This chapter provides an outline of the failure modes and mechanisms associated with most boiler tube failures in coal-fired power plants. Primary categories include stress rupture failures, water-side corrosion, fire-side corrosion, fire-side erosion, fatigue, operation failures, and insufficient quality control.

This chapter discusses the effects of corrosion on boiler tube surfaces exposed to water and steam. It describes the process of corrosion, the formation of scale, and the oxides of iron from which it forms. It addresses the primary types of corrosion found in boiler environments, including general corrosion, under-deposit corrosion, microbially induced corrosion, flow-accelerated corrosion, stress-assisted corrosion, erosion-corrosion, cavitation, oxygen pitting, stress-corrosion cracking, and caustic embrittlement. The discussion is supported by several illustrations and relevant case studies.

This chapter discusses equipment used for ferritic nitrocarburizing, including salt bath furnaces, atmosphere furnaces, and plasma furnaces. It also describes the processes involved in ferritic oxynitrocarburizing.

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 describes processes for evaluation of nitrided parts, including case depth and case hardness, and discusses the factors contributing to corrosion and distortion of parts after ferritic nitrocarburizing.

This chapter examines methods of internal corrosion prediction for multiphase pipelines and details methodologies to perform internal corrosion direct assessment for natural gas pipelines. Further, real-time monitoring techniques for assessing actual corrosion at critical locations are discussed.

This chapter provides a detailed account of crevice corrosion of metals. It begins by describing various critical factors influencing crevice corrosion. This is followed by a section presenting selected examples of crevice corrosion of stainless steel, nickel alloys, aluminum alloys, and titanium alloys in different environments. Methods that have been developed for differentiating and ranking the resistance of alloys toward crevice corrosion are then reviewed. The chapter concludes by discussing various strategies for the prevention of crevice corrosion, namely design awareness, use of inhibitors, and potential control methods.

This chapter discusses the particular corrosion problems encountered and the methods of control used in petroleum production and the storage and transportation of oil and gas up to the refinery. It begins by describing those aspects of corrosion that tend to be unique to corrosion as encountered in applications involving oil and gas exploration and production. This is followed by a section reviewing the methods of corrosion control, namely the proper selection of materials, protective coatings, cathodic protection systems, use of inhibitors, use of nonmetallic materials, and control of the environment. The chapter ends with a discussion on the problems encountered and protective measures that are based on the state-of-the-art as practiced daily by corrosion and petroleum engineers and production personnel.

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.

This chapter lists all of the references cited in the chapters on damage mechanisms.

This chapter begins with an overview of the history of ion nitriding. This is followed by sections that describe how the ion nitriding process works, glow discharge characteristics, process parameters requiring good control, and the applications of plasma processing. The chapter explores what happens in the ion nitriding process and provides information on its gas ratios. It describes the reactions that occur at the surface of the material being treated during iron nitriding and defines corner effect and nitride networking. Further, the chapter provides information on the stability of surface layers and processes involved in the degradation of surface finish and control of the compound zone formation. Gases primarily used for ion nitriding and the control parameters used in ion nitriding are also covered. The chapter also presents the philosophies and advantages of the plasma generation technique for nitriding. It concludes with processes involved in oxynitriding.

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 presents the primary considerations and mechanisms for corrosion and how they are involved in the selection of materials for process equipment in petroleum refineries and petrochemical plants. In addition, specific information on mechanical properties, corrosion, sulfide stress cracking, hydrogen-induced cracking, stress-oriented hydrogen-induced cracking, hydrogen embrittlement cracking, stress-corrosion cracking, velocity-accelerated corrosion, erosion-corrosion, and corrosion control is provided.

This chapter addresses in-service monitoring and corrosion testing of weldments. Three categories of corrosion monitoring are discussed: direct testing of coupons, electrochemical techniques, and nondestructive testing techniques. The majority of the test methods for evaluating corrosion of weldments are used to assess intergranular corrosion of stainless steels and high-nickel alloys. Other applicable tests evaluate pitting and crevice corrosion, stress-corrosion cracking, and microbiologically influenced corrosion. Each of these test methods is reviewed in this chapter.

Liquid metals are frequently used as a heat-transfer medium because of their high thermal conductivities and low vapor pressures. Containment materials used in such heat-transfer systems are subject to molten metal corrosion as well as other problems. This chapter reviews the corrosion behavior of alloys in molten aluminum, zinc, lead, lithium, sodium, magnesium, mercury, cadmium, tin, antimony, and bismuth. It also discusses the problem of liquid metal embrittlement, explaining how it is caused by low-melting-point metals during brazing, welding, and heat treating operations.

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.

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.

A fluidized-bed furnace system can be used for the gas nitriding process. This chapter focuses on fluidized-bed nitriding. It discusses the methods of heating a fluidized bed. The heating system can be electrical or gas, and internal or external. The chapter describes nitriding and oxynitriding processes in the fluidized-bed furnace. It also explains how to operate the fluid bed for nitriding. The chapter provides a discussion on the measurement of the gas dissociation.

This chapter describes issues related to corrosion of carbon steel weldments and remedial measures that have proven successful in specific cases. The forms of corrosion covered includes preferential heat affected zone corrosion, preferential weld metal corrosion, and galvanic corrosion. Industrial case studies demonstrating the necessity for testing each galvanic couple in the environment for which it is intended are presented. The chapter also discusses various factors associated with stress-corrosion cracking in oil refineries.

This chapter explains how mechanical processes, including erosion, cavitation, impingement, and fretting, contribute to the effects of corrosion in aluminum alloys. It describes the two main types of erosion-corrosion and the factors involved in cavitation and liquid impingement erosion along with testing and prevention methods. It also provides information on fretting corrosion and fretting fatigue.