Superalloys, although not strictly defined, are generally regarded as high-performance alloys based on group VIII elements (nickel, cobalt, or iron, with a high percentage of nickel) to which a multiplicity of alloying elements have been added. The defining feature of a superalloy is its combination of relatively high mechanical strength and surface stability at high operating temperatures. This chapter provides a brief history of the development of superalloys and discusses their use in the gas turbine engines.

The refractory metals include niobium, tantalum, molybdenum, tungsten, and rhenium. These metals are considered refractory because of their high melting points, high-temperature mechanical stability, and resistance to softening at elevated temperatures. This article discusses the composition, properties, fabrication procedures, advantages and disadvantages, and applications of these refractory metals and their alloys. A comparison of some of the properties of the refractory metals with those of iron, copper, and aluminum is given in a table. The article concludes with a brief section on refractory metal protective coatings.

This chapter discusses the types of fibers and matrix materials used in ceramic matrix composites and the role of interfacial coatings. It describes the methods used to produce ceramic composites, including powder processing, slurry infiltration and consolidation, polymer infiltration and pyrolysis, chemical vapor infiltration, directed metal oxidation, and liquid silicon infiltration.

A working knowledge of diffusion is necessary to understand and predict the behavior of metals and alloys during manufacturing and in certain types of service. This chapter covers the fundamentals of diffusion in solids and some of the applications in which diffusion plays a role. It discusses the mechanisms behind interstitial, substitutional, grain boundary, and surface diffusion, the derivation and use of Fick’s laws, and the basic principles of diffusion coating processes, including carburizing, nitriding, nitrocarburizing, cyaniding, carbonitriding, boriding, aluminizing, siliconizing, chromizing, vanadizing, and titanizing. It also discusses diffusion bonding and presents several approaches for dealing with oxide barrier problems.

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 begins with a brief review of the different types of surface treatments and coatings used in industry and their effect on properties and performance. It then discusses the importance of corrosion and wear treatments and the consequences of failing to properly implement them in critical industries such as mining, energy production, transportation, and mineral and chemical processing. The chapter also describes basic approaches to dealing with corrosion and wear in steel.

This chapter discusses the use of coating methods and materials and their impact on corrosion and wear behaviors. It provides detailed engineering information on a wide range of processes, including organic, ceramic, and hot dip coating, metal plating and cladding, and the use of weld overlays, thermal spraying, and various deposition technologies.

The basic concept for most methods of corrosion protection is to remove one or more of the electrochemical cell components so that the pure metal or metal alloy of interest will not corrode. Another widely used corrosion protection approach is to change the nature of the anode so that it becomes the cathode (cathodic protection). This chapter briefly reviews these methods of corrosion protection. The factors affecting corrosion behavior are covered. In addition, the chapter provides information on coatings and inhibitors, which are used in corrosion protection.

Ceramic-matrix composites possess many of the desirable qualities of monolithic ceramics, but are much tougher because of the reinforcements. This chapter explains how reinforcements are used in ceramic-matrix composites and how they alter energy-dissipating mechanisms and load-carrying behaviors. It compares the stress-strain curves for monolithic ceramics and ceramic-matrix composites, noting improvements afforded by the addition of reinforcements. It then goes on to discuss the key attributes, properties, and applications of discontinuously reinforced ceramic composites, continuous fiber ceramic composites, and carbon-carbon composites. It also describes a number of ceramic-matrix composite processing methods, including cold pressing and sintering, hot pressing, reaction bonding, directed metal oxidation, and liquid, vapor, and polymer infiltration.

This chapter covers a wide range of finishing and coating operations, including cleaning, honing, polishing and buffing, and lapping. It discusses the use of rust-preventative compounds, conversion coatings, and plating metals as well as weld overlay, thermal spray, and ceramic coatings and various pack cementation and deposition processes. It also discusses the selection and use of industrial paints and paint application methods.

This chapter provides practical information on surface treatments that work by altering the surface chemistry of metals and alloys. It discusses the use of phosphate and chromate conversion coatings as well as anodizing, steam oxidation, diffusion coatings, and pack cementation. The chapter also covers ion implantation and laser alloying.

This chapter addresses the general effects of composition, mechanical treatment, surface treatment, processing, and fabrication operations on the corrosion resistance of aluminum and its alloys. Different types of surface treatments covered include claddings, anodizing, and conversion coatings. The processing steps that can have relatively significant impact on corrosion resistance are homogenization, rolling, extrusion, quenching, aging, and annealing.

This chapter discusses the erosion and erosion-corrosion behaviors of metals and alloys. It includes data primarily related to particle-laden gas streams impacting on the metal surface. It also covers properties and applications and provides guidelines for materials selection.

All materials are susceptible to corrosion or some form of environmental degradation. Although no single material is suitable for all applications, usually there are a variety of materials that will perform satisfactorily in a given environment. The intent of this chapter is to review the corrosion behavior of the major classes of metals and alloys as well as some nonmetallic materials, describe typical corrosion applications, and present some unique weaknesses of various types of materials. It also aims to point out some unique material characteristics that may be important in material selection, and discuss, where appropriate, the characteristic forms of corrosion that attack specific materials. The materials addressed in this chapter include carbon steels, weathering steels, and alloy steels; nickel, copper, aluminum, titanium, lead, magnesium, tin, zirconium, tantalum, niobium, and cobalt and their alloys; polymers; and other nonmetallic materials, including rubber, carbon and graphite, and woods.

This chapter provides helpful guidelines for selecting a surface treatment for a given application. It identifies important design factors and applicable treatments for common design scenarios, materials, and operating conditions. It explains why heat treatments and finishing operations may be required before or after processing and how to estimate or predict coating thickness, case depth, hardness, and the likelihood of distortion. It also addresses related issues and considerations such as part handling and fixturing, surface preparation and cleaning requirements, processability, aesthetics, and the influence of design features.

This chapter is a detailed account of the applications of stainless steel in automotive and transport systems. The discussion covers exhaust systems, structural components, automotive components, trucks, and rail transport.

This chapter compares and contrasts surface-engineering processes based on process availability, corrosion and wear performance, distortion effects, penetration depth or attainable coating thickness, and cost. It provides both quantitative and qualitative information as well as measured property values.

This chapter first covers some basic principles of electrochemical corrosion and then some of the various types of corrosion. Some of the more common types of corrosion discussed include uniform corrosion, galvanic corrosion, pitting, crevice corrosion, erosion-corrosion, cavitation, fretting corrosion, intergranular corrosion, exfoliation, dealloying corrosion, stress-corrosion cracking, and corrosion fatigue. The chapter discusses the processes involved in corrosion control by retarding either the anodic or cathodic reactions. The rate of corrosion is reduced by conditioning of the metal, by conditioning the environment, and by electrochemical control. Finally, the chapter deals with high-temperature oxidation that usually occurs in the absence of moisture.

This chapter discusses corrosion prevention methods used with aluminum and its alloys. The methods range from relatively straightforward measures, such as proper handling and storage, to advanced early warning corrosion monitoring systems for military aircraft. The chapter summarizes the basic factors that influence design for corrosion resistance and discusses the use of conversion coatings, organic coatings, porcelain enameling, and electroplating. It also discusses corrosion monitoring methods used in chemical processing and refining industries.

Cold spray coatings technology has the potential to provide surface enhancement for applications in sectors such as defense and aerospace, oil and gas, power generation, medical, automotive, electronics, and railways. The ability to deposit clean metallic coatings is used in applications requiring corrosion/oxidation protection, erosion/wear protection, additive manufacturing, and fabricating free forms. This chapter discusses the function, advantages, and benefits of some of these applications.