Abstract: A coated article is prepared by furnishing an article substrate having a free sulfur content of less than about 1 part per million. The low-sulfur article may be made of a material selected to have a low sulfur content, provided with a scavenging element that reacts with free sulfur to produce a sulfur compound, or desulfurized by contact with a reducing gas such as hydrogen. A platinum-group metal layer is deposited over the article substrate, and a ceramic coating is applied over the platinum-group metal layer.

Abstract: A method for promoting the environmental resistance of nickel, iron and cobalt-base superalloys of the type alloyed to develop a protective oxide scale. The method entails a technique for removing sulfur during or subsequent to the casting operation. The method generally includes casting a superalloy article in a mold cavity, and then heat treating the article while surfaces of the article are in contact with a compound containing a sulfide and/or oxysulfide-forming element, such as yttria, calcium oxide, magnesia, scandia, ceria, hafnia, zirconia, titania, lanthana, alumina and/or silica. The heat treatment is performed at a temperature sufficient to cause sulfur within the superalloy article to segregate to the surfaces of the article and react with the sulfide-forming element, thereby forming sulfides at the interface with the compound.

Abstract: Method for producing a large, substantially hot tear-free superalloy gas turbine bucket useful in a large, land-based utility gas turbine engine, wherein a melt of a superalloy consisting essentially of, by weight: 13.7 to 14.3 percent chromium,  9.0 to 10.0 percent cobalt, 4.8 to 5.2 percent titanium, 2.8 to 3.2 percent aluminum, 2.8 to 4.3 percent tungsten, 1.0 to 1.5 percent molybdenum, 0.005 to 0.02  percent boron,   0 to 0.03 percent zirconium, 0.08 to 0.15 percent carbon, and 2.0 to 3.0 percent tantalum, or 1.0 to 1.5 percent columbium, or 2.0 to 2.5 percent hafnium, or 1.5 to 3.5 percent of a mixture of containing at least two of tantalum, columbium and hafnium, balance substantially nickel, is cast to produce said large gas turbine bucket.

Abstract: The localized pitting tendency of castable nickel-base superalloys in a high-temperature corrosive environment is suppressed without loss of desirable hot corrosion resistance, mechanical properties or microstructural stability characteristics by displacement of molybdenum and tungsten in the carbide phase to the matrix through the addition to the alloy of a comparatively small amount of tantalum, columbium or hafnium.

Abstract: A method and apparatus for forming a multilayer thermal barrier coating such that the coating is composed of substantially homogeneous layers of different ceramic materials. The method entails supporting an article within a coating apparatus and in proximity to ceramic ingots of the different ceramic materials, and then simultaneously directing electron beams at both ingots so as to maintain a portion of each ingot in a molten state. According to a particular aspect of this invention, vapors of both ceramic materials coexist within the coating apparatus, yet each ceramic material is sequentially deposited onto the article by sequentially interrupting exposure of surfaces of the article to the vapors, such that the vapors form homogeneous successive layers on the surface. Exposure of the article to one or more of the vapors can be interrupted with a baffle, such that the vapor of only one of the ceramic ingots is directly deposited on a given surface of the article at any instant.