High strength hot corrosion and oxidation resistant, directionally solidified nickel base superalloy and articles

Abstract

Corrosion and oxidation resistant, high strength, directionally solidified superalloy alloys and articles are described. The articles have a nominal composition in weight percent of about 12% Cr, 9% Co, 1.9% Mo, 3.8% W, 5% Ta, 3.6% Al, 4.1% Ti, 0.015% B, 0.1% C, up to about 0.02 Zr, balance essentially nickel, and include no intentional additions of hafnium or zirconium, and also have a small amounts of tantalum carbide. The resultant articles have good hot corrosion resistance and superior oxidation resistance and creep properties. The articles are preferably columnar grain, but may also be single crystal.

We claim:  
     
         1 . A directionally solidified article comprising a high strength, corrosion and oxidation resistant nickel base superalloy which comprises a matrix and from about 0.4 to 1.5 vol. % of a phase based on tantalum carbide, the alloy consisting essentially of, in weight percent, of: 10-13.5% chromium; 8-10% cobalt; 1.25-2.5% molybdenum; 3.25-4.25% tungsten; 4.5-6% tantalum; 3.25-4.5% aluminum; 3-4.75% titanium; 0.0025-0.025% boron; up to about 0.05% zirconium; 0.05-0.15% carbon; and having no intentional addition of niobium; no intentional addition of hafnium; and balance essentially nickel; wherein aluminum+titanium is between about 6.5-8%; said article having at least comparable hot corrosion resistance (measured at 1600° F.) and at least twice the oxidation resistance (measured at 2000° F.) when compared with a directionally solidified having a nominal composition of 14 Cr, 4.9 Ti, 1.5 Mo, 3.8 W, 2.8 Ta, 3 Al, 9.5 Co, 0.01 B, 0.02 Zr, 0.1 C, and balance Ni.  
     
     
         2 . The article of  claim 1 , wherein the article comprises a columnar grain, directionally solidified article.  
     
     
         3 . The article of  claim 2 , wherein the article has transverse ductility in excess of 5% at 1400° F. and at 1800° F.  
     
     
         4 . The article of  claim 1 , wherein the article comprises a single crystal article including a high angle boundary of up to at least about 20°.  
     
     
         5 . The article of  claim 1  having stress rupture resistance sufficient to ensure that a load of about 27 ksi applied ruptures only after more than 45 hours, and also has a time to 1% creep of more than 15 hours, at 1800° F.  
     
     
         6 . The article of  claim 5 , wherein stress rupture occurs only after more than 85 hours.  
     
     
         7 . The article of  claim 1 , having 11-13% chromium; 8.25-9.75% cobalt; 1.5-2.25% molybdenum; 3.4-4.3% tungsten; 4.7-5.5% tantalum; 3.3-4% aluminum; 3.75-4.3% titanium; 0.008-0.025% boron; up to about 0.04% zirconium; 0.04-0.15 carbon; wherein aluminum+titanium is between about 7-8%.  
     
     
         8 . The article of  claim 1 , having about 12% chromium; 9% cobalt; 1.9% molybdenum; 3.8% tungsten; 5% tantalum; 3.6% aluminum; 4.1% titanium; 0.015% boron; 0.025% zirconium; 0.10% carbon; up to about 0.02 Zr and having no intentional addition of niobium; no intentional addition of hafnium; balance essentially nickel.  
     
     
         9 . The article of  claim 1 , wherein the article comprises a gas turbine engine component.  
     
     
         10 . The article of  claim 9 , comprising a turbine blade or vane.  
     
     
         11 . The article of  claim 1 , further characterized by oxidation resistance at 2000° F. of roughly 2.5×, and creep rupture life at 1400° F. of roughly 2.4× and at 1800° F. of at least roughly 1.5× a similar article having a nominal composition of 14 Cr, 4.9 Ti, 1.5 Mo, 3.8 W, 2.8 Ta, 3 Al, 9.5 Co, 0.01 B, 0.02 Zr, 0.1 C, and balance Ni.  
     
     
         12 . A high strength, corrosion resistant, nickel base superalloy adapted for use in columnar grain directionally solidified articles, comprising in weight percent of about 12% chromium; 9% cobalt; 1.9% molybdenum; 3.8% tungsten; 5% tantalum; 3.6% aluminum; 4.1% titanium; 0.015% boron; 0.1% carbon; and having no intentional addition (and in any event less than about 0.02) zirconium and no intentional amount of niobium; balance essentially nickel and incidental impurities, and wherein aluminum+titanium is between about 6.5-8%; and including a matrix containing from about 0.4 to 1.5 vol. % of a phase based on tantalum carbide, the article is characterized by oxidation resistance at 2000° F. of roughly 2.5× and creep rupture life at 1400° F. of roughly 2.4× compared to a similar article having a nominal composition of 14 Cr, 4.9 Ti, 1.5 Mo, 3.8 W, 2.8 Ta, 3 Al, 9.5 Co, 0.01 B, 0.02 Zr, 0.1 C, and balance Ni.  
     
     
         13 . The alloy of  claim 9 , comprising a gas turbine engine component.  
     
     
         14 . The article of  claim 13 , comprising a turbine blade or vane.