Abstract: A coating system and method for forming the coating system on an article designed for use in a hostile environment, such as the superalloy turbine, combustor and augmentor components of a gas turbine engine. The method employs a nitrided zone in the surface of the superalloy substrate to inhibit the formation of deleterious topologically-close packed (TCP) phases in the substrate when protected by an aluminum-rich coating and optionally a thermal insulating ceramic layer. Superalloys of particular interest are those containing significant levels of TCP phase-forming elements, such as tungsten, rhenium, tantalum, molybdenum and chromium.

Abstract: A thermal barrier coating system and a method for forming the coating system on an article designed for use in a hostile thermal environment, such as superalloy turbine, combustor and augmentor components of a gas turbine engine. The coating system includes a carburized zone at the surface of a component on which a thermal barrier coating system is to be formed. An aluminum-rich bond coat is then formed on the carburized surface, followed by oxidation of the bond coat to form an aluminum oxide layer. A thermal insulating ceramic layer is then formed on the oxide layer, so as to be chemically bonded thereto. According to the invention, appropriately carburizing the surface of a component serves to form carbides that tie up refractory metals present in the underlying superalloy substrate of the component, and thereby prevents the detrimental effects of these metals on the bond coat-oxide layer interface.

Abstract: The present invention provides a nickel base superalloy having an improved combination of stress rupture life and microstructural stability with respect to the formation of TCP phases. A unique feature is the specific combination of the content of elements consisting of Al, Ti and W in a second range defined by their sum in a nickel base superalloy having high contents of rhenium, in excess of 1.3 atomic percent (about 4.0 weight percent) to lower the propensity for TCP phase formation and thus render the alloy more stable at high temperatures. The interaction of Ru with the remaining elements to modify the refractory element phase partitioning provides unique capabilities, causing elements to partition to the gamma phase or the gamma prime phase in a reverse direction than normally experienced in Ni-base superalloys. These Ni-base superalloys are termed Ru-containing Reverse Partitioning Ni-base Superalloys.

Abstract: A nickel base superalloy capable of being made into a single crystal article is provided with high temperature strength and improved stability by limiting the presence of an undesirable SRZ constituent. Significant to the control of formation of such undesirable constituents is the control of the amount of Re in the alloy in combination with elements such as Al, Cr, Ta, Mo, Co and W. A solution heat treatment is provided for additional control.

Abstract: A nickel base superalloy capable of being made into a single crystal article is provided with high temperature strength and improved stability by limiting the Presence of an undesirable SRZ constituent. Significant to the control of formation of such undesirable constituents is the control of the amount of Re in the alloy in combination with elements such as Al, Cr, Ta, Mo, Co and W. A solution heat treatment is provided for additional control.

Abstract: A method for determining the maximum temperature attained by an article formed of a nickel-based superalloy includes furnishing an article made of a nickel-based superalloy having a gamma/gamma-prime structure at intermediate temperatures and a single phase structure at high temperatures and characterized by a predetermined continuous relation between equilibrium volume fraction of gamma prime phase present and temperature over a transition temperature range. The article is heated with a temperature profile including a maximum temperature within the transition temperature range, and thereafter cooled to ambient temperature to produce a distribution of coarse gamma-prime particles and fine gamma-prime particles in a gamma matrix. The fraction of coarse gamma-prime particles present in the article is measured, and compared with the predetermined continuous relation between equilibrium volume fraction of gamma-prime phase as a function of temperature, to determine a maximum temperature reached by the article.

Abstract: One form of an improved cast, hollow, columnar grain nickel base alloy article is provided with outstanding elevated temperature stability as represented by oxidation resistance, an improved combination of longitudinal and transverse stress rupture properties, and a thin wall of less than about 0.035 inch, substantially free of cracks. Described is a heat treatment in combination with an alloy for providing such an article.

Abstract: A nickel-based superalloy consisting essentially of, in weight percent, from about 4 to about 5 percent chromium, from about 11 to about 14 percent cobalt, from about 4 to about 8 percent tungsten, from about 6 to about 10 percent tantalum, from about 5 to about 7 percent aluminum, from about 5.5 to about 8 percent rhenium, from about 0 to about 0.50 percent hafnium, from about 0 to about 0.07 percent carbon, from 0 to about 0.01 percent boron, from 0 to about 0.030 percent yttrium, from 0 to about 6 percent ruthenium, from 0 to about 1 percent molybdenum, from 0 to about 1 percent niobium, and the balance essentially nickel. Articles made from the superalloy of the invention are especially useful when cast as single crystal airfoils for use in advanced gas turbine engines.

Abstract: A composite grained cast article is provided from a superalloy casting in the single grained condition, in one form, by mechanically working a portion of the article intended to operate at a lower temperature of up to about 1300.degree. F. The mechanically worked portion is then recrystallized by heating to provide a multi-grained portion. In another form, the multi-grained portion is provided by selective use of grain nucleation material during solidification.