Search Results for surface activation

Examining and evaluating the nitrided case is generally accomplished by hardness testing and microscopic examination. This chapter discusses both characterization methods, as well as sample preparation. The chapter also discusses the processes involved in the etching of the sample after microhardness testing and provides practices that contribute to the safe preparation of specimens. Examples of nitrided case microstructures, using optical light microscopy, are also presented.

This chapter discusses the processes involved in the wetting, spreading, and chemical interaction of a braze on a nonmetal. The chapter reviews the key materials and process issues relating to the joining of nonmetals using active brazing. Emphasis is placed on the differences in brazing to metals by established methods. The chapter also describes the designing process and properties of metal/nonmetal joints.

This chapter familiarizes readers with the use of Fick’s laws of diffusion in heat treating, coating, and other metallurgical processes. It contains worked solutions to nearly 30 problems requiring the calculation of activation energy, diffusion coefficient, concentration level, surface layer thickness, case depth, and processing time and temperature. The selected problems deal with various types of iron, steel, and nonferrous alloys and processes ranging from aluminizing, chromizing, carburizing, and plasma nitriding to hydrogen dissipation, decarburizing, and oxidation. A few diffusion problems involving single-crystal silicon are also included.

This chapter presents the following groupings of metals and alloys that are soldered together: steel and iron-base alloys, aluminum and aluminum alloys, and copper and copper alloys. It also presents the ancillary materials and process methods that assist the solder filler metal in completing the solder joint through induction heating. The chapter focuses on the selection of fluxes and the use of inert gases or even vacuum to realize an oxide-free base material surface both before and during the soldering process.

This chapter provides a brief account of galvanic corrosion, which occurs when a metal or alloy is electrically coupled to another metal or conducting nonmetal in the same electrolyte. It begins by describing the galvanic series of metals and alloys useful for predicting galvanic relationships, followed by a brief section on polarization of metals or alloys. The effects of area, distance, and geometric shapes on galvanic-corrosion behavior are then discussed. Various alloys susceptible to galvanic corrosion are briefly reviewed. The chapter also discusses various modes of attack that lead to galvanic corrosion, along with methods for predicting and controlling galvanic corrosion.

This chapter familiarizes readers with the basic theory of molecular dynamics and its application in the study of materials. It explains how material properties and behaviors are determined through the iterative calculation of motion equations for a collection of atoms under a given set of conditions. It also provides a walk-through on the use of LAMMPS, an open-source molecular dynamics simulator, discussing the selections and inputs of relevance to practical materials problems.

This chapter discusses the principles of corrosion of metals in aqueous environments. The thermodynamics of aqueous corrosion is the subject of the first half of this chapter, which addresses concepts such as corrosion reactions and free-energy change, the relationship between free energy and electrochemical potential, the effect of ionic concentration on electrode potential, and the corrosion behavior of a metal based on its potential-pH diagram. The corrosion (potential-pH) behavior of iron, gold, copper, zinc, aluminum, and titanium are described. Understanding the kinetics of corrosion and the factors that control the rates of corrosion reactions requires examination of the concepts of polarization behavior and identification of the various forms of polarization in an electrochemical cell. These concepts, addressed in the remaining of this chapter, include anodic and cathodic reactions, the mixed-potential theory, and the exchange currents.

This chapter discusses the complex polarization characteristics of active-passive metals and addresses related problems in interpreting their corrosion behavior. It begins by presenting several experimentally derived polarization curves for iron, comparing and contrasting them with the iron-water Pourbaix diagram. It then explains how anodic polarization is extremely sensitive to the environment and, as a result, a reasonably complete curve for a given metal-environment system usually can only be inferred. It goes on to describe how such curves are constructed, demonstrating the procedures for a wide range of alloys and environments. The examples also show how factors such as alloy concentration, crystal lattice orientation, temperature, and dissolved oxygen affect corrosion behavior.

This chapter is a compilation of terms and definitions related to corrosion in the petrochemical industry.

This appendix is a compilation of terms and definitions associated with the processing, microstructure, and properties of powder metal stainless steels.

This chapter discusses the conditions under which carburization and metal dusting occur. It describes the chemical reactions and thermodynamic relationships that drive carburization and metal dusting attack and the factors that determine the amount of damage that metals and alloys are likely to sustain. The chapter also explains how carburization affects creep strength and fracture toughness, and how surface conditions and finish and the presence of sulfur affect metal dusting behaviors.

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.

This appendix is a compilation of terms and definitions related to corrosion.