Abstract: An investment casting process for a hollow component such as a gas turbine blade utilizing a ceramic core (10) that is cast in a flexible mold (24) using a low pressure, vibration assisted casting process. The flexible mold is cast from a master tool (14) machined from soft metal using a relatively low precision machining process, with relatively higher precision surfaces being defined by a precision formed insert (22) incorporated into the master tool. A plurality of identical flexible molds may be formed from a single master tool in order to permit the production of ceramic cores at a desired rate with a desired degree of part-to-part precision.

Abstract: A method for making a material system includes the steps of: providing a chamber, placing hollow geometric shapes in the chamber, closing the chamber, evacuating air from the chamber, feeding a binder for the shapes into the evacuated chamber to impregnate the geometric shapes, drying the binder permeated geometric shapes, and heating the hollow shapes and binder to provide a unitary, sintered material system.

Abstract: An airfoil (44) formed of a plurality of pre-fired structural CMC panels (46, 48, 50, 52). Each panel is formed to have an open shape having opposed ends (54) that are free to move during the drying, curing and/or firing of the CMC material in order to minimize interlaminar stresses caused by anisotropic sintering shrinkage. The panels are at least partially pre-shrunk prior to being joined together to form the desired structure, such as an airfoil (42) for a gas turbine engine. The panels may be joined together using a backing member (30), using flanged ends (54) and a clamp (56), and/or with a bond material (36), for example.

Abstract: A composite material (10) formed of a ceramic matrix composite (CMC) material (12) protected by a ceramic insulating material (14). The constituent parts of the insulating material are selected to avoid degradation of the CMC material when the two layers are co-processed. The CMC material is processed to a predetermined state of shrinkage before wet insulating material is applied against the CMC material. The two materials are then co-fired together, with the relative amount of shrinkage between the two materials during the firing step being affected by the amount of pre-shrinkage of the CMC material during the bisque firing step. The shrinkage of the two materials during the co-firing step may be matched to minimize shrinkage stresses, or a predetermined amount of prestress between the materials may be achieved. An aluminum hydroxyl chloride binder material (24) may be used in the insulating material in order to avoid degradation of the fabric (28) of the CMC material during the co-firing step.

Abstract: A method of coating an edge surface (30) of an anisotropic ceramic matrix composite material (10) for use in a high temperature environment is disclosed where the edge surface (30) has exposed reinforced fiber layers (20). A laser beam may be used to melt a portion of the ceramic matrix composite material (10) on the edge surface (30) forming a melt layer. The melt layer is retained proximate the edge surface and the laser beam is controlled to form an isotropic protective coating (32, 34) on a portion of the edge surface (30). A method may be used to form a component for use in a high temperature environment that includes directing a laser beam toward a ceramic matrix composite material (10), controlling the laser beam to melt a portion of the ceramic matrix composite material (10) and forming a homogeneous protective coating (32, 34) from a melt layer that exerts compression on at least a portion of the ceramic matrix composite material (10) when the melt layer is cooled.

Abstract: A green body ceramic matrix composite material (30) is formed using ceramic fibers (32) in an intermediate state disposed in a green body ceramic matrix material (34). The fibers may be in either a dry but unfired (green) condition or in a partially fired condition. Selective control of the degree of pre-firing (pre-shrinkage) of the fibers may be used to control the level of residual stresses within the resulting refractory material resulting from differential shrinkage of the fibers and the matrix material during processing of the composite material.

Abstract: A ceramic article having improved interlaminar strength and a method of forming the article. The article may be a ceramic matrix composite article. The methods of forming the articles increase the interlaminar strength of the article by forming indentations in the article during processing. The indentations may be tabs that are formed such that they provide one or more beneficial features for ceramic articles, such as CMC articles and hybrid structures. The tabs may be any of a variety of shapes, orientations, spacings, and combinations. In an alternative embodiment, the indentations are formed by pulling one or more fibers from one side of the ceramic layer to the other side. The articles have increased surface area, which helps to increase the bonding strength between the ceramic layer and any thermal barrier coating layer and/or ceramic core in the ceramic article.

Abstract: A thermal barrier layer (20) is formed by exposing an oxide ceramic material to a thermal regiment to create a surface heat affected zone effective to protect an underlying structural layer (18) of the material. The heat affected surface layer exhibits a lower strength and higher thermal conductivity than the underlying load-carrying material; however, it retains a sufficiently low thermal conductivity to function as an effective thermal barrier coating. Importantly, because the degraded material retains the same composition and thermal expansion characteristics as the underlying material, the thermal barrier layer remains integrally connected in graded fashion with the underlying material without an interface boundary there between.

Abstract: A stacked ceramic matrix composite lamellate assembly (10) including shear force bearing structures (48) for resisting relative sliding movement between adjacent lamellae. The shear force bearing structures may take the form of a cross-lamellar stitch (50), a shear pin (62), a warp (90) in the lamellae, a tongue (104) and groove (98) structure, or an inter-lamellar sealing member (112), in various embodiments. Each shear force bearing structure secures a subset of the lamellae, with at least one lamella being common between adjacent subsets in order to secure the entire assembly.

Abstract: An insulating material 14 adapted for use in a high temperature environment for coating a turbine component is provided. The insulating material comprises a plurality of geometric shapes 18. The insulating material further comprises a binder for binding together the geometric shapes. A plurality of discontinuous fibers is added to the binder. The discontinuous fibers are adapted to controllably affect one or more properties of the insulating material. For example, non-fugitive chopped fibers 50 may be added to affect a tensile strength property of the insulating material, and fugitive chopped fibers 52 may be added to affect a density property of the insulating material.

Abstract: A joining method for assembling components with complex shapes from CMC elements of simpler shapes. A first CMC element (30) is fabricated and fired to a selected first cured state. A second CMC element (36) is fabricated and left in a green state, or is fired to a second partially cured state that is less complete than that of the first cured state. The two CMC elements (30, 36) are joined in a mating interface that captures an inner joining portion (38) of the second element (36) within a surrounding outer joining portion (32) of the first element (30). The assembled elements (30, 36) are then fired together, resulting in differential shrinkage that compresses the outer joining portion (32) onto the inner joining portion (38), providing a tightly pre-stressed joint. Optionally, a refractory adhesive (42) may be used in the joint. Shrinkage of the outer joining portion (32) avoids shrinkage cracks in the adhesive (42).

Abstract: A method of manufacturing a hybrid structure (100) having a layer of CMC material (28) defining an interior passageway (24) and a layer of ceramic insulating material (18) lining the passageway. The method includes the step of casting the insulating material to a first thickness required for effective casting but in excess of a desired second thickness for use of the hybrid structure. An inner mold (14) defining a net shape desired for the passageway remains in place after the casting step to mechanically support the insulating material during a machining process used to reduce the thickness of the insulating material from the as-cast first thickness to the desired second thickness. The inner mold also provides support as the CMC material is deposited onto the insulating material. The inner mold may include a fugitive material portion (20) to facilitate its removal after the CMC material is formed.

Abstract: A method of manufacturing a composite structure uses a layer of an insulating material (22) as a mold for forming a substrate of a ceramic matrix composite (CMC) material (24). The insulating material may be formed in the shape of a cylinder (10) with the CMC material wound on an outer surface (14) of the cylinder to form a gas turbine combustor liner (20). Alternatively, the insulating material may be formed in the shape of an airfoil section (32) with the CMC material formed on an inside surface (36) of the insulating material. The airfoil section may be formed of a plurality of halves (42, 44) to facilitate the lay-up of the CMC material onto an easily accessible surface, with the halves then joined together to form the complete composite airfoil. In another embodiment, a box structure (102) defining a hot gas flow passage (98) is manufactured by forming insulating material in the shape of opposed airfoil halves (104) joined at respective opposed ends by platform members (109).

Abstract: A composite structure (62) having a bond enhancement member (76) extending across a bond joint (86) between a ceramic matrix composite (CMC) material (80) and a ceramic insulation material (82), and a method of fabricating such a structure. The bond enhancement member may extend completely through the CMC material to be partially embedded in a core material (84) bonded to the CMC material on an opposed side from the insulation material. A mold (26) formed of a fugitive material having particles (18) of a bond enhancement material may be used to form the CMC material. A two-piece mold (38, 46) may be used to drive a bond enhancement member partially into the CMC material. A compressible material (56) containing the bond enhancement member may be compressed between a hard tool (60) and the CMC material to drive a bond enhancement member partially into the CMC material.