This chapter provides an overview of the possible mechanisms of failure for heat treated steel components and discusses the techniques for examining fractures, ductile and brittle failures, intergranular failure mechanisms, and fatigue. It begins with a description of the general sources of component failure. This is followed by a section on the stages of a failure analysis, which can proceed one after the other or occur at the same time. These stages of analysis are collection of background data, preliminary visual examination, nondestructive testing, selection and preservation of specimens, mechanical testing, macroexamination, microexamination, metallographic examination, determination of the fracture mechanism, chemical analysis, exemplar testing, and analysis and writing the report. The chapter ends with a discussion on various processes involved in the determination of the fracture mechanism.

This chapter explains how to safely prepare beryllium alloy samples for metallographic analysis. It describes grinding, polishing, and etching procedures in detail. It also discusses the identification of major and minor constituents and the general appearance of beryllium microstructure.

Examining and evaluating the nitrided case is generally accomplished by hardness testing and microscopic examination. This chapter discusses both characterization methods, as well as sample preparation. The chapter also discusses the processes involved in the etching of the sample after microhardness testing and provides practices that contribute to the safe preparation of specimens. Examples of nitrided case microstructures, using optical light microscopy, are also presented.

In a perfect crystalline structure, there is an orderly repetition of the lattice in every direction in space. Real crystals contain a considerable number of imperfections, or defects, that affect their physical, chemical, mechanical, and electronic properties. Defects play an important role in processes such as deformation, annealing, precipitation, diffusion, and sintering. All defects and imperfections can be conveniently classified under four main divisions: point defects, line defects, planar defects, and volume defects. This chapter provides a detailed discussion on the causes, nature, and impact of these defects in metals. It also describes the mechanisms that cause plastic deformation in metals.

Duplex stainless steels are two-phase alloys based on the iron-chromium-nickel system. Duplex stainless steels offer corrosion resistance and cost advantages over the common austenitic stainless steels. Although there are some problems with welding duplex alloys, considerable progress has been made in defining the correct parameters and chemistry modifications for achieving sound welds. This chapter provides a basic understanding of the development, grade designations, microstructure, properties, and general welding considerations of duplex stainless steel. It also discusses the influence of ferrite-austenite balance on corrosion resistance and the influence of different welding conditions on various material properties of alloy 2205 (UNS S31803).

This chapter discusses the effect of heat treating on titanium alloys and the influence of time and temperature on critical properties and behaviors. It explains how heat treatments are used to make titanium stronger, tougher, more ductile, and easier to machine as well as more resistant to the effects of corrosion and thermal and mechanical fatigue. It describes accepted practices for stress relieving, aging, annealing, and post-treatment processing along with associated challenges and concerns.

This chapter describes the methods and equipment applicable to metallographic studies and discusses the preparation of specimens for examination by light optical microscopy. Five major operations for preparation of metallographic specimens are discussed: sectioning, mounting, grinding, polishing, and etching. The discussion covers their basic principles, advantages, types, and applications, as well as the equipment setup. The chapter includes tables that list etchants used for microscopic examination. It also provides information on microscopic examination, microphotography, and the effects of grain size on the structural properties of the material.

This chapter briefly outlines some of the basic aspects of failure analysis, describing some of the basic steps and major concerns in conducting a failure analysis. A brief review of failure types from fracture, distortion, wear-assisted failure, and environmentally assisted failure (corrosion) is also provided.

The building block of all matter, including metals, is the atom. This chapter initially provides information on atomic bonding and the crystal structure of metals and alloys, followed by a description of three crystal lattice structures of metals: face-centered cubic, hexagonal close-packed, and body-centered cubic. It then describes the four main divisions of crystal defects, namely point defects, line defects, planar defects, and volume defects. The chapter provides information on grain boundaries of metals, processes involved in atomic diffusion, and key properties of a solid solution. It also explains the aspects of a phase diagram that shows what phase or phases are present in the alloy under conditions of thermal equilibrium. Finally, a discussion on the applications of equilibrium phase diagrams is presented.

This chapter discusses various factors that affect corrosion of stainless steel weldments. It begins by providing an overview of the metallurgical factors associated with welding. This is followed by a discussion on preferential attack associated with weld metal precipitates in austenitic stainless steels as well as several forms of corrosion associated with welding. The effects of gas-tungsten arc weld shielding gas composition and heat-tint oxides on corrosion resistance are then covered. Microbiological corrosion of butt welds in water tanks is also illustrated. In addition, the chapter provides information on corrosion of ferritic and duplex stainless steel weldments.

This appendix provides a detailed overview of the crystal structure of metals. It describes primary bonding mechanisms, space lattices and crystal systems, unit cell parameters, slip systems, and crystallographic planes and directions as well as plastic deformation mechanisms, crystalline imperfections, and the formation of surface or planar defects. It also discusses the use of X-ray diffraction for determining crystal structure.

This chapter introduces many of the key concepts on which metallurgy is based. It begins with an overview of the atomic nature of matter and the forces that link atoms together in crystal lattice structures. It discusses the types of imperfections (or defects) that occur in the crystal structure of metals and their role in mechanical deformation, annealing, precipitation, and diffusion. It describes the concept of solid solutions and the effect of temperature on solubility and phase transformations. The chapter also discusses the formation of solidification structures, the use of equilibrium phase diagrams, the role of enthalpy and Gibb’s free energy in chemical reactions, and a method for determining phase compositions along the solidus and liquidus lines.

Carbon and low-alloy steels are the most frequently welded metallic materials, and much of the welding metallurgy research has focused on this class of materials. Key metallurgical factors of interest include an understanding of the solidification of welds, microstructure of the weld and heat-affected zone (HAZ), solid-state phase transformations during welding, control of toughness in the HAZ, the effects of preheating and postweld heat treatment, and weld discontinuities. This chapter provides information on the classification of steels and the welding characteristics of each class. It describes the issues related to corrosion of carbon steel weldments and remedial measures that have proven successful in specific cases. The major forms of environmentally assisted cracking affecting weldment corrosion are covered. The chapter concludes with a discussion of the effects of welding practice on weldment corrosion.

The nonferrous alloys described in this chapter include aluminum and aluminum alloys, copper and copper alloys, titanium and titanium alloys, zirconium and zirconium alloys, and tantalum and tantalum alloys. Some of the factors that affect the corrosion performance of welded nonferrous assemblies include galvanic effects, crevices, assembly stresses in products susceptible to stress-corrosion cracking, and hydrogen pickup and subsequent cracking. The emphasis is placed on the compositions, general welding considerations, and corrosion behavior of these alloys.

This appendix is a timeline of events related to the discovery, development, and commercialization of stainless steels.

The primary objective of carburizing and hardening gears is to secure a hard case and a relatively soft but tough core. For this process, low-carbon steels (up to a maximum of approximately 0.30% carbon), either with or without alloying elements (nickel, chromium, manganese, molybdenum), normally are used. The processes involved in hardening, tempering, recarburizing, and cold treatment of carburized and quenched gears are discussed. Next, the chapter reviews the selection of materials for carburized gears and considerations related to carbon content, core hardness, and microstructure. This is followed by sections discussing some problems that can be experienced in the carburizing process and how these can be addressed, including a section on shot peening to induce compressive residual stress at and below the surface. It then discusses the applications of carburized gears and finally presents a case history of distortion control of carburized and hardened gears.

Gas (atmosphere) carburizing is the de facto standard by which all other surface hardening techniques are measured and is the emphasis of this chapter. Initially, the chapter describes the process and equipment for gas carburizing. This is followed by sections discussing the processes involved in quenching, hardening, tempering, recarburizing, and cold treatment of carburized and quenched gears. Next, the chapter reviews the selection process of materials for carburized gears and provides information on carbon content, properties, and core hardness of gear teeth. The problems associated with carburizing are then covered, followed by the processes involved in heat treat distortion and shot peening of carburized and hardened gears. Information on grinding stock allowance on tooth flanks to compensate for distortion is also provided. The chapter further discusses the applications of carburized and hardened gears. Finally, it reviews vacuum carburizing and compares the attributes of conventional gas carburizing and vacuum carburizing.

This chapter examines the phenomena of deformation and fracture in metals, providing readers with an understanding of why it occurs and how it can be prevented. It begins with a detailed review of tension and compression stress-strain curves, explaining how they are produced and what they reveal about the load-carrying characteristics of engineering materials. It then discusses the use of failure criteria and the determination of yielding and fracture limits. It goes on to describe the mechanisms and appearances of brittle and ductile fractures and stress rupture, providing detailed images, diagrams, and explanations. It discusses the various factors that influence strength and ductility, including grain size, loading rate, and temperature. It also provides information on the origin of residual stresses, the concept of toughness, and the damage mechanisms associated with creep and stress rupture, stress corrosion, and hydrogen embrittlement.