Abstract: Superalloy articles are made more oxidation resistant by a process which includes heat treating the article in the presence of foreign chemical species, at a temperature at which the foreign chemical species reacts with and modifies any oxide film present on the article surface. The heat treatment is best carried out at a temperature above the gamma prime solvus temperature of the article and below the incipient melting temperature of the article. Alternatively, the heat treatment may be carried out within the range defined by the incipient melting temperature of the article and about 150.degree. C. below the incipient melting temperature of the article. At such temperatures the foreign chemical species reacts with and modifies the oxide film on the article surface. Sulfur is then able to diffuse through such modified film, and a more oxidation resistant component is produced.

Abstract: Thermomechanical fatigue failure in components in high performance gas turbine engines is diminished by providing the component with an overlay of a metallic coating and a strain isolating layer located between the surface of the component and the metallic coating overlay.

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: The oxidation-corrosion resistance of plasma sprayed MCrAlY overlay coatings is improved. The coating method involves plasma spraying the MCrAlY coating alloy onto a superalloy substrate, applying a chromium or aluminum envelope over the outer surface of the coating or mechanically working the outer surface to seal the surface against penetration by the high pressure isostatic atmosphere to be subsequently applied and then hot isostatically pressing the coated substrate to close the coating defects and diffuse at least a portion of the envelope, if present, into the overlay coating. The invention thus can provide an MCrAlY coating not only substantially free of pores, voids and the like defects but also having at least an outer zone enriched in chromium, aluminum or like metals.

Abstract: A method for coating a nickel-base superalloy substrate with a nickel-aluminide coating, saturated with chromium and containing no precipitated phases is disclosed which comprises enriching the superalloy substrate with chromium by diffusion of chromium into the substrate at a rate below that at which a pure or alloyed chromium layer forms and then growing a nickel aluminide coating on the chromium enriched substrate surface by the outward diffusion of nickel from the substrate into an aluminum-containing pack in which the source of aluminum is the stoichiometric intermetallic compound NiAl, or a metal powder mixture having the overall aluminum activity of NiAl.

Abstract: Porous carbon sheets suitable for use as fuel cell electrode support plates are produced by stabilizing acrylic filament precursors through the controlled addition of oxygen thereto. The stabilized filaments are thereafter chopped into short lengths, felted and pressed into sheets with the pressing step being performed at a temperature determined by the oxygen content of the stabilized filaments. The sheets are thereafter pyrolyzed to produce the desired porous substrate material.

Abstract: Porous carbon sheets suitable for use as fuel cell electrode support plates are produced from inexpensive carbonizable filaments. The filaments are chopped into short lengths, felted, sprayed with a binder and the binder is cured whereby sheets are defined. The sheets are thereafter pyrolyzed to convert both the binder and filaments to carbon and to thereby produce the desired porous substrate material.