Abstract: A method for weld repairing an article formed of a low-alloy steel, such as a steam turbine component. The method generally includes the step of depositing a first weld repair (14) on a surface of the article, during which a hard heat-affected zone (HAZ) (18) having a fine grain size is formed in the article beneath the surface on which the weld repair (14) is deposited. The first weld repair (14) and at least a portion of the HAZ (18) adjacent the first weld repair (14) are then locally heat treated at a temperature above a critical temperature A.sub.1 of the alloy from which the article is formed. As a result of this localized heat treatment, the original grain structures of the first weld repair (14) and the HAZ (18) are entirely replaced with a fine-grain structure with acceptable hardness. Thereafter, at least one additional weld repair layer (16) is deposited on the first weld repair (14).

Abstract: A method of depositing a bond coat (16) of a thermal barrier coating (TBC) system (14) for a component (10) designed for use in a hostile thermal environment. The method yields a bond coat (16) having an adequate surface roughness for adhering a plasma-sprayed ceramic layer (18), while also exhibiting high density and low oxide content. The method generally entails forming the bond coat (16) by depositing a metal powder on the substrate (12) using a plasma spray or high velocity oxy-fuel (HVOF) technique. The metal powder contains particles that are sufficiently large to incompletely melt during deposition, yielding a surface roughness of at least about 350 microinches Ra. The large particles cause the bond coat (16) to have relatively low density and a propensity to oxidize, both at the surface of the bond coat (16) and internally due to the porosity of the bond coat (16).

Abstract: A method for repairing the rim of a steam turbine rotor, and a weld material for repairing such rotors. The method generally includes the steps of removing a damaged rim and its associated dovetail region, so as to form a surface at the perimeter of the rim portion. A weld repair region is then formed on the surface, which is machined to reconstruct the rim portion and the dovetail region exclusively with the weld repair region. Thereafter, an appropriately configured blade is secured to the rim portion with the dovetail region. The method is particularly intended for the repair of a steel alloy rotor, such as a NiCrMoV, NiMoV and CrMoV alloy, while the weld repair is formed with a nickel-base superalloy whose mechanical and thermal properties are compatible with the repair method and the steel alloy over a broad temperature range.

Abstract: A high voltage generator armature bar (10) that exhibits improved performance by forming one or more of its conductive components from a conductive material that uses a tin oxide-based composition as a conductive filler. The armature bar (10) is of the type having one or more tiers of conductor strands (12), strand insulation (14), conductive internal grading (20), groundwall insulation (22), conductive slot armoring (24), and preferably a transposition filler (18). The conductive internal grading (20), the conductive slot armoring (24) and/or the transposition filler (18) contain a conductive filler of antimony-doped tin oxide that may constitute the entire conductive filler, or can be present as a shell on the filler particles.

Abstract: A braze material for repairing an article, and particularly industrial gas turbine engine nozzles formed from nickel-base superalloys. The braze material is composed of a nickel-base braze alloy that is preferably in powder form and dispersed in a suitable vehicle, such as a binder that forms a slurry with the powder. The braze alloy is formulated to be capable of withstanding the high temperature operating environment of an industrial gas turbine nozzle, and to have a melting temperature below the recrystallization temperature of the superalloy to be repaired. A desirable composition for the braze alloy, in weight percent, about 14 to 24 chromium, about 6 to 15 cobalt, about 0.7 to 2.5 boron, about 1.0 to 2.0 titanium, about 0.6 to 1.0 aluminum, about 1.0 to 1.4 tungsten, about 0.4 to 0.6 columbium, about 0.5 to 0.7 tantalum, and up to about 0.7 iron, with the balance being nickel and incidental impurities.

Abstract: A turbine rotor comprising a radially-inward portion of a steel alloy and a radially-outward rim portion circumscribing the radially-inward portion, the rim portion being formed by a weldment that includes a nickel-base superalloy region joining the rim portion to the inward portion of the turbine rotor, the nickel-base superalloy having a room temperature ultimate tensile strength of at least about 690 MPa.

Abstract: A method of depositing a bond coat (16) of a thermal barrier coating (TBC) system (14) for components designed for use in a hostile thermal environment, such as turbine, combustor and augmentor components (10) of a gas turbine engine. The method yields a bond coat (16) having an adequate surface roughness for adhering a plasma-sprayed ceramic layer (18) while also producing a bond coat (16) that is dense with low porosity, thereby yielding a thermal barrier coating system (14) that is highly resistant to spallation. The method generally entails forming the bond coat (16) by depositing two metal powders on the substrate (12) using either a vacuum plasma spraying (VPS) or high velocity oxy-fuel (HVOF) technique. The particle size distributions of the two powders are chosen to yield a bimodal (dual-peak) particle size distribution that will produce a VPS and HVOF bond coat (16) characterized by a macro-surface roughness of at least about 350 microinches Ra attributable to particles of the coarser powder.

Abstract: A method for weld repairing an article formed of a low-alloy steel, such as a steam turbine component. The method generally includes the step of depositing a first weld repair (14) on a surface of the article, during which a hard heat-affected zone (HAZ) (18) having a fine grain size is formed in the article beneath the surface on which the weld repair (14) is deposited. The first weld repair (14) and at least a portion of the HAZ (18) adjacent the first weld repair (14) are then locally heat treated at a temperature above a critical temperature A.sub.1 of the alloy from which the article is formed. As a result of this localized heat treatment, the original grain structures of the first weld repair (14) and the HAZ (18) are entirely replaced with a fine-grain structure with acceptable hardness. Thereafter, at least one additional weld repair layer (16) is deposited on the first weld repair (14).

Abstract: A threaded fastener and a method by which the fastener exhibits sufficiently enhanced fatigue strength so as to be suitable for use in gas compressors and turbines operating at relatively high service temperatures. The method entails a selective heat treatment to achieve a dramatic improvement in fatigue properties while not interfering with other required properties for the fastener. The heat treatment process preferentially develops a case-hardened region in those threads nearest a transition region between the threads and an unthreaded portion of the fastener. In contrast, the unthreaded portion and the threads furthest from the transition region need not be case-hardened. The hardening pattern in the threads yields a martensitic steel fastener that exhibits fatigue properties which are dramatically superior to otherwise identical fasteners.

Abstract: A spray tower for removing acidic gases and particulate matter from flue gases produced by processing operations of the type carried out in utility and industrial facilities. The spray tower is equipped with a tank that serves as a reservoir for an alkaline slurry used to remove acidic gases and particulate matter from the flue gases. The slurry is pumped from the tank to spraying devices located within the tower. The spray tower further includes an internal structure that enables the slurry to be oxidized and gently agitated within a limited region of the tank, and without the requirement for two separate aeration and agitation devices. As a result, the construction, operational and maintenance costs of the spray tower are significantly reduced as compared to prior art spray towers.

Abstract: A wet flue gas desulfurization process and system are provided for removing sulfur dioxide from flue gases produced by processing operations of the type carried out in utility and industrial plants. In particular, the desulfurization process utilizes an ammonia-based solution having a free ammonia constituent that reacts with sulfur dioxide to generate an ammonium sulfate solution that can be further reacted to produce potassium sulfate, a valuable fertilizer. A second byproduct of this process is then reacted to regenerate free gaseous ammonia, which can then be recovered for subsequent use in the desulfurization of flue gases.

Abstract: A resin composition is provided that is suitable for impregnating sheet material, including fabrics, films, paper and tapes of the type employed to form prepregs, such as tapes used to form electrical insulation layers on electrical components. The resin composition includes a solid or semi-solid epoxy resin having an epoxide functionality of at least 2.5, a metal acetylacetonate for catalyzing the epoxy resin, and an accelerator of bisphenol A-formaldehyde novolac catalyzed by an acidic catalyst and having a hydroxyl equivalent weight of 120. The resin composition is essentially unreactive at room temperature and at elevated temperatures sufficient to enable permeation of the sheet material by the resin in its manufacture, is essentially unreactive at temperatures required to remove moisture and volatiles during processing of articles wrapped or taped with the sheet material, and cures at a higher temperature without adversely affecting the cure characteristics of the resin composition.

Abstract: A spray tower is provided for removing gases and particulate matter from flue gases which are produced by processing operations of the type carried out in utility and industrial facilities. The spray tower is configured so as to minimize its overall height, such that construction, operational and maintenance costs of the tower are also minimized. A tank located at the base of the tower serves as a reservoir for an alkaline slurry used to remove gases and particulate matter from the flue gases. The slurry is pumped from the tank to spraying devices located within the tower. An inlet is located above the tank through which the flue gases are introduced into the tower. Disposed within the tower and adjacent the inlet is an enclosure having an upper end joined to the tower and a lower end defining an opening. Spraying devices are located within the enclosure, preferably at approximately the same height as the inlet, so as to enable the overall height of the tower to be reduced.

Abstract: This overvoltage surge arrester has a tubular porcelain housing having a bore, metal terminals at opposite ends of the porcelain housing, stacks of metal-oxide varistor disks located within the housing in angularly-spaced relationship about the bore, and venting means within the terminals for venting gases from the housing should an electric arc develop within the housing as a result of failure of a varistor disk. First liners of electrical insulating material having relatively high thermal conductivity are sandwiched between the stacks and the bore for providing effective heat transfer between the stacks and the porcelain housing. Additional liners are disposed on the bore in locations angularly between the first liners. These additional liners are of a thermal and electrical insulating material, a major portion of which is a ceramic selected from the group of alumina, thoria, zirconia, zircon, and spinel.

Abstract: This transformer core and coil assembly comprises (a) a low voltage coil surrounding a coil window and including first and second coil legs on opposite sides of the coil window, (b) a first plurality of side-by-side amorphous-steel core loops surrounding one of the coil legs, and (c) a second plurality of side-by-side amorphous-steel core loops surrounding the other of the coil legs. Extending between said coil legs in a position between two of said side-by-side core loops in the first plurality and between two of said side-by-side loops in the second plurality is a brace of plate form and of electrical insulating material for blocking motion of said coil legs toward each other in response to coil-collapsing forces developed by short-circuit currents through the low voltage coil, thereby protecting the amorphous-steel core loops from damage by these short-circuit produced forces tending to collapse the coil.

Abstract: A high purity martensitic stainless steel alloy containing only critically limited amounts of minor elements including manganese, silicon, tin, phosphorus, aluminum, antimony and arsenic has high strength and toughness and unique resistance to both reversible and irreversible embrittlement.

Abstract: Low viscosity, solventless, thermosetting resin compositions of bismaleimide resin composition and epoxy resins have unique heat stability and special utility as insulation for electric conductors to be used in the 200.degree.-250.degree. C. temperature range.

Abstract: A technique for indirectly determining the temperature of a fluid includes directing at least a portion of the fluid around the outside of a thermally conductive body so as to produce a substantially uniform temperature therein. The fluid temperature is then determined by measuring the resulting temperature within the body. In one embodiment, the fluid is directed around the body by enclosing the body in a shell which has an inlet opening, an outlet opening, and at least one passageway connecting the inlet opening to the outlet opening. In an embodiment which is particularly useful for gas turbine applications, the body is located inside of the outer casing of the turbine and is connected to a guide tube which extends through the outer casing in such a manner that the means employed for measuring the temperature within the body is insertable into and removable from the body through the guide tube.

Abstract: A dual-coupled resonator crystal is fine-tuned by frequency balancing the input and output resonators and thereafter plating a coupling adjust spot on the grounded side shadowing the unelectroded region of the front side of the crystal to produce a change in synchronous peak separation frequency. Thereafter, the front side electrodes are sequentially plated to bring plateback and synchronous peak separation frequency to their target values. Interim adjustments in synchronous peak separation frequency may be made during the tuning process to compensate for misalignment of the plating elements.