Directionally solidified casting with improved transverse stress rupture strength

Abstract

Directionally solidified columnar grain nickel base alloy casting consisting essentially of, in weight %, of about 11.6% to 12.70% Cr, about 8.50 to 9.5% Co, about 1.65% to 2.15% Mo, about 3.5% to 4.10% W, about 4.80% to 5.20% Ta, about 3.40 to 3.80% Al, about 3.9% to 4.25% Ti, about 0.05% to 0.11% C, about 0.003% to 0.015% B, balance essentially Ni and having substantial transverse stress rupture strength and ductility as compared to a similar casting without boron present.

1 . A method of making a directionally solidified casting, comprising introducing into a mold an alloy consisting essentially of, in weight %, about 9.5% to about 14% Cr, about 7% to about 11% Co, about 1% to about 2.5% Mo, about 3% to about 6% W, about 1% to about 6% Ta, about 3 to about 4% Al, about 3% to about 5% Ti, about 0 to about 1% Nb and balance essentially Ni and B in an amount of about 0.003% to about 0.015% B, and directionally solidifying the alloy in the mold to form a columnar grain casting having a plurality of columnar grains along an axis of the casting and having transverse stress rupture strength and ductility so improved that said casting is useful as a columnar grain gas turbine engine blade. 
     
     
         2 . (canceled) 
     
     
         3 . The method of  claim 1  wherein the directionally solidified casting has a stress rupture life of at least about 150 hours and elongation of at least about 2.5% when tested at a temperature of 750 degrees C. (1283 degrees F.) and stress of 660 Mpa (95.7 Ksi) applied perpendicular to a <001> crystal axis of said casting. 
     
     
         4 . A method making a directionally solidified casting, comprising providing a nickel base alloy consisting essentially of, in weight %, about 11.6% to about 12.70% Cr, about 8.50 to about 9.5% Co, about 1.65% to about 2.15% Mo, about 3.5% to about 4.10% W, about 4.80% to about 5.20% Ta, about 3.40 to about 3.80% Al, about 3.9% to about 4.25% Ti, about 0.05% to about 0.11% C, about 0.010% to about 0.015% B, and balance essentially Ni, introducing the alloy into a mold, and solidifying the alloy in the mold to form a casting having a plurality of columnar grains along an axis of the casting, having a directionally solidified columnar grain microstructure and having transverse stress rupture strength and ductility so improved that said casting is useful as a columnar grain gas turbine engine blade.