Forming cooling passages in combustion turbine superalloy castings

Abstract

Cooling passages ( 99, 105 ) are formed in components for combustion turbine engines, such as blades ( 92 ), vanes ( 104, 106 ), ring segments ( 110 ) or castings in transitions ( 85 ), during investment casting, through use of ceramic shell inserts ( 130 ) within the casting mold ( 152 ). Ceramic posts ( 134 ) formed in the ceramic shell insert ( 130 ) have profiles conforming to corresponding profiles of partially completed cooling passages ( 156 ). Posts ( 134 ) are removed after superalloy component casting, forming the partially completed cooling passages, which are subsequently completed by removing remaining superalloy material along the cooling passage path.

What is claimed is: 
     
         1 . A method for forming a cooling passage in an investment cast, superalloy component for a combustion turbine engine, comprising:
 providing a wax injection mold defining a mold cavity, whose mold cavity surface conforms to a corresponding surface profile of a component for a combustion turbine engine;   providing a ceramic shell insert, having an insert surface profile and at least one ceramic post projecting from the insert surface, which in combination conform to a corresponding surface profile of a partially completed cooling passage in the engine component;   inserting the ceramic shell insert into the wax injection mold, the shell insert surface and each ceramic post forming part of the mold cavity surface, each post projecting into the mold cavity;   filling the mold cavity with wax, enveloping each post therein;   hardening the wax, creating a wax pattern that embeds the ceramic shell insert and each post therein;   removing the wax injection mold, the hardened wax pattern, along with the insert surface and each ceramic post conforming to the component surface profile;   enveloping the hardened wax pattern and embedded ceramic shell insert in ceramic slurry;   firing the ceramic slurry, thereby hardening the slurry into an outer ceramic shell, which is joined to the ceramic shell insert, and eliminating the wax, the joined outer ceramic shell and ceramic shell insert defining a shell internal cavity, which conforms to the engine component profile, including each partially completed cooling passage;   filling the shell internal cavity with molten superalloy material, and cooling the superalloy material to form a component casting therein, the casting including each partially completed cooling passage;   removing the outer ceramic shell and ceramic shell insert, including each ceramic post, from the casting, exposing each partially completed cooling passage; and   completing at least one cooling passage by removing hardened, cast superalloy material from the casting to match a corresponding, completed cooling passage profile in the corresponding component.   
     
     
         2 . The method of  claim 1 , the ceramic shell insert having a plurality of ceramic posts, corresponding to a pattern of partially completed cooling passages in the engine component. 
     
     
         3 . The method of  claim 2 , further comprising the inserted ceramic posts projecting into the mold cavity, without touching any other mold cavity surface. 
     
     
         4 . The method of  claim 2 , further comprising inserting a ceramic core into the mold cavity, and inserting the ceramic shell insert into the mold, with the ceramic insert surface in opposed relationship with the ceramic core, forming a mold cavity void there between, prior to filling the mold cavity void with wax. 
     
     
         5 . The method of  claim 2 , further comprising the ceramic insert surface profile defining engineered surface features. 
     
     
         6 . The method of  claim 2 , at least one ceramic post projecting from the ceramic insert surface at an angle less than 90 degrees. 
     
     
         7 . The method of  claim 6 , the at least one ceramic post projecting from the ceramic insert surface at an angle of between 30 and 60 degrees. 
     
     
         8 . The method of  claim 2 , at least one ceramic post extending in a non-linear profile from the ceramic insert surface. 
     
     
         9 . The method of  claim 1 , further comprising completing at least one cooling passage by removing hardened, cast superalloy material from the component that is within the cooling passage path, so that the cooling passage extends completely through a wall formed within the component casting. 
     
     
         10 . The method of  claim 1 , further comprising forming a thermal barrier coating on the component casting, including the partially completed cooling passage, prior to completing the cooling passage. 
     
     
         11 . A method for forming a cooling passage in an investment cast, superalloy blade or vane component for a combustion turbine engine, the component having a component wall delimited by a wall outer surface, and a wall inner surface that defines a component cavity therein, the cooling passage extending through the component wall between its respective outer and inner surfaces, comprising:
 providing a wax injection mold defining a mold cavity, whose mold cavity surface conforms to a corresponding profile of an outer surface of a hollow blade or vane component for a combustion turbine engine;   providing a ceramic shell insert, having an insert surface profile and at least one ceramic post projecting from the insert surface, which in combination conform to a corresponding surface profile of a partially completed cooling passage in the outer surface of the engine component wall;   providing a ceramic core whose core outer surface conforms to a corresponding profile of a wall inner surface of the engine component;   inserting the ceramic core into the mold cavity, and inserting the ceramic shell insert into the mold, with the shell insert surface in opposed, spaced relationship with the ceramic core outer surface, forming a cavity void there between, which corresponds to a corresponding profile of the component wall respective outer and inner surfaces;   filling the mold cavity void with wax, enveloping each ceramic post therein;   hardening the wax, forming a wax pattern that embeds the ceramic core, and ceramic shell insert, including each ceramic post therein;   removing the wax injection mold, the hardened wax pattern, along with the ceramic core, ceramic shell insert surface and each ceramic post conforming to the component wall respective outer and inner surfaces profiles;   enveloping the hardened wax pattern and the respective embedded ceramic core and ceramic shell insert in ceramic slurry;   firing the ceramic slurry, thereby hardening the slurry into an outer ceramic shell, which is joined to the ceramic shell insert and the ceramic core, and eliminating the wax, the joined outer ceramic shell and ceramic insert defining a shell internal cavity, which conforms to the engine component wall outer surface profile, including each partially completed cooling passage, the ceramic core outer surface conforming to the engine component wall inner surface profile, and the ceramic shell cavity void conforming to the engine component wall;   filling the ceramic shell internal cavity void with molten superalloy material, and cooling the superalloy material to form a component casting therein, the casting including each partially completed cooling passage in the component outer wall surface;   removing the ceramic core, ceramic outer shell, and ceramic insert, including each ceramic post, from the casting, exposing each partially complete cooling passage in the outer surface of the component wall; and   completing at least one cooling passage through the component wall, by removing hardened, cast superalloy material that blocks remaining path of the cooling passage.   
     
     
         12 . The method of  claim 11 , further comprising forming a thermal barrier coating on the component casting, including the partially completed cooling passage, prior to completing the cooling passage. 
     
     
         13 . The method of  claim 12 , the ceramic shell insert having a plurality of ceramic posts, corresponding to a pattern of partially completed cooling passages in the engine component. 
     
     
         14 . The method of  claim 12 , further comprising the inserted ceramic posts projecting into the mold cavity, without touching any other mold cavity surface. 
     
     
         15 . The method of  claim 12 , at least one ceramic post projecting from the insert surface at an angle less than 90 degrees. 
     
     
         16 . The method of  claim 15 , the at least one ceramic post projecting from the insert surface at an angle of between 30 and 60 degrees. 
     
     
         17 . The method of  claim 12 , at least one ceramic post extending in a non-linear profile from the ceramic shell insert surface. 
     
     
         18 . The method of  claim 11 , the ceramic shell insert surface comprising:
 a plurality of ceramic posts, corresponding to a pattern of partially completed cooling passages in the engine component; and   engineered surface features, which are respectively defined in the insert surface profile.   
     
     
         19 . The method of  claim 11 , the at least one ceramic post projecting from the ceramic insert surface at an angle of between 30 and 60 degrees. 
     
     
         20 . The method of  claim 11 , at least one ceramic post extending in a non-linear profile from the ceramic shell insert surface.