Patent ID: 8597440

Claim:
A process of producing a steam turbine blade, the process comprising: casting the blade from a gamma prime-strengthened nickel-base superalloy having a composition of, by weight, 14.25-15.75% cobalt, 14.0-15.25% chromium, 4.0-4.6% aluminum, 3.0-3.7% titanium, 3.9-4.5% molybdenum, 0.05-0.09% carbon, 0.012-0.020% boron, maximum 0.5% iron, maximum 0.2% silicon, maximum 0.15% manganese, maximum 0.04% zirconium, maximum 0.015% sulfur, maximum 0.1% copper, balance nickel and incidental impurities, and an electron vacancy number of 2.32 maximum; solution heat treating the blade at a solution temperature of about 1100 to about 1200° C. in an inert atmosphere for a duration of about one to about four hours; cooling the blade to a first cooling temperature of about 1000 to about 1100° C.; cooling the blade to a second cooling temperature of about 500 to about 600° C.; cooling the blade to about room temperature; aging the blade at an aging temperature of about 700 to about 800° C. for about ten to about 20 hours; and then cooling the blade to about room temperature; wherein the blade has a 0.2% average yield strength of greater than 690 MPa over a temperature range of about 20° C. to about 760° C., a gamma prime phase content of about 45% to about 55% by volume at a temperature of about 760° C., and a sigma phase content of less than 5% by volume at a temperature of about 760° C.