United Technologies Corporation

United Technologies Company

Walter E Olson

Dinesh K Gupta

William Patrick Allen

Norman Pietruska

Michael S Milaniak

Peter J Draghi

Dennis M Ireland

Peter L Barilovich

Ryan H Sleight

Dilip M Shah

Alan David Cetel

David N Duhl

David A Rutz

Beth Kwiatkowski Abriles

Mark A Livings

Clark T Okawa

Edward J Grybowski

Mathew C Gartland

Sudhangsu Bose

A coating apparatus for coating interior surfaces of internal passages of a workpiece, such as a turbine engine component is provided. The coating apparatus comprises a vessel defining an internal space, a plate dividing the internal space into a first chamber and a second chamber, a divider supporting the plate, and the plate having at least one cut-out for receiving a portion of the workpiece having the internal passages to be coated.

Apparatus and method for coating internal surfaces of a turbine engine component

A method for coating internal surfaces of a turbine engine component comprises flowing an aluminide containing gas into passages in the turbine engine component so as to coat the internal surfaces formed by the passages, allowing the aluminide containing gas to flow through the passages and out openings in external surfaces of the turbine engine component, and flowing a volume of a gas selected from the group consisting of argon, hydrogen, and mixtures thereof over the external surfaces to minimize any build-up of an aluminide coating on the external surfaces.

Selective aluminide coating process

Novel materials and methods for repairing/reclassifying superalloy components are described herein. These materials are non-traditional blends of materials having a much higher base material content than traditional repair/reclassification materials. In embodiments used to repair/reclassify nickel-based components, these materials may comprise about 5-18.9 weight percent of a low melting point alloy and about 81.1-95 weight percent of a base material. In embodiments used to repair/reclassify cobalt-based components, these materials may comprise about 15-30 weight percent of a low melting point alloy and about 70-85 weight percent of a base material. These materials can be used to repair surface defects and/or build up worn or eroded areas of a component to meet precise dimensional and metallurgical requirements. These materials create robust repaired components having a dense, isothermally solidified structure having minimal borides and a high re-melt temperature.

Repair and reclassification of superalloy components

According to the invention, an article that is exposed to high temperatures, e.g., over 1000&deg; C. during operation is disclosed. In one embodiment, a turbine blade for a gas turbine engine includes a directionally solidified metallic substrate, e.g., a superalloy, which defines an airfoil, a root and a platform located between the blade and root. The platform has an underside adjacent the root, and a corrosion resistant noble metal-containing aluminide coating is located on portions of the blade susceptible to corrosion and/or stress corrosion cracking, such as the underside of the platform and the neck. The applied coating prevents corrosion and stress corrosion cracking of blade in these regions.

Article having corrosion resistant coating

According to the invention, an article that is exposed to high temperatures, e.g., over 1000&deg; C. during operation is disclosed. In one embodiment, a turbine blade for a gas turbine engine includes a directionally solidified metallic substrate, e.g., a superalloy, which defines an airfoil, a root and a platform located between the blade and root. The platform has an underside adjacent the root, and a corrosion resistant overlay coating such as an MCrAlY is located on the underside of the platform and the neck. The applied coating prevents corrosion and stress corrosion cracking of blade in these regions. Where the airfoil is also coated, the airfoil coating may have a composition different from that of the coating on the underplatform surfaces.

A fixture for selectively masking a turbine blade includes a locator with a separable receptacle having portals . Guide bars extend from the locator for guiding a pair of shield carriers between deployed and retracted positions. Each shield carrier has a shield projecting therefrom. In use, a turbine blade , whose root includes a fir tree attachment and a damper pocket , is mounted on the fixture so that the receptacle embraces the blade root. The shield carriers are translated along the guide bars until the shields penetrate through the portals and into the receptacle thus segregating the attachment from the damper pocket . Masking powder is then compressed into the receptacle to envelop the attachment while leaving the damper pocket unmasked. The fixture facilitates selective masking of the blade root so that when the receptacle and masked blade are subsequently exposed to a metal bearing vapor at an elevated temperature, the vapor coats the damper pocket but not the highly stressed attachment. In one variant of the invention, the shields are independent, consumable shields dimensioned and shaped to substantially conform to the size and shape of the damper pocket. The shields are made of a thermally decomposable material. In use, the shields are wedged into the damper pockets prior to blade masking. During the coating cycle, the shields decompose at a temperature lower than the temperature at which coating vapors are produced to expose the damper pocket to the vapors.

Masking fixture and method

A fixture for selectively masking a turbine blade,includes a locator,with a separable receptacle,having portals,Guide bars,extend from the locator for guiding a pair of shield carriers,between deployed and retracted positions. Each shield carrier has a shield,projecting therefrom. In use, a turbine blade,whose root,includes a fir tree attachment,and a damper pocket,is mounted on the fixture so that the receptacle embraces the blade root. The shield carriers are translated along the guide bars until the shields penetrate through the portals and into the receptacle thus segregating the attachment,from the damper pocket,Masking powder,is then compressed into the receptacle to envelop the attachment while leaving the damper pocket unmasked. The fixture facilitates selective masking of the blade root so that when the receptacle and masked blade are subsequently exposed to a metal bearing vapor at an elevated temperature, the vapor coats the damper pocket but not the highly stressed attachment. In one variant of the invention, the shields are independent, consumable shields dimensioned and shaped to substantially conform to the size and shape of the damper pocket. The shields are made of a thermally decomposable material. In use, the shields are wedged into the damper pockets prior to blade masking. During the coating cycle, the shields decompose at a temperature lower than the temperature at which coating vapors are produced to expose the damper pocket to the vapors.

The invention includes a low activity localized aluminide coating for a metallic article made by positioning a coating material, preferably in the form of a tape, on a portion of the article. The coating material comprises a binder, a halide activator, an aluminum source, and an inert ceramic material. The coating material and the article are heated in an inert atmosphere between about 1800.degree. F. (982.degree. C.) and about 2050.degree. F. (1121.degree. C.) for between about four and about seven hours thereby producing a low activity localized aluminide coating having an outward diffusion aluminide coating microstructure characterized by two distinct zones, an inner diffusion zone and an outer zone including between about 20-28 percent, by weight, aluminum.

Low activity localized aluminide coating

The oxidation resistance of MCrAlY-type overlay coatings is improved by incorporating small discrete oxide particles into the coating. The particles are preferably yttrium oxide, and the coating is applied by simultaneously plasma spraying MCrAlY-type powder particles and oxide particles onto a substrate in a nonoxidizing atmosphere. Improvements in resistance to rumpling has also been observed in coatings applied according to this invention.

Oxide containing MCrAlY-type overlay coatings

A powder mixture for applying gas phase aluminide coatings to nickel or cobalt base superalloys is described. A preferred mixture consists essentially of Co.sub.2 Al.sub.5, NH.sub.4 F.HF, and chromium metal. The mixture is substantially free of aluminum oxide.

Method for applying aluminide coatings to superalloys

A process for forming a diffusion coating to the surface of a metal article. The process is particularly adapted for forming diffusion aluminide coatings on metal blades and vanes used in gas turbine engines. According to the invention, halide vapor is caused to react with a source of aluminum to form an aluminum rich halide gas. This gas then reacts with the part surface to form the aluminide coating. A key aspect of the invention relates to the timing of the reaction between the halide vapor and the source of aluminum.

Process for applying gas phase diffusion aluminide coatings

Methods are described for forming an yttrium enriched aluminide coating on the surface of a nickel or cobalt base superalloy article. In one preferred embodiment, a pack mixture for forming the coating consists essentially of, by weight percent, 5-35 of an Al-Y-Si alloy, 1-20 CoI.sub.2, balance Y.sub.2 O.sub.3.

Powder mixture for making yttrium enriched aluminide coatings

A protective coating system for superalloys is described. The coating is an active element enriched aluminide, and can be formed by aluminizing an overlay coated superalloy, wherein during the aluminizing process, aluminum diffuses completely through the overlay coating and into the substrate. The coating system exhibits desirable oxidation resistance and resistance to thermal fatigue cracking, due to the presence of oxygen active elements in the overlay.

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Vernon, CT, United States of America

Walter E Olson