Abstract: A coating system and a method for forming the coating system, the method including coating a surface of a gas turbine engine turbine component having a metallic surface that is outside the combustion gas stream and exposed to cooling air during operation of the engine. A gel-forming solution including a ceramic metal oxide precursor is provided. The gel-forming solution is heated to a first preselected temperature for a first preselected time to form a gel. The gel is then deposited on the metallic surface. Thereafter the gel is fired at a second preselected temperature above the first preselected temperature to form a ceramic corrosion resistant coating comprising a ceramic metal oxide is selected from the group consisting of zirconia, hafnia and combinations thereof. The ceramic corrosion resistant coating having a thickness of up to about 127 microns and remaining adherent at temperatures greater than about 1000° F.

Abstract: A coating system and a method for forming the coating system, the method including coating a surface of a gas turbine engine turbine component having a metallic surface that is outside the combustion gas stream and exposed to cooling air during operation of the engine. A gel-forming solution including a ceramic metal oxide precursor is provided. The gel-forming solution is heated to a first preselected temperature for a first preselected time to form a gel. The gel is then deposited on the metallic surface. Thereafter the gel is fired at a second preselected temperature above the first preselected temperature to form a ceramic corrosion resistant coating comprising a ceramic metal oxide is selected from the group consisting of zirconia, hafnia and combinations thereof. The ceramic corrosion resistant coating having a thickness of up to about 127 microns and remaining adherent at temperatures greater than about 1000° F.

Abstract: An article comprising a turbine component other than an airfoil having a metal substrate and a ceramic corrosion resistant coating overlaying the metal substrate. This coating has a thickness up to about 5 mils (127 microns) and comprises a ceramic metal oxide selected from the group consisting of zirconia, hafnia and mixtures thereof. This coating can be formed by a method comprising the following steps: (a) providing a turbine component other than an airfoil comprising the metal substrate; (b) providing a gel-forming solution comprising a ceramic metal oxide precursor; (c) heating the gel-forming solution to a first preselected temperature for a first preselected time to form a gel; (d) depositing the gel on the metal substrate; and (e) firing the gel at a second preselected temperature above the first preselected temperature to form the ceramic corrosion resistant coating comprising the ceramic metal oxide.

Abstract: A beta-phase nickel aluminide (NiAl) overlay coating (24) and method for modifying the grain structure of the coating (24) to improve its oxidation resistance. The coating (24) is deposited by a method that produces a grain structure characterized by grain boundaries (44) exposed at the outer coating surface (36). The grain boundaries (44) may also contain precipitates (40) as a result of the alloyed chemistry of the coating (24). During or after deposition, the overlay coating (24) is caused to form new grain boundaries (34) that, though open to the outer surface (36) of the coating (24), are free of precipitates or contain fewer precipitates (40) than the as-deposited grain boundaries (44). New grain boundaries (34) are preferably produced by causing the overlay coating (24) to recrystallize during coating deposition or after deposition as a result of a surface treatment followed by heat treatment.

Abstract: An article and TBC coating system thereon that in combination exhibit significantly improved spallation resistance. The article comprises a substrate formed of a metal alloy containing ruthenium and one or more refractory elements (e.g., tantalum, tungsten, molybdenum, rhenium, hafnium, etc.). The substrate is protected by a coating system comprising an aluminum-containing bond coat on the surface of the substrate and a ceramic coating bonded to the substrate by the bond coat. The bond coat, preferably an aluminide, is deposited so as to be substantially free of ruthenium, though ruthenium is present in the bond coat as a result of diffusion from the substrate into the bond coat.

Abstract: A process for removing particles that become adherently sintered to an aluminized surface during an aluminiding process. The method is particularly suited for the removal of adherent particles that form as a result of oxidation of a metallic powder used as an aluminum source during slurry aluminiding processes, wherein the adherent particles become attached by sintering to the aluminized surface. The process includes contacting the aluminized surface with an aqueous caustic hydroxide solution until the particles are removed therefrom.

Abstract: A process capable of depositing a diffusion coating of uniform thickness on localized surface regions of a component. The process makes use of an adhesive mixture containing a binding agent that is consumed as part of the deposition process so as not to negatively affect the quality and uniformity of the resulting coating. The process entails mixing a particulate donor material containing a coating element, a dissolved activator, and a particulate filler to form an adhesive mixture having a formable, malleable consistency. The adhesive mixture is applied to a surface of the component, and the component is heated to a temperature sufficient to vaporize and react the activator with the coating element of the donor material, thereby forming a reactive vapor of the coating element. The reactive vapor reacts at the surface of the component to form a diffusion coating containing the coating element.

Abstract: The present invention is process for forming diffusion aluminide coatings on an uncoated surface of a substrate, without interdiffusing a sufficient amount of aluminum into a coating layer to adversely affect the coating growth potential and mechanical properties of said coating layer. A metal substrate is provided comprising an external surface and an internal passage therein defined by an internal surface, at least a portion of the external surface of the substrate being coated with a coating layer selected from the group consisting of ?-NiAl-base, MCrAlX, a line-of-sight diffusion aluminide, a non-line-of-sight diffusion aluminide, a pack diffusion aluminide, and a slurry diffusion aluminide on said substrate. The external surface of the substrate is cleaned. The metal substrate is subjected to a aluminum vapor phase deposition process performed using a fluorine-containing activator selected from the group consisting of AlF3, CrF3, NH4F, and combinations thereof, at a rate in the range of about 0.

Abstract: A beta-phase NiAl overlay coating containing a dispersion of ceramic particles and a process for depositing the overlay coating. If the coating is used to adhere a thermal barrier coating (TBC), the TBC exhibits improved spallation resistance as a result of the dispersion of ceramic particles having a dispersion-strengthening effect on the overlay coating. The overlay coating contains at least one reactive element and is deposited so that the some of the reactive element deposits as the ceramic particles dispersed in the overlay coating.

Abstract: A beta-phase nickel aluminide (NiAl) overlay coating (24) and method for modifying the grain structure of the coating (24) to improve its oxidation resistance. The coating (24) is deposited by a method that produces a grain structure characterized by grain boundaries (44) exposed at the outer coating surface (36). The grain boundaries (44) may also contain precipitates (40) as a result of the alloyed chemistry of the coating (24). During or after deposition, the overlay coating (24) is caused to form new grain boundaries (34) that, though open to the outer surface (36) of the coating (24), are free of precipitates or contain fewer precipitates (40) than the as-deposited grain boundaries (44). New grain boundaries (34) are preferably produced by causing the overlay coating (24) to recrystallize during coating deposition or after deposition as a result of a surface treatment followed by heat treatment.