Abstract: An article and a method for forming a single crystal casting are disclosed. The article includes a single crystal nickel-based superalloy having a composition including greater than about 80 ppm boron (B) and a substantially single crystal microstructure with at least one grain boundary. A creep rupture strength of the article is substantially maintained up to a mismatched grain boundary of about 40 degrees. The method for forming a single crystal casting includes positioning a mold on a cooling plate, the mold including a single crystal selector, providing a molten nickel-based superalloy composition in the mold, the molten composition including greater than about 80 ppm boron (B), cooling the molten composition with the cooling plate, and forming a unidirectional temperature gradient by withdrawing the mold from within a heat source to form the single crystal casting including a substantially single crystal microstructure having at least one grain boundary.

Abstract: A grain starter for use in solidification of molten metallic material forming an article having a directional grain structure and a method for solidifying an article having a directional grain structure with a substantial absence of stray grains. The grain starter comprises a grain-starting material that initiates grain growth in the molten metallic material in a preselected crystallographic direction. The grain-starting material has a melting temperature higher than the metallic material forming the article lest the grain starter be modified by contact with the molten material. The grain starter further includes a feature that modifies heat transfer characteristics of the metallic material in contact with it in order to produce an article having grains oriented in the preselected crystallographic orientation and modifies the profile of the advancing solidification front. The article is substantially free of stray grains not oriented in the preselected crystallographic direction.

Abstract: A grain starter for use in solidification of molten metallic material forming an article having a directional grain structure and a method for solidifying an article having a directional grain structure with a substantial absence of stray grains. The grain starter comprises a grain-starting material that initiates grain growth in the molten metallic material in a preselected crystallographic direction. The grain-starting material has a melting temperature higher than the metallic material forming the article lest the grain starter be modified by contact with the molten material. The grain starter further includes a feature that modifies heat transfer characteristics of the metallic material in contact with it in order to produce an article having grains oriented in the preselected crystallographic orientation and modifies the profile of the advancing solidification front. The article is substantially free of stray grains not oriented in the preselected crystallographic direction.

Abstract: A turbine bucket includes an airfoil and a shroud. The shroud includes first and second bearing surfaces, and the first and second bearing surfaces each comprise a single grain structure. A method for forming a turbine bucket includes orienting a mold vertically, wherein the mold includes a first portion that defines a shank, a second portion connected to the first portion that defines an airfoil, and a third portion connected to the second portion that defines a shroud, wherein the third portion includes first and second sides, and wherein the first portion is higher than the second portion and the second portion is higher than the third portion. The method further includes flowing a molten metal into the mold and selectively growing large single grains in at least one of the first or second sides.

Abstract: A turbine bucket includes an airfoil and a shroud. The shroud includes first and second bearing surfaces, and the first and second bearing surfaces each comprise a single grain structure. A method for forming a turbine bucket includes orienting a mold vertically, wherein the mold includes a first portion that defines a shank, a second portion connected to the first portion that defines an airfoil, and a third portion connected to the second portion that defines a shroud, wherein the third portion includes first and second sides, and wherein the first portion is higher than the second portion and the second portion is higher than the third portion. The method further includes flowing a molten metal into the mold and selectively growing large single grains in at least one of the first or second sides.

Abstract: A method of treating a component made of a non magnetic alloy on which a magnetic surface layer has formed includes: (a) engaging a magnet of a calibrated magnet gauge with a surface of the component; (b) disengaging the magnet from the surface of the component and measuring a force required to disengage the magnet; (c) correlating the force with a thickness of the magnetic surface layer; and (d) if the thickness of the surface layer is greater than a predetermined minimum thickness, removing the surface layer.

Abstract: A family of castable and weldable nickel-base alloys that exhibit a desirable balance of strength and resistance to corrosion and oxidation suitable for gas turbine engine applications. A first alloy consists essentially of, by weight, 1 8% to 20% cobalt, 22.2% to 22.8% chromium, 1.8% to 2.2% tungsten, greater than 1.5% to 2.3% aluminum, 1.6% to 2.4% titanium, where the sum of aluminum and titanium is 2.8% to 4.4%, 0.7% to 0.9% columbium, 0.9% to 1.9% tantalum, 0.003% to 0.009% boron, 0.002% to 0.02% zirconium, 0.05% to 0.10% carbon, with the balance essentially nickel and incidental impurities. A second alloy consists essentially of, by weight, 5% to 8% cobalt, 22.2% to 22.8% chromium, 1.8% to 2.2% tungsten, 1.2% to 2.3% aluminum, 1.6% to 2.4% titanium, where the sum of aluminum and titanium is 2.8% to 4.4%, 0.7% to 0.9% columbium, 0.9% to 1.9% tantalum, 0.003% to 0.009% boron, 0.002% to 0.02% zirconium, 0.05% to 0.10% carbon, with the balance essentially nickel and incidental impurities.

Abstract: A nickel-base alloy consists of, by weight, about 15.0 to about 17.0% chromium, about 7.0 to about 10.0% cobalt, about 1.0 to about 2.5% molybdenum, about 2.0 to about 3.2% tungsten, about 0.6 to about 2.5% columbium, less than 1.5% tantalum, about 3.0 to about 3.9% aluminum, about 3.0 to about 3.9% titanium, about 0.005 to about 0.060% zirconium, about 0.005 to about 0.030% boron, about 0.07 to about 0.15% carbon, the balance nickel and impurities. Preferably, columbium is present in an amount greater than tantalum. Tantalum can be essentially absent from the alloy, i.e., only at impurity levels.

Abstract: An aluminiding process that enables the cooling holes of an air-cooled component, such as a hot gas path component of a gas turbine engine, to be machined and then aluminized after all external surface coatings have been deposited. The aluminide coating is deposited using a slurry process capable of forming the aluminide coating on the component without damaging an existing ceramic coating on the component. The process involves applying an activator-free slurry containing aluminum particles that, when the component is sufficiently heated, melt and diffuse into the component surface to form the diffusion aluminide coating.

Abstract: A nickel-base alloy consists of, by weight, about 15.0 to about 17.0% chromium, about 7.0 to about 10.0% cobalt, about 1.0 to about 2.5% molybdenum, about 2.0 to about 3.2% tungsten, about 0.6 to about 2.5% columbium, less than 1.5% tantalum, about 3.0 to about 3.9% aluminum, about 3.0 to about 3.9% titanium, about 0.005 to about 0.060% zirconium, about 0.005 to about 0.030% boron, about 0.07 to about 0.15% carbon, the balance nickel and impurities. Preferably, columbium is present in an amount greater than tantalum. Tantalum can be essentially absent from the alloy, i.e., only at impurity levels.

Abstract: An aluminiding process that enables the cooling holes of an air-cooled component, such as a hot gas path component of a gas turbine engine, to be machined and then aluminized after all external surface coatings have been deposited. The aluminide coating is deposited using a slurry process capable of forming the aluminide coating on the component without damaging an existing ceramic coating on the component. The process involves applying an activator-free slurry containing aluminum particles that, when the component is sufficiently heated, melt and diffuse into the component surface to form the diffusion aluminide coating.

Abstract: Carbide-forming elements are added to nickel-based superalloys so as to minimize grain defects, such as freckle and stray grain defects. More specifically, carbide-forming elements that form from the liquid in the mushy zone of the solidification front of single crystal (SC) and directionally solidified (DS) nickel-based superalloys are added so as to reduce the formation of freckle and stray grain defects in such alloys. A preferred nickel-based superalloy includes, by weight, between about 6.00%-9.25% tantalum, 4.75%-6.50% tungsten, at least about 2.75% rhenium, between about 5.00% to about 7.00% aluminum, at least about 0.10% hafnium and carbon in an amount sufficient (typically between about 0.10-0.15% by weight) to form carbides with other constituents to reduce significantly freckle formation in the mushy zone of the superalloy during casting.