Abstract: In some examples, an article may include a substrate and a coating system on the substrate. The coating system may include a layer comprising a plurality of voids, wherein respective voids of the plurality of voids define respective void volumes; and a nucleating agent within at least some of the respective void volumes of the layer, wherein the nucleating agent is configured to induce crystallization of the molten CMAS. The coating system may include an environmental barrier coating, thermal barrier coating, and/or abradable coating.

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, techniques of repairing and/or reinforcing oxide-oxide ceramic matrix composite (CMC) materials using a metallic material. In one example, a method including applying a metallic material at an edge of an oxide-oxide CMC substrate; and heating the metallic material to diffuse the metal material into the oxide-oxide CMC substrate at the edge. In another example, a method including applying a metallic material onto a damaged area of the oxide-oxide CMC; applying a reinforcing phase material onto the damaged area of the oxide-oxide CMC; and heating the metallic material to diffuse the metallic material into the oxide-oxide CMC and attach the reinforcing phase material to the damaged area of the oxide-oxide CMC.

Abstract: An assembly for a gas turbine engine includes ceramic material containing (i.e. ceramic matrix composite) segments and joints that couple the segments together.

Abstract: In some examples, a braze material includes a first set of particles, a second set of particles, and a polymeric binder. The first set of particles includes a braze powder, where the braze powder comprises an Si-containing alloy. The first set of particles defines an average or median particle diameter between about 1 ?m and about 40 ?m. The second set of particles includes at least one of SiC or a transition metal carbide, where the second set of particles has a multimodal particle size distribution.

Abstract: The disclosure describes techniques for joining a first part including a ceramic or a CMC and a second part including a ceramic or a CMC using brazing. A technique may include positioning a filler material in a joint region between the first and second parts and a metal or alloy on a bulk surface of the filler material. The metal or alloy may be locally heated to melt the metal or alloy, which may infiltrate the filler material. A constituent of the molten metal or alloy may react with a constituent of the filler material to join the first and second parts. Another technique may include depositing a powder that includes the filler material and the metal or alloy in the joint region. Substantially simultaneously with depositing the powder, the powder may be locally heated. A constituent of the molten metal or alloy may react with a constituent of the filler material to join the first and second parts.

Abstract: An example article may include a component, a substrate including a first ceramic, a joining layer between the component and the substrate, and a joint surface coating between the substrate and the joining layer. The joint surface coating may include a diffusion barrier layer including a second ceramic material, and a compliance layer including at least one of a metal or a metalloid. An example technique may include holding a first joining surface of a coated component adjacent a second joining surface of a second component. The example technique may further include heating at least one of the coated component, the second component, and a braze material, and brazing the coated component by allowing the braze material to flow in a region between the first joining surface and the second joining surface.

Abstract: In some examples, techniques of repairing and/or reinforcing oxide-oxide ceramic matrix composite (CMC) materials using a metallic material. In one example, a method including applying a metallic material at an edge of an oxide-oxide CMC substrate; and heating the metallic material to diffuse the metal material into the oxide-oxide CMC substrate at the edge. In another example, a method including applying a metallic material onto a damaged area of the oxide-oxide CMC; applying a reinforcing phase material onto the damaged area of the oxide-oxide CMC; and heating the metallic material to diffuse the metallic material into the oxide-oxide CMC and attach the reinforcing phase material to the damaged area of the oxide-oxide CMC.

Abstract: A method of forming a composite article includes impregnating an inorganic fiber preform with a slurry composition. The slurry composition includes a particulate, a solvent, and a pre-gellant material. Gelling of the pre-gellant material in the slurry composition is initiated to immobilize the particulate and yield a gelled article, and substantially all solvent is removed from the gelled article to form a green composite article. The green composite article is then infiltrated with a molten infiltrant to form the composite article.

Abstract: One aspect of the present disclosure includes a turbine vane assembly comprising a vane made from ceramic matrix composite material having an outer wall extending between a leading edge and a trailing edge and between a first end and an opposing second end; an endwall made at least partially from a ceramic matrix composite material configured to engage the first end of the vane; and a retaining region including corresponding bi-cast grooves formed adjacent the first end of the vane and a receiving aperture formed in the endwall; wherein a bond is formed in the retaining region to join the vane and endwall together.

Abstract: An article having a substrate that includes a ceramic or a ceramic matrix composite, a bond layer on the substrate that includes silicon metal and a boria stabilizing agent, and at least one additional layer on the bond layer.

Abstract: In some examples, an article may include a substrate and a coating on the substrate. The substrate may include a superalloy, a ceramic, or a ceramic matrix composite. The coating may include a layer comprising a matrix material and a plurality of nanoparticles. The matrix material may include at least one of silica, zirconia, alumina, titania, or chromia, and the plurality of nanoparticles may include nanoparticles including at least one of yttria, zirconia, alumina, or chromia. In some examples, an average diameter of the nanoparticles is less than about 400 nm.

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 assembly comprising a ceramic matrix composite component, a monolithic insert, and a polymer char and a method for producing the same. The ceramic matrix composite component may include an exterior surface, with the monolithic insert bonded to the exterior surface of the ceramic matrix composite component. The polymer char may be sandwiched between the monolithic insert and the exterior surface of the ceramic matrix composite that may bond the monolithic insert to the ceramic matrix composite component.

Abstract: A ceramic matrix composite component and a ceramic insert, and a method for producing the same. The ceramic matrix composite component may include an exterior surface comprising silicon fibers in a silicon carbide matrix. The insert may include a continuous porosity bonded to the exterior surface of the ceramic matrix composite component. The silicon carbide matrix of the ceramic matrix composite component may extend into the porosity of the ceramic insert to bond the ceramic insert to the ceramic matrix composite component.

Abstract: An assembly comprising a ceramic matrix composite component, a ceramic insert, and a ply and a method for producing the same. The ceramic matrix composite component may comprise silicon carbide fibers in a silicon carbide matrix. The ceramic inset may be adjacent to the ceramic matrix composite component. The ply may at least partially cover the ceramic insert such that the ceramic insert may be sandwiched between the ply and the ceramic matrix composite component, and the ply may extend beyond the ceramic insert in at least one direction so that the ply is joined to the ceramic matrix composite. The ply may comprise at least one layer of silicon carbide fibers or carbon fibers in a silicon carbide matrix.

Abstract: In some examples, an article may include a substrate and a coating system on the substrate. The coating system may include a layer comprising a plurality of voids, wherein respective voids of the plurality of voids define respective void volumes; and a nucleating agent within at least some of the respective void volumes of the layer, wherein the nucleating agent is configured to induce crystallization of the molten CMAS. The coating system may include an environmental barrier coating, thermal barrier coating, and/or abradable coating.

Abstract: An assembly comprising a structural component and a sacrificial layer, and method for producing the same. The structural component may comprise silicon carbide fibers within a silicon carbide matrix. The sacrificial layer may be joined to the structural component and may comprising unarranged ceramic fibers, wherein the sacrificial layer may comprise a volume fiber fraction lower than a volume fiber fraction of the structural component.

Abstract: The disclosure describes techniques for joining a first part including a ceramic or a CMC and a second part including a ceramic or a CMC using brazing. A technique may include positioning a filler material in a joint region between the first and second parts and a metal or alloy on a bulk surface of the filler material. The metal or alloy may be locally heated to melt the metal or alloy, which may infiltrate the filler material. A constituent of the molten metal or alloy may react with a constituent of the filler material to join the first and second parts. Another technique may include depositing a powder that includes the filler material and the metal or alloy in the joint region. Substantially simultaneously with depositing the powder, the powder may be locally heated. A constituent of the molten metal or alloy may react with a constituent of the filler material to join the first and second parts.

Abstract: In some examples, a technique may include positioning a first part comprising a ceramic or ceramic matrix composite and a second part comprising a ceramic or a CMC adjacent to each other to define a joint region at the interface of the first part and the second part. In some examples, the joint region may be heated using at least one of a laser or a plasma arc source to heat the joint region to an elevated temperature. The first and second parts may be pressed together and cooled to join the first and second parts at the joint region. In other examples, a solid braze material including a filler material and a metal or alloy may be delivered to the joint region and locally heated to cause a constituent of the filler material and a constituent of the metal or alloy to react. When reacted, the constituents may form a solid material, which may join the first and second parts.