Search Results for nickel aluminides

Alloys based on ordered intermetallic compounds constitute a unique class of metallic material that form long-range ordered crystal structures below a critical temperature. Aluminides, a unique class of ordered intermetallic materials, possesses many attributes like low densities, high melting points, and good high-temperature strength that make them an attractive material for high-temperature structural application. This article discusses the properties, chemical composition, corrosion resistance, processing, fabrication, alloying effects and crystallographic data of nickel aluminides (Ni3Al and NiAl), iron aluminides (Fe3Al and FeAl) and titanium aluminides (alpha-2 alloys, orthorhombic alloys, and gamma alloys).

This article reviews the corrosion behavior of intermetallics for the modeling of the corrosion processes and for devising a strategy to create corrosion protective systems through alloy and coating design. Thermodynamic principles in the context of high-temperature corrosion and information on oxidation; sulfidation; hot corrosion of NiAl-, FeAl-, and TiAl-based intermetallics; and silicides are included. The article explores the thermodynamic consideration, ordering influencing kinetics, stress-cracking corrosion, and hydrogen embrittlement of aqueous corrosion. It also explains the practical issues dealing with the corrosion problems.

Ordered intermetallic compounds based on aluminides and silicides constitute a unique class of metallic materials that have promising physical and mechanical properties for structural applications at elevated temperatures. This article provides useful information on mechanical and metallurgical properties, material processing and fabrication, structural applications, mechanical behavior, environmental embrittlement, alloying effects, and crystal structure of aluminides of nickel, iron, titanium, and silicides. It describes the cleavage and intergranular fracture in trialuminides.

The corrosion issues in the compressor, combustor and turbine sections of industrial gas turbines used in steam production generally depend on the quality of the fuel, air, and water used in the engine than on the specific industrial application. This article focuses on the forms of corrosion and their preventive measures in the compressor, combustor and turbine sections of a steam turbine. The compressor section mainly suffers from aqueous corrosion; while in case of the combustor and turbine sections, which are made of nickel-base superalloys, high-temperature environmental attack in the form of high-temperature oxidation and hot corrosion are predominant. The effect of high-temperature oxidation and hot corrosion on the mechanical properties of superalloys is also discussed.

This article reviews the bulk deformation processes for various aluminide and silicide intermetallic alloys with emphasis on the gamma titanium aluminide alloys. It summarizes the understanding of microstructure evolution and fracture behavior during thermomechanical processing of the gamma aluminides with particular reference to production scaleable techniques, including vacuum arc and cold-hearth melting, isothermal forging, conventional hot forging, and extrusion. The selection and design of manufacturing methods, in the context of processing-cost trade-offs for gamma titanium aluminide alloys, are also discussed.

Metal-matrix composites (MMCs) are a class of materials with potential for a wide variety of structural and thermal management applications. They are nonflammable, do not outgas in a vacuum, and suffer minimal attack by organic fluids, such as fuels and solvents. This article presents an overview of the status of MMCs, and provides information on physical and mechanical properties, processing methods, distinctive features, and various types of continuously and discontinuously reinforced aluminum, magnesium, titanium, copper, superalloy, and intermetallic-matrix composites. It further discusses the property prediction and processing methods for MMCs.

High temperature corrosion may occur in numerous environments and is affected by factors such as temperature, alloy or protective coating composition, time, and gas composition. This article explains a number of potential degradation processes, namely, oxidation, carburization and metal dusting, sulfidation, hot corrosion, chloridation, hydrogen interactions, molten metals, molten salts, and aging reactions including sensitization, stress-corrosion cracking, and corrosion fatigue. It concludes with a discussion on various protective coatings, such as aluminide coatings, overlay coatings, thermal barrier coatings, and ceramic coatings.