A new class of multi-component rare earth multi-silicate materials has been created for use in harsh environments such as gas turbine engines. Moreover, by combining two-or-more rare earth disilicates the properties (for example, thermal expansion, thermal conductivity, etc.) can be tailored to fit specific applications, such as having a matching thermal expansion with that of silicon-based composites and a low thermal conductivity close to that of 1 W/m K. Applications can be extended for use with other material classes such as MCrAlY, MAX-phase, and refractory metal alloys, utilizing a thermal expansion of up to about 15−10.sup.−6 /° C. By mixing of specific sets of rare earth disilicates it is possible to obtain a high entropy or entropy stabilized mixture, and utilize features such as “sluggish diffusion”, and more.

A new class of multi-component rare earth multi-silicate materials has been created for use in harsh environments such as gas turbine engines. Moreover, by combining two-or-more rare earth disilicates the properties (for example, thermal expansion, thermal conductivity, etc.) can be tailored to fit specific applications, such as having a matching thermal expansion with that of silicon-based composites and a low thermal conductivity close to that of 1 W/m K. Applications can be extended for use with other material classes such as MCrAlY, MAX-phase, and refractory metal alloys, utilizing a thermal expansion of up to about 15−10.sup.−6 /° C. By mixing of specific sets of rare earth disilicates it is possible to obtain a high entropy or entropy stabilized mixture, and utilize features such as “sluggish diffusion”, and more.

A metal-silicon carbide-based composite material including: a composite part including a silicon carbide-based porous body constituted by a plurality of silicon carbide particles, and a metal that is infiltrated in the silicon carbide-based porous body; and first and second surface layers which contain a metal, and coat both main surfaces of the composite part. The metal contains at least one kind selected from the group consisting of aluminum and magnesium, and the amount of particles having a particle size of 300 μm or more in the plurality of silicon carbide particles is 5% by volume or less.

A metal-silicon carbide-based composite material including: a composite part including a silicon carbide-based porous body constituted by a plurality of silicon carbide particles, and a metal that is infiltrated in the silicon carbide-based porous body; and first and second surface layers which contain a metal, and coat both main surfaces of the composite part. The metal contains at least one kind selected from the group consisting of aluminum and magnesium, and the amount of particles having a particle size of 300 μm or more in the plurality of silicon carbide particles is 5% by volume or less.

A coated substrate is provided that comprises: a substrate; and a barrier coating comprising a compound having the formula: Ln.sub.2ABO.sub.8, where Ln comprises scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, or mixtures thereof; A comprises Si, Ti, Ge, Sn, Ce, Hf, Zr, or a combination thereof; and B comprises Mo, W, or a combination thereof. In one embodiment, B comprises Mo. A gas turbine is also provided that comprises the coated substrate described above.

A coated substrate is provided that comprises: a substrate; and a barrier coating comprising a compound having the formula: Ln.sub.2ABO.sub.8, where Ln comprises scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, or mixtures thereof; A comprises Si, Ti, Ge, Sn, Ce, Hf, Zr, or a combination thereof; and B comprises Mo, W, or a combination thereof. In one embodiment, B comprises Mo. A gas turbine is also provided that comprises the coated substrate described above.

Methods for tape deposition of a sacrificial coating on a CMC substrate are provided. The method comprises: applying a matrix material onto a surface of a film; drying the matrix material to remove the solvent; and transferring the dried matrix material from the film to the CMC substrate. The matrix material comprises a mixture of a rare earth silicate powder, a sintering aid, and a solvent.

Methods for tape deposition of a sacrificial coating on a CMC substrate are provided. The method comprises: applying a matrix material onto a surface of a film; drying the matrix material to remove the solvent; and transferring the dried matrix material from the film to the CMC substrate. The matrix material comprises a mixture of a rare earth silicate powder, a sintering aid, and a solvent.

An article comprises a substrate comprising a ceramic matrix composite; a first layer disposed over the substrate, the first layer comprising a substantially interconnected silicon source material, and a secondary material; and a second layer disposed over the first layer, the second layer comprising a membrane material in mass transfer communication with the silicon source material.

An article comprises a substrate comprising a ceramic matrix composite; a first layer disposed over the substrate, the first layer comprising a substantially interconnected silicon source material, and a secondary material; and a second layer disposed over the first layer, the second layer comprising a membrane material in mass transfer communication with the silicon source material.