy), Lutetium (Lu) and Cerium (Ce). In one embodiment, the rare earth element is Yttrium.
- the rare earth silicate in the second layer may, but need not, be the same rare earth silicate present in the first layer.
- the second layer may comprise up to and including about 12 percent, by weight, cordierite. In another, the second layer may comprise up to and including about 6 percent, by weight, of cordierite. In yet another embodiment, the second layer may comprise up to and including about 3 percent, by weight, of cordierite. In yet another embodiment, the second layer may not include any appreciable amount of cordierite. As used herein, the phrase "appreciable amount" is defined as an amount of cordierite that effects one or more characteristics of the rare earth silicate, and is not meant to include trace amounts of cordierite. In one embodiment, the second layer may comprise up to and including about 100 percent, by weight, of the rare earth silicate.
- the second layer may comprise up to and including about 97 percent, by weight, of the rare earth silicate. In another embodiment, the second layer may comprise up to and including about 94 percent, by weight, of the rare earth silicate. In yet another embodiment, the second layer may comprise up to and including about 88 percent, by weight, of the rare earth silicate.
- the second layer may have a CTE between and including about 3.6 x 10" 6 /°C to about 4.1 x 10" 6 /°C. In another embodiment, the second layer may have a CTE between and including about 3.9 x 10" 6 / o C to about 4.1 x 10- 6 /°C. In yet another embodiment, the second layer may have a CTE of about 4.0 x 10"6/ 0 C. In one embodiment, the percent, by weight, of cordierite present in the second layer may be less than the percent, by weight, of the cordierite present in the first layer.
- the presence of cordierite in the first layer may improve the bond between the second layer and the substrate, by providing a layer having a CTE greater than that of the substrate, but less than that of the second layer.
- the presence of cordierite in the second layer may perhaps strengthen the bond of the second layer to the first layer.
- presence of cordierite in the second layer which may be directly exposed to severe environments, may also adversely affect the recession rate of the second layer. In applications in which it is desirable to include cordierite in the second layer, a trade off in inter-layer bond strength and recession rate may result.
- Mixtures of cordierite and the rare earth silicate may be prepared by dry mixing commercially available powders.
- Powdered cordierite may have an average particle size of less than or equal to about 2.6 micron.
- Powdered Yittrium may have an average particle size of less than or equal to about 1 micron. In one embodiment, the powder may have an average particle size of about 0.5 micron.
- Powders may be formed from aggregates milled and screened to produce a desired particle size.
- a sol gel of the powder in tetraethyl ortho silicate (TEOS) may be formed, calcined, and milled to produce the powder or powder mixture of cordierite and the rare earth silicate.
- TEOS tetraethyl ortho silicate
- the first and/or second layers may be formed on the substrate by known methods, such as dip, pack cementation, chemical vapor deposition (CVD), plasma vapor deposition (PVD), slurry spray coating.
- CVD chemical vapor deposition
- PVD plasma vapor deposition
- the article to be coated may be dipped in a slurry containing the rare earth silicate and/or the mixture of the rare earth silicate and cordierite.
- Each of the first and second layers may have a thickness between and including about 2 microns to 100 microns.
- the thickness of the first layer may, but need not, be the same as the thickness of the second layer. In one embodiment, the thickness of the first layer is less than the thickness of the second layer. In another embodiment, the thickness of the first layer is greater than the thickness of the second layer. In one embodiment, the combined thickness of the first and the second layers may range between and including about 5 microns and about 200 microns. In another embodiment, the first and second layers may have a thickness between and including about 20 microns to about 50 microns. In another embodiment, the combined thickness of the first and second layers may range between and including about 50 and about 200 microns.
- Powders of rare earth silicates and mixtures of rare earth silicates and cordierite may be formed into slurries for dip coating.
- Slurries for dip coating may be water, solvent or polymer precursor based and may include processing aids and binders, such as polyethylene glycol (PEG) and polyphenylene vinylene (PPV).
- Coatings applied by the dipping process may be further densif ⁇ ed by known methods, such as reactive sintering, microwave sintering, and/or hot isostatic pressing (HIP).
- a substrate may be dipped in a water, solvent or polymer based slurry containing the mixture of the rare earth silicate and cordierite, and dried.
- the coated substrate may be sintered between and including about 1,200 0 C and about 1,400 0 C, and then cooled.
- the coated substrate may be heated and/or cooled at a rate of about 10 0 C to about 15 0 C per minute to or from the sintering temperature.
- the layered substrate is sintered at a temperature of about 1,325 0 C.
- the substrate may be maintained at the sintering temperature for about 1 hour to about 3 hours. Sintering may occur in a reducing environment.
- the layer may be sintered in Argon, oxygen or air.
- the coated substrate may then be dipped in a slurry containing the rare earth silicate or the mixture of the rare earth silicate and cordierite, dried, and sintered.
- cordierite may reduce undesirable interface stresses at the surface of the substrate and/or at the interface with the second layer.
- Cordierite may also act as a liquid phase sintering aid and may allow the coating to plastically deform during densification thereby relieving stresses and reducing the likelihood of crack formation due to shrinkage during densification.
- FIGS. Ia and Ib are micrographs showing embodiments of the present invention in which silicon nitride is coated with a first layer containing cordierite and Y 2 Si 2 O 7 and a second layer OfY 2 Si 2 O 7 .
- Test coupons of silicon nitride of about 30 mm x 12 mm x 5 mm were dip coated using one of four aqueous slurries of powdered compositions 1-4. - Si -
- Each slurry contained about 30 volume percent of the respective powered sample 1-4 of Y 2 Si 2 O 7 and cordierite, about 1 weight percent of Darvan 821, a surfactant available from R. T. Vanderbilt Company, Inc., Norwalk, CT, and the remaining volume percent of water.
- the viscosity of the slurries ranged from about 50 cps to about 100 cps.
- the test coupons were sintered at about l,300°C.
- Each sample was then dip coated to form a second layer OfY 2 Si 2 O 7 , dried and sintered again at about l,300°C.
- the coating formed are free from cracks, indicating that the intermediate layer may have reduced potential stresses between the silicon nitride substrate and the Y 2 Si 2 O 7 outer layer.
- Hot pressed monoliths of four potential coating compositions listed in Table I, were prepared.
- the coating composition powders were mixed in an aqueous solution and dried to form a powder.
- the powder was used to form 3 in. by 3 in. plates by hot pressing at about 1,300 0 C to about l,500°C for one hour in nitrogen at 3.3 ksi.
- the plates were machined into test coupons and used to evaluate material properties such as microstructure, density, CTE and environmental stability.
- Sample 1 had a weight loss of about 0.06 percent
- Sample 2 had a weight loss of about 0.25 percent
- Sample 3 had a weight loss of about 0.12 percent
- Sample 4 had a weight loss of about 0.56 percent after an exposure of 2,500 hours.
- the quartz sample had a weight loss of about 3 percent after only 1,500 hours
- silicon carbide had a weight loss of about 0.57 percent after an exposure of less than 1000 hours.
- an increase in percent, by weight, of cordierite increased the percent weight loss of the sample.
- Extrapolation of the test data in FIG. 2 to 10,000 hours resulted in a recession rate of Sample 1 of 4 microns, Sample 2 of 12 microns, Sample 3 of 9 microns, Sample 4 of 32 microns, and chemical vapor deposition of silicon carbide of 157 microns.
- any of Samples 2-4 may be used as a first layer and any of Samples 1-3 may be used as a second layer which may be exposed to severe environmental conditions.
- the substrate may be coated with a first layer having a composition of Sample 4 and then with a second layer having a composition of any of Samples 1-3.
- the substrate may be coated with a first layer having a composition of Sample 2, and then with a second layer having a composition of any of Samples 1 and 3.
- the substrate may be coated with a first layer having a composition of Sample 3 and a second layer having a composition of any of Samples 1-2 and 4.
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Abstract
The present invention relates generally to a multi-layered article suitable for services in severe environments. The article may be formed of a substrate, such as silicon carbide and/or silicon nitride. The substrate may have a first layer of a mixture of a rare earth silicate and Cordierite. The substrate may also have a second layer of a rare earth silicate or a mixture of a rare earth silicate and cordierite.
Description
ENVIRONMENTAL BARRIER COATING
FEDERALLY SPONSORED RESEARCH The Government of the United States of America has rights in this invention pursuant to Subcontract No. 44000017386 awarded by or for the U.S. Department of Energy under Prime Contract No. DE-AC05-00OR22725.
RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional
Application Serial No. 60/899,306 filed on February 2, 2007, entitled "ENVIRONMENTAL BARRIER COATING," which is herein incorporated by reference in its entirety for all purposes.
BACKGROUND OF INVENTION
1. Field of Invention
The present invention is directed to a multilayer system for protecting components exposed to environmental and thermal conditions and, particularly, barrier coating for components for heat engines, such as gas turbine engines.
2. Background
Ceramics are commonly used in high temperature structural applications such as gas turbine engines, internal combustion engines, and heat exchangers. In particular, silicon containing ceramics are often used in such extreme conditions, but are prone to rapid recession in combustion environments in which water vapor is typically produced. Temperature capability of structural components exposed to environmental and thermal conditions limit efficiency and emissions of gas turbine engines. Components used in gas turbine engines, which may be exposed to temperatures in excess of 1000 0C, should be strong and resist corrosion due to exposure to air streams as well as abrasion and shock resistance against collision with fine particles. In particular, components such as
turbine rotors, turbine blades, nozzles, combustors, scrolls, nozzle supports, seal rings, spring rings, diffiisers, ducts and shrouds in the engine hot section are susceptible to coating loss from spallation or erosion.
Silicon containing ceramics typically form a slow forming silica (SiO2) scale in clean oxidizing environments. However, water vapor, molten salts, or a reducing atmosphere present in the environment may react with the silica scale to form liquid silicates. Oxygen may then diffuse through the liquid silicate and oxidize the ceramic substrate. High water vapor levels result in the formation of hydrated silica species (Si(OH)x) and subsequent evaporation of the silica scale. Oxidizing and reducing gases in complex combustion atmospheres generate SiO(g) directly or SiO2 which is reduced to SiO(g). To reduce the rate of recession, ceramics may be coated as, for example, disclosed in U.S. Patent No. 6,759,151 issued to Lee; U.S. Patent No. 6,682,821 issued to Fukudome et al.; and U.S. Patent No. 6,645,649 issued to Tanaka et al.
SUMMARY OF INVENTION
The present invention generally relates to a multilayer system for protecting components.
The present invention provides, in one embodiment a multilayer article comprising a substrate, a first layer overlying at least one surface of the substrate, and a second layer overlying the first layer. The first layer comprises a first rare earth silicate and cordierite, and the second layer comprises a second rare earth silicate and up to about 12 percent, by weight, of cordierite.
In another embodiment, the present invention provides a multilayer article comprising a substrate, a first coating adjacent at least one surface of the substrate, and a second coating adjacent the first coating. The first coating consists essentially of a first rare earth silicate and cordierite, and the second coating comprises a second rare earth silicate.
BRIEF DESCRIPTION OF DRAWINGS In the drawings:
FIG. Ia is a micrograph of one sample of the present invention.
FIG. Ib is a micrograph of another sample of the present invention. FIG. 2 is a graph showing recession rates of various compositions of the present invention.
Other advantages, novel features and objects of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.
DETAILED DESCRIPTION This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having," "containing," "involving," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
In accordance with one or more embodiments, the present invention relates generally to a multilayer article suitable for service in environmental and thermal conditions. For example, the article may be exposed to humid conditions. Alternatively, the article may be exposed to high temperature conditions, such as 1000 0C or higher. During service, the article may be exposed to high velocity conditions of 5 m/sec to 50 m/sec. In one embodiment the article may be exposed to any two or more conditions of humidity, high temperature, and high velocity. One example of severe environmental conditions includes a gas jet turbine environment with humid, high velocity (5 m/sec to 50 m/sec), and high temperature (greater than about 10000C) conditions.
Embodiments of the present invention may generally comprise an article formed of a substrate. The substrate may by any material suitable for a particular purpose. In one embodiment, the material may be suitable for high temperature and/or high pressure structural applications. For example, the substrate may be a ceramic or a silicon- containing metal alloy. In one embodiment, the substrate is a silicon containing ceramic, such as silicon nitride, silicon carbide, silicon oxynitride including silicon aluminum
oxynitride, and combinations thereof. In one embodiment, the substrate may be silicon carbide having a coefficient of thermal expansion (CTE) of about 4.5 x 10"6/°C. In another embodiment, the substrate may be silicon nitride having a CTE of about 3.3 x 10" 6/°C. In another embodiment, the substrate may comprise at least about 50 percent, by weight, of silicon nitride. In another embodiment, the substrate consists essentially of silicon nitride.
The substrate may be partially or entirely overlaid with two or more layers of a mixture comprising cordierite and a rare earth silicate. As is known in the art, the mineral cordierite is magnesium aluminum silicate or Mg2Al4Si5Oj 8 and has a CTE of about 2.48 x 10"6/°C. As used herein, references to cordierite or any other material such as a rare earth silicate is meant to include the pure form of the material as well as forms including impurities. An amount of cordierite in each layer may decrease as that layer is further removed from the substrate. Accordingly, the amount of the rare earth silicate may increase in each layer as that layer is further removed from the substrate. The final outer layer may, but need not, comprise cordierite. Alternatively, the amount of cordierite in each layer may increase as that layer is further removed from the substrate. Accordingly, the amount of the rare earth silicate may decrease in each layer as that layer is further removed from the substrate.
In one embodiment, cordierite may be layered on one or more surfaces of the substrate forming a first layer. In one embodiment, the first layer may cover all surfaces of the substrate. In another embodiment, the first layer may be a coating disposed on the surface of the substrate. The first layer of cordierite overlaying the substrate may be a mixture of cordierite and a rare earth silicate. In one embodiment, the mixture of rare earth silicate and the ratio of the rare earth silicate to cordierite may be selected to provide a composition having a CTE similar to that of the substrate. In another embodiment, the mixture of rare earth silicate and the ratio of the rare earth silicate to cordierite may be selected to provide an intermediate CTE, between that of the substrate and that of any additional layers. Providing a first layer having an intermediate CTE or a CTE similar to that of the substrate may reduce or eliminate inter layer stresses between the outer layer and the substrate during formation of the layer or in service operation of the article, which may lead to premature failure.
The rare earth silicate may be any OfRE2Si2O7, RE2SiO5, and combinations thereof, where RE is a rare earth element. The rare earth element may be selected from any rare earth element suitable for a particular purpose. In one embodiment, the rare earth element may be any one of yttrium (Y), ytterbium (Yb), erbium (Er), samarium (Sm), dysprosium (Dy), lutetium (Lu), and cerium (Ce). In one embodiment, the rare earth element is Yttrium. In yet another embodiment, the first layer consists essentially of cordierite and the rare earth silicate. As used herein, the phrase "consisting essentially of is used to list major components of a mixture, and is not meant to exclude impurities or trace levels of components which do not affect one or more characteristics of the mixture. The first layer adjacent the substrate may have a CTE similar to that of a CTE of the substrate. In one embodiment, the first layer may have a CTE ranging between and including about 3.2 x 10"6/oC to about 4.0 x 10-6/°C. In another embodiment, the first layer may have a CTE ranging between and including about 3.6 x 10"6/°C to about 4.0 x 10"6/°C. In yet another embodiment, the CTE of the first layer may range between and including about 3.8 x 10"6/oC.
In one embodiment, the first layer may comprise at least about 6 percent, by weight of cordierite. In another embodiment, the first layer may comprise between and including about 6 percent, by weight, and about 43 percent, by weight, of cordierite. In yet another embodiment, the first layer may comprise between and including about 12 percent, by weight of cordierite and about 25 percent, by weight, of cordierite. In one embodiment, the first layer may comprise about 12 percent, by weight, of cordierite. In another embodiment, the first layer may comprise about 25 percent, by weight, of cordierite.
In one embodiment, the first layer may comprise at least about 50 percent, by weight, of the rare earth silicate. In another embodiment, the first layer may comprise between and including about 57 percent, by weight, and about 94 percent, by weight, of the rare earth silicate. In yet another embodiment, the first layer may comprise between and including about 57 percent, by weight, and about 88 percent, by weight, of the rare earth silicate. In another embodiment, the first layer may comprise about 75 percent, by weight, of the rare earth silicate. In yet another embodiment, the first layer may consist essentially of the rare earth silicate and cordierite.
A second layer comprising a rare earth silicate may overlay a portion or the entire first layer and may form a coating disposed on the first layer. The second layer may, but need not, comprise cordierite. The rare earth silicate in the second layer may be any rare earth silicate suitable to withstand a severe environment. The rare earth silicate may be any OfRE2Si2O7, RE2SiO5, and combinations thereof, where RE is a rare earth element. The rare earth element may be selected from any rare earth element suitable for a particular purpose, In one embodiment, the rare earth element may be any one of Yttrium (Y), ytterbium (YB), Erbium (Er), Samarium (Sm), Dysprosium (Dy), Lutetium (Lu) and Cerium (Ce). In one embodiment, the rare earth element is Yttrium. The rare earth silicate in the second layer may, but need not, be the same rare earth silicate present in the first layer.
In one embodiment, the second layer may comprise up to and including about 12 percent, by weight, cordierite. In another, the second layer may comprise up to and including about 6 percent, by weight, of cordierite. In yet another embodiment, the second layer may comprise up to and including about 3 percent, by weight, of cordierite. In yet another embodiment, the second layer may not include any appreciable amount of cordierite. As used herein, the phrase "appreciable amount" is defined as an amount of cordierite that effects one or more characteristics of the rare earth silicate, and is not meant to include trace amounts of cordierite. In one embodiment, the second layer may comprise up to and including about 100 percent, by weight, of the rare earth silicate. In another embodiment, the second layer may comprise up to and including about 97 percent, by weight, of the rare earth silicate. In another embodiment, the second layer may comprise up to and including about 94 percent, by weight, of the rare earth silicate. In yet another embodiment, the second layer may comprise up to and including about 88 percent, by weight, of the rare earth silicate.
The second layer may have a CTE between and including about 3.6 x 10"6/°C to about 4.1 x 10"6/°C. In another embodiment, the second layer may have a CTE between and including about 3.9 x 10"6/oC to about 4.1 x 10-6/°C. In yet another embodiment, the second layer may have a CTE of about 4.0 x 10"6/0C. In one embodiment, the percent, by weight, of cordierite present in the second layer may be less than the percent, by weight, of the cordierite present in the first layer. Without being bound by any particular theory, the presence of cordierite in the first layer
may improve the bond between the second layer and the substrate, by providing a layer having a CTE greater than that of the substrate, but less than that of the second layer. The presence of cordierite in the second layer may perhaps strengthen the bond of the second layer to the first layer. However, presence of cordierite in the second layer, which may be directly exposed to severe environments, may also adversely affect the recession rate of the second layer. In applications in which it is desirable to include cordierite in the second layer, a trade off in inter-layer bond strength and recession rate may result.
Mixtures of cordierite and the rare earth silicate may be prepared by dry mixing commercially available powders. Powdered cordierite may have an average particle size of less than or equal to about 2.6 micron. Powdered Yittrium may have an average particle size of less than or equal to about 1 micron. In one embodiment, the powder may have an average particle size of about 0.5 micron. Powders may be formed from aggregates milled and screened to produce a desired particle size. A sol gel of the powder in tetraethyl ortho silicate (TEOS) may be formed, calcined, and milled to produce the powder or powder mixture of cordierite and the rare earth silicate.
The first and/or second layers may be formed on the substrate by known methods, such as dip, pack cementation, chemical vapor deposition (CVD), plasma vapor deposition (PVD), slurry spray coating. In one embodiment, the article to be coated may be dipped in a slurry containing the rare earth silicate and/or the mixture of the rare earth silicate and cordierite.
Each of the first and second layers may have a thickness between and including about 2 microns to 100 microns. The thickness of the first layer may, but need not, be the same as the thickness of the second layer. In one embodiment, the thickness of the first layer is less than the thickness of the second layer. In another embodiment, the thickness of the first layer is greater than the thickness of the second layer. In one embodiment, the combined thickness of the first and the second layers may range between and including about 5 microns and about 200 microns. In another embodiment, the first and second layers may have a thickness between and including about 20 microns to about 50 microns. In another embodiment, the combined thickness of the first and second layers may range between and including about 50 and about 200 microns.
Powders of rare earth silicates and mixtures of rare earth silicates and cordierite may be formed into slurries for dip coating. Slurries for dip coating may be water, solvent
or polymer precursor based and may include processing aids and binders, such as polyethylene glycol (PEG) and polyphenylene vinylene (PPV). Coatings applied by the dipping process, may be further densifϊed by known methods, such as reactive sintering, microwave sintering, and/or hot isostatic pressing (HIP). In one embodiment, a substrate may be dipped in a water, solvent or polymer based slurry containing the mixture of the rare earth silicate and cordierite, and dried. The coated substrate may be sintered between and including about 1,200 0C and about 1,400 0C, and then cooled. In one embodiment, the coated substrate may be heated and/or cooled at a rate of about 10 0C to about 15 0C per minute to or from the sintering temperature. In one embodiment, the layered substrate is sintered at a temperature of about 1,325 0C. The substrate may be maintained at the sintering temperature for about 1 hour to about 3 hours. Sintering may occur in a reducing environment. In one embodiment, the layer may be sintered in Argon, oxygen or air. The coated substrate may then be dipped in a slurry containing the rare earth silicate or the mixture of the rare earth silicate and cordierite, dried, and sintered.
Without being bound by any particular theory, the presence of cordierite in the first layer may reduce undesirable interface stresses at the surface of the substrate and/or at the interface with the second layer. Cordierite may also act as a liquid phase sintering aid and may allow the coating to plastically deform during densification thereby relieving stresses and reducing the likelihood of crack formation due to shrinkage during densification.
EXAMPLES
The invention may be further understood with reference to the following examples, which are intended to serve as an illustration only, and not as limitations of the present invention as defined in the claims herein.
EXAMPLE I
FIGS. Ia and Ib are micrographs showing embodiments of the present invention in which silicon nitride is coated with a first layer containing cordierite and Y2Si2O7 and a second layer OfY2Si2O7. Test coupons of silicon nitride of about 30 mm x 12 mm x 5 mm were dip coated using one of four aqueous slurries of powdered compositions 1-4.
- Si - Each slurry contained about 30 volume percent of the respective powered sample 1-4 of Y2Si2O7 and cordierite, about 1 weight percent of Darvan 821, a surfactant available from R. T. Vanderbilt Company, Inc., Norwalk, CT, and the remaining volume percent of water. The viscosity of the slurries ranged from about 50 cps to about 100 cps. After dip coating, the test coupons were sintered at about l,300°C. Each sample was then dip coated to form a second layer OfY2Si2O7, dried and sintered again at about l,300°C. As seem in Figs. Ia and Ib, the coating formed are free from cracks, indicating that the intermediate layer may have reduced potential stresses between the silicon nitride substrate and the Y2Si2O7 outer layer.
EXAMPLE II
Hot pressed monoliths of four potential coating compositions, listed in Table I, were prepared. The coating composition powders were mixed in an aqueous solution and dried to form a powder. The powder was used to form 3 in. by 3 in. plates by hot pressing at about 1,3000C to about l,500°C for one hour in nitrogen at 3.3 ksi. The plates were machined into test coupons and used to evaluate material properties such as microstructure, density, CTE and environmental stability.
Table I
As can be seen from Table I, an increase in percent, by weight, of cordierite lowered the CTE of the sample when compared to 100 percent, by weight, Y2Si2O7, allowing compositions of to be tailored to a desired CTE. High Pressure Keiser Rig Testing of Samples 1-4 was performed with results shown in FIG. 2. The tests were performed at 1250 0C, 18 atm water vapor, 20 atm total
pressure, and at a low flow of 33 10"4 m/s for a total of 2,500 hours. For comparison, samples of quartz, and chemical vapor deposition silicon carbide were also tested and results reported in FIG. 2. As seen in Fig. 2, Sample 1 had a weight loss of about 0.06 percent, Sample 2 had a weight loss of about 0.25 percent, Sample 3 had a weight loss of about 0.12 percent and Sample 4 had a weight loss of about 0.56 percent after an exposure of 2,500 hours. In comparison, the quartz sample had a weight loss of about 3 percent after only 1,500 hours and silicon carbide had a weight loss of about 0.57 percent after an exposure of less than 1000 hours. As seen in FIG. 2, an increase in percent, by weight, of cordierite increased the percent weight loss of the sample. Extrapolation of the test data in FIG. 2 to 10,000 hours resulted in a recession rate of Sample 1 of 4 microns, Sample 2 of 12 microns, Sample 3 of 9 microns, Sample 4 of 32 microns, and chemical vapor deposition of silicon carbide of 157 microns.
The results shown in FIG. 2 indicate that any of Samples 2-4 may be used as a first layer and any of Samples 1-3 may be used as a second layer which may be exposed to severe environmental conditions. For example, in one embodiment, the substrate may be coated with a first layer having a composition of Sample 4 and then with a second layer having a composition of any of Samples 1-3. Likewise, the substrate may be coated with a first layer having a composition of Sample 2, and then with a second layer having a composition of any of Samples 1 and 3. In another embodiment, the substrate may be coated with a first layer having a composition of Sample 3 and a second layer having a composition of any of Samples 1-2 and 4.
Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. For example, other layers in addition to the first and second layers noted above may be applied to the substrate, and may provide a sequential reduction or increase in the amount of cordierite present in each layer as the layer becomes further removed from the substrate. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.
What is claimed is:
Claims
1. A multilayer article comprising: a substrate; a first layer overlying at least one surface of the substrate, the first layer comprising a first rare earth silicate and cordierite; and a second layer overlying the first layer, the second layer comprising a second rare earth silicate and up to about 12 percent, by weight, of cordierite.
2. The article of claim 1, wherein the substrate comprises a silicon containing ceramic.
3. The article of claim 2, wherein the silicon containing ceramic is selected from the group consisting of silicon nitride, silicon carbide, silicon oxinitride, and combinations thereof.
4. The article of claim 1, wherein the first layer is disposed on a surface of the substrate.
5. The article of claim 4, wherein the second layer is disposed on a surface of the first layer.
6. The article of claim 1, wherein the first layer comprises greater than about 50 percent, by weight, of the first rare earth silicate.
7. The article of claim 6, wherein the first layer comprises a balance of cordierite.
8. The article of claim 6, wherein the first layer comprises from about 57 percent, by weight, to about 94 percent, by weight, of the first rare earth silicate.
9. The article of claim 8, wherein the first layer comprises from about 57 percent, by weight, to about 88 percent, by weight, of the first rare earth silicate.
10. The article of claim 8, wherein the first layer comprises a balance of cordierite.
11. The article of claim 10, wherein the first layer comprises greater than about 6 percent, by weight, cordierite.
12. The article of claim 11, wherein the first layer comprises from about 6 percent, by weight, to about 43 percent, by weight, of cordierite.
13. The article of claim 12, wherein the first layer comprises from about 12 percent, by weight, to about 25 percent, by weight, of cordierite.
14. The article of claim 13, wherein the first layer comprises about 12 percent, by weight, of cordierite.
15. The article of claim 13, wherein the first layer comprises about 25 percent, by weight, of cordierite.
16. The article of claim 1, wherein the second layer comprises up to about 6 percent, by weight, cordierite.
17. The article of claim 16, wherein the second layer comprises up to about 3 percent, by weight, cordierite.
18. The article of claim 17, wherein the second layer comprises about 97 percent, by weight, of the second rare earth silicate.
19. The article of claim 1, wherein the first rare earth silicate is a silicate selected from the group consisting OfRE2SiOs, RE2Si2O7, and combinations thereof, wherein
RE is a rare earth element selected from the group consisting of yttrium, ytterbium, erbium, samarium, dysprosium, lutetium, and cerium.
20. The article of claim 19, wherein the first rare earth silicate is RE2Si2O7.
21. The article of claim 20, wherein the RE is yttrium.
22. The article of claim 19, wherein the second rare earth silicate is a silicate selected from the group consisting OfRE2SiO5, RE2Si2O7, and combinations thereof, wherein
RE is a rare earth element selected from the group consisting of yttrium, ytterbium, erbium, samarium, dysprosium, lutetium, and cerium.
23. The article of claim 22, wherein the first rare earth silicate and the second rare earth silicate are RE2Si2O7.
24. The article of claim 22, wherein the first rare earth silicate and the second rare earth silicate are Y2Si2O5.
25. The article of claim 2, wherein the substrate comprises at least 50 % silicon nitride.
26. The article of claim 25, wherein the substrate consists essentially of silicon nitride.
27. The article of claim 25, wherein the first rare earth silicate is a silicate selected from the group consisting OfRE2SiO5, RE2Si2O7, and combinations thereof, wherein RE is a rare earth element selected from the group consisting of yttrium, ytterbium, erbium, samarium, dysprosium, lutetium, and cerium.
28. The article of claim 27, wherein the second rare earth silicate is a silicate selected from the group consisting OfRE2SiO5, RE2Si2O7, and combinations thereof, wherein RE is a rare earth element selected from the group consisting of yttrium, ytterbium, erbium, samarium, dysprosium, lutetium, and cerium.
29. The article of claim 28, wherein the first rare earth silicate and the second rare earth silicate are RE2Si2O7.
30. The article of claim 29, wherein the rare earth element is yttrium.
31. The article of claim 30, wherein the first layer comprises greater than about 50 percent, by weight, of the first rare earth silicate.
32. The article of claim 31, wherein the first layer comprises from about 57 percent, by weight, to about 94 percent, by weight, of the first rare earth silicate.
33. The article of claim 32, wherein the first layer comprises greater than about 6 percent, by weight, cordierite.
34. The article of claim 33, wherein the first layer comprises from about 6 percent, by weight, to about 43 percent, by weight, of cordierite.
35. The article of claim 34, wherein the second layer comprises up to about 6 percent, by weight, cordierite.
36. The article of claim 35, wherein the second layer comprises up to about 3 percent, by weight, cordierite.
37. The article of claim 2, wherein the substrate comprises at least 50 percent, by weight, silicon carbide.
38. The article of claim 37, wherein the substrate consists essentially of silicon carbide.
39. The article of claim 1, wherein the second layer consists essentially of the rare earth silicate.
40. The article of claim 1, wherein the first layer has a coefficient of thermal expansion from about 3.2 x 10"6/0C to about 4.0 x 10-6/°C.
41. The article of claim 40, wherein the first layer has a coefficient of thermal expansion from about 3.6 x 10"6/oC to about 4.0 x 10-6/°C.
42. The article of claim 40, wherein the first layer has a coefficient of thermal expansion of about 3.8 x 10-6/°C.
43. The article of claim 41, wherein the second layer has a coefficient of thermal expansion from about 3.6 x 10"6/oC to about 4.1 x 10-6/°C.
44. The article of claim 43, wherein the second layer has a coefficient of thermal expansion from about 3.9 x 10-6/°C to about 4.1 x 10'6/oC.
45. The article of claim 44, wherein the second layer has a coefficient of thermal expansion of about 4.0 x 10-6/°C.
46. A multilayer article comprising: a substrate; a first coating adjacent at least one surface of the substrate, the first coating consisting essentially of a first rare earth silicate and cordierite; and a second coating comprising a second rare earth silicate adjacent the first coating.
47. The article of claim 46, wherein the substrate comprises a silicon containing ceramic.
48. The article of claim 47, wherein the silicon containing ceramic is selected from the group consisting of silicon nitride, silicon carbide, silicon oxinitride, and combinations thereof.
49. The article of claim 46, wherein the second coating further comprises up to about 6 percent, by weight, of cordierite.
50. The article of claim 46, wherein the first layer comprises greater than about 50 percent, by weight, of the first rare earth silicate.
51. The article of claim 50, wherein the first layer comprises from about 57 percent, by weight, to about 94 percent, by weight, of the first rare earth silicate.
52. The article of claim 51, wherein the first layer comprises from about 57 percent, by weight, to about 88 percent, by weight, of the first rare earth silicate.
53. The article of claim 51, wherein the first layer comprises a balance of cordierite.
54. The article of claim 53, wherein the first layer comprises greater than about 6 percent, by weight, cordierite.
55. The article of claim 54, wherein the first layer comprises from about 6 percent, by weight, to about 43 percent, by weight, of cordierite.
56. The article of claim 55, wherein the first layer comprises from about 12 percent, by weight, to about 25 percent, by weight, of cordierite.
57. The article of claim 56, wherein the first layer comprises about 12 percent, by weight, of cordierite.
58. The article of claim 57, wherein the first layer comprises about 25 percent, by weight, of cordierite.
59. The article of claim 46, wherein the second layer comprises up to about 6 percent, by weight, cordierite.
60. The article of claim 59, wherein the second layer comprises up to about 3 percent, by weight, cordierite.
61. The article of claim 59, wherein the second layer comprises about 97 percent, by weight, of the second rare earth silicate.
62. The article of claim 46, wherein the first rare earth silicate is a silicate selected from the group consisting OfRE2SiO5, RE2Si2O7, and combinations thereof, wherein
RE is a rare earth element selected from the group consisting of yttrium, ytterbium, erbium, samarium, dysprosium, lutetium, and cerium.
63. The article of claim 60, wherein the first rare earth silicate is RE2Si2O7.
64. The article of claim 63, wherein the RE is yttrium.
65. The article of claim 63, wherein the second rare earth silicate is a silicate selected from the group consisting OfRE2SiO5, RE2Si2O7, and combinations thereof, wherein RE is a rare earth element selected from the group consisting of yttrium, ytterbium, erbium, samarium, dysprosium, lutetium, and cerium.
- I8 ¬
60. The article of claim 65, wherein the first rare earth silicate and the second rare earth silicate are RE2Si2O7.
67. The article of claim 65, wherein the first rare earth silicate and the second rare earth silicate are Y2SiO5.
68. The article of claim 46, wherein the substrate is silicon nitride.
69. The article of claim 46, wherein the substrate is silicon carbide.
70. The article of claim 46, wherein the second layer consists essentially of the rare earth silicate.
71. The article of claim 46, wherein the first layer has a coefficient of thermal expansion from about 3.2 x 10"6/°C to about 4.0 x 10-6/°C.
72. The article of claim 71, wherein the second layer has a coefficient of thermal expansion from about 3.9 x 10"6/oC to about 4.1 x 10-6/°C.
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PCT/US2008/052783 WO2008109214A2 (en) | 2007-02-02 | 2008-02-01 | Environmental barrier coating |
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US (1) | US8334062B1 (en) |
WO (1) | WO2008109214A2 (en) |
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Also Published As
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US20120315492A1 (en) | 2012-12-13 |
US8334062B1 (en) | 2012-12-18 |
WO2008109214A3 (en) | 2008-11-27 |
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