Abstract: A ceramic matrix composite (CMC) is formed using a three-dimensional (3-D) woven preform by removing the set of sacrificial fibers from the 3-D woven preform and allowing a metal or metal alloy infiltrate the 3-D woven preform. The 3-D woven preform is formed by a method that includes providing a woven layer comprising a first set of ceramic fibers oriented in a first (x) direction woven with a second set of ceramic fibers oriented in a second (y) direction; stacking a plurality of woven layers on top of each other, said woven layers providing a two-dimensional (2-D) preform; weaving a set of sacrificial fibers in a third (z) direction with the 2-D preform, said weaving providing the 3-D woven preform; and shaping the 3-D woven preform into a predetermined shape.

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 method of processing a CMC component includes preparing a fiber preform having a predetermined shape, and positioning the fiber preform with tooling having holes facing one or more surfaces of the fiber preform. After the positioning, a clamping pressure is applied to the tooling to force portions of the one or more surfaces of the fiber preform into the holes, thereby forming protruded regions of the fiber preform. During the application of the clamping pressure, the fiber preform is exposed to gaseous reagents at an elevated temperature, and a matrix material is deposited on the fiber preform to form a rigidized preform including surface protrusions. After removing the tooling, the rigidized preform is infiltrated with a melt for densification, and a CMC component having surface bumps is formed. When the CMC component is assembled with a metal component, the surface bumps may reduce diffusion at high temperatures.

Abstract: A method of making a fiber preform for ceramic matrix composite (CMC) fabrication comprises laminating an arrangement of fibers between polymer sheets comprising an organic polymer, which may function as a fugitive binder during fabrication, to form a flexible prepreg sheet. A plurality of the flexible prepreg sheets are laid up in a predetermined geometry to form a stack, and the stack is heated to soften the organic polymer and bond together the flexible prepreg sheets into a bonded prepreg structure. Upon cooling of the bonded prepreg structure, a rigid preform is formed. The rigid preform is heated at a sufficient temperature to pyrolyze the organic polymer. Thus, a porous preform that may undergo further processing into a CMC is formed.

Abstract: A method of controllably coating a fiber preform has been developed. The method includes infiltrating a fiber preform with a first solvent to form a solvent-filled preform. After the infiltration, a slurry is applied to one or more outer surfaces of the solvent-filled preform to form a slurry coating thereon. The slurry coating comprises particulate solids dispersed in a second solvent having a vapor pressure higher than that of the first solvent. The slurry coating and the solvent-filled preform are dried. During drying, the second solvent evaporates from the slurry coating before the first solvent evaporates from the solvent-filled preform. The slurry coating dries to form a porous surface coating comprising the particulate solids on the one or more outer surfaces of the solvent-filled preform. The drying of the solvent-filled preform continues after formation of the porous surface coating to remove the first solvent.

Abstract: A method of processing a ceramic matrix composite (CMC) component includes extracting silicon from a surface region of the CMC component such that free silicon is present in the surface region at a reduced amount of about 5 vol. % or less. The extraction comprises contacting the surface region with a wicking medium comprising an element reactive with silicon. The extraction is carried out at an elevated temperature prior to assembling the CMC component with a metal component.

Abstract: A method of forming a moisture-tolerant coating on a silicon carbide fiber includes exposing a silicon carbide fiber to a gaseous N precursor comprising nitrogen at an elevated temperature, thereby introducing nitrogen into a surface region of the silicon carbide fiber, and exposing the silicon carbide fiber to a gaseous B precursor comprising boron at an elevated temperature, thereby introducing boron into the surface region of the silicon carbide fiber. Silicon-doped boron nitride is formed at the surface region of the silicon carbide fiber without exposing the silicon carbide fiber to a gaseous Si precursor comprising Si. Thus, a moisture-tolerant coating comprising the silicon-doped boron nitride is grown in-situ on the silicon carbide fiber.

Abstract: An apparatus for coating specimens includes a reaction chamber and a plurality of reaction modules in the reaction chamber for containing specimens to be coated, where each reaction module includes a module inlet and a module outlet. A plurality of conduits are configured to be in fluid communication with at least one gas source external to the reaction chamber, and each of the conduits terminates in one of the reaction modules for delivery of gaseous reagents to the specimens to be coated. The module outlets are in fluid communication with the reaction chamber for expulsion of gaseous reaction products from the reaction modules.

Abstract: A blade for a gas turbine engine, and methods of manufacture of such a blade having a continuous density gradient so that the portion of the blade nearest the rotator shaft is of a higher density than the portion of the blade furthest from the rotator shaft.

Abstract: A method of slurry infiltration and cleaning to fabricate a ceramic matrix composite (CMC) component with an internal cavity or bore comprises inserting a number of rods into a hollow portion of a porous fiber preform, thereby forming a rod arrangement substantially filling the hollow portion. Each of the rods has a low-friction surface comprising a coefficient of static friction of about 0.1 or less. The porous fiber preform is exposed to a slurry comprising particulate solids in a liquid carrier, and the slurry infiltrates the porous fiber preform. Some fraction of the particulate solids is deposited within interstices of the porous fiber preform to form an impregnated fiber preform, and another fraction of the particulate solids is deposited within the hollow portion as excess slurry. After slurry infiltration, the rods are withdrawn from the hollow portion, and at least some of the excess slurry is removed with the rods.

Abstract: A segmented turbine shroud for radially encasing a rotatable turbine in a gas turbine engine comprising a carrier, a ceramic matrix composite (CMC) seal segment, and an elongated pin. The carrier defines a pin-receiving carrier bore and the CMC seal segment defines a pin-receiving seal segment bore. The elongated pin extends through the carrier bore and the seal segment bore. The pin-receiving carrier bore includes a cantilevered member such that the carrier bore has a length sufficient to effect radial flexion between the carrier bore and the pin received within the carrier bore during operation of the turbine.

Abstract: A segmented turbine shroud for radially encasing a turbine in a gas turbine engine comprises a carrier comprising a flange; a ceramic matrix composite (CMC) seal segment comprising a portion defining a pin-receiving bore; an elongated pin extending through the pin-receiving bore; a bushing surrounding the elongated pin within the bore; and a flexible mounting member, the flexible mounting member being connected to the bushing and the carrier flange to thereby flexibly mount the CMC seal segment to the carrier.

Abstract: A cartridge for a ceramic matrix composite (CMC) seal segment of a segmented turbine shroud of a gas turbine engine is provided. The cartridge comprises a carrier segment and a CMC seal segment. A surface of the carrier segment and a surface of the CMC seal segment form a mating region proximate the entire perimeter of the CMC seal segment. The carrier segment surface may comprise a channel, and a compressible mating element may be disposed within the channel. Air may be supplied to a cavity, formed by the carrier and CMC seal segment, and the mating region.

Abstract: A method of melt infiltration for producing a ceramic matrix composite comprises applying a surface slurry onto one or more outer surfaces of an impregnated porous preform. The surface slurry comprises a solvent and particulate solids, and the preform comprises a framework of ceramic fibers loaded with particulate matter. The surface slurry is dried to form a porous layer comprising the particulate solids on the one or more outer surfaces of the impregnated porous preform. After forming the porous layer, an end portion of the impregnated porous preform that includes at least part of the porous layer is immersed in a molten material, and the molten material is infiltrated into the impregnated porous preform from the end portion. The porous layer serves as a wick to transport the molten material over the one or more outer surfaces, thereby enabling melt infiltration of the impregnated porous preform from other portions thereof.

Abstract: A method of melt infiltration for producing a ceramic matrix composite comprises applying a non-wetting coating onto one or more outer surfaces of a porous fiber preform. The non-wetting coating comprises a non-wetting material with which molten silicon has a contact angle of at least about 45°. After applying the non-wetting coating, an uncoated portion of the porous fiber preform is immersed into a molten material comprising silicon, and the molten material is infiltrated into the porous fiber preform through the uncoated portion. The non-wetting coating serves as a barrier to inhibit or prevent the molten material from penetrating the one or more outer surfaces. After infiltration of the molten material into the porous fiber preform, the molten material is cooled to form a ceramic matrix composite, and the non-wetting coating is removed.

Abstract: A ceramic matrix composite (CMC) seal segment for use in a segmented turbine shroud for radially encasing a turbine in a gas turbine engine. The CMC seal segment comprises an arcuate flange having a surface facing the turbine and a portion defining a bore for receiving an elongated pin, with the bore having a length that is at least 70% of the length of the elongated pin received therein. The CMC seal segment is carried by the carrier by at least one of the elongated pins being received within the bore. The CMC seal segment portion defining a pin-receiving bore is radially spaced from the arcuate flange by a spacing flange extending radially outward from the arcuate flange.