Abstract: According to this invention, the oxidation resistance of alumina scale forming nickel based superalloys is significantly improved by controlling the level of sulfur in the alloy composition. According to one preferred embodiment of the invention, the superalloys contain less than 5 parts per million, by weight, of sulfur. Most preferably, they contain less than 2 parts per million, by weight, of sulfur.

Abstract: In a compressor rotor assembly of an axial flow gas turbine engine, wherein the rotor disk has a circumferential blade retaining slot for receiving the root of each blade of a row of blades, a ladder seal is provided between the slot and the blade platforms to limit the leakage of working medium gases from the flow path and through the slot. During engine operation, the seal moves radially outwardly into sealing relation with the underside surface of each platform. At the same time, radially inwardly extending flanges of the seal move radially outwardly into sealing relation with the sidewalls of the disk slot.

Abstract: An abrasive, wear resistant layer is applied to the tip surface of a superalloy gas turbine blade by high temperature sintering operation which produces a high strength bond between the layer and the blade, minimizes gamma prime phase growth, and prevents recrystallization in the blade. Important features of the invention include removing plastic strain damage from the tip surface prior to the sintering operation, using induction heating techniques to sinter a layer of metal powder particles and ceramic particulates to the blade tip surface, and shielding the airfoil and root portion of the blade from the radiant heating source during the sintering operation while at the same time, conductively removing heat from the blade.

Abstract: A thin film noble metal temperature sensor includes adjacent layers of metals and metal oxides on the surface of a component. The most preferred sequence of layers are: a NiCoCrAlY layer applied directly to the component surface; a thermally grown aluminum oxide layer on the NiCoCrAly layer; a sputtered layer of aluminum oxide on the thermally grown layer of aluminum oxide; a FeCrAl layer on the sputtered aluminum oxide layer; and layer of platinum and platinum-rhodium on the FeCrAl layer.

Abstract: A method and apparatus are disclosed which are useful for fabricating integrally bladed rotors. In particular, the method and apparatus are used to increase the twist of the blades on the rotor from a first degree of twist to a second degree of twist under superplastic forming conditions. The apparatus is constructed and arranged such that the method can be carried out at ambient atmospheric conditions. A key feature of the invention is that the blade twisting dies are present in the blade heating zone only when the dies contact the blade. When the dies are not in contact with the blades, they are at ambient conditions where oxidation is at a minimum.

Abstract: A method and apparatus are disclosed which are useful for fabricating integrally bladed rotors. In particular, the method and apparatus are used to increase the twist of the blades on the rotor from a first degree of twist to a second degree of twist under superplastic forming conditions. The apparatus is constructed and arranged such that the method can be carried out at ambient atmospheric conditions. A key feature of the invention is that the blade twisting dies are present in the blade heating zone only when the dies contact the blade. When the dies are not in contact with the blades, they are at ambient conditions where oxidation is at a minimum.

Abstract: Methods are described for forming an yttrium enriched aluminide coating on the surface of a nickel or cobalt base superalloy article. In one preferred embodiment, a pack mixture for forming the coating consists essentially of, by weight percent, 5-35 of an Al-Y-Si alloy, 1-20 CoI.sub.2, balance Y.sub.2 O.sub.3.

Abstract: The adherence of protective chromia (chromium oxide) scales on Ni-Cr coatings is substantially improved by limiting the amount of sulfur in the coating composition to below about 5 parts per million by weight. Volatilization of the chromium oxide scale is also reduced by controlling the sulfur content. The coatings of this invention have improved resistance to oxidation and hot corrosion degradation than the coatings of the prior art.

Abstract: This invention relates to a method for removing an oxide scale from the surface of a hot rolled copper rod in an in-line process. The method comprises the steps of passing the rod through a chamber containing a reducing atmosphere, the chamber being immediately adjacent to the exit end of the rod rolling mill. The rod passes through the hydrogen containing chamber while it is still hot from the rolling operation, and the reducing atmosphere reduces the oxide scale to metallic copper. After passing through the chamber, the rod is cooled in an aqueous bath and then coiled.

Abstract: An improved structural strut for use in the fan section of a high bypass ratio gas turbine engine is described. The strut includes two I-beam shaped structural supports which are substantially perpendicular to each other, and extend along the major and minor axes of the strut, from the strut base to the strut tip. Face sheets, preferably made of composite material, are attached to both of the I-beam supports for acoustic damping effects.

Abstract: An abrasive, wear resistant layer is applied to the tip surface of a superalloy gas turbine blade by high temperature sintering operation which produces a high strength bond between the layer and the blade, minimizes gamma prime phase growth, and prevents recrystallization in the blade. Important features of the invention include the use of an inductively heated graphite susceptor to heat the blade, and a refractory metal shield which surrounds the airfoil and root portions of the blade while leaving the tip portion exposed to the heat source.

Abstract: Methods are described for making a mirror useful in reflecting high energy laser radiation. The mirrors are comprised of an intermediate coating layer applied to the mirror substrate and a reflective coating layer applied to the intermediate layer. Plasma spray techniques are used to apply a readily polishable intermediate coating layer at high deposition rates.

Abstract: An apparatus and method for forming essentially contaminant free metal powders of varying particle diameter by utilizing a separate gas percolation chamber for admitting a separate clean variable pressure percolating gas into a molten metal passing through a transfer tube, forming a metal froth which is sprayed into a reduced pressure collection chamber. The metal froth then disintegrates providing a finely divided powder which is cooled in the suspension state and collected. By utilizing a separate percolation chamber for independently pressurizing the metal froth, impurities are reduced and froth characteristics and controllably modifiable thereby providing essentially contaminant free metal powder of varying particle diameter. In addition, pressure equalization means are disclosed for overcoming pressure imbalances on start-up.

Abstract: Defects in green, unsintered ceramic casting cores which contain a thermoplastic binder are repaired according to this invention. In a preferred embodiment, a mixture of a volatilizable solvent and ceramic particles are applied to the defect. The solvent softens the binder in the core, and the loose ceramic particles patch the defect area. After the solvent volatilizes, the binder hardens and binds the newly applied particles to the core. Then, the repaired core is heated to a first temperature to volatilize the binder, and then to a second, higher temperature to sinter the ceramic particles to each other.

Abstract: Processes for providing an inert gas protective atmosphere during shut down periods of a copper melting shaft furnace are described. Upon shut down of the furnace, liquid nitrogen is introduced into the furnace interior and forms gaseous nitrogen upon vaporization. A two-stage process is employed with the initial introduction of liquid nitrogen at a high rate to flush out all oxygen bearing atmospheres from the furnace, followed by the introduction of liquid nitrogen at a lower rate sufficient to maintain the protective nitrogen atmosphere.

Abstract: This invention relates to a method for making porous metal plasma sprayed abradable seals. Radiation transmission techniques are utilized to determine the as-sprayed density of a deposit containing metal and polymer powder particles. Based on the measuring density, a mathematical prediction is made of what the surface hardness of the sprayed deposit will be after it has been machined and then heated to remove the polymer powder particles. If the predicted hardness is outside of the desired range, changes are made in the plasma spray parameters.

Abstract: The surface of green (unsintered) casting cores which contain ceramic particles and a thermoplastic binder are bonded to each other by softening the binder in each core and applying a layer of ceramic particles to the surface of at least one of the cores to be joined, assembling the cores to each other such that the core surfaces are in close contact with each other; causing the binder to reharden; and then heating the cores to volatilize the thermoplastic binder and to sinter the ceramic particles in the cores to each other.

Abstract: A nickel base superalloy composition useful in the cast+HIP+heat treated condition is described. Articles having the invention composition have properties which are comparable to similarly processed IN718 articles. The invention alloys have an as-cast microstructure which is substantially free from Laves phase, even at slow solidification rates. As a result, the alloys are significantly more weldable than IN718. This desirable microstructure is achieved by modifications of the chromium, molybdenum, iron, and nickel contents compared to the typical IN718 composition.

Abstract: A very thin abrasive material on a substrate is comprised of ceramic particulates contained within a metal matrix. The particulates extend fully through the matrix from the substrate surface to the machined free surface of the abrasive. In a representative 0.38 mm abrasive the particulates are sized normally at 0.42-0.50 mm and have an aspect ratio of less than 1.9 to 1. This enables a high density of particulates, in the range 33-62 per cm.sup.2, while at the same time ensuring good bonding in that most of the particulates are fully surrounded by matrix. When the abrasive is applied to the tip of a superalloy gas turbine engine blade, about 10-50% of the matrix metal is removed after machining. This allows the machined ceramic particulates to project into space and to thus better interact with ceramic abradable seals. In the preferred practice of the invention the particulates are alumina coated silicon carbide contained in a nickel superalloy matrix.

Abstract: This invention relates to the application of plasma sprayed coatings to the surface of components which have small holes therein, such as hollow, air cooled blades or vanes used in turbine engines. Coating material is prevented from depositing on the wall surface of the holes by the presence of fugitive plugs in the holes during the coating process. The plugs are removed after the coating has been applied, resulting in the holes being open and unobstructed.