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 article discusses the chemical susceptibility of a polymeric material. The discussion covers significant absorption and transportation of an environmental reagent by the polymer; the chemical susceptibility of additives; and thermal degradation, thermal oxidative degradation, photo-oxidative degradation, environmental corrosion, and chemical corrosion of polymers. It also includes some of the techniques used to detect changes in structure during polymer exposure to hostile environments. In addition, the article describes the effects of environment on polymer performance, namely plasticization, solvation, swelling, environmental stress cracking, polymer degradation, surface embrittlement, and temperature effects.

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 chapter describes the conditions under which environmental degradation is likely to occur in polymer matrix composites and the potential damage it can cause. It discusses the problems associated with moisture absorption and exposure to solvents, fuels, ultraviolet radiation, lightning strikes, thermal oxidation, and extreme temperatures. It also discusses the factors that influence flammability.

This chapter covers the fatigue and fracture behaviors of ceramics and polymers. It discusses the benefits of transformation toughening, the use of ceramic-matrix composites, fracture mechanisms, and the relationship between fatigue and subcritical crack growth. In regard to polymers, it covers general characteristics, viscoelastic properties, and static strength. It also discusses fatigue life, impact strength, fracture toughness, and stress-rupture behaviors as well as environmental effects such as plasticization, solvation, swelling, stress cracking, degradation, and surface embrittlement.

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.

Combustion turbines consist of a compressor, a combustor, and a turbine. As commonly configured, the compressor and turbine mount on a single shaft that connects directly to a generator. This chapter reviews the materials of construction, damage mechanisms, and life-assessment techniques for nozzles and buckets. It also presents key information from a detailed review of the literature and the results of a survey on combustion-turbine material problems.

This chapter provides an introduction to various forms of corrosion, namely uniform corrosion, localized corrosion, mechanically assisted degradation, environmentally induced cracking, microbiologically influenced corrosion, and metallurgically influenced corrosion.

This chapter discusses five forms of mechanically assisted degradation of metals: erosion, fretting, fretting fatigue, cavitation and water drop impingement, and corrosion fatigue. Emphasis is placed on the mechanisms and the factors affecting these forms of degradation.

Unlike metals, in which fatigue failures are due to a single crack that grows to a critical length, the effects of fatigue in composites are much more distributed and varied. As the chapter explains, there are five major damage mechanisms that contribute to the progression of composite fatigue, those being matrix cracking, fiber breaking, crack coupling, delamination initiation, and delamination growth. The chapter describes each mechanism in detail along with related factors. It also discusses the primary differences between composites and metals, the effect of manufacturing defects, damage tolerance, and testing and certification.

This article provides details on several of the classifications of polymer wear mechanisms, using wear data and micrographs from published works. The primary goals are to present the mechanisms of polymer wear and to quantify wear in terms of wear rate. The discussion begins by providing information on the processes involved in interfacial and cohesive wear. This is followed by sections describing the wear process and applications of elastomers, thermosets, glassy thermoplastics, and semicrystalline thermoplastics. The effects of environmental and lubricant on the wear failures of polymers are then discussed. The article further includes a case study describing the tribological performance of nylon. It ends by presenting some examples of wear failures of plastics.

This chapter discusses the effect of fatigue on polymers, ceramics, composites, and bone. It begins with a general comparison of polymers and metals, noting important differences in microstructure and cyclic loading response. It then presents the results of several studies that shed light on the fatigue behavior and crack growth mechanisms of common structural polymers and moves on from there to discuss the fatigue behavior of bone and how it compares to stable and cyclically softening metals. It also discusses the fatigue characteristics of engineered and composited ceramics and ceramic fiber-reinforced metal-matrix composites.

This chapter discusses the use of mechanical fastening and adhesive bonding, the primary methods for joining polymer matrix composites. It describes and analyzes the basic types of mechanically fastened joints, including single-hole and multirow bolted composite joints. It then reviews the advantages and disadvantages of adhesively bonded joints and compares and contrasts the long-term performance of various joint designs. The chapter also discusses the merits of stepped-lap and bonded-bolted joints.

This article describes in more detail the fundamental building-block level, atomic, then expands to a discussion of molecular considerations, intermolecular structures, and finally supermolecular issues. An explanation of important thermal, mechanical, and physical properties of engineering plastics and commodity plastics follows, and the final section briefly outlines the most common plastics manufacturing processes.

The power generating industry has become proficient at predicting how long a component will last under a given set of operating conditions. This chapter explains how such predictions are made in the case of boiler tubes. It identifies critical damage mechanisms, progressive failure pathways, and relevant test and measurement procedures. It describes life assessment methods based on hardness, wall thickness, scale formation, microstructure, and creep. It also includes a case study on the determination of the residual life of a secondary superheater tube.

This article provides a review of the biodegradation mechanisms of plastics, presents the definitions, and describes the means of measurement of biodegradation and biodeterioration. Various experimental examples of microbial degradation, namely fungal attack in cellophane and amylose films, starch-based polyethylene films, films with modified starch additives, poly(3-hydroxybutyrate-valerate)-biodegradable plastic, and biodisintegration and biodegradation studies of plastic-starch blends, are also presented.

This article describes the mechanisms of moisture-induced damage in polymeric materials, covering the characteristics of important structural plastics; the effects of moisture on glass transition temperature, modulus, creep, and stress relaxation of plastic materials; and moisture-induced fatigue failure in composites. The effect of moisture on the mechanical properties of thermoset resins and thermoplastics are also discussed.

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.

Superalloys tend to operate in environments where they are subjected to high-temperature corrosion, oxidation, and the erosive effects of hot gases. This chapter discusses the nature of these attacks and the effectiveness of various protection methods. It describes the primary forms of oxidation, the development of protective oxides, and the conditions associated with mixed gas corrosion and hot corrosion attack. It discusses oxidation and corrosion testing, the equipment used, and various ways to present the associated data. It describes the effect of gaseous oxidation on different alloys, discusses the formation of oxide scale in the presence of mixed gases, and explains how alloy composition contributes to oxide growth. The chapter discusses the underlying chemistry of hot corrosion, how to identify its effects, and how it progresses under various conditions. It also discusses protective coatings, including aluminide diffusion, overlay, and thermal barrier types, and how they perform in different environments based on their ability to tolerate strain.

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.