Abstract: A process for forming a coating on a surface of a substrate, so that heating of the coating material is selective and sufficient to cause at least partial melting of the coating material and permit bonding to the substrate without excessively heating the substrate so as not to significantly degrade its properties. The process generally entails forming a brazing paste containing powder particles dispersed in a binder. The particles are formed of a composition that is susceptible to microwave radiation. The brazing paste is then applied to the surface of the substrate and subjected to microwave radiation so that the particles couple with the microwave radiation and are sufficiently heated to burn off the binder and then at least partially melt to form an at least partially molten layer on the substrate. The microwave radiation is then interrupted to allow the at least partially molten layer to cool, solidify, and form the coating.

Abstract: A process and apparatus for forming wires, such as wires used as feedstock in welding, brazing, and coating deposition processes. The process and apparatus generally entail feeding through a passage a quantity of powder particles of a size and composition that render the particles susceptible to microwave radiation. As the particles travel through the passage, the particles within the passage are subjected to microwave radiation so that the particles couple with the microwave radiation and are sufficiently heated to melt at least a radially outermost quantity of particles within the passage. The particles are then cooled so that the radially outermost quantity of particles solidifies to yield a wire having a consolidated outermost region surrounding an interior region of the wire.

Abstract: A process for heating powder materials by microwave radiation so that heating and sintering or melting progressively and directionally occurs within the powder materials. The process generally entails forming a structure from a powder by arranging the powder in a mass according to size of particles of the powder so that the particles are progressively arranged within at least a region of the mass from smallest to largest. The mass is then subjected to microwave radiation so that the particles within the mass progressively couple with the microwave radiation according to size, the smallest particles coupling first and heating faster than larger particles of the powder, and the largest particles coupling last and heating slower than smaller particles of the powder. As a result of the progressive arrangement of the particles, the mass is progressively and directionally heated by the microwave radiation.

Abstract: A process and apparatus for brazing a metal alloy component, such as a superalloy component of a gas turbine engine. The process employs a plasma torch in a non-transferred arc mode to generate an electric arc between an electrode and a housing in which an orifice is defined. A plasma gas is flowed through the arc so as to ionize the plasma gas, and the resulting ionized plasma gas is discharged through the orifice to form a plasma jet. The plasma torch is configured so that the plasma jet is shrouded from a surrounding oxidizing atmosphere by a shielding gas flowing cocurrently with the plasma jet. A braze alloy material is introduced into the plasma jet, which is directed at a surface of the component to form a brazement that is metallurgically bonded to the component without melting the component.

Abstract: A method for manufacturing a brazed part is disclosed that includes coating a substrate surface to be joined by first cold spraying a braze filler metal powder upon the surface to clean the surface followed by further spray the powder to form a coating layer of a braze alloy upon the surface. The coated surface is assembled with another surface to be joined and brazed together to form the brazed part. The substrate and braze alloy may be nickel-based super alloy materials.

Abstract: A process for forming a coating on a surface of a substrate, so that heating of the coating material is selective and sufficient to cause at least partial melting of the coating material and permit bonding to the substrate without excessively heating the substrate so as not to significantly degrade its properties. The process generally entails forming a brazing paste containing powder particles dispersed in a binder. The particles are formed of a composition that is susceptible to microwave radiation. The brazing paste is then applied to the surface of the substrate and subjected to microwave radiation so that the particles couple with the microwave radiation and are sufficiently heated to burn off the binder and then at least partially melt to form an at least partially molten layer on the substrate. The microwave radiation is then interrupted to allow the at least partially molten layer to cool, solidify, and form the coating.

Abstract: A process and apparatus for forming wires, such as wires used as feedstock in welding, brazing, and coating deposition processes. The process and apparatus generally entail feeding through a passage a quantity of powder particles of a size and composition that render the particles susceptible to microwave radiation. As the particles travel through the passage, the particles within the passage are subjected to microwave radiation so that the particles couple with the microwave radiation and are sufficiently heated to melt at least a radially outermost quantity of particles within the passage. The particles are then cooled so that the radially outermost quantity of particles solidifies to yield a wire having a consolidated outermost region surrounding an interior region of the wire.

Abstract: A process for heating powder materials by microwave radiation so that heating and sintering or melting progressively and directionally occurs within the powder materials. The process generally entails forming a structure from a powder by arranging the powder in a mass according to size of particles of the powder so that the particles are progressively arranged within at least a region of the mass from smallest to largest. The mass is then subjected to microwave radiation so that the particles within the mass progressively couple with the microwave radiation according to size, the smallest particles coupling first and heating faster than larger particles of the powder, and the largest particles coupling last and heating slower than smaller particles of the powder. As a result of the progressive arrangement of the particles, the mass is progressively and directionally heated by the microwave radiation.

Abstract: A compliant seal assembly for a rotating machine is provided. The seal assembly includes a static member, a movable member and a biasing member. The static member is rigidly fixed to the machine at its fore and aft ends. The movable portion has a first sealing surface configured to seal against a rotating member and a rear surface, which may be exposed to a fluid pressure to urge the first sealing surface toward a sealing position with the rotating member. The static and the movable members further include sealing surfaces at their fore, aft and end faces to seal against leakage of gas between the static and the movable members. The biasing member is configured to support the movable member on the static member and to urge the movable member away from the sealing position so as to reduce force on the rotating member during contact of the rotating member with the first sealing surface of the movable member.

Abstract: Shroud covers for buckets of gas turbines sometimes overlap one another. To repair a shroud cover overlap and preclude further overlap during turbine operation, a first weld bead of high hardness material is applied along the radial inside surface of the overlapping cover and adjacent an intermediate edge of the Z-shaped edges of the covers. Additional weld beads of a more ductile material are applied along the same surface behind the initial weld bead to structurally support the high hardness initially applied weld material. By building up weld material along the inside radial face of the overlapping cover adjacent the overlapped edge of the adjoining cover, the thickness of the overlapping cover is increased to preclude shroud cover overlap during further turbine operation.

Abstract: Shroud covers for buckets of gas turbines sometimes overlap one another. To repair a shroud cover overlap and preclude further overlap during turbine operation, a first weld bead of high hardness material is applied along the radial inside surface of the overlapping cover and adjacent an intermediate edge of the Z-shaped edges of the covers. Additional weld beads of a more ductile material are applied along the same surface behind the initial weld bead to structurally support the high hardness initially applied weld material. By building up weld material along the inside radial face of the overlapping cover adjacent the overlapped edge of the adjoining cover, the thickness of the overlapping cover is increased to preclude shroud cover overlap during further turbine operation.