This chapter is dedicated mostly to the metallurgical effects on the corrosion behavior of corrosion-resistant alloys. It begins with a section describing the importance of alloying elements on the corrosion behavior of nickel alloys. The chapter considers the metallurgical effects of alloy composition for heat-resistant alloys, nickel corrosion-resistant alloys, and nickel-base alloys. This chapter also discusses the corrosion implications of changing the alloy microstructure via solid-state transformation, second-phase precipitation, or cold work. It concludes with a comparison of corrosion behavior between cast and wrought product forms.

Nickel-base castings are produced from a group of alloys with compositions that are typically greater than 50% Ni and less than 10% iron. This chapter presents the casting compositions of nickel-base alloys. It then provides an overview of heat treatment, mechanical properties, and applications of nickel-base castings.

This chapter describes the physical properties of steels used for castings. The properties covered include density, modulus of elasticity, Poisson's ratio, shear modulus, thermal expansion, thermal conductivity, specific heat, thermal diffusivity, electrical resistivity, and magnetic properties.

Nickel-base alloys are generally used in harsh environments that demand either corrosion resistance or high-temperature strength. This article first describes the general welding characteristics of nickel-base alloys. It then describes the weldability of solid-solution nickel-base alloys in terms of grain boundary precipitation, grain growth, and hot cracking in the heat-affected zone; fusion zone segregation and porosity; and postweld heat treatments. Next, the article analyzes the welding characteristics of dissimilar and clad materials. This is followed by sections summarizing the various types and general weldability of age-hardened nickel-base alloys. The article then discusses the composition, welding metallurgy, and properties of cast nickel-base superalloys. Finally, it provides information on the welding of dissimilar metals, filler metal selection for welding clad materials and for overlay cladding, service conditions during repair, and welding procedural idiosyncrasies of cobalt-base alloys.

This chapter describes the metallurgy of superalloys and the extent to which it can be controlled. It discusses the alloying elements, crystal structures, and processing sequences associated with more than a dozen phases that largely determine the characteristics of superalloys, including their properties, behaviors, and microstructure. It examines the role of more than 20 alloying elements, including phosphorus (promotes carbide precipitation), boron (improves creep properties), lanthanum (increases hot corrosion resistance), and carbon and tungsten which serve as matrix stabilizers. It explains how precipitates provide strength by impeding deformation under load. It also discusses the factors that influence grain size, shape, and orientation and how they can be controlled to optimize mechanical and physical properties.

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 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.

The qualities that make superalloys excellent engineering materials also make them difficult to machine. This chapter discusses the challenges involved in machining superalloys and the factors that determine machinability. It addresses material removal rates, cutting tool materials, tool life, and practical issues such as set up time, tool changes, and production scheduling. It describes several machining processes, including turning, boring, planing, trepanning, shaping, broaching, drilling, tapping, thread milling, and grinding. It also provides information on toolholders, fixturing, cutting and grinding fluids, and tooling modifications.

This chapter discusses the application of investment casting to nickel- and cobalt-base superalloys. It describes the production of polycrystalline and single crystal castings, the materials normally used, and the part dimensions and tolerances typically achieved. It explains how patterns, molds, and shells are produced, discusses the practice of directional solidification, and examines an assortment of turbine components cast from nickel- and cobalt-base alloys. The chapter also addresses casting problems such as inclusions, porosity, distortion, core shift, and leaching and explains how to avoid them.

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

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 chapter examines the effect of heat treating and other processes on the microstructure-property relationships that occur in superalloys. It discusses precipitation and grain-boundary hardening and how they influence the phases, structures, and properties of various alloys. It explains how the delta phase, which is used to control grain size in IN-718, improves strength and prevents stress-rupture embrittlement. It describes heat treatments for different product forms, discusses the effect of tramp elements on grain-boundary ductility, and explains how section size and test location influence measured properties. It also provides information and data on the physical and mechanical properties of superalloys, particularly tensile strength, creep-rupture, fatigue, and fracture, and discusses related factors such as directionality, porosity, orientation, elongation, and the effect of coating and welding processes.

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.

This appendix provides additional information on superalloy microstructures. It includes several micrographs showing metallographic features mentioned in the text but not illustrated elsewhere in the book. It also discusses carbide reactions that occur during heat treating and demonstrates the use of electron vacancy calculations to estimate the resistance of superalloys to the formation of topologically close-packed phases.

This appendix includes selected references on topics related to the production and application of superalloys, including properties and microstructure; melting/ingot breakdown; forging/powder metallurgy; machining, heat treating, joining, refurbishment/repair; investment casting; coatings/corrosion; and modeling.