Abstract: Provided is a method for heat treating a precipitation-hardened article having a thick section and a thin section so that the thin section can be solution annealed while the metallurgical structure of the thick section is substantially unaffected by the solution-annealing process. The method restores the microstructure of the thin section uniformly by solution annealing the thin section to achieve a preselected microstructure but without affecting the microstructure of the thick section.

Abstract: A method of repairing a thermal barrier coating on a component designed for use in a hostile thermal environment, such as turbine, combustor and augmentor components of a gas turbine engine. The method is particularly suited for completely removing a thermal insulating ceramic layer of thermal barrier coating system that includes a metallic bond coat, such as a diffusion aluminide or MCrAlY coating, between the surface of the component and the ceramic layer, while leaving the bond coat substantially undamaged. Furthermore, the method of this invention includes a technique by which ceramic material within cooling holes in the component can be removed without damaging the underlying bond coat. The process steps generally include removing the ceramic layer from the surface of the component by subjecting the ceramic layer to a caustic solution at an elevated temperature and pressure, and then removing ceramic material from the cooling hole by carefully directing a high-velocity fluid stream into the cooling hole.

Abstract: A cast turbine airfoil to which a squealer tip is added. The turbine airfoil is cast slightly undersize. The squealer tip is comprised of an alloy that is different from the cast alloy of the airfoil, the oxidation resistance and strength of the squealer tip alloy being greater than the strength of the turbine airfoil alloy. The cast turbine alloy having the added squealer tip can utilize a material in the squealer tip that is more difficult to cast than the cast alloy material, yet is more suited for severe environmental conditions and temperature extremes.

Abstract: A method for repairing the shroud surfaces of a gas turbine engine to provide corrosion and oxidation resistance of the shroud segments while also restoring the dimensional integrity of the shroud segments. The method entails removing the oxidation and corrosion products from the shroud segment, removing preexisting coating materials, applying a material compatible with the shroud segment substrate material, machining the surface, applying a corrosion-resistant, oxidation-resistant and rub-compliant material to the shroud segment using a HVOF process, machining the shroud segment to preselected dimensions and applying an aluminide coating for improved oxidation and corrosion resistance of the repaired surfaces.

Abstract: A heating apparatus and method for welding a superalloy article. The apparatus and method of this invention provide for pre-weld and post-weld heat treatments to be performed on an article within the same enclosure in which the welding operation is performed. The apparatus accurately controls the temperature of the component to be welded throughout the temperature treatment profiles with the use of means for welding the article, means for heating the article, and means for sensing the article temperature. The apparatus also works in conjunction with a memory storage device that stores appropriate pre-weld and post-weld heat treatment temperature profiles and a welding temperature profile for the article.

Abstract: A nickel-base superalloy article which is susceptible to strain-age cracking and has a directionally oriented, single crystal, or equiaxed grain structure is repaired with minimal welding heat input into the article. The article is first heated to a welding temperature of from about 1650.degree. F. to about 2000.degree. F. in an inert atmosphere. A damaged area of the article is weld repaired using a plasma-transferred arc welder which vaporizes a filler metal in a plasma arc and deposited the vaporized metal onto the article to form a weld overlay. Minimal additional heat is added to the article during welding, as the weldment metal is vaporized remotely from the article.

Abstract: An apparatus and method for welding a superalloy article. The apparatus generally entails an enclosure adapted for containing a superalloy article, a polarity-reversing plasma transferred arc welder apparatus for welding a localized region of the article, an induction coil for heating the localized region, and elements for sensing and controlling the temperature of the localized region. The induction coil is placed in close proximity to the localized region of the article so that the temperature of the localized region is largely determined and quickly altered by the output of the coil. The polarity-reversing plasma transferred arc welding apparatus is operated at very low currents of not more than forty-five amps, so that the welding apparatus has only a secondary heating affect compared to the induction coil.

Abstract: 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.

Abstract: An environmental resistant spot type coating is provided on a selected, discrete surface area of a high temperature operating article, by applying to the area a layer of at least one of the elements selected from Pt, Rh and Pd, and preferably Pt, to a thickness of about 0.0002" to less than 0.0006" and an average distribution of at least about 0.07 grams per square inch. The layer is heated at about 1800-2050.degree. F. for about 1/2-4 hours to diffuse the element with the surface area. Then the layer is aluminided to provide an average total coating thickness of about 0.001-0.005". The article provided includes an environmental resistant additive coating diffused with the selected discrete area. The coating comprises an outer portion of at least about 17 wt. % of the selected element, and an aluminide of the surface area or substrate. In one form, the outer portion is a two phase outer portion: a first phase of an aluminide of the selected element at a content of at least about 40 wt.

Abstract: Chromium is deposited on a surface using a coating tape having a source layer including a powdered source of chromium, a solid reactant that reacts with solid chromium at elevated temperature to produce a gaseous chromium-containing compound, an inert powder dispersed with the powdered source of chromium, and a binder. Preferably, a porous media layer including a porous media material and a binder is affixed to the source layer. The coating tape is positioned adjacent to the surface of the substrate, with the porous media layer, where present, in contact with the surface. The coating tape and substrate are placed into a container, and the container is heated to elevated temperature in a non-oxidizing atmosphere. The gaseous chromium-containing compound is produced and chromium is deposited from the gaseous chromium-containing compound onto the surface of the substrate.

Abstract: The present invention provides an apparatus to repair gouged out and damaged leading and trailing edges of gas turbine engine blades, particularly fan blades, by cutting away a curved section including the damaged area and forming a blend radius along the repaired edge. The apparatus includes a unique machine tool guide having an adjustable cutting depth guide and mountable to a hand held machine tool driver, such as a 90 degree angle head air motor, that drives a rotary cutter.

Abstract: The present invention provides a method and apparatus to repair gouged out and damaged leading and trailing edges of gas turbine engine blades, particularly fan blades, by cutting away a curved section including the damaged area and forming a blend radius along the repaired edge. The apparatus includes a unique machine tool guide having an adjustable cutting depth guide and mountable to a hand held machine tool driver, such as 90 degree angle head air motor, that drives a rotary cutter.