Turbine airfoil casting method

Abstract

A method for making a turbine airfoil includes: (a) providing a mold having: (i) a core; (ii) an outer shell surrounding the core such that the core and the outer shell cooperatively define a cavity in the shape of an airfoil having at least one outer wall; and (iii) a core support extending from the core to the outer shell through a portion of the cavity that defines the at least one sidewall; (b) introducing molten metal alloy into the cavity and surrounding the core support; (c) solidifying the alloy to form an airfoil casting having at least one outer wall which has at least one core support opening passing therethrough; (d) removing the mold so as to expose the airfoil; and (e) sealing the at least one core support opening in the airfoil with a metal alloy metallurgically bonded to the at least one outer wall.

1 . A method for making a turbine airfoil, comprising:
 (a) providing a mold having:
 (i) a core; 
 (ii) an outer shell surrounding the core such that the core and the outer shell cooperatively define a cavity in the shape of an airfoil having at least one outer wall; and 
 (iii) a core support extending from the core to the outer shell through a portion of the cavity that defines the at least one sidewall; 
   (b) introducing molten metal alloy into the cavity and surrounding the core support;   (c) solidifying the alloy to form an airfoil casting having at least one outer wall which has at least one core support opening passing therethrough;   (d) removing the mold so as to expose the airfoil; and   (e) sealing the at least one core support opening in the airfoil with a metal alloy metallurgically bonded to the at least one outer wall.   
   
   
       2 . The method of  claim 1  wherein step (e) is carried out by:
 (a) melting an alloy power using laser energy;   (b) introducing the melted powder into the at least one core support opening; and   (c) allowing the melted powder to cool and solidify in the at least one core support opening.   
   
   
       3 . The method of  claim 2  wherein the alloy power has a composition substantially the same as an alloy composition of the airfoil. 
   
   
       4 . The method of  claim 1  wherein step (e) is carried out by:
 (a) introducing an alloy powder into the at least one core support opening;   (b) using laser energy, melting the alloy powder and heating the outer wall; and   (c) allowing the melted powder to cool and solidify in the at least one core support opening.   
   
   
       5 . The method of  claim 4  wherein the alloy power has a composition substantially the same as an alloy composition of the airfoil. 
   
   
       6 . The method of  claim 1  wherein the airfoil has a directionally solidified or single crystal microstructure, and the solidified powder in the at least one core support opening has substantially the same microstructure as the airfoil. 
   
   
       7 . The method of  claim 1  wherein the core support is a cylindrical rod. 
   
   
       8 . The method of  claim 1  wherein the core support comprises fused quartz. 
   
   
       9 . The method of  claim 1  wherein the mold comprises:
 (i) a core; and   (ii) an outer shell surrounding the core, the outer shell having two spaced-apart sidewalls disposed on opposite sides of the core; and   (iii) a core support extending from the one of the sidewalls of the outer shell, through the core, to the other sidewall of the outer shell.   
   
   
       10 . The method of  claim 9  wherein the airfoil includes spaced-apart pressure and suction side outer walls each having a core support opening therein, the core support openings being coaxial to each other. 
   
   
       11 . The method of  claim 1  wherein the mold defines an integral turbine blade including the airfoil and a shank, the airfoil and the shank respectively defining opposite ends of the turbine blade. 
   
   
       12 . The method of  claim 11  wherein the core support is positioned in the airfoil at an end of the turbine blade opposite from the shank.