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: 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.

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: 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 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

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: 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.

Abstract: 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.

Abstract: A core or insert primarily for the production of metal and alloy castings, e.g. of complicated internal shape, is a refractory body comprising essentially a water-soluble salt and a calcium silicate, the calcium silicate being present in amount of at least 45%, by weight, based on the total weight of calcium silicate and water-soluble salt, and the water-soluble salt and the calcium silicate having a particular particle size distribution. The calcium silicate is preferably a wollastonite.The core may be removed from the cast or moulded article by dissolution in water.

Abstract: A fired ceramics compact for use in casting of a super alloy material consisting of a solid solution of BaO and Al.sub.2 O.sub.3 wherein the composition of the solid solution lies on or between a first and a second eutectic composition, the first and the second eutectic compositions being adjacent and occurring to either respective side of stoichiometric BaO.Al.sub.2 O.sub.3 in a phase diagram of the solid solution.

Abstract: A refractory mould core for producing metallic castings of complicated internal shape formed from a water-soluble salt having the following particle size distribution:100% by weight of the particles have a size less than 750 .mu.m;90% by weight of the particles have a size of 8-600 .mu.m;80% by weight of the particles have a size of 5.5-500 .mu.m;70% by weight of the particles have a size of 4-400 .mu.m;60% by weight of the particles have a size of 2.8-350 .mu.m;50% by weight of the particles have a size of 2.0-280 .mu.m;40% by weight of the particles have a size of 1.6-220 .mu.m;30% by weight of the particles have a size of 1.0-180 .mu.m;20% by weight of the particles have a size of 0.3-160 .mu.m;10% by weight of the particles have a size of 0.1-125 .mu.m.