Abstract: Provided is a method for heat treating a precipitation-hardened article having a thick section and a thin section so that the thin section can be solution annealed while the metallurgical structure of the thick section is substantially unaffected by the solution-annealing process. The method restores the microstructure of the thin section uniformly by solution annealing the thin section to achieve a preselected microstructure but without affecting the microstructure of the thick section.

Abstract: A method for producing a thermal barrier coating/environmental barrier coating system on a silicon containing material substrate includes applying an environmental barrier coating (EBC) over the silicon containing material substrate; and applying a thermal barrier coating (TBC) over the EBC. The thermal barrier coating includes a compound having a primary constituent portion and a stabilizer portion stabilizing said primary constituent. The primary constituent portion of the thermal barrier coating includes hafnia present in an amount of at least about 5 mol % of the primary constituent and the stabilizer portion of said thermal barrier coating includes at least one metal oxide comprised of cations with a +2 or +3 valence present in the amount of about 10 to about 40 mol % of the thermal barrier coating.

Abstract: A protective coating for use on a silicon-containing substrate, and deposition methods therefor. The coating has a barium-strontium-aluminosilicate (BSAS) composition that is less susceptible to degradation by volatilization and in corrosive environments as a result of having at least an outer surface region that consists essentially of one or more stoichiometric crystalline phases of BSAS and is substantially free of a nonstoichiometric second crystalline phase of BSAS that contains a substoichiometric amount of silica. The coating can be produced by carrying out deposition and heat treatment steps that result in the entire coating or just the outer surface region of the coating consisting essentially of the stoichiometric celsian phase.

Abstract: Provided is a method for heat treating a precipitation-hardened article having a thick section and a thin section so that the thin section can be solution annealed while the metallurgical structure of the thick section is substantially unaffected by the solution-annealing process. The method restores the microstructure of the thin section uniformly by solution annealing the thin section to achieve a preselected microstructure but without affecting the microstructure of the thick section.

Abstract: An article and method for stabilization of a nickel-based superalloy coated with a diffusion aluminide coating. The region below the aluminide coating is first carburized to form refractory carbides. The article is cleaned and masked as required so that regions that will not have an aluminide coating are not carburized. After placing the article into a furnace and heating in a non-oxidizing atmosphere to a carburizing temperature, a carburizing gas is introduced, and the near surface region is carburized to a depth of about 100 microns. Refractory carbides are formed in this region. When a diffusion aluminide coating is formed on the article, the refractory elements, being present as refractory carbides, are not available to form detrimental TCP phases.

Abstract: In accordance with an embodiment of the invention, an article is provided. The article comprises a substrate comprised of silicon containing material, an environmental barrier coating (EBC) overlying the substrate and a thermal barrier coating (TBC) on the environmental barrier coating. The thermal barrier coating comprising a compound having a rhombohedral phase.

Abstract: An article and method for stabilization of a nickel-based superalloy coated with a diffusion aluminide coating. The region below the aluminide coating is first carburized to form refractory carbides. The article is cleaned and masked as required so that regions that will not have an aluminide coating are not carburized. After placing the article into a furnace and heating in a non-oxidizing atmosphere to a carburizing temperature, a carburizing gas is introduced, and the near surface region is carburized to a depth of about 100 microns. Refractory carbides are formed in this region. When a diffusion aluminide coating is formed on the article, the refractory elements, being present as refractory carbides, are not available to form detrimental TCP phases.

Abstract: An article and method for stabilization of a nickel-based superalloy coated with a diffusion aluminide coating. The region below the aluminide coating is first carburized to form refractory carbides. The article is cleaned and masked as required so that regions that will not have an aluminide coating are not carburized. After placing the article into a furnace and heating in a non-oxidizing atmosphere to a carburizing temperature, a carburizing gas is introduced, and the near surface region is carburized to a depth of about 100 microns. Refractory carbides are formed in this region. When a diffusion aluminide coating is formed on the article, the refractory elements, being present as refractory carbides, are not available to form detrimental TCP phases.

Abstract: In accordance with an embodiment of the invention, a thermal barrier coating for inclusion in a thermal barrier coating/environmental barrier coating system (TBC/EBC system) for use on a silicon based substrate is disclosed. The thermal barrier coating comprising up to about 9 mol percent of a stabilizer and up to 91 mol percent of primary oxide selected from the group consisting of zirconia, hafnia and mixtures thereof. The stabilizer comprises: a first metal oxide selected from the group consisting of yttria, calcia, ceria, scandia, magnesia, india and mixtures thereof, a second metal oxide of a trivalent metal atom selected from the group consisting of lanthana, gadolinia, neodymia, samaria, dysprosia, ytterbia, erbia, and mixtures thereof. The first metal oxide is in an amount of from about 3 to about 5 mol %, the second metal oxide is in an amount of from about 0.25 to about 6 mol %.

Abstract: An article comprising a substrate formed of a silicon-comprising material, such as an article exposed to the hostile thermal environment of a gas turbine engine. The article further comprises an environmental barrier layer, e.g., an alkaline earth metal aluminosilicate, and a physical barrier layer overlying the environmental barrier layer. The physical barrier layer comprises zirconia or hafnia stabilized with an oxide of a metal selected from the group consisting of magnesium, calcium, scandium, yttrium, and lanthanide metals; and a low CTE oxide selected from the group consisting of niobia and tantala; and mixtures thereof. A method for preparing an environmental barrier coating system on a substrate formed of a silicon-comprising material is also disclosed.

Abstract: In accordance with an embodiment of the invention, a thermal barrier coating (TBC) for inclusion in a thermal barrier coating/environmental barrier coating system (TBC/EBC system) for use on a silicon containing material substrate is provided. The TBC comprises a compound having a primary constituent portion and a stabilizer portion stabilizing said primary constituent. The primary constituent portion of the TBC comprises hafnia present in an amount of at least about 5 mol % of the primary constituent. The stabilizer portion of said thermal barrier coating comprises at least one metal oxide comprised of cations with a +2 or +3 valence present in the amount of about 10 to about 40 mol % of the thermal barrier coating.

Abstract: In accordance with an embodiment of the invention, a thermal barrier coating (TBC) for inclusion in a thermal barrier coating/environmental barrier coating system (TBC/EBC system) for use on a silicon containing material substrate is provided. The TBC comprises a compound having a primary constituent portion and a stabilizer portion stabilizing said primary constituent. The primary constituent portion of the TBC comprises hafnia present in an amount of at least about 5 mol % of the primary constituent. The stabilizer portion of said thermal barrier coating comprises at least one metal oxide comprised of cations with a +2 or +3 valence present in the amount of about 10 to about 40 mol % of the thermal barrier coating.

Abstract: A coating system for Si-containing materials, particularly Si-based composites used to produce articles exposed to high temperatures. The coating system is a compositionally-graded thermal/environmental barrier coating (T/EBC) system that includes an intermediate layer containing yttria-stabilized hafnia (YSHf) and mullite, alumina and/or an aluminosilicate, which is used in combination with an inner layer between a Si-containing substrate and the intermediate layer and a thermal-insulating top coat overlying the intermediate layer. The intermediate layer provides environmental protection to the silicon-containing substrate, and has a coefficient of thermal expansion between that of the top coat and that of the inner layer so as to serve as a transition layer therebetween. The intermediate layer is particular well suited for use in combination with an inner layer of an alkaline earth metal aluminosilicate (such as BSAS) and a top coat formed of YSZ or YSHf.

Abstract: In accordance with an embodiment of the invention, an article is provided. The article comprises a substrate comprised of silicon containing material, an environmental barrier coating (EBC) overlying the substrate and a thermal barrier coating (TBC) on the environmental barrier coating. The thermal barrier coating comprising a compound having a rhombohedral phase.

Abstract: According to an embodiment of the invention, disclosed is a composite comprising a porous thermal barrier coating on a metallic part and an impermeable barrier coating adjacent to the outer surface of the thermal barrier coating. The impermeable barrier coating is dense and non-porous and comprises a rare earth silicate, the impermeable barrier coating thereby preventing infiltration of the contaminant composition into the thermal barrier coating.

Abstract: In accordance with an embodiment of the invention, an article is provided. The article comprises a substrate comprised of silicon containing material, an environmental barrier coating (EBC) overlying the substrate and a thermal barrier coating (TBC) on the environmental barrier coating. The thermal barrier coating comprising a compound having a rhombohedral phase.

Abstract: A protective coating for use on a silicon-containing substrate, and deposition methods therefor. The coating has a barium-strontium-aluminosilicate (BSAS) composition that is less susceptible to degradation by volatilization and in corrosive environments as a result of having at least an outer surface region that consists essentially of one or more stoichiometric crystalline phases of BSAS and is substantially free of a nonstoichiometric second crystalline phase of BSAS that contains a substoichiometric amount of silica. The coating can be produced by carrying out deposition and heat treatment steps that result in the entire coating or just the outer surface region of the coating consisting essentially of the stoichiometric celsian phase.

Abstract: A protective coating for use on a silicon-containing substrate, and deposition methods therefor. The coating has a barium-strontium-aluminosilicate (BSAS) composition that is less susceptible to degradation by volatilization and in corrosive environments as a result of having at least an outer surface region that consists essentially of one or more stoichiometric crystalline phases of BSAS and is substantially free of a nonstoichiometric second crystalline phase of BSAS that contains a substoichiometric amount of silica. The coating can be produced by carrying out deposition and heat treatment steps that result in the entire coating or just the outer surface region of the coating consisting essentially of the stoichiometric celsian phase.

Abstract: An article comprising a substrate formed of a silicon-comprising material, such as an article exposed to the hostile thermal environment of a gas turbine engine. The article further comprises an environmental barrier layer, e.g., an alkaline earth metal aluminosilicate, and a top coat comprising hafnia stabilized with from about 0.5 mole % to about 10 mole % of an oxide of a metal selected from the group consisting of magnesium, calcium, scandium, yttrium, and lanthanide metals, and mixtures thereof. The article optionally comprises a transition layer between the environmental barrier layer and the top coat. A method for preparing a thermal/environmental barrier coating on a substrate formed of a silicon-comprising material is also disclosed.

Abstract: A hollow airfoil is fabricated by providing a casting mold assembly including a casting mold, a casting core, and a standoff spacer that prevents the casting core from contacting the casting mold to define a casting space. A first nickel-base superalloy is cast into the casting space and solidified to form the hollow airfoil. The presence of a through-hole extending through a wall of the hollow airfoil is identified, and the through-hole is closed by welding using a second nickel-base superalloy, without using any freestanding closure element.