Failures in boilers and other equipment taking place in power plants that use steam as the working fluid are discussed in this article. The discussion is mainly concerned with failures in Rankine cycle systems that use fossil fuels as the primary heat source. The general procedure and techniques followed in failure investigation of boilers and related equipment are discussed. The article is framed with an objective to provide systematic information on various damage mechanisms leading to the failure of boiler tubes, headers, and drums, supplemented by representative case studies for a greater understanding of the respective damage mechanism.

The primary fossil fuels are generally defined as coal, oil, natural gas, tar sands, and shale oil. This article discusses the characteristics and the types of fuels used in fossil and fuel industries. It describes the energy conversion in fuels and outlines the efficiency of a heat engine with the help of the Carnot equation.

This article describes the metallurgy and process specifics of subcritical annealing, which involves heating below the lower critical temperature such that austenite does not form during subcritical annealing. It provides information on the nominal subcritical annealing temperatures of plain carbon, low-alloy and high-alloy steels and temperature-time relations of subcritical annealing. Practical implications for induction annealing and induction normalizing are included. The article concludes by describing induction softening, which softens the threaded area on carburized components such as hypoid pinion gears, to prevent the occurrence of delayed fractures from occurring.

This article describes the control of water chemistry in the steam cycle of a power plant for achieving corrosion control, deposition prevention, and higher cycle efficiency. It discusses the materials requirements of the components exposed to supercritical water in supercritical (SC) and ultrasupercritical (USC) power plants. These components include high-pressure steam piping and headers, superheater and reheater tubing, water wall tubing in the boiler, high-and intermediate-pressure rotors, rotating blades, and bolts in the turbine section. The article reviews the boiler alloys, used in SC and USC boilers, such as ferritic steels, austenitic steels, and nickel-base alloys. It provides information on the materials used in turbine applications such as ferritic rotor steels, turbine blade alloys, and bolting materials. The article explains various factors influencing steamside corrosion in SC power plants. It also deals with the role of overall efficiency in the USC power generation.

This article explains the main types and characteristic causes of failures in boilers and other equipment in stationary and marine power plants that use steam as the working fluid with examples. It focuses on the distinctive features of each type that enable the failure analyst to determine the cause and suggest corrective action. The causes of failures include tube rupture, corrosion or scaling, fatigue, erosion, and stress-corrosion cracking. The article also describes the procedures for conducting a failure analysis.

This article is a comprehensive collection of the thermodynamic equations and property relations of the first and second laws of thermodynamics that are applicable to closed-system consisting of several homogeneous and heterogeneous phases.

This article illustrates typical wear and friction issues encountered in gas and steam turbines and their consequences as well as commonly adopted materials solutions. It contains tables that present the summary of wear and friction related issues encountered in steam turbines and gas turbines. The article outlines the differences in the operating conditions and the nature of the components involved in gas and steam turbines. It discusses the constraints and applicable coating solutions for wear and friction issues, and concludes with a broad set of challenges that need to be addressed to improve performance and operability of gas and steam turbines.

This article discusses the microstructural processes that take place during plastic deformation and presents a plain phenomenological and general description of the cyclic stress-strain (CSS) response. It emphasizes the microstructural aspects of cyclic loading on single-phase materials tested in initially soft, dislocation-poor conditions resulting from a prior heat treatment. The article discusses deformation-induced phase transformations in austenitic stainless steels and commercial age-hardened aluminum alloys. It describes the interaction of dislocations and the strengthening of second-phase particles. The article also provides a description of the framework used to model the CSS response on a physical basis.

High-temperature exposure of materials occurs in many applications such as power plants (coal, oil, natural gas, and nuclear), land-based gas turbine and diesel engines, gas turbine engines for aircraft, marine gas turbine engines for shipboard use, waste incineration, high-temperature fuel cells, and missile components. This article discusses high-temperature corrosion in boilers, diesel engines, gas turbines, and waste incinerators. Boilers are affected by stress rupture failures, waterside corrosion failures, fireside corrosion failures, and environmental cracking failures. Contamination of combustion fuel in diesel engines can cause high-temperature corrosion. Gas turbine engines are affected by hot corrosion. Refractory-lined incinerators and alloy-lined incinerators are discussed. The article provides case studies for each component failure.

The principal types of elevated-temperature mechanical failure are creep and stress rupture, stress relaxation, low- and high-cycle fatigue, thermal fatigue, tension overload, and combinations of these, as modified by environment. This article briefly reviews the applied aspects of creep-related failures, where the mechanical strength of a material becomes limited by creep rather than by its elastic limit. The majority of information provided is applicable to metallic materials, and only general information regarding creep-related failures of polymeric materials is given. The article also reviews various factors related to creep behavior and associated failures of materials used in high-temperature applications. The complex effects of creep-fatigue interaction, microstructural changes during classical creep, and nondestructive creep damage assessment of metallic materials are also discussed. The article describes the fracture characteristics of stress rupture. Information on various metallurgical instabilities is also provided. The article presents a description of thermal-fatigue cracks, as distinguished from creep-rupture cracks.

This article examines a type of corrosion that occurs when solids (primarily metals) are exposed to liquid metal environments. It describes the principle mechanisms of liquid metal corrosion, including dissolution, impurity and interstitial reactions, alloying, and compound reduction. It also provides guidelines for materials selection and alloy development based on liquid metal corrosion reactions.

Tempering of induction-hardened steel is a form of subcritical heat treatment, primarily carried out to increase ductility, toughness, and dimensional stability, to relieve residual stresses, and to obtain specific values of mechanical properties. This article describes tempering with emphasis on different time-temperature exposure requirements for furnace and induction tempering. It discusses two parametric methods for correlating equivalent time-temperature condition: Hollomon-Jaffe tempering correlation and Grange-Baughman tempering correlation. The article describes different methods of induction tempering, namely, single-shot, progressive or continuous, scanning, and static heating methods. The effects of induction heating variables and hardenability on tempering response are examined. The article also provides examples of how tempering affects the mechanical properties of induction-hardened steels.

This article provides information on the typical experimental observations of formation and propagation of small fatigue cracks under various stress states and explores the relation to long crack fracture mixed-mode fracture mechanics. It discusses state I crystallographic and stage II normal stress-dominated growth, along with some observations regarding the influence of combined stress state on the propagation of small cracks. The article discusses the differences between low-cycle fatigue and high-cycle fatigue (HCF) behaviors. Several other features of multiaxial fatigue are also explained, including mean stress effects, sequences of stress/strain amplitude or stress state, nonproportional loading and cycle counting, and HCF fatigue limits. In addition, the article covers the formation and propagation of cracks on the order of several grain sizes in diameter in initially isotropic and ductile structural alloys.

This article describes the heat treating (stress relieving, normalizing, annealing, quenching, tempering, martempering, austempering, and age hardening) of different types of steels, including ultrahigh-strength steels, maraging steels, and powder metallurgy steels. Tabulating the recommended temperatures for normalizing and austenitizing, it provides information on mechanism, cooling media, principal variables, process procedures, and applications of heat treating. In addition, the article gives a short note on the cold and cryogenic treatment of steel.

High-temperature corrosion can occur in numerous environments and is affected by various parameters such as temperature, alloy and protective coating compositions, stress, time, and gas composition. This article discusses the primary mechanisms of high-temperature corrosion, namely oxidation, carburization, metal dusting, nitridation, carbonitridation, sulfidation, and chloridation. Several other potential degradation processes, namely hot corrosion, hydrogen interactions, molten salts, aging, molten sand, erosion-corrosion, and environmental cracking, are discussed under boiler tube failures, molten salts for energy storage, and degradation and failures in gas turbines. The article describes the effects of environment on aero gas turbine engines and provides an overview of aging, diffusion, and interdiffusion phenomena. It also discusses the processes involved in high-temperature coatings that improve performance of superalloy.