Cores for use in precision investment casting

Abstract

Concepts for fabricating improved cores for investment casting are described. The cores are composite which include refractory metal elements and ceramic elements. The refractory metal elements are provided to enhance the mechanical properties of the core and/or to permit the fabrication of cores having shapes and geometries that could not otherwise be achieved. In one embodiment, the entire core may be made of refractory metal components. The cores may be used to investment cast gas turbine superalloy components.

1 . A composite core for use in an investment casting process to produce an internal passage in an investment casting which comprises 
 a) a ceramic element    b) a refractory metal element attached to said ceramic element,    
     
     
         2 . A composite core as in  claim 1  wherein said ceramic element is an oxide ceramic.  
     
     
         3 . A composite core as in  claim 1  wherein said refractory metal element is coated with at least one oxidation resistant coating layer.  
     
     
         4 . A composite core as in  claim 1  wherein said refractory metal element comprises at least one wire.  
     
     
         5 . A composite core as in  claim 1  wherein said refractory metal element comprises at least one sheet.  
     
     
         6 . A composite core as in  claim 1  wherein said refractory metal element is embedded in said ceramic element.  
     
     
         7 . A composite core as in  claim 1  wherein said refractory metal element is attached to the surface of the ceramic element.  
     
     
         8 . A composite core as in  claim 7  wherein said attachment is a mechanical attachment.  
     
     
         9 . A composite core as in  claim 7  wherein said attachment is a chemical bond.  
     
     
         10 . A mold-core assembly useful in the production of investment castings, having internal passages, which comprises 
 a) a composite core assembly including 
 a) a ceramic element  
 b) a refractory metal element attached to said ceramic element, the external contour of the combined ceramic and refractory metal elements corresponding essentially to the contour of the desired predetermined internal passage along with gating and feeding elements.  
 c) a ceramic shell mold surrounding said core, and spaced away from said core to define a cavity  
 d) means in said shell mold for filling said cavity with molten metal.  
   
     
     
         11 . A. east article which comprises a cast superalloy body which contains a composite core captured within said superalloy body, said composite core comprising 
 a) a ceramic element    b) a refractory metal element attached to said ceramic element, the external contour of the combined ceramic elements corresponding essentially to the contour of the desired predetermined internal passage along with gating and feeding elements.    
     
     
         12 . A composite core for use in investment castings of superalloys, comprising at least one ceramic element and at least one refractory metal element, said core having at least a element having a dimension of less than about 0.015 inches.  
     
     
         13 . An as cast superalloy article having an internal passage having a dimension of less than about 0.012 inches.  
     
     
         14 . A core producing a superalloy investment casting including a refractory metal element forming the trailing edge of said core.  
     
     
         15 . A core and shell assembly for use in producing a superalloy investment casting including at least one refractory metal element attached to said core and to said shell.