Abstract: A method is provided for removing an environmental barrier coating from a coated component. The method may include contacting the coated component with an etchant liquid that comprises 5% by volume to 70% by volume of hydrogen fluoride and a solvent. The hydrogen fluoride reacts with silicon oxide in a thermally grown oxide layer positioned between a bondcoat and the environmental barrier coating. The bondcoat is positioned within the coated component between a silicon-containing substrate and the thermally grown oxide layer, and the bondcoat comprises a silicon-containing material.

Abstract: A method is provided for removing a bondcoat and an environmental barrier coating from a coated component. The method may include contacting the coated component with an etchant liquid comprising phosphoric acid, 5% by volume to 70% by volume of hydrogen fluoride, and a solvent. The hydrogen fluoride and the phosphoric acid react with a composition in the bondcoat. The bondcoat is positioned within the coated component between a silicon-containing substrate and the environmental barrier coating, and the bondcoat comprises mullite.

Abstract: Coated components and their methods of formation are provided. The coated component includes: a ceramic matrix composite substrate comprising silicon carbide and having a surface; a bond coat on the surface of the substrate; and an environmental barrier coating on the bond coat. The bond coat includes a plurality of discrete particles dispersed within a matrix phase that includes mullite. The plurality of discrete particles includes an oxygen getter and a transition metal oxide.

Abstract: Environmental barrier coatings including a bondcoat layer including silicon and a rare earth silicate-based hermetic layer and rare earth silicate-based non-hermetic layer are provided. The rare earth silicate-based hermetic layer is deposited on the bondcoat via a thermal spray process and has an elastic modulus ranging from 100 GPa to 180 GPa. The at least one rare earth silicate-based non-hermetic layer is deposited on the rare earth silicate-based hermetic layer and has an elastic modulus ranging from 50 GPa to 100 GPa. Coated gas turbine engine components and methods for coating gas turbine engine components are also provided.

Abstract: A method is provided for removing an environmental barrier coating from a coated component. The method may include contacting the coated component with an etchant liquid that comprises 5% by volume to 70% by volume of hydrogen fluoride and a solvent. The hydrogen fluoride reacts with silicon oxide in a thermally grown oxide layer positioned between a bondcoat and the environmental barrier coating. The bondcoat is positioned within the coated component between a silicon-containing substrate and the thermally grown oxide layer, and the bondcoat comprises a silicon-containing material.

Abstract: A method is provided for removing a bondcoat and an environmental barrier coating from a coated component. The method may include contacting the coated component with an etchant liquid comprising phosphoric acid, 5% by volume to 70% by volume of hydrogen fluoride, and a solvent. The hydrogen fluoride and the phosphoric acid react with a composition in the bondcoat. The bondcoat is positioned within the coated component between a silicon-containing substrate and the environmental barrier coating, and the bondcoat comprises mullite.

Abstract: Methods are provided for repairing a defect on a silicon-containing substrate. The method may include applying a powder mixture into the defect of an existing coating on a surface of the silicon-containing substrate, wherein the powder mixture comprises silicon and germanium at a Ge mole fraction of 0.01 to 0.3; and heat treating the powder mixture within the defect at a sintering temperature that is 1150° C. to 1400° C. to form a repaired bondcoat within the defect. Repaired components are also provided that include a repaired bondcoat formed within the defect on the silicon-containing substrate, wherein the repaired bondcoat comprises a silicon-germanium phase comprising a Ge mole fraction of germanium of 0.01 to 0.3 and a Si mole fraction of silicon of 0.7 to 0.99.

Abstract: Methods are provided for repairing a defect on a silicon-containing substrate. The method may include applying a powder mixture into the defect of an existing coating on a surface of the silicon-containing substrate, wherein the powder mixture comprises silicon and germanium at a Ge mole fraction of 0.01 to 0.3; and heat treating the powder mixture within the defect at a sintering temperature that is 1150° C. to 1400° C. to form a repaired bondcoat within the defect. Repaired components are also provided that include a repaired bondcoat formed within the defect on the silicon-containing substrate, wherein the repaired bondcoat comprises a silicon-germanium phase comprising a Ge mole fraction of germanium of 0.01 to 0.3 and a Si mole fraction of silicon of 0.7 to 0.99.

Abstract: An article for high temperature service is presented herein. One embodiment is an article including a substrate having a silicon-bearing ceramic matrix composite; and a layer disposed over the substrate, wherein the layer includes silicon and a dopant, the dopant including aluminum. In another embodiment, the article includes a ceramic matrix composite substrate, wherein the composite includes a silicon-bearing ceramic and a dopant, the dopant including aluminum; a bond coat disposed over the substrate, where the bond coat includes elemental silicon, a silicon alloy, a silicide, or combinations including any of the aforementioned; and a coating disposed over the bond coat, the coating including a silicate (such as an aluminosilicate or rare earth silicate), yttria-stabilized zirconia, or a combination including any of the aforementioned.

Abstract: Methods are provided for repairing a defect on a silicon-containing substrate. The method may include applying a powder mixture into the defect of an existing coating on a surface of the silicon-containing substrate, wherein the powder mixture comprises silicon and germanium at a Ge mole fraction of 0.01 to 0.3; and heat treating the powder mixture within the defect at a sintering temperature that is 1150° C. to 1400° C. to form a repaired bondcoat within the defect. Repaired components are also provided that include a repaired bondcoat formed within the defect on the silicon-containing substrate, wherein the repaired bondcoat comprises a silicon-germanium phase comprising a Ge mole fraction of germanium of 0.01 to 0.3 and a Si mole fraction of silicon of 0.7 to 0.99.

Abstract: Methods for preparing an environmental barrier coating and the resulting coating are provided. The methods and products include the incorporation of a continuous ceramic inner layer and a segmented ceramic outer layer on a CMC component. The segmented ceramic outer layer may be formed by thermal spray techniques. The coating is more stable at higher temperatures and provides for a longer lifetime of the coated component.

Abstract: A composition is provided that includes a silicon-containing material (e.g., a silicon metal and/or a silicide) and about 0.001% to about 85% of a Ga-containing compound, an In-containing compound, or a mixture thereof. The silicon-based layer can be a bond coating directly on the surface of the substrate. Alternatively or additionally, the silicon-based layer can be an outer layer defining a surface of the substrate, with an environmental barrier coating on the surface of the substrate. A coated component is also provided, as well as a method for coating a ceramic component. Gas turbine engines are also provided that include such a ceramic component.

Abstract: Coated components and their methods of formation are provided. The coated component includes: a ceramic matrix composite substrate comprising silicon carbide and having a surface; a bond coat on the surface of the substrate; and an environmental barrier coating on the bond coat. The bond coat includes a plurality of discrete particles dispersed within a matrix phase that includes mullite. The plurality of discrete particles includes an oxygen getter and a transition metal oxide.

Abstract: A coated component, along with methods of its formation, are provided. The coated component may include a ceramic matrix composite substrate comprising silicon carbide and having a surface, a bond coat on the surface of the substrate, and an environmental barrier coating on the bond coat. The bond coat includes a plurality of discrete particles dispersed within a matrix phase, with the matrix phase formed from mullite and defining 60% to 98% by volume of the bond coat. The plurality of discrete particles include an oxygen getter and has 50% of its volume or greater formed from particles having an average size of 10 ?m to 100 ?m.

Abstract: Environmental barrier coatings including a bondcoat layer including silicon and a rare earth silicate-based hermetic layer and rare earth silicate-based non-hermetic layer are provided. The rare earth silicate-based hermetic layer is deposited on the bondcoat via a thermal spray process and has an elastic modulus ranging from 100 GPa to 180 GPa. The at least one rare earth silicate-based non-hermetic layer is deposited on the rare earth silicate-based hermetic layer and has an elastic modulus ranging from 50 GPa to 100 GPa. Coated gas turbine engine components and methods for coating gas turbine engine components are also provided.

Abstract: Coated components, along with methods of their formation, are provided. The coated component includes a ceramic substrate having a surface; an intermediate layer on the surface of the ceramic substrate; and an environmental barrier coating on the intermediate layer. The intermediate layer includes a carbon-sink material that inhibits accumulation of free carbon from a carbon-containing species within the intermediate layer, the ceramic substrate, or both.

Abstract: An article for high temperature service is presented herein. One embodiment is an article including a substrate having a silicon-bearing ceramic matrix composite; and a layer disposed over the substrate, wherein the layer includes silicon and a dopant, the dopant including aluminum. In another embodiment, the article includes a ceramic matrix composite substrate, wherein the composite includes a silicon-bearing ceramic and a dopant, the dopant including aluminum; a bond coat disposed over the substrate, where the bond coat includes elemental silicon, a silicon alloy, a silicide, or combinations including any of the aforementioned; and a coating disposed over the bond coat, the coating including a silicate (such as an aluminosilicate or rare earth silicate), yttria-stabilized zirconia, or a combination including any of the aforementioned.

Abstract: A composition is generally provided that includes a silicon-containing material (e.g., silicon metal and/or a silicide) and a boron-doped refractory compound, such as about 0.001% to about 85% by volume of the boron-doped refractory compound (e.g., about 1% to about 60% by volume). In one embodiment, a bond coating on a surface of a ceramic component is generally provided with the bond coating including such a composition, with the silicon-containing material is silicon metal.

Abstract: An article for high temperature service is presented herein. One embodiment is an article including a substrate having a silicon-bearing ceramic matrix composite; and a layer disposed over the substrate, wherein the layer includes silicon and a dopant, the dopant including aluminum. In another embodiment, the article includes a ceramic matrix composite substrate, wherein the composite includes a silicon-bearing ceramic and a dopant, the dopant including aluminum; a bond coat disposed over the substrate, where the bond coat includes elemental silicon, a silicon alloy, a silicide, or combinations including any of the aforementioned; and a coating disposed over the bond coat, the coating including a silicate (such as an aluminosilicate or rare earth silicate), yttria-stabilized zirconia, or a combination including any of the aforementioned.

Abstract: A coated component, along with methods of its formation and use, is provided. The coated component includes a ceramic matrix composite (CMC) substrate comprising silicon carbide and having a mullite bondcoat on its surface. The mullite bondcoat includes an oxygen getter phase contained within a mullite phase. For example, the mullite bondcoat may include 60% to 98% by volume of the mullite phase. An environmental barrier coating is on the mullite bondcoat.