A composite substrate includes, in this order: a ceramic plate; a metal layer containing at least one selected from the group consisting of aluminum and an aluminum alloy; and a thermal sprayed layer containing at least one selected from the group consisting of copper and a copper alloy, and an intermetallic compound containing copper and aluminum as constituent elements is scattered between the metal layer and the thermal sprayed layer.

A composite substrate includes, in this order: a ceramic plate; a metal layer containing at least one selected from the group consisting of aluminum and an aluminum alloy; and a thermal sprayed layer containing at least one selected from the group consisting of copper and a copper alloy, and an intermetallic compound containing copper and aluminum as constituent elements is scattered between the metal layer and the thermal sprayed layer.

A coating method includes depositing a slurry including a coarsely particulate ceramic and a finely particulate ceramic on a base material configured with an oxide-based ceramics matrix composite such that a proportion of coarse particles decreases towards a surface of the base material; forming a bond coating by performing a heat treatment on the base material on which the slurry has been deposited; and forming a top coating by thermally spraying a ceramic onto the bond coating. The oxide-based ceramics matrix composite is an alumina silica type oxide-based ceramics matrix composite. The coarsely particulate ceramic and the finely particulate ceramic are alumina-based powder.

A coating method includes depositing a slurry including a coarsely particulate ceramic and a finely particulate ceramic on a base material configured with an oxide-based ceramics matrix composite such that a proportion of coarse particles decreases towards a surface of the base material; forming a bond coating by performing a heat treatment on the base material on which the slurry has been deposited; and forming a top coating by thermally spraying a ceramic onto the bond coating. The oxide-based ceramics matrix composite is an alumina silica type oxide-based ceramics matrix composite. The coarsely particulate ceramic and the finely particulate ceramic are alumina-based powder.

Methods for forming a coating on a surface of a substrate are provided. The method can include: preheating the surface of the substrate; spraying a slurry suspension onto the surface of the substrate to form a coating, wherein the slurry composition comprises a rare earth compound, a sintering agent, and a solvent, wherein the rare earth compound has the formula: A.sub.1-bB.sub.bZ.sub.1-dD.sub.dMO.sub.6 where A is Al, Ga, In, Sc, Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Fe, Cr, Co, Mn, Bi, or a mixture thereof; b is 0 to 0.5; Z is Hf, Ti, or a mixture thereof; D is Zr, Ce, Ge, Si, or a mixture thereof; d is 0 to 0.5; and M is Ta, Nb, or a mixture thereof; and thereafter, heat treating the coating to densify the coating from an initial porosity to a sintered porosity.

Methods for forming a coating on a surface of a substrate are provided. The method can include: preheating the surface of the substrate; spraying a slurry suspension onto the surface of the substrate to form a coating, wherein the slurry composition comprises a rare earth compound, a sintering agent, and a solvent, wherein the rare earth compound has the formula: A.sub.1-bB.sub.bZ.sub.1-dD.sub.dMO.sub.6 where A is Al, Ga, In, Sc, Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Fe, Cr, Co, Mn, Bi, or a mixture thereof; b is 0 to 0.5; Z is Hf, Ti, or a mixture thereof; D is Zr, Ce, Ge, Si, or a mixture thereof; d is 0 to 0.5; and M is Ta, Nb, or a mixture thereof; and thereafter, heat treating the coating to densify the coating from an initial porosity to a sintered porosity.

An article may include a substrate, such as a silicon-containing ceramic matrix composite, an environmental barrier coating (EBC) layer on the substrate, and a CMAS-resistant EBC layer on the EBC layer. The EBC layer may include at least one rare-earth disilicate (REDS). The CMAS-resistant EBC layer may include at least one rare-earth monosilicate (REMS) configured to react with CMAS to form crystalline reaction products. The CMAS-resistant EBC layer may include a plurality of vertical cracks extending from a surface of the CMAS-resistant EBC layer at least partially into the CMAS-resistant EBC layer. Additionally, or alternatively, the EBC layer may include a plurality of vertical cracks extending from a surface of the EBC layer into at least a portion of the EBC layer.

An article may include a substrate, such as a silicon-containing ceramic matrix composite, an environmental barrier coating (EBC) layer on the substrate, and a CMAS-resistant EBC layer on the EBC layer. The EBC layer may include at least one rare-earth disilicate (REDS). The CMAS-resistant EBC layer may include at least one rare-earth monosilicate (REMS) configured to react with CMAS to form crystalline reaction products. The CMAS-resistant EBC layer may include a plurality of vertical cracks extending from a surface of the CMAS-resistant EBC layer at least partially into the CMAS-resistant EBC layer. Additionally, or alternatively, the EBC layer may include a plurality of vertical cracks extending from a surface of the EBC layer into at least a portion of the EBC layer.

A part includes a substrate having, adjacent to a surface of the substrate, at least a portion that is made of a material that contains silicon, and an environmental barrier formed on the surface of the substrate, the environmental barrier including a first layer including at least one first rare earth silicate and presenting grains with a mean size less than or equal to 1 μm; and a second layer covering the first layer, the second layer including at least one rare earth silicate and presenting grains with a mean size greater than 1 μm.

A part includes a substrate having, adjacent to a surface of the substrate, at least a portion that is made of a material that contains silicon, and an environmental barrier formed on the surface of the substrate, the environmental barrier including a first layer including at least one first rare earth silicate and presenting grains with a mean size less than or equal to 1 μm; and a second layer covering the first layer, the second layer including at least one rare earth silicate and presenting grains with a mean size greater than 1 μm.