Abstract: A treatment process for treating an article including a superalloy having a degraded microstructure is presented. The process includes subjecting the article to a first heat-treatment including successively heating and cooling the article between a low-end temperature and a high-end temperature and subjecting the article to a second heat-treatment at a solution annealing temperature in a range of from about 80 degrees Fahrenheit below a gamma-prime solvus temperature of the superalloy to about 80 degrees Fahrenheit above the gamma-prime solvus temperature of the superalloy after performing the first heat-treatment. The low-end temperature is in a range of from about 1000 degrees Fahrenheit to about 1800 degrees Fahrenheit and the high-end temperature is in a range of from about 1900 degrees Fahrenheit to about 2250 degrees Fahrenheit.

Abstract: Gas turbine engine turbine blade includes a silicon-modified aluminide coating on at least an under platform region formed from a slurry composition being substantially free of hexavalent chromium. The silicon-modified aluminide coating provides oxidation resistance comparable to PtAl coatings without adding a weight penalty.

Abstract: A method for joining a plurality of single crystal members includes providing a bonding foil with a composition match with that of the members and with a bonding temperature within the gamma prime solution temperature range of the members, but below the melting temperature of the foil and below the incipient melting temperature of the members. The foil is disposed between and in contact with opposing members to be joined while heated to and held at the bonding temperature for at least 10 hours.

Abstract: A method for repairing a nickel-base superalloy article, such as a gas turbine stationary flowpath shroud having flowpath cooling holes therein that has previously been in service, includes the steps of providing the nickel-base superalloy article that has previously been in service; and applying a restoration to a surface of the article. The restoration is applied by the steps of providing a restoration nickel-base alloy, wherein the restoration nickel-base alloy preferably has no more than about 15 weight percent chromium and no more than about 0.01 percent yttrium, thereafter applying a restoration coating of the restoration nickel-base alloy to the surface of the article by a hyper-velocity oxyfuel metal spray process or a low-pressure plasma spray process, and thereafter heating the article with the restoration coating applied to the surface thereof to a sufficiently high temperature to diffusion bond the restoration coating to the surface of the article. The article is then returned to service.

Abstract: Formation of a silicon-modified aluminide coating on the under platform region of a superalloy gas turbine engine blade for improved corrosion and oxidation resistance. The coating is formed from a slurry composition including colloidal silica and aluminum-based powder and is substantially free of hexavalent chromium. The coating provides aluminum and silicon content in the outer 25% of a coating thickness of at least about 20% by weight aluminum and about 3% by weight silicon.

Abstract: A method for repairing a nickel-base superalloy article, such as a gas turbine stationary flowpath shroud having flowpath cooling holes therein that has previously been in service, includes the steps of providing the nickel-base superalloy article that has previously been in service; and applying a restoration to a surface of the article. The restoration is applied by the steps of providing a restoration nickel-base alloy, wherein the restoration nickel-base alloy preferably has no more than about 15 weight percent chromium and no more than about 0.01 percent yttrium, thereafter applying a restoration coating of the restoration nickel-base alloy to the surface of the article by a hyper-velocity oxyfuel metal spray process or a low-pressure plasma spray process, and thereafter heating the article with the restoration coating applied to the surface thereof to a sufficiently high temperature to diffusion bond the restoration coating to the surface of the article. The article is then returned to service.

Abstract: A damaged gas turbine blade which has previously been in service, and which is made of a base metal, is furnished. Any damaged material is removed from the damaged blade tip. The damaged blade tip is weld repaired with a nickel-base superalloy that is more resistant to oxidation resistance than is the base metal in the operating environment of the tip-repaired gas turbine blade. The method does not include any step of coating a lateral surface of the repaired blade tip with a non-ceramic coating after the step of weld repairing.

Abstract: A damaged gas turbine blade which has previously been in service, and which is made of a base metal, is furnished. Any damaged material is removed from the damaged blade tip. The damaged blade tip is weld repaired with a nickel-base superalloy that is more resistant to oxidation resistance than is the base metal in the operating environment of the tip-repaired gas turbine blade. The method does not include any step of coating a lateral surface of the repaired blade tip with a non-ceramic coating after the step of weld repairing.

Abstract: Formation of a silicon-modified aluminide coating on the under platform region of a superalloy gas turbine engine blade for improved corrosion and oxidation resistance. The coating is formed from a slurry composition including colloidal silica and aluminum-based powder and is substantially free of hexavalent chromium. The coating provides aluminum and silicon content in the outer 25% of a coating thickness of at least about 20% by weight aluminum and about 3% by weight silicon.

Abstract: A method of repairing a turbine blade and the blade repaired thereby. The blade comprises a platform that has become bowed as a result of high temperature creep, with the result that the platform has a concave surface and an oppositely-disposed convex surface. The method generally comprises welding the concave surface to build up a weldment on the concave surface, cooling the weldment during which the weldment shrinks, the convex surface becomes flatter, and the concave surface beneath the weldment becomes flatter, and then removing a surface portion of the weldment so as to create a substantially flat weldment surface overlying the substantially straightened concave surface.

Abstract: A nickel-base superalloy article, such as a gas turbine stationary flowpath shroud that has previously been in service, is repaired by applying a restoration coating to a surface of the article. The restoration coating is applied by providing a precursor mixture, wherein the precursor mixture has no more than about 15 weight percent chromium and no more than about 0.01 percent yttrium, and wherein the precursor mixture includes a higher-melting-point alloy component and a lower-melting-point alloy component. The precursor mixture is applied to the surface of the article, in a form such as a preform of the alloy components. The article with the precursor mixture applied to the surface thereof is heated to a sufficiently high temperature to melt the lower-melting-point alloy component, thereby forming the restoration coating on the surface of the article.

Abstract: A stationary shroud of a gas turbine engine made of a base metal is repaired by removing any damaged material from a flow-path region of the stationary shroud to leave an initially exposed base-metal flow-path surface; and applying a base-metal restoration overlying the initially exposed flow-path surface. The base-metal restoration is applied by furnishing a source of a structural material that is compatible with the base metal, and depositing the source of the structural material overlying the initially exposed base-metal flow-path surface of the stationary shroud by plasma transferred arc welding to form a repaired base-metal flow-path surface. An environmentally resistant rub coating may be applied overlying the base-metal restoration.

Abstract: The present invention provides for a squealer tip to include some proportion of a highly oxidation-resistant material, and a method for casting same, such that if any environmental coating were removed, the tip would retain some increased level of environmental resistance. The oxidation-resistant material optionally may also be a high abrasion resistance material, such that recession of the tip due to rubbing against a stator would be reduced. In a preferred embodiment, an abrasion-resistant and/or oxidation-resistant material is placed and suitably anchored into the tip region of a wax precursor used to cast a turbine airfoil. During the casting operation, the abrasion-resistant and/or oxidation-resistant material is not completely melted. As the alloy used to form the majority of the turbine blade solidifies, the abrasion and/or oxidation resistant material is incorporated into the turbine airfoil by the solidification of the alloy around it.