This chapter provides a brief overview of nickel-iron-base, cobalt-base, and nickel-base superalloys, discussing their basic metallurgy and defining characteristics.

The microstructure of superalloys is highly complex, with a large number of dispersed intermetallics and other phases that modify alloy behavior through their composition, morphology, and distribution. This chapter provides an overview of the most notable phases, including the matrix phase and geometrically and topologically close-packed phases, and describes how superalloy microstructure can be modified via heat treatments and directional solidification. It also discusses the role of carbides, borides, oxides, and nitrides and the detrimental effects of sulfocarbides.

Superalloys are nickel, iron-nickel, and cobalt-base alloys designed for high-temperature applications, generally above 540 deg C. This chapter covers the metallurgy, composition, and properties of cast and wrought superalloys. It provides information on melting, heat treating, and secondary fabrication processes. It also covers coating technology, including aluminide diffusion and overlay coatings, and addresses the advantages and disadvantages of superalloys in various applications.

This chapter provides a brief introduction to superalloys and their high-temperature capabilities. It explains how and why they were developed and highlights some of their unique properties, behaviors, and characteristics. It discusses their basic metallurgy, how they are processed, and where they are typically used. It also includes nominal composition data for more than 120 superalloys and a concise overview of the major topics in the book.

This chapter provides basic materials selection information for iron-nickel-, nickel-, and cobalt-base superalloys. It discusses mechanical and physical properties, the effect of service temperature, and the comparative strengths of wrought and cast product forms. It includes several large data tables along with reference information and a detailed application example based on the design of a gas turbine disk.

Superalloys tend to operate in environments where they are subjected to high-temperature corrosion, oxidation, and the erosive effects of hot gases. This chapter discusses the nature of these attacks and the effectiveness of various protection methods. It describes the primary forms of oxidation, the development of protective oxides, and the conditions associated with mixed gas corrosion and hot corrosion attack. It discusses oxidation and corrosion testing, the equipment used, and various ways to present the associated data. It describes the effect of gaseous oxidation on different alloys, discusses the formation of oxide scale in the presence of mixed gases, and explains how alloy composition contributes to oxide growth. The chapter discusses the underlying chemistry of hot corrosion, how to identify its effects, and how it progresses under various conditions. It also discusses protective coatings, including aluminide diffusion, overlay, and thermal barrier types, and how they perform in different environments based on their ability to tolerate strain.

This chapter discusses the progress that has been made in the development of superalloy operating temperatures, properties, and performance. It also provides forward-looking projections based on advances in process modeling, alloying, and production techniques.

This article discusses the composition, structure, and properties of iron-nickel-, nickel-, and cobalt-base superalloys and the effect of major alloying and trace elements. It describes the primary and secondary roles of each alloying element, the amounts typically used, and the corresponding effect on properties and microstructure. It also covers mechanical alloying and weldability and includes nominal composition data on many wrought and cast superalloys.