Abstract: A method for producing a low reactivity tungsten impregnated ceramic mold for casting refractory metals such as titanium is described. The method involves impregnation of a standard ceramic shell mold with an aqueous solution of tungstic acid and ammonium hydroxide. The saturated mold is then dried and fired to convert the tungsten compound to metallic tungsten or tungsten oxides. The process may be repeated several times to achieve the desired tungsten concentration.

Abstract: An interlayer for transient liquid phase diffusion bonding of the nickel, cobalt and iron alloys is provided between surfaces to be joined as a thin lamellar composite.

Abstract: A surface treatment for a class of metallic articles is described. The treatment involves the melting of a thin surface layer of the article by a concentrated energy source, within a narrow set of parameters. The melting step is performed in a manner which maximizes the temperature gradient between the melted and unmelted portion of the article, consequently, cooling and solidification upon the removal of the energy source is extremely rapid and can produce unique microstructures. The preferred energy source is a continuous wave laser, and in the preferred embodiment, a flowing inert gas cover is used to minimize melt contamination and plasma formation. The technique may be used to produce amorphous surface layers in a specific class of eutectic alloys. In another class of alloys, based on the transition metals and containing precipitates rich in one or more metalloids, uniquely fine microstructures may be produced.

Abstract: Nickel base superalloy single crystal articles formed from an alloy family and heat treated are described as is the process employed. The articles are substantially free from cobalt and the grain boundary strengtheners such as carbon, boron, and zirconium. The heat treatment process homogenizes the microstructure, and refines the gamma prime morphology.

Abstract: This disclosure relates to an alloy in the nickel-aluminum-molybdenum system of approximately eutectic composition, and articles made by directional solidification of the alloy. The alloy is preferably directionally solidified to produce an article which has a microstructure consisting of a ductile matrix containing ductile reinforcing fibers. The matrix comprises a continuous microstructure of the gamma nickel solid solution phase, and also preferably contains the gamma prime (Ni.sub.3 Al) intermetallic phase in either precipitate or continuous form. The ductile continuous reinforcing phase consists of alpha molybdenum in fibrous form. The nominal composition of the alloy is 4.6 weight percent aluminum, 35.8 weight percent molybdenum, balance essentially nickel.

Abstract: A process for the production of ceramic-metal assemblies which are joined by a graded layer of a metal-ceramic mixture is described. The effect of the processing sequence is to vary the prestress between the metal and ceramic components. The assemblies are produced by heating at elevated temperatures and the process of the invention involves preferential cooling of the metal portion of the assembly.

Abstract: A class of structural oxidation resistant ceramic base materials are described. The materials consist of an oxide matrix, which is resistant to the transport of oxygen by diffusion, and this matrix contains metallic fibers of a material which develops a stable protective oxide layer. The overall material composition is approximately eutectic so that the fiber-matrix combination can be formed by solidification directly from the melt. Directional solidification may be employed to produce a structure with oriented fibers.

Abstract: Supported fibrous skeletal metal catalysts and methods of producing such catalysts are described. The catalysts are produced by directionally solidifying a eutectic composition to produce a microstructure consisting of oriented intermetallic single crystal fibers in a metallic matrix. Selective means are employed to remove a portion of the matrix to expose a portion of the fibers. Leaching means are employed to preferentially remove one of the atomic species from the exposed intermetallic fiber. The exposed leached fibers are porous, have a high surface area and display catalytic activity, depending upon the starting eutectic composition.

Abstract: Coatings are described which are particularly suited for the protection of nickel and cobalt superalloy articles at elevated temperatures. The protective nature of the coatings is due to the formation of an alumina layer on the surface of the coating which serves to reduce oxidation/corrosion. The coatings contain aluminum, chromium, and one metal chosen from the group consisting of nickel and cobalt or mixtures thereof. The coatings further contain a small controlled percentage of hafnium which serves to greatly improve the adherence and durability of the protective alumina film on the surface of the coating.

Abstract: Cobalt base alloys for use at elevated temperatures are disclosed that possess excellent resistance to oxidation/corrosion at elevated temperatures in combination with mechanical properties which exceed those of similar alloys currently in use. The resistance to oxidation/corrosion is afforded by a particular combination of aluminum and chromium which act to form a protective alumina layer and a synergistic combination of hafnium and yttrium which act to promote adherence of the alumina. Refractory metal additions are utilized to improve the mechanical properties. The alloys of the invention are suited for use in gas turbine engines as well as industrial applications such as furnaces and chemical process apparatus.

Abstract: In filling voids in or between metallic articles, as in the repair of cracks or other surface defects in castings, the void is filled with a powder mix which upon heat treatment fills the void. The filler powder mix is a blend of at least two distinct powder components and in terms of overall composition preferably corresponds to that of article being repaired. The components comprising the mix are selected to provide a transient liquid phase and isothermal resolidification of a portion of the mix at the temperature below the article melting point. A subsequent heat treatment is preferably utilized for homogenization.

Abstract: High surface area skeletal metal catalysts and methods of producing such catalysts are described. The production involves solidification of certain eutectic compositions to produce a microstructure of intermetallic fibers in solid solution matrix. The matrix is preferentially removed to provide loose intermetallic fibers which may then be leached to provide a porous structure. Directional solidification is a preferred step in the production process.

Abstract: A thermomechanical treatment to improve the fatigue strength of articles made from one of a class of alpha beta titanium alloys. The treatment involves heating the alloy into the beta field, hot deforming the alloy at a temperature within the beta field, rapidly quenching the alloy to room temperature to produce a hexagonal martensite structure and then tempering at an intermediate temperature so as to produce a structure in which discrete equiaxed beta phase particles are presented in an acicular alpha matrix. This structure is particularly resistant to the initiation and propagation of fatigue cracks.

Abstract: An interlayer for transient liquid phase diffusion bonding of the nickel, cobalt and iron alloys is provided between surfaces to be joined as a thin lamellar composite.

Abstract: Coatings are described which are particularly suited for the protection of nickel and cobalt superalloy articles at elevated temperatures. The protective nature of the coatings is due to the formation of an alumina layer on the surface of the coating which serves to reduce oxidation/corrosion. The coatings contain aluminum, chromium, yttrium (or other oxygen active elements) and a metal chosen from the group consisting of nickel, cobalt and iron or mixtures thereof. The coatings further contain a controlled percentage of silicon which serves to greatly improve the protection afforded by the alumina film to the surface of the coating.

Abstract: This invention concerns composite articles, particularly those which contain single crystal components. A method is disclosed for joining single crystals together so that the resultant article is free from high angle grain boundaries and therefore possesses exceptional mechanical properties.

Abstract: This disclosure relates to a eutectic alloy, and article made from the alloy, in the nickel-aluminum-molybdenum system which may be directionally solidified to produce a microstructure consisting of a ductile matrix phase of gamma prime or gamma prime/gamma containing a reinforcing fibrous or lamellar refractory metal alpha second phase. The nominal composition of the base alloy is 8 weight percent aluminum, 27 weight percent molybdenum, balance nickel. Minor elemental additions may be made to modify the mechanical properties of the first phase and/or the second phase. The directionally solidified alloy of the invention is characterized by exceptional anisotropic tensile properties, high isotropic ductilities, combined with good oxidation resistance and satisfactory sulfidation resistance at elevated temperatures.

Abstract: In filling voids in or between metallic articles, as in the repair of cracks or other surface defects in castings, the void is filled with a powder mix which upon heat treatment fills the void. The filler powder mix is a blend of at least two distinct powder components and in terms of overall composition preferably corresponds to that of article being repaired. The components comprising the mix are selected to provide a transient liquid phase and isothermal resolidification of a portion of the mix at the temperature below the article melting point. A subsequent heat treatment is preferably utilized for homogenization.

Abstract: Coatings are described which are particularly suited for the protection of nickel and cobalt superalloy articles at elevated temperatures. The protective nature of the coatings is due to the formation of an alumina layer on the surface of the coating which serves to reduce oxidation/corrosion. The coatings contain aluminum, chromium, and one metal chosen from the group consisting of nickel and cobalt or mixtures thereof. The coatings further contain a small controlled percentage of hafnium which serves to greatly improve the adherence and durability of the protective alumina film on the surface of the coating.

Abstract: A thermomechanical treatment for producing useful microstructures in the nickel base superalloys is described. The process is applied to material which has been placed in a condition of super-plasticity, and utilizes isothermal hot deformation under conditions which produce a uniform dislocation density and a resultant propensity for abnormal grain growth. The material is then recrystallized in a thermal gradient to produce a final structure consisting of elongated grains.