Abstract: A turbine engine component includes an annular array of airfoils which extend between inner and outer shroud rings. In order to accommodate thermal expansion of the airfoils, space is provided in a shroud ring rail. To provide space in the shroud ring rail, core material is positioned at the ends of the airfoils. The core material may be preformed separetely from the airfoils or may be a coating which is applied to end portions of the airfoils. Wax pattern material partially encloses the end portions of the airfoils and core material. The shroud ring pattern and the core material are covered with ceramic mold material to form a mold. The shroud ring pattern is then removed from the mold to leave the core material disposed in the shroud ring mold cavity at the end portions of the airfoils. As the mold is preheated, bonds between the core material and the airfoils are broken and the core material is gripped between end portions of the airfoils and the ceramic mold material.

Abstract: A mold is used to cast an article as a single crystal having selected primary and secondary orientations. The mold includes an article mold having a configuration corresponding to the configuration of the article to be cast. A starter section contains a starter cavity in which one or more crystals form. A seed crystal is disposed in the starter cavity. A crystal selector has a passage which extends between an upper end of the starter and a lower end of the article mold. To promote the growth in the crystal selector passage of a crystal having primary and secondary orientations corresponding to the selected primary and secondary orientations of the article, the longitudinal central axis of the crystal selector passage is disposed in a single plane which is parallel to a plane containing the selected primary orientation axis of the single crystal article and the selected secondary orientation axis of the single crystal article.

Abstract: A mold structure includes an article mold having a mold cavity with a configuration corresponding to the configuration of the article to be cast. A starter section contains a starter cavity in which a plurality of crystals form. A crystal selector has a passage which extends between an upper end of the starter cavity and a lower end of the article mold cavity. To promote the growth in the crystal selector passage of a crystal having primary and secondary orientations corresponding to selected primary and secondary orientations of the article, the crystal selector passage has a portion which slopes downwardly in the direction of solidification of metal along the crystal selector passage. Without the use of a seed crystal, the cast article will have a secondary orientation axis which is almost always within plus or minus 30 degrees of a selected secondary orientation axis.

Abstract: During the casting of reactive metals, the depletion of reactive elements from molten metal in an article mold cavity is prevented by blocking a feeder passage after filling an article mold cavity with the molten metal. To block the feeder passage, a valve member is floated on the molten metal. As the level of the molten metal rises, the valve member moves into sealing engagement with a valve seat. To make a mold structure containing the valve member, the valve member is positioned in a pattern of the mold structure. After covering the pattern with ceramic mold material, the pattern is removed to leave the valve member in the mold structure.

Abstract: An improved method of casting provides for the blocking of the upper end portion of a mold structure during preheating of the mold structure in a furnace and/or withdrawal of the mold structure from the furnace. The mold structure is raised into a furnace chamber with a cover blocking the upper end portion of the mold structure. In the illustrated embodiment of the invention, the cover moves upwardly through the furnace chamber to a location immediately above an upper sidewall of the furnace chamber. When the mold has been preheated, the cover is removed and molten metal is pored into the mold structure. The cover is then replaced on the mold structure. The molten metal in the mold structure is solidified by slowly withdrawing the mold structure from the furnace chamber with the cover blocking the upper end portion of the mold structure. Once the mold structure has been completely withdrawn from the furnace chamber and the molten metal in the mold structure has solidified, the cover is removed.

Abstract: A turbine engine component having an annular array of airfoils disposed between inner and outer shroud rings is made by a method which includes molding bodies of positioning material around central portions of the airfoils. The bodies of positioning material are placed in an annular array. Inner and outer shroud ring pattern dies cooperate with the bodies of positioning material to form inner and outer shroud ring pattern mold cavities. Pattern material is injected into the inner and outer shroud ring pattern mold cavities. The pattern material engages the airfoils, the positioning material, and the shroud ring pattern dies. The pattern material is solidified to form one piece annular inner and outer shroud ring patterns. The shroud ring patterns are covered with a ceramic mold material to form a mold. The inner and outer shroud ring patterns are then removed from the mold to leave shroud ring mold cavities.

Abstract: A baffle retard the transfer of heat from a mold structure to a chill plate during casting of molten metal. The baffle includes a circular support portion and a plurality of flexible segments which extend from the support portion. Each of the segments is engageable with an irregular side portion of the mold structure. During a casting operation, the chill plate and mold structure are lowered from a furnace chamber. As they are lowered, the baffle is maintained in engagement with an irregular side portion of the mold structure until the irregular side portion moves below the baffle. To maintain the baffle in engagement with the irregular side portion of the mold structure during lowering of the mold structure, the flexible segments of the baffle resiliently flex toward and away from the central axis of the baffle. The flexible segments of the baffle may advantageously be formed of a graphite foil.

Abstract: An improved turbine engine component includes an annular array of airfoils which extend between inner and outer shroud rings. In order to accommodate thermal expansion of the airfoils, cavities are provided in one of the shroud rings. The cavities may be formed by moving a shroud ring under the influence of forces applied to the shroud ring by a gating system. The cavities which are formed in the shroud ring to accommodate thermal expansion of the airfoils may be open-ended, completely closed-ended or partially closed-ended. When a turbine engine component having cavities in an inner shroud ring is to be formed, molten metal in an outer shroud ring mold cavity is first solidified to firmly grip outer ends of the airfoils. The molten metal in an inner shroud ring mold cavity is then solidified. As the molten metal in the inner shroud ring mold cavity solidifies, the gating system contracts to pull the metal in the inner shroud ring mold cavity inwardly relative to the airfoils.

Abstract: A turbine engine component includes an annular array of airfoils which extend between inner and outer shroud rings. In order to accommodate thermal expansion of the airfoils, space is provided in a shroud ring rail. To provide space in the shroud ring rail, core material is positioned at the ends of the airfoils. The core material may be preformed separately from the airfoils or may be a coating which is applied to end portions of the airfoils. Wax pattern material partially encloses the end portions of the airfoils and core material. The shroud ring pattern and the core material are covered with ceramic mold material to form a mold. The shroud ring pattern is then removed from the mold to leave the core material disposed in the shroud ring mold cavity at the end portions of the airfoils. As the mold is preheated, bonds between the core material and the airfoils are broken and the core material is gripped between end portions of the airfoils and the ceramic mold material.

Abstract: Reactive metals, such as titanium or nickel-chrome superalloys containing rare earths, are cast with mold and/or core surface areas formed from an improved slurry. The improved slurry contains yttria to form an inert surface which is exposed to the molten reactive metal. In order to prevent premature gelation of the slurry, the forming of defects in the mold and/or core surface areas, and the forming of defects in the cast article, the slurry contains a source of hydroxyl ions. The source of hydroxyl ions is sufficient to result in the slurry having a pH of at least 10.2 six days after initially mixing the slurry. The source of hydroxyl ions may be a metal alkali or an organic hydroxide. It is believed that the source of hydroxyl ions functions as a hydration suppressant for the yttria to prevent premature gelation of the slurry. The slurry contains a silicon oxide (SiO.sub.2) to alkali ratio which is equivalent to a silicon oxide to sodium oxide (Na.sub.

Abstract: A single crystal selector has a passage into which a plurality of crystals grow from a starter cavity and from which a single crystal emerges into an article mold cavity. The single crystal selector passage includes a linear lower vertical portion which extends upwardly away from an end portion on the starter cavity. A linear vertical upper portion of the selector passage extends downwardly from a lower end portion of the article mold cavity. A single bend portion of the selector passage extends between the upper and lower portions of the selector passage. A support element extends upwardly from a lower section of the selector to an upper section of the selector to at least partially support a single bend section of the selector. The single bend portion of the selector passage has a generally circular cross sectional configuration with a diameter which is less than 0.25 inches. The single bend portion of the selector passage extends sidewardly for a distance which is at least 1.

Abstract: A long thin article having an enlarged end portion, such as a vane having a long thin airfoil and a shroud at the end of the airfoil, is cast by using a chill at the enlarged end portion of an article mold cavity. The chill is engaged by molten metal at the enlarged end portion of the article mold cavity. The molten metal quickly solidifies adjacent to the chill to eliminate the formation of defects. The chill is advantageously located in a pocket disposed at one end of the article mold cavity. The chills are placed in the pockets with the molds in an up-side-down orientation. The mold is then turned right-side-up and placed on a chill plate. The chills project from the mold and support the mold above the chill plate. During casting of an article, heat is transmitted from the enlarged end portion of the article through chill to the chill plate.

Abstract: An improved mold has a coating of material having a relatively high emissivity. The surface of the coating has an emissivity which is at least twice as great as the emissivity of the surface of the ceramic mold material. When the mold is removed from a furnace chamber, the surface of the coating radiates heat at a relatively high rate. In one embodiment of the invention, the coating is applied to only a portion of the surface of a ceramic mold. In another embodiment of the invention, the coating of material having a relatively high emissivity is applied to only a portion of a crystal selector on a mold for a single crystal article. The relatively high rate of radiation of heat from the coated portion of the crystal selector increases the rate of growth of an adjacent single crystal grain. If desired, the entire mold can be covered with the coating of material having a relatively high emissivity. The coating of material having a high emissivity may be formed of graphite.

Abstract: A long, thin article or portion of an article of an equiaxed metal is cast without providing gates along the length of a portion of a mold cavity in which the long thin portion of the article is cast. Prior to casting the article, the lower half of the long thin portion of the article mold is heated into a temperature range in which the highest temperature is close to but less than the solidus temperature of the metal of the article. Molten metal is conducted into the long thin portion of the article mold cavity at a location other than along the length of the long thin portion of the article mold cavity. During solidification of the molten metal, molten metal is simultaneously solidified along surface areas in the lower half of the long thin portion of the mold cavity and along surface areas in the upper half of the long thin portion of the mold cavity.

Abstract: A chill plate moves the mold structure into a furnace, A baffle is supported in an open central portion of an array of article molds by a plurality of support elements. The support elements extend through spaces between the article molds into engagement with a furnace to support the baffle during withdrawal of the article molds from the furnace. In one embodiment of the invention, the support elements are engaged with the furnace by rotating the chill plate through a small arc. When the article molds have been almost completely withdrawn from the furnace, the baffle plate is disposed adjacent to the upper ends of the article molds. At this time, the chill plate is again rotated to disengage the support elements from the furnace. When this happens, the baffle drops downwardly onto the chill plate.

Abstract: An improved mold includes an upper mold section having a primary distribution system which is connected with a furnace and a lower mold section which is withdrawn from the furnace on a chill plate. A baffle plate is supported from the primary distribution system. The lower mold section includes a secondary distribution system which is connected in fluid communication with the primary distribution system at separable joints. The secondary distribution system is connected in fluid communication with article molds which are disposed in an annular array. During pouring of molten metal, reaction forces are transmitted to the chill plate from the pour cup through a support post and baffle plate. Once the article molds have been filled with molten metal, the chill plate is lowered. The primary distribution system which is connected to the furnace, remains stationary.

Abstract: An improved apparatus and method is used to cast a plurality of articles in a mold structure having a plurality of article molds disposed in an array having an open central portion. The article molds are filled with molten metal while the mold structure is supported on a chill plate. An inner baffle plate is disposed in the central portion of the array of article molds and retards the transfer of heat from the article molds to the chill plate. The inner baffle plate is supported by a support structure which extends through the chill plate. After the article molds have been filled with molten metal, the chill plate and mold structure are lowered relative to the inner baffle plate to increase the rate of heat transfer from the article molds to the chill plate through the open central portion of the array of article molds. Thereafter, the inner baffle plate and support structure are lowered with the chill plate and mold structure.

Abstract: A mold structure has a plurality of article molds disposed in an array with an open central space. A gating system is connected with upper ends of the article molds and a base is connected with lower ends of the article molds. A baffle plate is inserted into the open central space between the article molds. The baffle plate has an area which is greater than the area of an opening in the base. A lower side of the baffle plate overlies an area on the base which extends completely around the opening in the base. To insert the baffle plate through the opening in the base, a slit is formed in the baffle plate. A portion of the base is received in the slit and then the baffle plate is rotated to turn it through the opening in the base. An alternative method of inserting the baffle plate is by partially folding the baffle plate and inserting the folded baffle plate through the opening in the base of the mold structure.

Abstract: Both a pattern member and a body of expansion material are covered with a layer of ceramic mold material. The body of expansion material has a coefficient of thermal expansion which is greater than the coefficient of thermal expansion of the ceramic mold material. The layer of ceramic mold material and the body of expansion material are heated. This results in a cracking of the layer of ceramic mold material by the body of expansion material due to greater thermal expansion of the body of expansion material as it is heated. During the step of heating the ceramic mold material and body of expansion material, the pattern member is melted to separate the pattern from the layer of ceramic mold material.

Abstract: In order to maintain fluid tight seals between open ended article mold cavities and a chill plate and to prevent cracking of article molds at connections with a base plate, the base plate has sections which can be moved relative to each other under the effect of thermal expansion forces transmitted from a molten metal distribution system connected with the upper ends of the article molds. The base plate may be formed as one piece with stress concentration areas. During the casting of articles, stresses in the base plate crack the base plate at the areas of stress concentration to form the separate sections of the base plate. The areas of stress concentration can be formed by slots or grooves in the base plate. The areas of stress concentration can also be formed by bodies of expansion material having a greater coefficient of thermal expansion than the ceramic material of the base plate.