Abstract: A method of refurbishing a transition duct (100) for a gas turbine system includes providing the transition duct. The transition duct has a first wall (221) defining a first passageway (110) and having holes (223) through a metal layer (322) and a ceramic layer (323), and the transition duct also has a second wall (222) adjacent to and separate from the first wall and external to the first passageway, where the first and second walls define a second passageway (210) coupled to the first passageway through the holes in the first wall. The method further includes masking the holes in the first wall, sealing the first passageway, and after sealing the first passageway, using a liquid etchant to chemically remove the ceramic layer from the first wall while keeping the liquid etchant out of the second passageways.

Abstract: A method of joining superalloy substrates together comprises diffusion bonding the superalloy substrates by depositing an activator directly on the surface of the joint to be bonded and thereafter subjecting the joint to heat and pressure. The heat and pressure causes the surface of the superalloy, in the presence of the activator, to diffusion bond without the use of a brazing alloy. By eliminating the brazing alloy, a high strength, high temperature bond is achieved, yet there is no molten brazing alloy to be drawn through capillary action into any fine features surrounding the joint being bonded, and there is no residue left at the interface that would diminish the mechanical or chemical properties of the joint.

Abstract: A method of joining superalloy substrates together comprises diffusion bonding the superalloy substrates by depositing an activator directly on the surface of the joint to be bonded and thereafter subjecting the joint to heat and pressure. The heat and pressure causes the surface of the superalloy, in the presence of the activator, to diffusion bond without the use of a brazing alloy. By eliminating the brazing alloy, a high strength, high temperature bond is achieved, yet there is no molten brazing alloy to be drawn through capillary action into any fine features surrounding the joint being bonded, and there is no residue left at the interface that would diminish the mechanical or chemical properties of the joint.

Abstract: A method of joining superalloy substrates together comprises diffusion bonding the superalloy substrates by depositing an activator directly on the surface of the joint to be bonded and thereafter subjecting the joint to heat and pressure. The heat and pressure causes the surface of the superalloy, in the presence of the activator, to diffusion bond without the use of a brazing alloy. By eliminating the brazing alloy, a high strength, high temperature bond is achieved, yet there is no molten brazing alloy to be drawn through capillary action into any fine features surrounding the joint being bonded, and there is no residue left at the interface that would diminish the mechanical properties of the joint.

Abstract: A method of joining superalloy substrates together comprises diffusion bonding the superalloy substrates by depositing an activator directly on the surface of the joint to be bonded and thereafter subjecting the joint to heat and pressure. The heat and pressure causes the surface of the superalloy, in the presence of the activator, to diffusion bond without the use of a brazing alloy. By eliminating the brazing alloy, a high strength, high temperature bond is achieved, yet there is no molten brazing alloy to be drawn through capillary action into any fine features surrounding the joint being bonded, and there is no residue left at the interface that would diminish the mechanical properties of the joint.

Abstract: A method is provided for bonding a ceramic thermal barrier coating to a nickel or cobalt based superalloy substrate for use in high temperature applications such as gas turbine engines. The method comprises roughening the superalloy substrate itself to produce a surface roughness, preferably from 100 to 350 microinches Roughness Average (RA). The roughened surface of the substrate is treated with a diffusion coating, preferably aluminide or platinum-aluminide to provide oxidation and hot corrosion resistance, while substantially preserving the micro-topography of the roughened surface. A ceramic thermal barrier coating is applied directly to the diffusion treated surface, preferably using an air plasma spray. The surface roughness, which is left substantially undisturbed by the diffusion coating treatment, is altered by the air plasma sprayed ceramic to form a series of interlocking microstructures that firmly attach the ceramic thermal barrier coating to the diffusion treated superalloy substrate.

Abstract: A process is provided for welding a gamma-prime precipitation-strengthened nickel base superalloy by heating the weld area and adjacent region to a ductile temperature, welding while maintaining the entire weld area and adjacent region at the ductile temperature and holding the weldment, weld area and adjacent region at the ductile temperature until the entire weld has solidified. The ductile temperature is above the aging temperature but below the incipient melting temperature of the superalloy.

Abstract: A process is provided for welding a gamma-prime precipitation-strengthened nickel base superalloy by heating the weld area and adjacent region to a ductile temperature, welding while maintaining the entire weld area and adjacent region at the ductile temperature and holding the weldment, weld area and adjacent region at the ductile temperature until the entire weld has solidified. The ductile temperature is above the aging temperature but below the incipient melting temperatures of the superalloy.

Abstract: Aluminized nickel-base, cobalt-base and nickel-cobalt-base heat resistant alloy substrates are provided in which, prior to aluminizing the substrate, the substrate is provided with a thin coating of rhodium and thereafter a thin coating of platinum, the coatings being diffusion bonded to the substrate, such that when the prepared substrate is aluminized by pack cementation, a compositely structured coating is obtained characterized by improved resistance to high temperature oxidation and sulfidation.

Abstract: Aluminized nickel-base, cobalt-base and nickel-cobalt-base heat resistant alloy substrates are provided in which, prior to aluminizing the substrate, the substrate is provided with a thin coating of rhodium and thereafter a thin coating of platinum, the coatings being diffusion bonded to the substrate, such that when the prepared substrate is aluminized by pack cementation, a compositely structured coating is obtained characterized by improved resistance to high temperature oxidation and sulfidation.