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.

We claim:  
     
         1 . A directionally solidified columnar grain nickel base alloy casting, consisting essentially of, in weight %, of about 9.5% to 14% Cr, about 7% to 11% Co, about 1% to 2.5% Mo, about 3% to 6% W, about 1% to 6% Ta, about 3% to 4% Al, about 3% to 5% Ti, about 0 to 1% Nb, and balance essentially Ni and B present in an amount effective to substantially improve transverse stress rupture strength of said casting as compared to a similar casting without boron present.  
     
     
         2 . The casting of  claim 1  wherein B is present in the range of about 0.003% to about 0.015% by weight.  
     
     
         3 . The casting of  claim 1  that 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 in a direction perpendicular to a <001> crystal axis of said casting.  
     
     
         4 . The casting of  claim 1  which is gas turbine engine blade having a length of about 20 centimeters to about 90 centimeters.  
     
     
         5 . A 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 substantially improved transverse stress rupture strength as compared to a similar casting without boron present.  
     
     
         6 . The casting of  claim 5  that 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.  
     
     
         7 . A directionally solidified columnar grain nickel base alloy casting having a nominal composition consisting essentially of, in weight %, of about 12.00% Cr, about 9.00% Co, about 1.85% Mo, about 3.70% W, about 5.10% Ta, about 3.60% Al, about 4.00% Ti, about 0.0125% B, about 0.09% C, balance essentially Ni and having 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.  
     
     
         8 . A method of making a directionally solidified casting, comprising casting an alloy consisting essentially of, in weight %, of about 9.5% to 14% Cr, about 7% to 11% Co, about 1% to 2.5% Mo, about 3% to 6% W, about 1% to 6% Ta, about 3% to 4% Al, about 3% to 5% Ti, about 0 to 1% Nb and balance essentially Ni and B in an amount effective to substantially improve transverse stress rupture strength into a mold, and directionally solidifying the alloy in the mold to form a columnar grain casting having substantially improved transverse stress rupture strength by virture of the inclusion of boron in said alloy as compared to a similar casting without boron present.  
     
     
         9 . The method of  claim 8  wherein B is included in an amount of about 0.003% to about 0.015% by weight.  
     
     
         10 . The method of  claim 8  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.  
     
     
         11 . A method making a directionally solidified casting, comprising providing a nickel base alloy 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, and balance essentially Ni, casting the alloy into a mold, and solidifying the alloy in the mold to form a casting having a directionally solidified columnar grain mcirostructure having substantially improved transverse stress rupture strength as compared to a similar casting without boron present.  
     
     
         12 . Nickel base alloy 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.