Abstract: A method for forming a thermal barrier coating system on an article subjected to a hostile thermal environment, such as the hot gas path components of a gas turbine engine. The coating system is generally comprised of a ceramic layer and an environmentally resistant beta phase nickel aluminum intermetallic (&bgr;-NiAl) bond coat that adheres the ceramic layer to the component surface. A thin aluminum oxide scale forms on the surface of the &bgr;-NiAl during heat treatment. The &bgr;-NiAl may contain alloying elements in addition to nickel and aluminum in order to increase the environmental resistance of the &bgr;-NiAl. The &bgr;-NiAl powder having a size in the range of 20-50 microns is applied using air plasma spray techniques to produce a surface having a roughness of 400 microinches or rougher. The ceramic top coat can be applied using inexpensive thermal spray techniques to greater thicknesses than achievable otherwise because of the rough surface finish of the underlying &bgr;-NiAl bond coat.

Abstract: A method for coating an article includes preparing a coating precursor paint including aluminum-containing pigment particles, a temporary organic binder comprising an acrylic, and a solvent for the temporary organic binder. The coating precursor paint is applied to a surface of the article and thereafter heated to a temperature of from about 1200° F. to about 2100° F. in a non-oxidizing environment.

Abstract: A heat treatment process that will restore the mechanical properties of an aircraft engine article that includes a cast Inconel 718 portion welded to a wrought portion. The heat treatment process includes placing an article that includes the Inconel 718 cast portion into a heat treatment chamber, evacuating the chamber to a suitable atmosphere, heating the chamber in a manner that minimizes distortion of the cast portion to a temperature in the range of 1950° F. to 2050° F., holding the temperature in that range for a period of time sufficient to solution all the delta phase precipitates, and then cooling the article to room temperature in a manner that minimizes distortion of the article. After solution heat treatment, the wrought portion of the engine part can be removed and replaced and the engine article can be reprocessed.

Abstract: A method for restoring thickness to load-bearing components of gas turbine engines, and for repairing a honeycomb structured gas turbine engine component. A surface of the component such as the backing surface of a honeycomb component after honeycomb removal is roughened and cleaned. A selected build-up material is deposited onto the substrate by high velocity oxy-fuel deposition or low pressure plasma spray. The component is heat treated to enhance the bond between the deposited material particles, and between the deposited material and the substrate by diffusion.

Abstract: A PVD process and apparatus (120) for depositing a coating (132) from multiple sources (110,111) of different materials. The process and apparatus (120) are particularly intended to deposit a beta-nickel aluminide coating (132) containing zirconium, hafnium, yttrium and/or cerium, whose vapor pressures are sufficiently lower than NiAl to require a different evaporation rate in order to achieve higher deposition rates and better control of the coating chemistry. The PVD process and apparatus (120) entail feeding at least two materials (110,111) into a coating chamber (122) and melting the materials (110,111) at different rates to form separate molten pools (114,115) thereof. Articles (130) to be coated are suspended within the coating chamber (122), and transported with a support apparatus (118) relative to the two molten pools (114,115) so as to deposit a coating (132) with a controlled composition that is a mixture of the first and second materials (110,111).

Abstract: A gas turbine component, such as a turbine disk or a rotating seal, is fabricated by furnishing a substrate shaped as a gas turbine component made of a nickel-base superalloy, and oxidizing the substrate to produce an oxidized substrate having thereon a layer comprising an oxide and having a thickness of at least about 500 Angstroms. The step of oxidizing is performed prior to entry of the component into service and in an atmosphere that does not contain combustion gas. The oxidized gas turbine component is thereafter placed into service.

Abstract: A gas turbine component, such as a turbine disk or a rotating seal, is fabricated by furnishing a substrate shaped as a gas turbine component made of a nickel-base superalloy, and oxidizing the substrate to produce an oxidized substrate having thereon a layer comprising an oxide and having a thickness of at least about 500 Angstroms. The step of oxidizing is performed prior to entry of the component into service and in an atmosphere that does not contain combustion gas. The oxidized gas turbine component is thereafter placed into service.

Abstract: A surface of a nickel-base article such as an internal surface of a gas turbine airfoil is protected with a donor layer of aluminum and at least one other element. To form the protective layer, a donor alloy is contacted to the protected surface of the article, and simultaneously the article and the donor alloy are heated to a coating temperature that is greater than about 0.7 of the absolute solidus temperature of the donor alloy but is such that the donor alloy remains in the form of a condensed phase contacting the protected surface of the article. The donor alloy is thereafter interdiffused into the protected surface of the article.

Abstract: A welding filler metal is manufactured by casting a nickel-base alloy as an extrusion rod having a diameter of from about 0.2 inch to about 0.5 inch. The extrusion rod has at least about 12 grains in the cross section of the extrusion rod. The extrusion rod is extruded in a single extrusion operation to a filler-metal diameter of less than about 0.1 inch and using an areal extrusion ratio of at least about 9:1 to form the welding filler metal. Preferably, the process is used to make a nickel-base superalloy welding filler metal of a diameter of about 0.05-0.06 inch from an extrusion-rod casting of about 1/4 inch diameter and having at least about 12 grains in the cross section.

Abstract: A method for restoring thickness to load-bearing components of gas turbine engines, and for repairing a honeycomb structured gas turbine engine component. A surface of the component such as the backing surface of a honeycomb component after honeycomb removal is roughened and cleaned. A selected build-up material is deposited onto the substrate by high velocity oxy-fuel deposition or low pressure plasma spray. The component is heat treated to enhance the bond between the deposited material particles, and between the deposited material and the substrate by diffusion.

Abstract: An internal passage of an article such as a gas turbine airfoil is coated with an aluminum-containing coating. To accomplish this coating process, a coating slurry of a mixture of a carrier component of water and a hectorite clay or a bentonite clay, together with a solids component of a source of aluminum, a halide activator, and an oxide dispersant, is prepared. The coating slurry is applied to the internal passage of the gas turbine airfoil and dried. The gas turbine airfoil and the applied coating slurry are heated to form an aluminum-containing coating bonded to the internal passage of the gas turbine airfoil. Excess coating material is removed from the article internal passage.

Abstract: A method is provided for refurbishing a service operated metallic coating on a substrate alloy, the coating including at least within a coating outer surface at least one oxide chemically grown from at least one coating element, for example Al, and chemically bonded with the coating outer surface as a result of thermal exposure during service operation. Growth of the oxide has depleted at least a portion of the coating element from the coating. The method comprises removing the oxide from the coating outer surface while substantially retaining the metallic coating, thereby exposing in the coating outer surface at least one surface void that had been occupied by the oxide. The retained metallic coating is mechanically worked, substantially without removal of the retained coating, to close the void, providing a treated metallic coating surface over which a refurbishing coating is applied.

Abstract: A method is provided for refurbishing a service operated metallic coating on a substrate alloy, the coating including at least within a coating outer surface at least one oxide chemically grown from at least one coating element, for example Al, and chemically bonded with the coating outer surface as a result of thermal exposure during service operation. Growth of the oxide has depleted at least a portion of the coating element from the coating. The method comprises removing the oxide from the coating outer surface while substantially retaining the metallic coating, thereby exposing in the coating outer surface at least one surface void that had been occupied by the oxide. The retained metallic coating is mechanically worked, substantially without removal of the retained coating, to close the void, providing a treated metallic coating surface over which a refurbishing coating is applied.