Fiber-reinforced metal-matrix composites have carved out a niche in applications requiring high strength to weight ratios, but they are susceptible to failure when exposed to high temperatures and cyclic loads. This chapter discusses the obstacles that must be overcome to improve the creep-fatigue behavior of these otherwise promising materials. It addresses six areas that have been the focus of intense research, including thermal-expansion and elastic-viscoplastic mismatch, thermally induced biaxiality and interply stresses, creep and cyclic relaxation of residual stresses, and enhanced interfaces for oxidation.

This chapter discusses the properties and applications of beryllium intermetallic compounds. It describes the crystal structure of key beryllides, the metals they contain, and important properties such as high-temperature strength, thermal conductivity and expansion, oxidation resistance, and density. It explains how beryllide intermetallics are formed using sputter deposition, diffusion, and powder metal methods.

Stainless steel retains strength and has excellent oxidation resistance from room temperature to nearly 1000 deg C relative to competitive materials. This chapter focuses on the high-temperature oxidation of stainless steel by oxygen or water vapor. It begins by discussing the thermodynamic conditions and electrochemical nature of oxidation and providing information on transient oxidation. This is followed by a description of Wagner's theory for metal oxidation. The volatile nature of Cr 2 O 3 is then reviewed. The chapter further discusses the causes and preventive measures of spalling and cracking of oxide scale. It ends with a section providing information on oxidation behaviors under less-oxidizing atmospheres.

This chapter discusses the alloy composition, metallurgy, mechanical behavior, stabilization, texture, anisotropy, high-temperature properties, and corrosion and oxidation resistance of ferritic stainless steels.

Aluminum has many outstanding properties, leading it to be used for a wide range of applications. It offers excellent strength-to-weight ratio, good corrosion and oxidation resistance, high electrical and thermal conductivity, exceptional formability, and relatively low cost. This chapter examines the metallurgy, composition, processing, and mechanical properties of aluminum and its alloys, both cast and wrought forms. It also covers heat treating and basic temper designations, including annealed, work hardened, solution heat treated, and solution heated treated and aged. The chapter concludes with information on corrosion and oxidation resistance.

Many metallic components, such as retorts in heat treat furnaces, furnace heater tubes and coils in chemical and petrochemical plants, waterwalls and reheater tubes in boilers, and combustors and transition ducts in gas turbines, are subject to oxidation. This chapter explains how oxidation affects a wide range of engineering alloys from carbon and Cr-Mo steels to superalloys. It discusses the kinetics and thermodynamics involved in the formation of oxides and the effect of surface and bulk chemistry. It provides oxidation data for numerous alloys and intermetallics in terms of weight gain, metal loss, depth of attack, and oxidation rate. It also discusses the effect of metallurgical and environmental factors such as oxygen concentration, high-velocity combustion gas streams, chromium depletion and breakaway, component thickness, and water vapor.

This chapter describes a number of corrosion testing methods for sintered stainless steels, including immersion, salt spray, and electrochemical tests, ferric chloride and ferroxyl tests, and elevated-temperature oxidation resistance tests. It also provides corrosion resistance and performance data from various sources.

The unique advantages of the nitriding process were recognized by German researchers in the early 1920s. It was used to treat steels for applications that required: high torque, high wear resistance; abrasive wear resistance; corrosion resistance; and high surface compressive strength. This chapter focuses on key process considerations and factors that helped nitriding gain acceptance. These factors include a low-temperature process, no quench requirement, minimal distortion, high hardness values, and resistance to oxidation.

The toughness of a material is its ability to absorb energy in the form of plastic deformation without fracturing. It is thus a measure of both strength and ductility. This chapter describes the fracture and toughness characteristics of metals and their effect on component lifetime and failure. It begins with a review of the ductile-to-brittle transition behavior of steel and the different ways to measure transition temperature. It then explains how to predict fracture loads using linear-elastic fracture mechanics and how toughness is affected by temperature and strain rate as well as grain size, inclusion content, and impurities. It also presents the theory and use of elastic-plastic fracture mechanics and discusses the causes, effects, and control of temper embrittlement in various types of steel.

This chapter provides a detailed overview of the creep behavior of metals and how to account for it when determining the remaining service life of components. It begins with a review of creep curves, explaining how they are plotted and what they reveal about the operating history, damage mechanisms, and structural integrity of the test sample. In the sections that follow, it discusses the effects of stress and temperature on creep rate, the difference between diffusional and dislocation creep, and the use of time-temperature-stress parameters for data extrapolation. It explains how to deal with time dependent deformation in design, how to estimate cumulative damage under changing conditions, and how to assess the effect of multiaxial stress based on uniaxial test data. It also includes information on rupture ductility, creep fracture, and creep-crack growth and their effect on component life and performance.

This chapter describes the phenomenological aspects of fatigue and how to assess its effect on the life of components operating in high-temperature environments. It explains how fatigue is measured and expressed and how it is affected by loading conditions (stress cycles, amplitude, and frequency) and factors such as temperature, material defects, component geometry, and processing history. It provides a detailed overview of the damage mechanisms associated with high-cycle and low-cycle fatigue as well as thermal fatigue, creep-fatigue, and fatigue-crack growth. It also demonstrates the use of tools and techniques that have been developed to quantify fatigue-related damage and its effect on the remaining life of components.

This chapter covers the failure modes and mechanisms of concern in steam turbines and the methods used to assess remaining component life. It provides a detailed overview of the design considerations, material requirements, damage mechanisms, and remaining-life-assessment methods for the most-failure prone components beginning with rotors and continuing on to casings, blades, nozzles, and high-temperature bolts. The chapter makes extensive use of images, diagrams, data plots, and tables and includes step-by-step instructions where relevant.

This chapter provides conversion factors for common engineering units.

The ability to accurately assess the remaining life of components is essential to the operation of plants and equipment, particularly those in service beyond their design life. This, in turn, requires a knowledge of material failure modes and a proficiency for predicting the near and long term effects of mechanical, chemical, and thermal stressors. This chapter presents a broad overview of the types of damage to which materials are exposed at high temperatures and the approaches used to estimate remaining service life. It explains how operating conditions in power plants and oil refineries can cause material-related problems such as embrittlement, creep, thermal fatigue, hot corrosion, and oxidation. It also discusses the factors and considerations involved in determining design life, defining failure criteria, and implementing remaining-life-assessment procedures.

This chapter covers the failure modes and mechanisms associated with boiler components and the tools and techniques used to assess damages and predict remaining component life. It begins with a review of the design and operation of a utility boiler and the materials used in construction. It then describes the various causes of failure in boiler tubes, headers, and steam pipes, explaining how and why they occur, how they are diagnosed, and how to mitigate their effects. The final and by far largest section in the chapter is a tutorial on damage and life assessment techniques for boiler components and assemblies. It demonstrates the use of various methods, including analytical techniques that estimate life expenditure based on operating history, component geometry, and material properties; predictive methods based on the extrapolation of failure statistics; methods that predict life based on dimensional measurements; methods based on metallographic studies; methods based on temperature estimates; and a method for estimating remaining life under creep conditions based on stress-rupture testing of service-exposed material samples. The chapter also discusses the use of fracture mechanics and presents a number of cases in which life assessments are made based on the integration of several methods.

This chapter covers the failure modes and mechanisms of concern in hydroprocessing reactor vessels and the methods used to assess lifetime and performance. It begins with a review of the materials used in the construction of pressure-vessel shells, the challenges they face, and the factors that determine shell integrity. The discussion addresses key properties and design parameters including allowable stress, fracture toughness, the effect of microstructure and composition on embrittlement, high-temperature creep, and subcritical crack growth. The chapter also provides information on the factors that affect cladding integrity and ends with a section on life-assessment techniques.

Increasing the efficiency of power plants by operating at higher temperatures and pressures and adding a double-reheat feature comes at the expense of shortened lifetimes for critical components. This chapter provides an overview of the material-related problems associated with advanced steam plants and their respective solutions. The discussion covers the selection of materials on a component-specific basis for boilers as well as steam turbines.

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.