Airfoil casting methods

Abstract

In the castings of a turbine element, a sheet casting core is assembled to a feedcore. The sheet casting core and feedcore are placed in a die. A sacrificial pattern material is molded over the casting core and feedcore to form a pattern including an airfoil. The sheet casting core extends from at or adjacent a trailing edge of the airfoil. The sheet casting core has a first array of open areas and a second array of portions interspersed with the open areas. A first portion of the die has a third array of projections contacting the second array.

1 . A method comprising:
 assembling a sheet casting core to a feedcore;   placing the sheet casting core and feed core in a die; and   molding a sacrificial pattern material over the sheet casting core and feedcore to form the pattern including an airfoil and the sheet casting core extending from at or adjacent a trailing edge of the airfoil,   
     wherein:
 the sheet casting core has a first array of open areas and a second array of portions interspersed with the open areas; and 
 a first portion of the die has a third array of projections contacting the second array. 
 
   
   
       2 . The method of  claim 1  wherein:
 the placing comprises positioning relative to a first die element and then assembling a second die element to the first die element.   
   
   
       3 . The method of  claim 1  wherein:
 the molding comprises introducing a wax as said sacrificial pattern material.   
   
   
       4 . The method of  claim 1  wherein:
 the assembling is entirely before the placing.   
   
   
       5 . The method of  claim 1  wherein:
 the third array falls along a pressure side of the airfoil; and   the third array includes 5-50 such projections.   
   
   
       6 . The method of  claim 1  wherein:
 the feedcore comprises a molded ceramic; and   the sheet casting core consists essentially of a refractory metal-based member, optionally coated.   
   
   
       7 . The method of  claim 1  wherein:
 the sheet casting core has a thickness of 1.2-7.6 mm along a majority of a surface area.   
   
   
       8 . The method of  claim 1  wherein:
 the sheet casting core has an essentially uniform thickness of 2-3 mm along a majority of a surface area.   
   
   
       9 . A casting core and die assembly for molding an airfoil pattern having pressure and suction sides, the assembly comprising:
 a feedcore;   a sheet casting core assembled to the feedcore;   a die at least partially containing the feedcore and sheet casting core and including first and second surface sections shaped to respectively form the airfoil pattern pressure and suction sides; and   means on the die and sheet casting core for forming an array of trailing edge slots open along one side of a pressure side and a suction side of an airfoil to be cast via the airfoil pattern.   
   
   
       10 . The assembly of  claim 9  wherein:
 each of the slots has an opening along said one side having a length and a width; and   for at least some of the slots, the length is at least 50% of the width.   
   
   
       11 . The assembly of  claim 9  wherein:
 the one side is the pressure side of the airfoil.   
   
   
       12 . The assembly of  claim 9  wherein:
 each of the slots has an opening along said one side; and   for at least some of the slots, opening has an arcuate leading extremity.   
   
   
       13 . The assembly of  claim 9  wherein:
 the feedcore consists essentially of a ceramic; and   the sheet casting core comprises a refractory metal-based sheet.   
   
   
       14 . The assembly of  claim 9  wherein:
 the sheet casting core has a thickness of 1.2-7.6 mm along a majority of a surface area.   
   
   
       15 . The assembly of  claim 9  wherein:
 the sheet casting core has an essentially uniform thickness of 2-3 mm along a majority of a surface area.