Methods of forming an environmental barrier coating are disclosed. A method includes disposing a powder-based coating on a substrate, heat-treating the powder-based coating at a temperature greater than 800° C. and less than 1200° C. to form a porous coating that includes surface-connected pores, infiltrating at least some of the surface-connected pores of the porous coating with an infiltrant material to form an infiltrated coating, and sintering the infiltrated coating at a temperature greater than 1200° C. and less than 1500° C. to form the environmental barrier coating on the substrate.

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.

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.

An article may include a substrate defining at least one at least partially obstructed surface. The substrate includes at least one of a ceramic or a ceramic matrix composite. The article also may include a multilayer, multi-microstructure environmental barrier coating on the at least partially obstructed substrate. The multilayer, multi-microstructure environmental barrier coating includes a first layer comprising a rare earth disilicate and a substantially dense microstructure; and a second layer on the first layer. The second layer includes a columnar microstructure and at least one of a rare earth monosilicate or a thermal barrier coating composition comprising a base oxide comprising zirconia or hafnia; a primary dopant comprising ytterbia; a first co-dopant comprising samaria; and a second co-dopant comprising at least one of lutetia, scandia, ceria, gadolinia, neodymia, or europia.

An article may include a substrate defining at least one at least partially obstructed surface. The substrate includes at least one of a ceramic or a ceramic matrix composite. The article also may include a multilayer, multi-microstructure environmental barrier coating on the at least partially obstructed substrate. The multilayer, multi-microstructure environmental barrier coating includes a first layer comprising a rare earth disilicate and a substantially dense microstructure; and a second layer on the first layer. The second layer includes a columnar microstructure and at least one of a rare earth monosilicate or a thermal barrier coating composition comprising a base oxide comprising zirconia or hafnia; a primary dopant comprising ytterbia; a first co-dopant comprising samaria; and a second co-dopant comprising at least one of lutetia, scandia, ceria, gadolinia, neodymia, or europia.

An article may include a substrate defining at least one at least partially obstructed surface. The substrate includes at least one of a ceramic or a ceramic matrix composite. The article also may include an environmental barrier coating on the at least partially obstructed substrate. The environmental barrier coating includes a layer including a rare earth disilicate and a microstructure comprising closed porosity.

An article may include a substrate defining at least one at least partially obstructed surface. The substrate includes at least one of a ceramic or a ceramic matrix composite. The article also may include an environmental barrier coating on the at least partially obstructed substrate. The environmental barrier coating includes a layer including a rare earth disilicate and a microstructure comprising closed porosity.

Components having an environmental barrier coating and a sintered layer overlying the environmental barrier coating, the sintered layer defining an outer surface having a lower surface roughness than the environmental barrier coating. The sintered layer is formed from a slurry applied to and then sintered on the environmental barrier coating. The sintered layer comprises a primary material, at least one sintering aid dissolved in the primary material, and optionally a secondary material. The sintering aid contains at least one doping composition. The primary material is a rare earth disilicate or a rare earth monosilicate and is doped with the doping composition so as to be either a doped rare earth disilicate or a doped rare earth monosilicate. The optional secondary material is a reaction product of the primary material and any of the sintering aid not dissolved in the primary material.

Components having an environmental barrier coating and a sintered layer overlying the environmental barrier coating, the sintered layer defining an outer surface having a lower surface roughness than the environmental barrier coating. The sintered layer is formed from a slurry applied to and then sintered on the environmental barrier coating. The sintered layer comprises a primary material, at least one sintering aid dissolved in the primary material, and optionally a secondary material. The sintering aid contains at least one doping composition. The primary material is a rare earth disilicate or a rare earth monosilicate and is doped with the doping composition so as to be either a doped rare earth disilicate or a doped rare earth monosilicate. The optional secondary material is a reaction product of the primary material and any of the sintering aid not dissolved in the primary material.

A gas turbine blade may have a bond coat applied to its surface. A porous substrate may be applied to the bond layer and one or more protective layers may be applied to the bond layer such that the fiber mesh is embedded between the bond layer and the protective layer to prevent creep.