Abstract: 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.

Abstract: The disclosure relates generally to recession resistant gas turbine engine articles that comprise a silicon containing substrate, and related coatings and methods. The present disclosure is directed, inter alia, to an engine article comprising a silicon substrate which is coated with a chemically stable porous oxide layer. The present disclosure also relates to articles comprising a substrate and a bond coat on top comprising a two phase layer of interconnected silicon and interconnected oxide, followed by a layer of silicon. The present disclosure further relates to a recession resistant article comprising an oxide in a silicon containing substrate, such that components of the silicon containing substrate is interconnected with oxides dispersed in the substrate and form the bulk of the recession resistant silicon containing article.

Abstract: A method for forming a ceramic matrix composite article includes forming by melt infiltration a ceramic matrix composite substrate inducing a ceramic fiber reinforcement material in a ceramic matrix material having a free silicon proportion and forming by chemical vapor infiltration a ceramic matrix composite outer layer including a ceramic fiber reinforcement material in a ceramic matrix material having no free silicon proportion disposed on at least a portion of the substrate.

Abstract: Ceramic matrix composite articles include, for example, a plurality of unidirectional arrays of fiber tows in a matrix having a monomodal pore size distribution, and a fiber volume fraction between about 15 percent and about 35 percent. The articles may be formed by, for example, providing a shaped preform comprising a prepreg tape layup of unidirectional arrays of fiber tows, a matrix precursor, and a pore former, curing the shaped preform to pyrolyze the matrix precursor and burnout the pore former so that the shaped preform comprises the unidirectional arrays of fiber tows and a porous matrix having a monomodal pore size distribution, and subjecting the cured shaped preform to chemical vapor infiltration to densify the porous matrix so that the ceramic matrix composite article has a fiber volume fraction between about 15 percent and about 35 percent.

Abstract: Ceramic matrix composite articles include, for example, a plurality of unidirectional arrays of fiber tows in a matrix having a monomodal pore size distribution, and a fiber volume fraction between about 15 percent and about 35 percent. The articles may be formed by, for example, providing a shaped preform comprising a prepreg tape layup of unidirectional arrays of fiber tows, a matrix precursor, and a pore former, curing the shaped preform to pyrolyze the matrix precursor and burnout the pore former so that the shaped preform comprises the unidirectional arrays of fiber tows and a porous matrix having a monomodal pore size distribution, and subjecting the cured shaped preform to chemical vapor infiltration to densify the porous matrix so that the ceramic matrix composite article has a fiber volume fraction between about 15 percent and about 35 percent.

Abstract: Ceramic matrix composite articles include, for example, a plurality of unidirectional arrays of fiber tows in a matrix having a monomodal pore size distribution, and a fiber volume fraction between about 15 percent and about 35 percent. The articles may be formed by, for example, providing a shaped preform comprising a prepreg tape layup of unidirectional arrays of fiber tows, a matrix precursor, and a pore former, curing the shaped preform to pyrolyze the matrix precursor and burnout the pore former so that the shaped preform comprises the unidirectional arrays of fiber tows and a porous matrix having a monomodal pore size distribution, and subjecting the cured shaped preform to chemical vapor infiltration to densify the porous matrix so that the ceramic matrix composite article has a fiber volume fraction between about 15 percent and about 35 percent.

Abstract: An article comprises a substrate comprising a ceramic matrix composite; a first layer disposed over the substrate, the first layer comprising an interconnected first silicide, and a second phase; and a second layer disposed over the first layer, the second layer comprising a second silicide in mass transfer communication with the first silicide.

Abstract: A turbine assembly is provided. The turbine assembly includes a gas turbine engine including at least one hot gas path component formed at least partially from a ceramic matrix composite material. The turbine assembly also includes a treatment system positioned to receive a flow of exhaust gas from the gas turbine engine. The treatment system is configured to remove water from the flow of exhaust gas to form a flow of treated exhaust gas, and to channel the flow of treated exhaust gas towards the at least one hot gas path component. The at least one hot gas path component includes a plurality of cooling holes for channeling the flow of treated exhaust gas therethrough, such that a protective film is formed over the at least one hot gas path component.

Abstract: An environmental barrier coating system for a component of a gas turbine includes at least one rare earth disilicate layer and at least one rare earth monosilicate layer. At least one of the at least one rare earth disilicate layer or the at least one rare earth monosilicate layer includes an alkaline earth oxide dopant.

Abstract: According to a method set forth herein a plurality of preform plies having first and second preform plies can be associated together to define a preform. The preform can be subject to chemical vapor infiltration (CVI) processing to define a ceramic matrix composite (CMC) structure.

Abstract: A ceramic matrix composite article includes a melt infiltration ceramic matrix composite substrate comprising a ceramic fiber reinforcement material in a ceramic matrix material having a free silicon proportion, and a chemical vapor infiltration ceramic matrix composite outer layer comprising a ceramic fiber reinforcement material in a ceramic matrix material having essentially no free silicon proportion disposed on an outer surface of at least a portion of the substrate.

Abstract: A method of operating a gas turbine engine includes measuring an exhaust gas temperature of the gas turbine engine. A first stage turbine nozzle assembly of the gas turbine engine is adjusted to a first position. A firing temperature of the gas turbine engine is determined based on the exhaust gas temperature. The firing temperature is compared to a threshold value and a difference value is determined therefrom. If the difference value exceeds a threshold value, the first stage turbine nozzle assembly is adjusted to a second position such that the firing temperature is substantially equal to the threshold value.

Abstract: The present disclosure relates to ceramic matrix composites made by chemical vapor infiltration, methods of making the ceramic matrix composites, and ceramic matrix composite turbine components for use in a hot gas pathway. A method of fabricating a ceramic matrix composite is provided that can include the steps of: (i) forming a plurality of holes in a ceramic matrix composite preform of desired shape; and (ii) densifying the preform by a chemical vapor infiltration process to form a part or most of the matrix. A ceramic matrix composite is also provided that can be used in hot combustion gases made according to the aforementioned ceramic matrix composite fabrication method described herein.

Abstract: An article for use in aggressive environments is presented. In one embodiment, the article comprises a substrate and a self-sealing and substantially hermetic sealing layer comprising an alkaline-earth aluminosilicate disposed over the bondcoat. The substrate may be any high-temperature material, including, for instance, silicon-bearing ceramics and ceramic matrix composites. A method for making such articles is also presented. The method comprises providing a substrate; disposing a self-sealing alkaline-earth aluminosilicate layer over the substrate; and heating the sealing layer to a sealing temperature at which at least a portion of the sealing layer will flow.

Abstract: The disclosure relates generally to recession resistant gas turbine engine articles that comprise a silicon containing substrate, and related coatings and methods. The present disclosure is directed, inter alia, to an engine article comprising a silicon substrate which is coated with a chemically stable porous oxide layer. The present disclosure also relates to articles comprising a substrate and a bond coat on top comprising a two phase layer of interconnected silicon and interconnected oxide, followed by a layer of silicon. The present disclosure further relates to a recession resistant article comprising an oxide in a silicon containing substrate, such that components of the silicon containing substrate is interconnected with oxides dispersed in the substrate and form the bulk of the recession resistant silicon containing article.

Abstract: The present disclosure relates to methods and systems for reducing silica recession of silicon-containing ceramics or silicon-containing ceramic composites, particularly those exposed to a combustion gas or to combustion gas environments, including those exposed to high temperature combustion gas environments. The methods and systems involve silicon-doping of compressed air and/or removal of moisture from compressed air prior to co-mingling the treated compressed air with the combustion gas to which the silicon-containing ceramics or silicon-containing ceramic composites are exposed.

Abstract: High-temperature machine components, more particularly, articles capable of operating in high-temperature environments, including for example turbines of gas engines, may be formed of a high temperature ceramic matrix composite that includes a ceramic substrate including silicon; an environmental harrier coating system including a silicon containing bond coat; and a diffusion barrier layer of a carbide or a nitride between the substrate of the article and the silicon bond coat of the environmental barrier coating system. The diffusion harrier layer selectively prevents or reduces the diffusion of boron and impurities from the substrate to the bond coat of the environmental barrier coating system.

Abstract: The present disclosure relates to methods and systems for reducing silica recession of silicon-containing ceramics or silicon-containing ceramic composites, particularly those exposed to a combustion gas or to combustion gas environments, including those exposed to high temperature combustion gas environments. The methods and systems involve silicon-doping of compressed air and/or removal of moisture from compressed air prior to co-mingling the treated compressed air with the combustion gas to which the silicon-containing ceramics or silicon-containing ceramic composites are exposed.

Abstract: The present disclosure relates to methods and systems for reducing silica recession of silicon-containing ceramics or silicon-containing ceramic composites, particularly those exposed to a combustion gas or to combustion gas environments, including those exposed to high temperature combustion gas environments. The methods and systems involve silicon-doping of compressed air and/or removal of moisture from compressed air prior to co-mingling the treated compressed air with the combustion gas to which the silicon-containing ceramics or silicon-containing ceramic composites are exposed.

Abstract: A system comprises a plurality of components disposed to define a gas path. At least one component comprises a silicon-bearing substrate over which is disposed a coating, and the coating comprises a recession-resistant material exposed to the gas path. A silicon source is disposed in fluid communication with the gas path and is configured to be delivered to the gas path to maintain, in gas flowing in the gas path over the coating, a silicon mass concentration in the range from about 1.