Abstract: There is provided by the present invention nickel-base superalloys for producing single crystal articles having improved tolerance to low angle grain boundaries and an improved balance between cyclic oxidation and hot corrosion resistance. The improved tolerance arises from the discovery that nickel-base superalloys suitable for casting as single crystal articles can be improved by the addition of small, but controlled, amounts of boron and carbon, and optionally hafnium, and is manifested principally by improved grain boundary strength. As one result of this increased grain boundary strength, grain boundary mismatches far greater than the 6.degree. limit for prior art single crystal superalloys can be tolerated in single crystal articles made from the nickel-base superalloys of this invention. This translates, for example, into lower inspection costs and higher casting yields as grain boundaries over a broader range can be accepted by visual inspection techniques without resort to expensive X-ray techniques.

Abstract: A nickel-base superalloy, particularly adapted for use in gas turbine engine single crystal blades and vanes is provided with a specific composition and heat treated in a particular manner to exhibit an improved balance of critical high temperature mechanical properties and resistance to oxidation and hot corrosion significantly superior to presently available alloys. In its broad form, the alloy composition comprises, by weight, 7-12% Cr, 1-5% Mo, 3-5% Ti, 3-5% Al, 5-15% Co, 3-12% W, up to 10% Re, 2-6% Ta, up to 2% Cb, up to 3% V, up to 2% Hf, the balance being essentially nickel and incidental impurities. Nickel-base superalloy single crystal articles formed of the alloy are described, as is the method, including heat treatment, employed to make the article.

Abstract: The present invention is directed to a heat treatment for nickel-base superalloys used to make single crystal parts and components for gas turbine engines. The heat treatment is conducted in a vacuum or inert atmosphere and includes the steps of solutionizing in a temperature range sufficient to achieve solution of at least 95% of the .gamma.' phase, preferably 2385.degree.-2395.degree. F., for 2 hours; cooling to 2000.degree. F. at 100.degree. F./min minimum, furnace cooling to 1200.degree. F. in 60 min. or less and thereafter cooling to room temperature; heating to 2050.degree..+-.25.degree. F. for 4 hours; furnace cooling to below 1200.degree. F. in 6 min. or less and thereafter to room temperature; and heating to 1650.degree..+-.25.degree. F. for 4 hours and thereafter furnace cooling to room temperature.

Abstract: An article having improved fatigue crack growth resistance is provided through an improved nickel-base superalloy and an improved method which controls grain size and a strain rate found to be critical in processing. The alloy is selected to have a gamma prime content in the range of about 30-46 volume percent and a resistance to cracking upon rapid quenching from a selected supersolvus solutioning temperature to a selected quenching temperature. The article produced has an improved balance and combination of fatigue crack growth resistance and tensile, creep, and stress rupture properties.

Abstract: A cast nickel-base alloy article having a complex internal passage and a columnar grain structure is provided with an improved combination of castability and mechanical properties through a control of the amount of gamma prime phase and its related phase formers, a careful control of Co and Al along with Hf and a control of the gamma solution strengtheners, particularly Mo and W.