Heat Treatment of Alloys Having Elements for Improving Grain Boundary Strength

Abstract

A method of producing a component wherein a directionally solidified columnar grained cast superalloy material is heat treated such that a secondary phase of the alloy is only partly solved, thereby providing improved transverse stress rupture strength compared to fully solved alloys.

1 . A method of forming a component, comprising:
 casting a nickel based alloy as a directionally solidified columnar grained or single crystal structure comprising a secondary phase; and   heat treating the cast alloy to only partially solve the secondary phase.   
     
     
         2 . The method of  claim 1 , further comprising heat treating the cast alloy to solve only between 30% and 90% of the secondary phase. 
     
     
         3 . The method of  claim 1 , wherein the heat treating is performed at a temperature less than a full solution temperature of the cast alloy. 
     
     
         4 . The method of  claim 1 , wherein the heat treating is performed at a full solution temperature of the cast alloy but for only a duration of time such that the secondary phase is not fully solved. 
     
     
         5 . The method of  claim 1 , further comprising casting the alloy to comprise boron in an amount of about 0.003% to about 0.0175%. 
     
     
         6 . A method of forming a component, comprising:
 casting a directionally solidified nickel based superalloy consisting essentially of, in weight %:   
       about 11.6% to 12/70% Cr, 
       about 8.5% to 9.5% Co, 
       about 1.65% to 2.15% Mo, 
       about 3.5% to 4.10% W, 
       about 4.8% to 5.20% Ta, 
       about 3.4% to 3.8% Al, 
       about 3.9% to 4.25% Ti, 
       about 0.05% to 0.11% C, 
       about 0.003% to 0.0175% B, 
       balance essentially Ni; and
 heat treating the cast alloy until a γ′ secondary phase of the alloy is only partially solved. 
 
     
     
         7 . The method of  claim 6 , further comprising heat treating the cast alloy only until the secondary phase is less than 90% solved. 
     
     
         8 . The method of  claim 7 , wherein the heat treating is performed at a temperature less than a full solution temperature of the cast alloy. 
     
     
         9 . The method of  claim 7 , wherein the heat treating is performed at less 1250 degrees C. 
     
     
         10 . The method of  claim 7 , wherein the heat treating is performed at 1213° C. for at least 1 hour. 
     
     
         11 . The method of  claim 7 , wherein the heat treating is performed at a full solution temperature of the cast alloy but for only a duration of time such that the secondary phase is not fully solved. 
     
     
         12 . The method of  claim 6 , wherein the heat treating is performed at 1250 degrees C. only until the secondary phase is between 30% and 90% solved.