TABLE OF CONTENTS The role of materials with high-temperature capability in many load-carrying components in industrial applications has already been introduced in Chapter 1. Although nonmetallic materials such as monolithic ceramics and ceramic composites are making inroads into some of these applications, the demand for materials is met predominantly by metallic alloys. These alloys are selected because of high melting point, strength (tensile strength, creep strength, fatigue strengths), ductility and toughness, and low density wherever possible. The environmental resistance of the alloys is seldom adequate. High-temperature coatings, the primary focus of this book, are therefore used extensively to protect the alloys from oxidation, corrosion, heat, and other processes of degradation.
Although alloys of many metals find specialized applications in several fields, such as the electrical industry, electronics, medical equipment, and prosthetic devices, four groups of alloys based on the metals aluminum, titanium, iron, and nickel and cobalt support the bulk of the demand in industrial processes. The range of density-corrected strengths of these classes of alloys as a function of temperature is shown schematically in Fig. 3.1 It is clear from the figure that aluminum, with its low melting point, 660 C (1220 F), and its commercially available alloys with temperature capability limited to about 150 C (300 F), does not satisfy requirements for high-temperature application. The only alloys relevant to our interest include the nickel and cobalt base alloys and to some extent the titanium alloys and steels. The mechanisms by which these alloys are strengthened are briefly discussed...
