Abstract: A method of repairing damaged airfoils. The method comprises the steps of stripping thermal barrier coatings from the airfoil. After the coatings are removed, cracks are removed from the airfoil. Cracks that appear in the bond coat area over the airfoil fillet portion are removed by locally grit blasting the fillet portion of the airfoil. This operation also results in locally removing the bond coating from the fillet portion. Cracks and other damage sustained by the airfoil tip are removed and replaced by welding superalloy material. The airfoil then may be cleaned by thermal etching. The airfoil is then placed in a plating tool permitting preferential plating of airfoil areas from which plating has been removed. After plating, the airfoil is then heat treated to diffuse the platinum coating with the superalloy substrate materials. The diffusion heat treated airfoil is aluminided by any aluminiding process, forming a PtAl coating.

Abstract: A method of repairing damaged airfoils. The method comprises the steps of stripping thermal barrier coatings from the airfoil. After the coatings are removed, cracks are removed from the airfoil. Cracks that appear in the bond coat area over the airfoil fillet portion are removed by locally grit blasting the fillet portion of the airfoil. This operation also results in locally removing the bond coating from the fillet portion. Cracks and other damage sustained by the airfoil tip are removed and replaced by welding superalloy material. The airfoil then may be cleaned by thermal etching. The airfoil is then placed in a plating tool permitting preferential plating of airfoil areas from which plating has been removed. After plating, the airfoil is then heat treated to diffuse the platinum coating with the superalloy substrate materials. The diffusion heat treated airfoil is aluminided by any aluminiding process, forming a PtAl coating.

Abstract: 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.

Abstract: 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.

Abstract: 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.

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: 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: 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.