General Electric Company

Warren Tan King

John Herbert Wood

Arthur Samuel Peck

Stephen Daniel Graham

Cyril Gerard Beck

Srikanth Chandrudu Kottilingam

Wendy Howard Murphy

Shan Liu

Carl S Wukusick

Earl W Ross

Srinivasan Raghavan

Tresa M Pollock

Dayananda Narayana

Gangjigang Feng

Christine Louise Zemsky

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.

Composite geometrical design for a grain starter in a bridgman investment casting process

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.

System and method for reducing grain boundaries in shrouded airfoils

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.

Nickel-base alloy

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.

Nickel-base-alloy

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.

Aluminide coating process

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.

Nickel-based superalloys exhibiting minimal grain defects

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. These alloys are especially useful when directionally solidified as hot-section components of aircraft gas turbine engines, particularly rotating blades and stationary vanes. The superalloy contains by weight percent, 7-12 Cr, 5-15 Co, 0.5-5 Mo, 3-12 W, 2-6 Ta, 2-5 Ti, 3-5 Al, 0- 2 Cb, 0.1-0.2 Hf, 0.05-0.07 C, 0.002-0.05 B, and nickel.

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Mauldin, SC, United States of America

Warren Tan King