Abstract: In various aspects, a preheater, a directed flow chemical vapor infiltration/chemical vapor deposition (CVI/CVD) furnace, and/or an installation jig are described. In one example, a preheater includes a central inlet; a circuitous gas flow path downstream of the central inlet; a plenum section downstream of the circuitous gas flow path; and an outlet diffuser plate defining a plurality of apertures fluidly configured to couple the preheater to a furnace working zone, wherein the outlet diffuser plate is downstream of the plenum section, wherein the circuitous gas flow path is fluidly coupled to the plenum section by an outer circumferential slot opening.

Abstract: A method to form a machinable ceramic matrix composite comprises forming a porous ceramic multilayer on a surface of a fiber preform. In one example, the porous ceramic multilayer comprises a gradient in porosity in a direction normal to the surface. In another example, the porous ceramic multilayer includes low-wettability particles having a high contact angle with molten silicon, where an amount of the low-wettability particles in the porous ceramic multilayer varies in a direction normal to the surface. After forming the porous ceramic multilayer, the fiber preform is infiltrated with a melt, and the melt is cooled to form a ceramic matrix composite with a surface coating thereon. An outer portion of the surface coating is more readily machinable than an inner portion of the surface coating. The outer portion of the surface coating is machined to form a ceramic matrix composite having a machined surface with a predetermined surface finish and/or dimensional tolerance.

Abstract: A method of producing a melt infiltrated ceramic matrix composite (CMC) article that includes the steps of: forming a ceramic fiber preform; optionally, rigidizing the ceramic fiber preform with a fiber interphase coating via a Chemical Vapor Infiltration (CVI) process, infiltrating a ceramic slurry into the porous body or preform, conducting one or more secondary operations, and finally, melt infiltrating the preform with molten silicon or a silicon alloy to form the CMC article. The infiltration of a ceramic slurry into a ceramic fiber preform to form a green body is performed along with the use of convection and/or conduction as heat transfer mechanisms, such that the ceramic slurry does not require the incorporation of a pre-gelation material in order for the slurry to remain within the green body during subsequent processing steps.

Abstract: A method may include depositing, from a slurry, suspension, or tape, on a surface of an additively manufactured component comprising a metal or alloy, powder comprising at least one of a metal, an alloy, or a ceramic; sintering the powder to form a surface layer on the additively manufactured component; and hot isostatic pressing the additively manufactured component and the surface layer.

Abstract: In various aspects, a preheater, a directed flow chemical vapor infiltration/chemical vapor deposition (CVI/CVD) furnace, and/or an installation jig are described. In one example, a preheater includes a central inlet; a circuitous gas flow path downstream of the central inlet; a plenum section downstream of the circuitous gas flow path; and an outlet diffuser plate defining a plurality of apertures fluidly configured to couple the preheater to a furnace working zone, wherein the outlet diffuser plate is downstream of the plenum section, wherein the circuitous gas flow path is fluidly coupled to the plenum section by an outer circumferential slot opening.

Abstract: In some examples, a multilevel retort assembly. The assembly includes a base defining a base perimeter; and a plurality of shells. Each shell has a diffuser plate support and a perimeter with a substantially similar shape as the base perimeter. The plurality of shells are stacked on each other, mechanically supported by the base, and surround an inner retort volume. The at least one shell of the plurality of shells defines a removable window. The assembly also includes a plurality of diffuser plates, each diffuser plate supported by a corresponding diffuser plate support of the plurality of diffuser plate supports.

Abstract: The disclosure describes braze tape coatings and technique to form articles with differing physical properties in different layers or regions of the article. An example method includes forming a braze tape defining at least one layer that includes a first segment and a second segment. A portion of the second segment in the plane is adjacent to a portion of the first segment in a plane of the layer. The method also includes positioning the braze tape on a surface of a substrate, the plane of the layer of the braze tape being parallel to the surface of the substrate. The method also includes heating the braze tape to melt a constituent of at least one of the first coating material and the second coating material to form a densified coating on the surface of the substrate.

Abstract: In various aspects, a preheater, a directed flow chemical vapor infiltration/chemical vapor deposition (CVI/CVD) furnace, and/or an installation jig are described. In one example, a preheater includes a central inlet; a circuitous gas flow path downstream of the central inlet; a plenum section downstream of the circuitous gas flow path; and an outlet diffuser plate defining a plurality of apertures fluidly configured to couple the preheater to a furnace working zone, wherein the outlet diffuser plate is downstream of the plenum section, wherein the circuitous gas flow path is fluidly coupled to the plenum section by an outer circumferential slot opening.

Abstract: A method of treating a component adapted for use in a gas turbine engine is described herein. The component may comprise ceramic matrix composite materials. The treatment to the ceramic matrix composite component may reduce or eliminate the wear or damage of crack propagation in the ceramic matrix composite component.

Abstract: Methods of pressure assisted melt infiltration of fiber preforms are provided. The fiber preform is provided inside of a pressure vessel. The pressure vessel projects into a molten material contained in a crucible. The pressure vessel has an opening located below a surface of the molten material through which the molten material enters the pressure vessel. An end of the fiber preform contacts the molten material within the pressure vessel. The pressure vessel and crucible are located in a furnace. The molten material is pulled within the pressure vessel by increasing a first pressure at a first port of the furnace so the first pressure is higher than a second pressure at a second port of the pressure vessel. The second port is located above the molten material located within the pressure vessel. The fiber preform is infiltrated with the molten material.

Abstract: In some examples, a slurry infiltration fixture. The infiltration fixture includes a fixture main body that includes a slurry introduction channel and a plurality of fixture walls defining a cavity configured to receive a porous component. The cavity includes a component volume and a reservoir volume. The plurality of fixture walls includes a shape configured to define a fixed offset between the porous component and the plurality of fixture walls and a fixed volume for slurry between the plurality of fixture walls and the porous component. The slurry introduction channel is configured introduce the slurry into the cavity through an opening proximate a bottom of the cavity.

Abstract: A method of forming an aperture in a ceramic matrix composite material is provided. The method may comprise drilling a pilot hole into the ceramic matrix composite material and spiral machining the pilot hole to enlarge a diameter of the pilot hole, wherein the enlarged pilot hole is the aperture in the ceramic matrix composite material. The method may comprise spiral machining the pilot hole in a radial direction with a tool to enlarge a diameter of the pilot hole until the aperture in the ceramic matrix composite material is formed. The tool may have a first diameter in a section of the tool and a second diameter on either side of the section of the tool or on both sides of the section of the tool, wherein the second diameter is larger than the first diameter.

Abstract: A method to produce a ceramic matrix composite part, wherein the method comprises providing a ceramic fiber preform. Wherein the ceramic fiber preform includes a three-dimensional framework of a plurality of ceramic fibers. The method comprising, prior to melt infiltration, adding a layer of machinable stock to a target area of the ceramic fiber preform, melt infiltrating the ceramic fiber preform, forming the ceramic matrix composite part by cooling the melt infiltrated ceramic fiber preform, and machining the part in the target area where the machinable stock is located.

Abstract: In some examples, a method may include depositing, from a slurry comprising particles including silicon metal, a bond coat precursor layer including the particles comprising silicon metal directly on a ceramic matrix composite substrate. The method also may include locally heating the bond coat precursor layer to form a bond coat comprising silicon metal. Additionally, the method may include forming a protective coating on the bond coat. In some examples, an article may include a ceramic matrix composite substrate, a bond coat directly on the substrate, and a protective coating on the bond coat. The bond coat may include silicon metal and a metal comprising at least one of Zr, Y, Yb, Hf, Ti, Al, Cr, Mo, Nb, Ta, or a rare earth metal.

Abstract: A method to produce a ceramic matrix composite part, wherein the method comprises providing a ceramic fiber preform. Wherein the ceramic fiber preform includes a three-dimensional framework of a plurality of ceramic fibers. The method comprising, prior to melt infiltration, adding a layer of machinable stock to a target area of the ceramic fiber preform, melt infiltrating the ceramic fiber preform, forming the ceramic matrix composite part by cooling the melt infiltrated ceramic fiber preform, and machining the part in the target area where the machinable stock is located.

Abstract: A turbine shroud assembly for a gas turbine engine includes a shroud wall extending circumferentially partway around a central reference axis to define a gas path of the gas turbine engine. An attachment feature extends radially from the shroud wall. A foam is located at least on the shroud wall.

Abstract: A method of fabricating cooling features on a CMC component may comprise compressing a fabric preform within tooling including holes and/or recesses facing the fabric preform. During the compression, portions of the fabric preform are pushed into the holes and/or recesses. Gases are delivered through the tooling to deposit a matrix material on exposed surfaces of the fabric preform while the fabric preform is being compressed. The matrix material builds up on the portions of the fabric preform pushed into the holes and/or recesses, and a rigidized preform with surface protrusions is formed. The tooling is removed, and the rigidized preform is densified, thereby forming a CMC component including raised surface features.

Abstract: A method of producing a ceramic matrix composite including a protective ceramic coating thereon comprises applying a surface slurry onto an outer surface of an impregnated fiber preform. The surface slurry includes particulate ceramic solids dispersed in a flowable preceramic polymer comprising silicon, and the impregnated fiber preform comprises a framework of ceramic fibers loaded with particulate matter. The flowable preceramic polymer is cured, thereby forming on the outer surface a composite layer comprising a cured preceramic polymer with the particulate ceramic solids dispersed therein. The cured preceramic polymer is then pyrolyzed to form a porous ceramic layer comprising silicon carbide, and the impregnated fiber preform and the porous ceramic layer are infiltrated with a molten material comprising silicon. After infiltration, the molten material is cooled to form a ceramic matrix composite body with a protective ceramic coating thereon.

Abstract: A turbine vane assembly adapted for use in a gas turbine engine includes a support and a turbine vane arranged around the support. The support is made of metallic materials. The turbine vane is made of ceramic matrix composite materials to insulate the metallic materials of the support.

Abstract: A method of altering a surface of a ceramic matrix composite to aid in nodule removal is described. A fiber preform comprising a framework of ceramic fibers is heated to a temperature at or above a melting temperature of silicon. During the heating, the fiber preform is infiltrated with a molten material comprising silicon. After the infiltration, the fiber preform is cooled, and the infiltrated fiber preform is exposed to a gas comprising nitrogen during cooling. Silicon nitride may be formed by a reaction of free (unreacted) silicon at or near the surface of the infiltrated fiber preform with the nitrogen. Thus, a ceramic matrix composite having a surface configured for easy nodule removal is formed. Any silicon nodules formed on the surface during cooling may be removed without machining or heat treatment.