Abstract: An example article includes a substrate and a barrier coating on the substrate. The barrier coating includes a matrix including a rare-earth disilicate extending from an inner interface facing the substrate to an outer surface opposite the inner interface. The barrier coating includes a graded volumetric distribution of rare-earth oxide rich (REO-rich) phase regions in the matrix along a direction from the inner interface to the outer surface. The graded volumetric distribution defines a first volumetric density of the REO-rich phase regions at a first region of the matrix adjacent the outer surface. The graded volumetric distribution defines a second volumetric density of the REO-rich phase regions at a second region of the matrix adjacent the inner surface. The second volumetric density is different from the first volumetric density. An example technique includes forming the barrier coating on the substrate of a component.

Abstract: The disclosure describes articles and techniques that include an airfoil having a hybrid coating system to provide improved particle impact resistance and improve CMAS attack resistance on the pressure side of the airfoil and improved thermal load protection on the suction side of the airfoil. An example article for a gas turbine engine may include a substrate, and a hybrid environmental barrier coating (EBC) including a relatively dense EBC layer on a first portion of the substrate and a relatively porous EBC layer on a second portion of the substrate, where the first portion of the substrate is different from the second portion of the substrate, and wherein at least a portion of the relatively porous EBC layer overlaps at least a portion of the relatively dense EBC layer in an overlap region.

Abstract: A method includes predicting a composition of calcium-magnesium-aluminum-silicate (CMAS) to be encountered by a high temperature mechanical system during use of the high temperature mechanical system. The method further includes selecting a composition of a CMAS-resistant barrier coating layer based at least in part on the predicted composition of CMAS. The CMAS-resistant barrier coating layer includes a base composition and at least one secondary oxide selected based on the predicted composition of CMAS. The at least one secondary oxide includes at least one of an oxide of a divalent element, an oxide of a trivalent element, or an oxide of a tetravalent element. The CMAS-resistant barrier coating layer comprises greater than 0 mol. % and less than about 7 mol. % of the at least one secondary oxide.

Abstract: In some examples, an article for a high-temperature mechanical system including a substrate and a doped calcia-magnesia-alumina-silicate resistant (doped CMAS-resistant) layer on the substrate. The doped CMAS-resistant layer is a thermal barrier coating or an environmental barrier coating and includes a calcia dopant.

Abstract: A method includes depositing a porous silicon coat on a substrate to form a bulk phase of a bond coat and introducing a reactive gas into pores of the porous silicon coat. The reactive gas reacts with silicon adjacent the pores of the porous silicon coat to form a ceramic phase of the bond coat comprising a silicon-based ceramic and reduce porosity of the porous silicon coat. A temperature of the reactive gas is greater than about 1000° C.

Abstract: An article may include a substrate, a plurality of cooling holes in the substrate, wherein each of the plurality of cooling holes defines substantially the same diameter measured parallel to an outer surface of the substrate, and a coating on the surface of the substrate. In accordance with these examples, the coating covers and substantially blocks a first set of cooling holes from the plurality of cooling holes and leaves a second set of cooling holes from the plurality of cooling holes substantially uncovered. In some examples, an article including a substrate, a plurality of cooling holes in the substrate, and a coating on the substrate. In accordance with these examples, the coating covers and partially occludes each cooling hole of the plurality of cooling holes, and the coating does not extend into any of the plurality of cooling holes.

Abstract: An article for use in a high-temperature environment that includes a substrate including a superalloy material, a ceramic, or a ceramic matrix composite, and an abradable coating on the substrate, the abradable coating including a rare earth silicate and a dislocator phase, the dislocator phase forms one or more distinct phase regions in the abradable coating and comprises at least one of hafnium diboride (HfB2), zirconium diboride (ZrB2), tantalum nitride (TaN or Ta2N), tantalum carbide (Ta2C), titanium diboride (TiB2), zirconium carbide (ZrC), hafnium carbide (HfC), tantalum diboride (TaB2), hafnium nitride (HfN), or niobium carbide (NbC).

Abstract: A method that includes introducing a suspension comprising a coating material and a carrier into a heated plume of a thermal spray device. The coating material may include silicon or a silicon alloy. The method further includes directing the coating material using the heated plume toward a substrate that includes a ceramic or a ceramic matrix composite and depositing the coating material to form a bond coat directly on the substrate such that the bond coat defines a porosity of less than about 3 percent by volume.

Abstract: An article includes a substrate, a bond coat on the substrate, and a multilayer environmental barrier coating (EBC) on the bond coat. The multilayer EBC includes a first EBC layer defining a first thickness and a second EBC layer defining a second thickness. The first EBC layer includes a first rare earth disilicate and a first concentration of a sintering aid that includes alumina. The second EBC layer includes a second rare earth disilicate and a second concentration of the sintering aid that includes alumina, less than the first concentration of the sintering aid.

Abstract: In one example, a method for forming an environmental barrier coating (EBC) on a substrate. The method may include depositing an environmental barrier coating (EBC) on a substrate via a thermal spray apparatus to form an as-deposited EBC; heat treating the as-deposited EBC at or above a first temperature for first period of time following the deposition of the as-deposited EBC on the substrate; and cooling the as-deposited EBC to a second temperature following the heat treatment at a controlled rate over a second period of time to form a heat-treated EBC on the substrate. The first temperature, the first period of time, the controlled rate, and the second period of time may be selected to increase a weight percent of crystalline phase in the heat-treated EBC compared to the as-deposited EBC.

Abstract: In some examples, a plasma spray physical vapor deposition system includes a vacuum pump; a vacuum chamber; a coating material source; a plasma spray device configured to generate a plasma plume including vaporized coating material; and a funnel. The funnel has an inlet opening and an outlet opening smaller than the inlet opening. The funnel is configured and positioned to receive the plasma plume through the inlet opening and direct the plasma plume out of the outlet opening.

Abstract: An example article includes a substrate and a barrier coating on the substrate. The barrier coating includes a matrix including a rare-earth disilicate extending from an inner interface facing the substrate to an outer surface opposite the inner interface. The barrier coating includes a graded volumetric distribution of rare-earth oxide rich (REO-rich) phase regions in the matrix along a direction from the inner interface to the outer surface. The graded volumetric distribution defines a first volumetric density of the REO-rich phase regions at a first region of the matrix adjacent the outer surface. The graded volumetric distribution defines a second volumetric density of the REO-rich phase regions at a second region of the matrix adjacent the inner surface. The second volumetric density is different from the first volumetric density. An example technique includes forming the barrier coating on the substrate of a component.

Abstract: An article may include a substrate including a metal or alloy; a bond coat directly on the substrate; an intermediate ceramic layer on the bond coat; and an abradable ceramic layer directly on the intermediate ceramic layer. The intermediate ceramic layer includes a stabilized tetragonal prime phase constitution and defines a first porosity. The abradable ceramic layer includes zirconia or hafnia stabilized in the tetragonal prime phase by a second mixture including between about 5 wt. % and about 10 wt. % ytterbia, between about 0.5 wt. % and about 2.5 wt. % samaria, and between about 1 wt. % and about 4 wt. % of at least one of lutetia, scandia, ceria, neodymia, europia, or gadolinia, and a balance zirconia or hafnia. The abradable ceramic layer defines a second porosity, and the second porosity is higher than the first porosity.

Abstract: The disclosure describes articles and techniques that include an airfoil having a hybrid coating system to provide improved particle impact resistance and improve CMAS attack resistance on the pressure side of the airfoil and improved thermal load protection on the suction side of the airfoil. An example article for a gas turbine engine may include a substrate, and a hybrid environmental barrier coating (EBC) including a relatively dense EBC layer on a first portion of the substrate and a relatively porous EBC layer on a second portion of the substrate, where the first portion of the substrate is different from the second portion of the substrate, and wherein at least a portion of the relatively porous EBC layer overlaps at least a portion of the relatively dense EBC layer in an overlap region.

Abstract: In some examples, method including forming an EBC layer on a substrate, wherein the EBC layer exhibits an initial porosity; forming a layer of silicate glass on a surface of the EBC layer; and melting the silicate glass on the surface of the EBC layer to infiltrate the EBC layer with the molten silicate glass to decrease the porosity of the EBC layer from the initial porosity to a final porosity.

Abstract: An article may include a substrate including a ceramic or a CMC; a bond layer on the substrate; and a diffusion barrier layer between the substrate and the bond layer. The diffusion barrier layer may include at least one of molybdenum metal, tantalum metal, tungsten metal, or niobium metal. In some examples, the article may include a stabilizing layer that includes at least one of a silicide of molybdenum (MoSi2), tantalum (TaSi2), tungsten (WSi2), or niobium (NbSi2), between the diffusion barrier layer and the bond layer.

Abstract: An article includes a substrate, a bond coat on the substrate, and a multilayer environmental barrier coating (EBC) on the bond coat. The multilayer EBC includes a first EBC layer defining a first thickness and a second EBC layer defining a second thickness. The first EBC layer includes a first rare earth disilicate and a first concentration of a sintering aid that includes alumina. The second EBC layer includes a second rare earth disilicate and a second concentration of the sintering aid that includes alumina, less than the first concentration of the sintering aid.

Abstract: An article may include a substrate including a ceramic matrix composite (CMC); a composite coating layer including a first coating material that includes a rare-earth disilicate and a second coating material that includes at least one of a rare-earth monosilicate, a CMAS-resistant material, or a high-temperature dislocating material, where the second coating material forms a substantially continuous phase in the composite coating layer.

Abstract: An article for use in a high-temperature environment that includes a substrate including a superalloy material, a ceramic, or a ceramic matrix composite, and an abradable coating on the substrate, the abradable coating including a rare earth silicate and a dislocator phase, the dislocator phase forms one or more distinct phase regions in the abradable coating and comprises at least one of hafnium diboride (HfB2), zirconium diboride (ZrB2), tantalum nitride (TaN or Ta2N), tantalum carbide (Ta2C) titanium diboride (TiB2), zirconium carbide (ZrC), hafnium carbide (HfC), tantalum diboride (TaB2), hafnium nitride (HfN), or niobium carbide (NbC).

Abstract: A method includes predicting a composition of calcium-magnesium-aluminum-silicate (CMAS) to be encountered by a high temperature mechanical system during use of the high temperature mechanical system. The method further includes selecting a composition of a CMAS-resistant barrier coating layer based at least in part on the predicted composition of CMAS. The CMAS-resistant barrier coating layer includes a base composition and at least one secondary oxide selected based on the predicted composition of CMAS. The at least one secondary oxide includes at least one of an oxide of a divalent element, an oxide of a trivalent element, or an oxide of a tetravalent element. The CMAS-resistant barrier coating layer comprises greater than 0 mol. % and less than about 7 mol. % of the at least one secondary oxide.