The refractory metals include niobium, tantalum, molybdenum, tungsten, and rhenium. These metals are considered refractory because of their high melting points, high-temperature mechanical stability, and resistance to softening at elevated temperatures. This article discusses the composition, properties, fabrication procedures, advantages and disadvantages, and applications of these refractory metals and their alloys. A comparison of some of the properties of the refractory metals with those of iron, copper, and aluminum is given in a table. The article concludes with a brief section on refractory metal protective coatings.

This article discusses the role of alloying in the production and use of common refractory metals, including molybdenum, tungsten, niobium, tantalum, and rhenium. It provides an overview of each metal and its alloys, describing the compositions, properties, and processing characteristics as well as the effect of alloying elements. It also discusses strengthening mechanisms and, where appropriate, corrosion behavior.

All materials are susceptible to corrosion or some form of environmental degradation. Although no single material is suitable for all applications, usually there are a variety of materials that will perform satisfactorily in a given environment. The intent of this chapter is to review the corrosion behavior of the major classes of metals and alloys as well as some nonmetallic materials, describe typical corrosion applications, and present some unique weaknesses of various types of materials. It also aims to point out some unique material characteristics that may be important in material selection, and discuss, where appropriate, the characteristic forms of corrosion that attack specific materials. The materials addressed in this chapter include carbon steels, weathering steels, and alloy steels; nickel, copper, aluminum, titanium, lead, magnesium, tin, zirconium, tantalum, niobium, and cobalt and their alloys; polymers; and other nonmetallic materials, including rubber, carbon and graphite, and woods.

Medium-carbon steels are typically hardened for high-strength, high-fatigue-resistant applications by austenitizing, quenching to martensite, and tempering. This chapter explains how microalloying with vanadium, niobium, and/or titanium provides an alternate way to improve the mechanical properties of such steels. It also addresses microalloyed forging steels and explains how nontraditional bainitic microstructures can be produced by direct cooling after forging.

Alloy steels are alloys of iron with the addition of carbon and one or more of the following elements: manganese, chromium, nickel, molybdenum, niobium, titanium, tungsten, cobalt, copper, vanadium, silicon, aluminum, and boron. Alloy steels exhibit superior mechanical properties compared to plain carbonsteels as a result of alloying additions. This chapter describes the beneficial effects of these alloying elements in steels. It discusses the mechanical properties, nominal compositions, advantages, and engineering applications of various classes of alloy steels. They are low-alloy structural steels, SAE/AISI alloy steels, high-fracture-toughness steels, maraging steels, austenitic manganese steels, high-strength low-alloy steels, dual-phase steels, and transformation-induced plasticity steels.

This chapter covers a broad range of low-carbon steels optimized for structural applications. Low-carbon structural steels are generally considered the highest-strength steels that can be welded without undue difficulty, even in the field. They include mild steels, carbon-manganese and niobium- and vanadium-containing steels, and high-strength low-alloy steels. Chapter 5 discusses the composition, microstructure, and properties of these workhorse materials and explains how to identify the cause of production-related issues such as lamellar tearing and ferrite-pearlite banding. It also describes some of the alloying variations that have been developed to improve machinability and the mechanisms by which they work.

This article discusses the effect of alloying on high-strength low-alloy (HSLA) steels. It explains where HSLA steels fit in the continuum of commercial steels and describes the six general categories into which they are divided. It provides composition data for standard types or grades of HSLA steel along with information on available mill forms, key characteristics, and intended uses. The article explains how small amounts of alloying elements, particularly vanadium, niobium, and titanium, control not only the properties of HSLA steels, but also their manufacturability.

Hydrogen damage is a form of environmentally assisted failure that results most often from the combined action of hydrogen and residual or applied tensile stress. This chapter classifies the various forms of hydrogen damage, summarizes the various theories that seek to explain hydrogen damage, and reviews hydrogen degradation in specific ferrous and nonferrous alloys. The preeminent theories for hydrogen damage are based on pressure, surface adsorption, decohesion, enhanced plastic flow, hydrogen attack, and hydride formation. The specific alloys covered are iron-base, nickel, aluminum, copper, titanium, zirconium, vanadium, niobium, and tantalum alloys.

This appendix contains tables that list the composition and capabilities of etchants that reveal the microstructure of metals and alloys, including aluminum, chromium, cobalt, copper, lead, magnesium, molybdenum, nickel, niobium, palladium, platinum, radioactive metals, rare earth metals, rhenium, rhodium, selenium, tellurium, silicon, silver, tantalum, tin, titanium, tungsten, vanadium, and zinc, as well as carbides, oxides, and nitrides.

This chapter discusses the alloy composition, metallurgy, mechanical behavior, stabilization, texture, anisotropy, high-temperature properties, and corrosion and oxidation resistance of ferritic stainless steels.

This chapter discusses the typical compositional ranges of superalloys, the role of major base metals (iron, cobalt, and nickel), and the effects of common alloying additions. It describes how chromium, aluminum, and titanium as well as refractory elements, grain-boundary elements, reactive elements, and oxides influence mechanical properties and behaviors. It also discusses the effect of trace elements.

This article discusses the effect of alloying on the composition, structure, properties, and processing characteristics of ordered intermetallic compounds, including nickel aluminides, iron aluminides, and titanium aluminides. It includes several data tables along with a list of typical applications.

This chapter discusses the basic principles of alloying and their practical application in the production of titanium mill products and engineered parts. It begins with a review of the atomic and crystal structure of titanium and the conditions for interstitial and substitutional alloying. It then describes the different classes of alloying elements, their effect on mechanical properties and behaviors, and their influence on phase transitions and transformations. The chapter also discusses the role of intermetallic compounds and their effect on crystal structure and creep behavior.

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.

This chapter provides an overview of the composition, microstructures, processing, deformation mechanism, mechanical properties, formability, and special attributes of complex-phase steels.

This chapter is a detailed account of the applications of stainless steel in automotive and transport systems. The discussion covers exhaust systems, structural components, automotive components, trucks, and rail transport.

This chapter provides information on the properties and behaviors of stainless steels and stainless steel powders. It begins with a review of alloy designation systems and grades by which stainless steels are defined. It then describes the composition, metallurgy, and engineering characteristics of austenitic, ferritic, martensitic, duplex, and precipitation hardening stainless steel powders and metal injection molding grades.

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 chapter discusses the classification, composition, properties, and applications of five types of stainless steels: austenitic, ferritic, duplex, martensitic, and precipitation-hardening steels. It discusses the process involved in argon oxygen decarburization that is used to refine stainless steel. The chapter also provides information on the classification and composition of stainless steel castings. It concludes with a brief description of the Schaeffler constitution diagram which is useful in predicting the type of stainless steel as a function of its alloy content.

Boilers are often classified based on the maximum operating temperature and pressure for which they are designed. Classifications, in ascending order, are subcritical, supercritical, ultra-supercritical, and to advanced ultra-supercritical. At each higher operating point comes greater efficiency, as well as greater demand on construction materials. This chapter discusses the primary requirements for boiler tube materials, including oxidation and corrosion resistance, fatigue strength, thermal conductivity, and the ability to resist creep and rupture. It also provides information on various steels and alloys, covering cost, engineering specifications, and ease of use.