Trw Limited

Pcc Airfoils, Inc.

William S Blazek

Thomas S Piwonka

Philip N Atanmo

James D Jackson

Harold L Wheaton

Jerry L Hasch

A turbine engine component is made by forming a heat resistant layer on each airfoil of a plurality of airfoils. This heat resistant layer has a higher melting temperature than the melting temperature of material forming the airfoil. After heat resistant layers have been formed on the airfoils, a mold is formed around the airfoils. Molten metal is poured into the mold. The molten metal engages the heat resistant layers on the airfoils and solidifies to form a shroud ring. As the molten metal solidifies, slip joints between the solidified metal and end portions of the airfoils are free of bonds. The heat resistant layer is at least partially formed of chromium sesquioxide (Cr.sub.2 O.sub.3). A layer of chromium sesquioxide is formed by heating a nickel-chrome superalloy airfoil. As the airfoil is heated, the layer of metal immediately adjacent to the outer surface of the airfoil is depleted of chromium. This results in the formation of an outer layer of chromium sesquioxide and an inner layer from which the chromium has been depleted. Both layers have a higher melting temperature than the melting temperature of the material forming the airfoil.

Method of making a turbine engine component

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. The shroud ring mold cavity is then filled with molten metal which is solidified to form the shroud ring. The core material is then removed from the shroud ring to leave space to accommodate thermal expansion of the airfoils.

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. Core material may be positioned at the ends of the airfoils to at least partially form the shroud ring cavities.

Method of making an improved turbine engine component

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. The shroud ring mold cavity is then filled with molten metal which is solidified to form the shroud ring. The core material is then removed from the shroud ring to leave space to accomodate thermal expansion of the airfoils.

An improved method is provided to cast a one-piece wheel having a circular hub and a plurality of airfoils. The method includes providing a mold having a circular main section and a plurality of open-ended airfoil forming sections. Each of the airfoil forming sections has a thick leading edge portion and a thin trailing edge portion. During a casting operation, the mold is preheated while it is spaced from a chill. The mold and chill are then moved into abutting engagement with the chill extending across the open outer end portion of the airfoil forming sections. The relatively thick leading edge portions of the airfoil forming sections are disposed adjacent to a portion of the chill. Molten metal is poured into the mold cavity and flows outwardly through the airfoil forming sections into engagement with the chill. This results in solidification of columnar grains of metal in a direction toward the center of the mold cavity. As the molten metal is solidifying, heat is conducted at a greater rate from the relatively thick leading edge portions of the airfoils than from the relatively thin trailing edge portions of the airfoils. Therefore, the columnar grains grow in a direction parallel to the central axes of the airfoils.

Method of casting a one-piece wheel

To form a turbine engine component, metal airfoils are positioned in an annular array. Outer end portions of the airfoils are embedded in a wax outer shroud ring pattern and inner end portions of the airfoils are embedded in a wax inner shroud ring pattern. A mold is formed by covering the metal airfoils and the shroud ring patterns with ceramic mold material. The wax of the shroud ring patterns is then removed from the mold to leave inner and outer shroud ring mold ring cavities. The shroud ring mold cavities are filled with molten metal which is solidified to form inner and outer shroud rings interconnecting the airfoils. To accommodate thermal expansion of the airfoils relative to the shroud rings, a slip joint is provided between at least one end portion of each of the airfoils and a shroud ring. To enable the slip joint to be formed, molten metal solidifies in the shroud ring to be formed, molten metal solidifies in the shroud ring cavities free of metallurgical bonds to the airfoils. The shroud rings may be formed of metal having different compositions and crystallographic structures than the metal of the airfoils.

Turbine engine component and method of making the same

An improved method of assembling molds enables the size of successive molds to be adjusted to provide cast articles having a desired size. In practicing the method, a first or initial mold is assembled in a fixture. This initial mold is used to form a cast article. The cast article formed in the initial mold is measured to determine the extent to which the dimensions of the article deviate from predetermined design dimensions. The fixture is then adjusted to compensate for the deviations in the dimensions of the cast article from the intended or design dimensions. A second mold is then assembled in the fixture. Since the fixture has been adjusted to compensate for the inaccuracies in the first mold, a product cast with the second mold will have dimensions closer to the desired dimensions.

Method of assembling molds

An improved apparatus for assembling molds enables the size of successive molds to be adjusted to provide cast articles having a desired size. In using the apparatus, a first or initial mold is assembled in a fixture. This initial mold is used to form a cast article. The cast article formed in the initial mold is measured to determine the extent to which the dimensions of the article deviate from predetermined design dimensions. The fixture is then adjusted to compensate for the deviations in the dimensions of the cast article from the intended or design dimensions. A second mold is then assembled in the fixture. Since the fixture has been adjusted to compensate for the inaccuracies in the first mold, a product cast with the second mold will have dimensions closer to the desired dimensions.

Apparatus for use in casting an article

A plurality of mold wall segments are positioned in a circular array in an adjustable fixture to form a mold assembly. The fixture includes a base with a plurality of upstanding pin members. Two of the pin members engage the bottom portion of each mold wall segment. Each pin member is eccentrically mounted on a disc. By rotating the discs relative to their base, the mold wall segments may be moved inward or outward. This movement varies the diameter of the lower portion of the mold assembly. The pin members have threaded end portions which enable the pin members to be moved along their upstanding central axes. This movement varies the height of the lower portion of the mold assembly. In addition, the fixture includes a plurality of radially extending adjusting rods, each rod engages a radially inner side surface of a mold segment. By moving the rods radially inward or outward, each mold wall segment is caused to tilt or rotate about an axis extending through the upper end portions of the pin members which engage the bottom portions of that mold wall segment. This movement varies the diameter of the upper portion of the mold assembly. In one embodiment of the invention, the mold segments of inner and outer annular arrays of mold segments are independently movable relative to each other.

Method and apparatus for use in casting an article

An improved method is utilized to make a mold for a cast product having a plurality of spaced apart surfaces. Although the method could be used for forming molds for different products, the method is advantageously used to form a mold for a cast product having a plurality of airfoils disposed in a circular array. To form the mold, a plurality of airfoil pattern segments are placed in a circular array with surfaces of the segments abutting at joints which are free of material interconnecting the segments. A coating of liquid ceramic mold material is applied over the airfoil pattern segments. Since the joints between the airfoil pattern segments are free of interconnecting material, the liquid ceramic mold material can flow into the joints. After the ceramic mold material has been dried and the airfoil pattern segments disposed of, the ceramic mold material which entered the joints between the airfoil pattern segments forms a plurality of relatively thin projections from the main wall of the mold. These thin projections are broken away before the product is cast in the mold. During the application of the ceramic coating to the airfoil pattern segments, the relatively flexible wax airfoil pattern segments are advantageously supported by a relatively rigid annular pattern member which is disposed outwardly of the airfoil segments.

Method of making a mold

An improved method of forming inner and outer sections of a shroud with an airfoil extending between them includes forming the airfoil and shrouds in sections. An upper or convex section of an airfoil is formed with a radially inner section of the shroud while a concave or lower section of the airfoil is formed with a radially outer section of the shroud. A free end portion of the convex or upper airfoil section is inserted into an opening formed in the outer shroud section while a free end portion of the concave or lower airfoil section is inserted into an opening formed in the inner shroud section. The free end portions of the airfoil sections are then connected with the shroud sections to form a complete airfoil and a portion of the inner and outer shroud sections. Although the convex or upper airfoil section is disclosed herein as being integrally formed with the inner shroud section and the concave or lower airfoil section is disclosed as being integrally formed with the outer shroud section, this relationship is a matter of choice and could be reversed if desired.

Method of forming an airfoil with inner and outer shroud sections

The present invention provides an improved method of forming a metal article having a plurality of airfoils which extend outwardly from a hub. The metal airfoils are formed separately from the hub. In forming a mold to cast the article, blade portions of the metal airfoils are coated with wax. The metal airfoils are then placed in a circular array and are covered with a coating of liquid ceramic mold material. This wet coating of ceramic mold material is dried to form an annular mold wall section having a plurality of recesses in which the blades of the metal airfoils are disposed. The wax coating over the metal airfoil blades is subsequently removed from the recesses to provide space between the blades and the side walls of the recesses. The annular mold wall section in which the blade containing recesses are formed is then connected with top and bottom mold sections to further define a mold cavity having a configuration corresponding to the hub portion of the article. Before casting, the mold is preheated to a relatively high temperature with the blade portions of the airfoils in their associated recesses. As the mold is preheated, the metal airfoils expand to completely fill the recesses in which the blade portions of the airfoils are disposed. Molten metal is then poured into the mold cavity and cooled to form a hub which interconnects the roots of the airfoils.

Method of forming metal article having plurality of airfoils extending

A segmented mold assembly is utilized to cast a turbine engine component having a relatively heavy hub from which relatively light vanes project. The mold assembly includes a plurality of sections which are formed of a ceramic mold material and are interconnected at flange joints. The mold sections are advantageously formed by repetitively dipping patterns in a slurry of liquid ceramic mold material to form wet coatings on the patterns. These wet coatings are dried and separated from the patterns to form the mold sections. The mold sections which are used to cast the vanes retard the removal of heat from the vanes to provide time for the hub to solidify. This can be accomplished by using relatively thick walled mold sections to form the mold cavities in which vanes are cast and relatively thin walled mold sections to form the cavity in which the hub is cast. This could also be accomplished by forming the vane mold section of material having a relatively low rate of heat removal and the hub mold section of a material having a relatively high rate of heat removal.

Mold assembly and method of making the same

A segmented mold assembly is utilized to cast a turbine engine component having an annular inner wall and an annular outer wall which are interconnected by a plurality of struts or vanes. The mold assembly includes a plurality of sections which are formed of a ceramic mold material and are interconnected at flange joints. A pair of mold sections are advantageously formed simultaneously by repetitively dipping a single pattern in a slurry of liquid ceramic mold material to form a wet coating on the pattern. This wet coating of ceramic mold material is then dried. After a covering of the desired thickness has been built up by repetitively dipping and drying the coatings on the wax pattern, the wax pattern is destroyed. To facilitate separating the mold sections after destroying the wax pattern, at least some of the wet coatings are wiped away in an area between portions of the wet coatings which will eventually form the mold sections.

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Valley City, OH, United States of America

William S Blazek