This chapter describes the designations of carbon and low-alloy steels and their general characteristics in terms of their response to hardening and mechanical properties. The steels covered are low-carbon steels, higher manganese carbon steels, boron-treated carbon steels, H-steels, free-machining carbon steels, low-alloy manganese steels, low-alloy molybdenum steels, low-alloy chromium-molybdenum steels, low-alloy nickel-chromium-molybdenum steels, low-alloy nickel-molybdenum steels, low-alloy chromium steels, and low-alloy silicon-manganese steels. The chapter provides information on residual elements, microalloying, grain refinement, mechanical properties, and grain size of these steels. In addition, the effects of free-machining additives are also discussed.

Heat treatment of steel involves a number of processes to condition the microstructure and obtain desired properties. This includes various methods namely, annealing, normalizing, and hardening by quenching and tempering. This chapter focuses on general heat treatment procedures and the applications of particular types or grades of carbon and low-alloy steels. The discussion covers carbon steel classification for heat treating, tempering of quenched carbon steels, and austempering of steel. In addition, the chapter discusses the effects of alloying and hardenability on steel and provides information on martempering of steel.

This chapter covers the friction and wear behaviors of carbon, alloy, and tool steels. It begins a review of commercially available shapes and forms. It then describes the metallurgy and microstructure of various designations and grades of each type of steel and explains how it affects their performance in adhesive and abrasive wear applications and in environments where they are subjected to solid particle, droplet, slurry, and cavitation erosion and fretting damage.

Boiler tubes operating at high temperatures under significant pressure are vulnerable to stress rupture failures. This chapter examines the cause, effect, and appearance of such failures. It discusses the conditions and mechanisms that either lead to or are associated with stress rupture, including overheating, high-temperature creep, graphitization, and dissimilar metal welds. It explains how to determine which mechanisms are in play by interpreting fracture patterns and microstructural details. It also describes the investigation of several carbon and low-alloy steel tubes that failed due to stress rupture.

Heat treatment is the most common way of altering the mechanical, physical, and even chemical properties of steels. This chapter describes the changes that occur in carbon and low-alloy steels during conventional heat treatments. It explains how austenite decomposition largely defines the final microstructure, and how the associated phase transformations are driven by nucleation and growth processes. It describes diffusionless and diffusive growth mechanisms and provides detailed information on the properties, structure, and behaviors of the transformation products produced, namely martensite and bainite. It also discusses the formation of austenite, the control and measurement of austenitic grain size, the characteristics of ferritic microstructures, and the methods used to classify ferrite morphology.

This chapter discusses the evolution of engineering alloy steels, namely chromium, nickel, and nickel-chromium alloy steels. The discussion includes the automotive demand and development of specifications for the alloy steels. It also covers various research on heat treatment of alloy steels, providing information on hardening, transformation of austenite, hardenability testing, and tempering of as-quenched martensite.

This chapter addresses the issue of stress-corrosion cracking (SCC) in carbon and low-alloy steels. It discusses crack initiation, propagation, and fracture in aqueous chloride, hydrogen sulfide, sulfuric acid, hydroxide, ammonia, nitrate, ethanol, methanol, and hydrogen gas environments. It explains how composition and microstructure influence SCC, as do mechanical properties such as strength and fracture toughness and processes such as welding and cold work. It also discusses the role of materials selection and best practices for welding.

This chapter describes nondestructive evaluation (NDE) test methods and their relative effectiveness for diagnosing the cause of stress-corrosion cracking (SCC) service failures. It discusses procedures for analyzing various types of damage in carbon and low-alloy steels, high-strength low-alloy steels, hardenable stainless steels, austenitic stainless steels, copper-base alloys, titanium and titanium alloys, aluminum and aluminum alloys, and nickel and nickel alloys. It identifies material-environment combinations where SCC is known to occur, provides guidelines on how to characterize cracking and fracture damage, and explains what to look for during macroscopic and microscopic examinations as well as chemical and metallographic analyses. It also includes nearly a dozen case studies investigating SCC failures in various materials.

High-strength steels are susceptible to stress-corrosion cracking (SCC) even in moist air. This chapter identifies such steels and the applications where they are typically found. It provides information on crack growth kinetics and crack propagation models in which hydrogen embrittlement is the predominant mechanism. It explains how different application variables affect SCC, including loading mode, state of stress, type of steel, temperature, electrochemical potential, heat treatment, and deformation processes. It also compares SCC characteristics in different high-strength steels and discusses the influence of composition, steelmaking practice, and application environment.

This chapter takes a practical approach to the problem of stress-corrosion cracking (SCC) in stainless steels, explaining how different application environments affect different grades of stainless steel. It describes the causes of stress-corrosion cracking in chloride, caustic, polythionic acid, and high-temperature environments and the correlating effects on austenitic, ferritic, duplex, martensitic, and precipitation hardening stainless steels and nickel-base alloys. It also discusses the contributing effects of sensitization and hydrogen embrittlement and the role of composition, microstructure, and thermal history. Sensitization is particularly detrimental to austenitic stainless steels, and in many cases, eliminating it will eliminate the susceptibility to SCC. The chapter includes an extensive amount of data and illustrations.

Irradiation-assisted stress-corrosion cracking (IASCC) has been a topic of engineering interest since it was first reported in the 1960s, having been observed in stainless steel cladding on light water reactor fuel elements. This chapter summarizes the results of decades of investigation, showing that IASCC can essentially be defined as the intergranular cracking of austenitic alloys in high-temperature water, where both the material and its environment have been altered by radiation. Of the many interactions that can occur when metals and water are exposed to radiation, the international consensus is that the three with the greatest impact on crack growth rates are the formation of material defects, radiation-induced segregation, and chemical reactions that increase the corrosion potential of water. The chapter discusses each of these in great detail, and includes information on predictive modeling as well.

ASTM and other standards organizations have developed a number of tests for evaluating stress-corrosion cracking (SCC) under various conditions. This appendix lists many of the SCC tests that have been approved for specific materials and operating environments.

This chapter discusses the conditions and sequence of events that lead to stress-corrosion cracking (SCC) and the mechanisms by which it progresses. It explains that the stresses involved in SCC are relatively small and, in most cases, work in combination with the development of a surface film. It describes bulk and surface reactions that contribute to SCC, including dissolution, mass transport, absorption, diffusion, and embrittlement, and their role in crack nucleation and growth. It also discusses crack tip chemistry, grain-boundary interactions, and the effect of stress-intensity on crack propagation rates, and describes several mechanical fracture models, including corrosion tunnel, film-induced cleavage, and tarnish rupture models.

Nickel and nickel-base alloys are specified for many applications, such as oil and gas production, power generation, and chemical processing, because of their resistance to stress-corrosion cracking (SCC). Under certain conditions, however, SCC can be a concern. This chapter describes the types of environments and stress loads where nickel-base alloys are most susceptible to SCC. It begins with a review of the physical metallurgy of nickel alloys, focusing on the role of carbides and intermetallic phases. It then explains how SCC occurs in the presence of halides (such as chlorides, bromides, iodides, and fluorides), sulfur-bearing compounds (such as H2S and sulfur-oxyanions), high-temperature and supercritical water, and caustics (such as NaOH), while accounting for temperature, composition, microstructure, properties, environmental contaminants, and other factors. The chapter also discusses the effects of hydrogen embrittlement and provides information on test methods.

Aluminum is protected by a barrier oxide film that, if damaged, reforms immediately in most environments. Despite this inherent corrosion resistance, there are conditions where aluminum alloys, like many materials, are subject to the effects of stress-corrosion cracking (SCC). This chapter describes those conditions, focusing initially on the effects of alloying elements and temper on solution potential and how it compares to other metals. It then addresses the issue of intergranular corrosion and its role in SCC. It explains how factors such as stress loads, grain structure, and environment determine whether or not stress-corrosion cracking develops in a susceptible alloy. It also provides stress-corrosion ratings for many alloys, tempers, and product forms and includes information on hydrogen-induced cracking.

This chapter addresses the challenge of selecting an appropriate stress-corrosion cracking (SCC) test to evaluate the serviceability of a material for a given application. It begins by establishing a generic model in which SCC is depicted in two stages, initiation and propagation, that further subdivide into several zones plus a transition region. It then discusses SCC test standards before describing basic test objectives and selection criteria. The chapter explains how to achieve the required loading conditions for different tests and how to prepare test specimens to determine elastic strain, plastic strain, and residual stress responses. It also describes the difference between smooth and precracked specimens and how they are used, provides information on slow-strain-rate testing and how to assess the results, and discusses various test environments and procedures, including tests for weldments. The chapter concludes with a section on how to interpret time to failure, threshold stress, percent survival, stress intensity, and propagation rate data, and assess the precision of the associated tests.

This chapter describes the conditions under which copper-base alloys are susceptible to stress-corrosion cracking (SCC) and some of the environmental factors, such as temperature, pH, and corrosion potential, that influence crack growth and time to failure. It explains that, although most of the literature has been concerned with copper zinc alloys in ammoniacal solutions, there are a number of alloy-environment combinations where SCC has been observed. The chapter discusses several of these cases and the effect of various application parameters, including composition, microstructure, heat treatment, cold working, and stress intensity. It also provides information on stress-corrosion testing, mitigation techniques, and basic cracking mechanisms.

Amorphous alloys, because of their lack of crystallographic slip planes, are assumed to be insensitive to the selective corrosion attack that causes stress-corrosion cracking (SCC) in crystalline alloys. However, under certain conditions, melt-spun amorphous alloys have proven vulnerable to SCC due to hydrogen embrittlement. This chapter presents findings from several studies on this phenomenon, describing test conditions as well as cracking and fracture behaviors. It also discusses the effect of deformation on corrosion behavior, particularly for alloys without strongly passivating elements.

Titanium alloys are generally resistant to stress-corrosion cracking (SCC), but under certain conditions, the potential for problems exists. This chapter identifies the types of service environments where titanium alloys have exhibited signs of SCC. It begins by describing the nominal composition, designation, and grade of nearly two dozen commercial titanium alloys and the different types of media (including oxidizers, organic compounds, hot salt, and liquid metal) in which SCC has been observed. It discusses the mechanical and metallurgical factors that influence SCC behavior and examines the cracking and fracture mechanisms that appear to be involved. The chapter also includes information on SCC test standards and provides detailed guidelines on how to prevent or mitigate the effects of SCC.

Although zirconium resists stress-corrosion cracking (SCC) where many alloys fail, it is susceptible in Fe3+- and Cu2+-containing solutions, concentrated HNO3, halogen vapors, mercury, cesium, and CH3OH + halides. This chapter explains how composition, texture, stress levels, and strain rate affect the SCC behavior of zirconium and its alloys. It describes environments known to induce SCC, including aqueous solutions, organic liquids, hot and fused salts, and liquid metals. It also discusses cracking mechanisms and SCC prevention and control techniques.