Nickel-Based Superalloy and Heat Treatment for Salt Environments

Abstract

An alloy has, by weight: nickel (Ni) as a largest constituent; 6.7% to 7.5% chromium; 1.8% to 2.3% molybdenum; 4.75% to 10.3% cobalt; 5.3% to 5.9% aluminum; 2.8% to 3.2% rhenium; 3.7% to 7.3% tungsten; and 6.0% to 9.0% tantalum.

What is claimed is: 
     
         1 . An alloy comprising, by weight:
 nickel (Ni) as a largest constituent;   6.7% to 7.5% chromium;   1.8% to 2.3% molybdenum;   4.75% to 10.3% cobalt;   5.3% to 5.9% aluminum;   2.8% to 3.2% rhenium;   3.7% to 7.3% tungsten; and   6.0% to 9.0% tantalum.   
     
     
         2 . The alloy of  claim 1  comprising, by weight:
 nickel (Ni) as said largest constituent; 
 6.8% to 7.2% chromium; 
 1.8% to 2.2% molybdenum; 
 4.9% to 10.2% cobalt; 
 5.35% to 5.7% aluminum; 
 2.9% to 3.1% rhenium; 
 3.8% to 7.2% tungsten; and 
 6.1% to 8.9% tantalum. 
 
     
     
         3 . The alloy of  claim 1  wherein, by weight, one or more of:
 a titanium content, if any, is no more than 0.50%; 
 a boron content, if any, is no more than 0.01%; 
 a yttrium content, if any, is no more than 0.02%; 
 a sulfur content, if any, is no more than 5 ppm; 
 a hafnium content, if any is no more than 0.50%; 
 a silicon content, if any, is no more than 0.50%; and 
 a carbon content, if any, is no more than 0.10%. 
 
     
     
         4 . The alloy of  claim 1  wherein, by weight, one or more of:
 a sulfur content, if any, is no more than 1 ppm; 
 a hafnium content is 0.050% to 0.15%; 
 a silicon content, if any, is no more than 0.30%; and 
 a carbon content, if any, is no more than 0.10%. 
 
     
     
         5 . The alloy of  claim 1  wherein, by weight:
 a combined content, if any, of elements other than nickel, chromium, cobalt, aluminum, rhenium, tungsten, tantalum, molybdenum, if any, sulfur, if any, hafnium, if any, silicon, if any, and carbon, if any, is no more than 1.0%. 
 
     
     
         6 . The alloy of  claim 1  wherein, by weight:
 a combined content, if any, of elements other than nickel, chromium, cobalt, aluminum, rhenium, tungsten, tantalum, molybdenum, if any, sulfur, if any, hafnium, if any, silicon, if any, and carbon, if any, is no more than 0.75%. 
 
     
     
         7 . The alloy of  claim 1  wherein, by weight:
 an individual content, if any, of every element other than nickel, chromium, cobalt, aluminum, rhenium, tungsten, tantalum, molybdenum, if any, sulfur, if any, hafnium, if any, silicon, if any, and carbon, if any, is no more than 0.50%. 
 
     
     
         8 . The alloy of  claim 1  wherein, by weight:
 an individual content, if any, of every element other than nickel, chromium, cobalt, aluminum, rhenium, tungsten, tantalum, molybdenum, if any, sulfur, if any, hafnium, if any, silicon, if any, and carbon, if any, is no more than 0.40%. 
 
     
     
         9 . The alloy of  claim 1  wherein, by weight:
 the combined content of chromium, cobalt, and aluminum is 17.0% to 23.0%. 
 
     
     
         10 . The alloy of  claim 1  wherein, by weight:
 the combined content of chromium, cobalt, and aluminum is 17.5% to 22.5%. 
 
     
     
         11 . The alloy of  claim 10  wherein, by weight:
 the combined content of tungsten and tantalum is 8.0% to 14.0%. 
 
     
     
         12 . The alloy of  claim 10  wherein, by weight:
 the combined content of tungsten and tantalum is 12.0% to 13.0%. 
 
     
     
         13 . The alloy of  claim 1  wherein, by weight:
 the combined content of rhenium, tungsten, and tantalum is 9.0% to 16.5%. 
 
     
     
         14 . The alloy of  claim 13  wherein, by weight:
 the combined content of rhenium, tungsten, and tantalum is 10.0% to 15.5%. 
 
     
     
         15 . The alloy of  claim 1  further comprising, by weight:
 yttrium, lanthanum, and/or cerium up to 0.05% combined. 
 
     
     
         16 . The alloy of  claim 1  having one to-all of:
 an average 1500 F/90 ksi salt rupture life of at least 450 hours; and 
 an average 1500 F/100 ksi salt rupture life of at least 150 hours; 
 an average 1800 F/36 ksi air rupture life of at least 150 hours; and 
 an average 1850 F/38 ksi air rupture life of at least 40 hours. 
 
     
     
         17 . The alloy of  claim 1  having one-to-all of:
 an average 1500 F/90 ksi salt rupture life of at least 300 hours; and 
 an average 1500 F/100 ksi salt rupture life of at least 100 hours; 
 an average 1800 F/36 ksi air rupture life of at least 140 hours; and 
 an average 1850 F/38 ksi air rupture life of at least 38 hours. 
 
     
     
         18 . The alloy of  claim 1  in single-crystal (SX) form. 
     
     
         19 . A turbine blade comprising a substrate formed of the alloy of  claim 1  and further comprising:
 an attachment root; 
 an airfoil extending from a proximal end to a tip; 
 a platform between the airfoil and the attachment root; and 
 a thermal barrier coating atop the substrate at least along the airfoil, wherein:
 the thermal barrier coating is not along the root and platform underside. 
 
 
     
     
         20 . The alloy of  claim 1 , heat treated by a method comprising:
 a solution heat treat for a period of at least 4.0 hours; and   after the solution heat treat, an intermediate heat treatment at 1950 F to 2075 F for 3.5 hours to 4.5 hours followed by a final aging precipitation heat at a temperature of 1575 F to 1675 F for a period of 4.0 hours to 32.0 hours.