General Electric Company

Howard John Farr

D Sangeeta

Edward Brittain Stokes

Himanshu B Vakil

Keith Humphries Betscher

Curtis Alan Johnson

Heinz Jaster

Richard Roy Worthing, Jr

Jerry Donald Schell

Thomas J Cartier, Jr

Alexander S Allen

Stephen Joseph Ferrigno

Leo Spitz MacDonald

Paul J Monson

Thomas Joseph Kelly

Nripendra Nath Das

Jeffrey Allen Conner

Roger Dale Wustman

Warren Davis Grossklaus, Jr

Mark Alan Rosenzweig

Raymond William Heidorn

Jim D Reeves

Patricia A Charles

Scott A Welsh

Jerald M Kauffman

Christopher J Cunningham

Jeffrey A Bauer

Thomas J Kelley

Eric C Hemsath

Randall L Hobbs

Method for stripping ceramic coatings from the surfaces of articles. The apparatus includes a dedicated pressure vessel, such as an autoclave, which is maintained at an elevated temperature. Caustic solution is preheated to a first elevated temperature before injecting it into the autoclave, and the caustic solution is filtered and cooled after use in the autoclave. The articles are stripped of coating by maintaining the articles at an elevated temperature and pressure for a predetermined time. Various options include the use of analytical equipment to maintain the chemistry of the caustic solution and use of a volatile organic solution to prepressurize the autoclave and shorten cycle time. The articles are transferred to a separate pressure vessel after completion of the stripping operation so that the autoclave used for stripping can be maintained at an elevated temperature, thereby shortening the cycle time for stripping of additional articles.

Method for removing ceramic coatings from component surfaces

Analysis equipment for determining a concentration of an organic component and a caustic component of a reusable organic caustic solution that has been utilized for removing a ceramic coating from a metallic component at elevated temperatures and pressures, such as in an autoclave. Sensors are positioned between a filter for removing particles of the ceramic coating dispersed in the reusable organic caustic solution from the reusable organic caustic solution and a storage tank storing the reusable organic caustic solution after removal from the autoclave. The sensors measure physical properties of the reusable organic caustic solution after removal of the particles from the reusable organic caustic solution, such as electrical conductivity, opacity, refractive index, density, fluidity and the speed of sound in the solution.

Analysis equipment for determining physical properties of an organic solution

A method for forming a metal-containing layer on a substrate is disclosed. A slurry of the metal is first deposited on the substrate; followed by heating to remove volatile material from the slurry, and to form a layer of the metal. In another embodiment, a slurry of aluminum is deposited over the slurry of the metal, before or after the metal has been heat-treated to some degree. A diffusion heat treatment results in a coating which includes the noble-metal aluminide compound. Related articles are also disclosed.

Metal slurry coatings on substrates, and related articles

A method for determining the concentration of at least one acid or base in a complex solution is described. Multiple physical property values are first measured for the solution. The physical properties can be defined in the form of a set of solution property equations. The measured physical property values are then inserted into the solution property equations. When the equations are simultaneously solved, the desired concentration of the acid or basic component can be determined.

Method for determining the quantities of acids or bases in complex compositions

Method for applying coatings on substrates

A method for recovering Pt from Pt-bearing coating on a gas turbine engine component. The component is contacted with a chemical stripping agent to dissolve away constituents of the coating and produce a Pt-bearing film of acid oxidation products at the surface of the component. The film is removed from the component to produce a Pt-rich residue containing at least about 10% Pt. The Pt-rich residue is collected and refined to recover Pt therefrom.

Method for recovering platinum from platinum-containing coatings on gas turbine engine components

Apparatus for stripping ceramic coatings from the surfaces of articles. The apparatus includes a dedicated pressure vessel, such as an autoclave, which is maintained at an elevated temperature. Caustic solution is preheated to a first elevated temperature before injecting it into the autoclave, and the caustic solution is filtered and cooled after use in the autoclave. The articles are stripped of coating by maintaining the articles at an elevated temperature and pressure for a predetermined time. Various options include the use of analytical equipment to maintain the chemistry of the caustic solution and use of a volatile organic solution to prepressurize the autoclave and shorten cycle time. The autoclave is maintained in a nitrogen chamber to minimize the risks associated with volatile components. The articles are transferred to a separate pressure vessel after completion of the stripping operation so that the autoclave used for stripping can be maintained at an elevated temperature, thereby shortening the cycle time for stripping of additional articles.

Apparatus and process to clean and strip coatings from hardware

A method for removing products of hot corrosion and oxidation from selective portions of surfaces of a gas turbine engine, such as coatings and substrates, following exposure of the surfaces to hot oxidative gases of the turbine exhaust. The method involves a high temperature chemical reaction and has no detrimental effect on adjacent coatings and substrates that have not been attacked by the hot exhaust gases.

Method for locally removing oxidation and corrosion product from the surface of turbine engine components

A method of removing a diffusion aluminide coating on a component designed for use in a hostile environment, such as superalloy turbine, combustor and augmentor components of a gas turbine engine. The method selectively removes an aluminide coating by stripping aluminum from the coating without causing excessive attack, alloy depletion and gross thinning of the underlying superalloy substrate. Processing steps generally include contacting the coating with a mixture that contains a halogen-containing activator and a metallic powder containing an aluminide-forming metal constituent, such as by pack cementation-type process. The mixture is then heated to a temperature sufficient to vaporize the halogen-containing activator and for a duration sufficient to cause the halogen-containing activator to provide a transfer mechanism for the removal of aluminum from at least a portion of the diffusion aluminide coating, while the metallic powder absorbs the removed aluminum.

Method for stripping aluminum from a diffusion coating

An aqueous caustic process can be used for replacing a thermal barrier coating on a metal surface. In the process, the metal surface is contacted with a caustic solution to remove the thermal barrier coating. The processing conditions for contacting the caustic solution are selected to avoid the formation of a peel layer during a subsequent application of a replacement thermal barrier coating and heat treatment. A replacement thermal barrier coating is then reapplied to the metal surface.

Caustic process for replacing a thermal barrier coating

A wet chemical process for removing an abrasive oxide coating from the surface of a rotating turbine engine component, such as a tooth that forms a rotating air seal with a complementary sealing member. The process generally entails subjecting the coating to a caustic solution at an elevated pressure. The caustic solution is preferably a mixture of water and a base, such as sodium or potassium hydroxide, with the addition of an organic compound being a preferred constituent in a sufficient amount as a solvent media for the caustic solution. A suitable caustic solution contains the base and water at a ratio of about one to one (1:1). If present, the organic compound may constitute about one to about ninety-eight weight percent of the solution. The process is preferably carried out in an autoclave charged with the caustic solution. Under an elevated pressure and preferably an elevated temperature, the caustic solution is capable of completely removing an alumina seal tooth coating without damaging an underlying bond coat or the tooth substrate.

Wet chemical process for removing an abrasive alumina seal tooth coating

An abrasive coating suitable for forming an abrasive blade tip of a gas turbine engine. The coating is characterized as being capable of abrading a ceramic shroud at elevated temperatures during the in-service operation of the engine, and being resistant to oxidation and hot corrosion within the engine environment. The abrasive coating includes an MCrAl alloy layer, a ceramic layer overlying the alloy layer so as to form an outer surface of the abrasive coating, and abrasive particles dispersed between the alloy layer and the ceramic layer so that at least some of the abrasive particles are partially embedded in the alloy layer and also partially embedded in the ceramic layer. In addition, at least some of the abrasive particles project above the outer surface of the abrasive coating formed by the ceramic layer.

Abrasive ceramic matrix turbine blade tip and method for forming

A method of removing metallic compositions, such as abradable rub coatings, environmental coatings, bond coats and braze alloys, from the surface of a cobalt-base substrate, such as turbine shrouds and vanes of gas turbine engines. The method is particularly suited for the removal of nickel-base braze alloys and aluminum-containing coatings, the latter of which includes abradable MCrAlY coatings and environmentally-protective diffusion aluminide coatings. The process generally entails contacting such metallic compositions with an aqueous solution containing hydrochloric acid and nitric acid and at a solution temperature of about 130.degree. F. to about 180.degree. F. The solution completely removes nickel-base alloys and aluminum-containing compositions from a cobalt-base substrate without removal or damage to the underlying substrate.

Method for chemically stripping a cobalt-base substrate

A method for forming a blade tip on a turbine blade of a gas turbine engine includes providing a powder alloy from a family of environmentally-resistant powder alloys and forming the blade tip by melting and fusing the powder alloy to the turbine blade. The blade tip alloys preferably have a chemical composition of, in weight percent, about 14 to about 18 percent chromium, about 6.45 to about 6.95 percent aluminum, about 9.75 to about 11.45 percent cobalt, about 5.95 to about 6.55 percent tantalum, about 1.85 to about 2.35 percent rhenium, about 0.05 to about 1.75 percent hafnium, about 0,006 to about 0.03 percent zirconium, about 0.02 to about 0.11 percent carbon, up to about 1.1 percent silicon, up to about percent 0.01 percent boron, with the balance being nickel and typical impurities.

Method for forming an environmentally resistant blade tip

A family of environmentally-resistant alloys is provided which are suitable for forming a blade tip for a turbine blade of a gas turbine engine. The blade tip alloys preferably have a chemical composition of, in weight percent, about 14 to about 18 percent chromium, about 6.45 to about 6.95 percent aluminum, about 9.75 to about 11.45 percent cobalt, about 5.95 to about 6.55 percent tantalum, about 1.85 to about 2.35 percent rhenium, about 0.05 to about 1.75 percent hafnium, about 0.006 to about 0.03 percent zirconium, about 0.02 to about 0.11 percent carbon, up to about 1.1 percent silicon, up to about percent 0.01 percent boron, with the balance being nickel and typical impurities.

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Blue Ash, OH, United States of America

Howard John Farr