Search Results for strain-age embrittlement

A brittle fracture occurs at stresses below the material's yield strength (i.e., in the elastic range of the stress-strain diagram). This chapter focuses on brittle fracture in metals and, more specifically, ferrous alloys. It lists the factors that must all be present simultaneously in order to cause brittle fracture in a normally ductile steel. The chapter then discusses the macroscale characteristics and microstructural aspects of brittle fracture. A summary of the types of embrittlement experienced by ferrous alloys is presented. The chapter concludes with a brief section providing information on mixed fracture morphology.

The appendix provides a glossary of practical heat treating terms.

This chapter is a compilation of terms and definitions related to corrosion in the petrochemical industry.

Steels with martensitic and tempered martensitic microstructures, though sometimes perceived as brittle, exhibit plasticity and ductile fracture behavior under certain conditions. This chapter describes the alloying and tempering conditions that produce a ductile form of martensite in low-carbon steels. It also discusses the effect of tempering temperature on the mechanical behavior and deformation properties of medium-carbon steels.

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 article discusses the effects of alloying on the properties and behaviors of maraging steels. It describes how maraging steels differ from conventional steels in that they are strengthened, not by carbon, but by the precipitation of intermetallic compounds. It explains how maraging steels typically have high levels of nickel, cobalt, and molybdenum with little carbon content and how that affects their dimensional stability, fracture toughness, weldability, and resistance to stress-corrosion cracking.

This chapter discusses the causes and effects of ductile and brittle fracture and their key differences. It describes the characteristics of ductile fracture, explaining how microvoids develop and coalesce into larger cavities that are rapidly pulled apart, leaving bowl-shaped voids or dimples on each side of the fracture surface. It includes SEM images showing how the cavities form, how they progress to final failure, and how dimples vary in shape based on loading conditions. The chapter, likewise, describes the characteristics of brittle fracture, explaining why it occurs and how it appears under various levels of magnification. It also discusses the ductile-to-brittle transition observed in steel, the characteristics of intergranular fracture, and the causes of embrittlement.

This article discusses the various options for controlling fatigue and fracture in welded steel structures, the factors that influence them the most, and some of the leading codes and standards for designing against these failure mechanisms. The two most widely used approaches discussed for fatigue control in welded joints are the S-N curve approach and the fracture mechanics assessment methods.

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 discusses two damage mechanisms in which stress plays a major role. In the one case, stress causes cracks in the oxide scale on metals, leading to preferential corrosion attack. An example from industry of this type of failure is the circumferential cracking that occurs on the waterwall tubes of supercritical coal-fired boilers fired under low NOx combustion conditions, conducive to the production of sulfidizing environments. In the other case, stress contributes to brittle fracture in the form of intergranular cracking. The phenomenon, which is known by various names, typically occurs at the lower end of the intermediate temperature range and has been observed in ferritic steels, stainless steels, Fe-Ni-Cr alloys, and nickel-base alloys, as described in the chapter.

This chapter compares and contrasts the high-temperature behaviors of metals and composites. It describes the use of creep curves and stress-rupture testing along with the underlying mechanisms in creep deformation and elevated-temperature fracture. It also discusses creep-life prediction and related design methods and some of the factors involved in high-temperature fatigue, including creep-fatigue interaction and thermomechanical damage.

This chapter is a compilation of terms and definitions related to component failure analysis.

This chapter discusses different thermal processes applicable to the various alloy groups of stainless steels, namely austenitic, ferritic, martensitic, precipitation hardening, and duplex stainless steels. The processes discussed include soaking, annealing, stress relieving, austenitizing, tempering, aging, and conditioning.

Uranium alloys are used in applications requiring dense metals, but they have little resistance to oxidation and corrosion and are susceptible to environmentally assisted cracking, particularly when processed to high strength levels. This chapter describes the conditions under which uranium alloys are most prone to cracking. It discusses testing and characterization methods, cracking phenomenology, material properties, and microstructure. It also provides suggestions for avoiding and overcoming environmentally assisted cracking problems.

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.

Stainless steels derive their name from their exceptional corrosion resistance, which is attributed to their finely tuned compositions. This chapter discusses the alloying elements used in stainless steels and the some of the processing challenges they present. One of the biggest challenges is that stainless steels cannot be hardened by heat treatment. As a result, they are highly sensitive to processing-induced defects and the formation of detrimental phases. The chapter explains how alloy design, phase equilibria, microstructure, and thermomechanical processing can be concurrently optimized to produce high-quality austenitic, ferritic, and duplex stainless steels.