This chapter discusses the important role of metallography and the metallographer in predicting and understanding the properties of metals and alloys. Examples are presented of a metallographer working as part of a team in a research laboratory of a large steel company and a metallographer working alone at a small iron foundry. The three basic areas in all metallography laboratories are discussed: the specimen preparation area, the polishing/etching area, and the observation/micrography area. Important safety issues in a metallographic laboratory are also considered.

Several specialized instruments are available for the metallographer to use as tools to gather key information on the characteristics of the microstructure being analyzed. These include microscopes that use electrons as a source of illumination instead of light and x-ray diffraction equipment. This chapter describes how these instruments can be used to gather important information about a microstructure. The instruments covered include image analyzers, transmission electron microscopes, scanning electron microscopes, electron probe microanalyzers, scanning transmission electron microscopes, x-ray diffractometers, microhardness testers, and hot microhardness testers. A list of other instruments that are usually located in a research laboratory or specialized testing laboratory is also provided.

This chapter instructs the metallographer on the basic skills required to prepare a polished metallographic specimen. It is organized in a chronological sequence starting with the information-gathering process on the material being investigated, then moving on to sectioning, mounting, grinding, and polishing processes, and ending with methods used to properly store metallographic specimens. The discussion covers the preparation procedures, the materials being investigated, and equipment used to perform these procedures.

Molybdenum thermal spray coatings are used in aerospace and other industries for wear resistance applications. Metallographic sample preparation of molybdenum coatings presents unique challenges. The purpose of the investigation described in this article is to determine Accepted Practices for sample preparation to better understand the process related microstructures of thermal spray molybdenum powders. The committee followed a round robin approach to assess metallographic sample preparation by a variety of laboratories. The article summarizes the results of the committee’s work.

This chapter discusses the techniques applicable to the diagnosis of corrosion failures, including visual and microscopic examination of corroded surfaces and microstructure; chemical analysis of the metal, corrosion products, and bulk environment; nondestructive evaluation methods; corrosion testing techniques; and mechanical testing techniques. A guide to investigative techniques used in corrosion failure analysis is provided in a table, describing the advantages and limitations of each technique. The principal stages of the investigation and analysis of corrosion failures discussed in the chapter are: collection of background information and sampling; preliminary laboratory examination; detailed metallographic and fractographic examinations; chemical analysis of corrosion products and bulk materials; corrosion testing for quality control; mechanical testing for quality control; and analysis of results and report writing.

Abradable coatings (such as Ni-4Cr-4Al/bentonite) are used throughout jet engines, primarily as sacrificial coatings into which moving components wear. This article presents the Accepted Practice for sample preparation of abradable coatings for metallographic analysis, based on round robin testing by several laboratories.

This chapter explains how to prepare metallographic samples for light microscopy and how to anticipate and avoid related problems. It describes standard practices and procedures for sectioning, mounting, grinding, and polishing and identifies common defects along with their causes and cures. It also provides recommendations for handling specific materials and addresses safety concerns.

This chapter describes the various features of the metallurgical microscope. Key concepts are defined such as resolving power, the virtual image, bright- and dark-field illumination, numerical aperture, focal length, image contrast, depth of field, and spherical and chromatic aberration. Metallurgical microscope features such as apochromatic objectives, hyperplane oculars, vertical illuminators, counting reticles, widefield oculars, polarization filters, field diaphragms, interferometers, and tungsten-halogen lamps are explained. The optical system, nosepiece, types of objectives (the lens assembly close to the specimen) and eyepieces, and components of the illumination system are all explained. The last part of this chapter describes special procedures involved in using and calibrating the metallurgical microscope.

This chapter provides guidelines for conducting metallographic evaluations and offers suggestions on how to effectively report the results. It explains how the approach depends on the objective of the evaluation, which is usually to measure a structural feature, test a hypothesis, or investigate structure-related effects. The chapter addresses each case, tailoring its guidelines and suggestions accordingly.

This chapter explains how to safely prepare beryllium alloy samples for metallographic analysis. It describes grinding, polishing, and etching procedures in detail. It also discusses the identification of major and minor constituents and the general appearance of beryllium microstructure.

This chapter describes the methods and equipment applicable to metallographic studies and discusses the preparation of specimens for examination by light optical microscopy. Five major operations for preparation of metallographic specimens are discussed: sectioning, mounting, grinding, polishing, and etching. The discussion covers their basic principles, advantages, types, and applications, as well as the equipment setup. The chapter includes tables that list etchants used for microscopic examination. It also provides information on microscopic examination, microphotography, and the effects of grain size on the structural properties of the material.

This appendix is a compilation of tables helpful to metallographers in characterizing irons and steels. The tables include AISI/SAE designations and specific composition ranges for various steels and irons, listings of companies that sell metallographic equipment and supplies, and compositions and usage guidance for etchants, chemical polishing solutions, and coatings.

This chapter discusses the tools and techniques of light microscopy and how they are used in the study of materials. It reviews the basic physics of light, the inner workings of light microscopes, and the relationship between resolution and depth of field. It explains the difference between amplitude and optical-phase features and how they are revealed using appropriate illumination methods. It compares images obtained using bright field and dark field illumination, polarized and cross-polarized light, and interference-contrast techniques. It also discusses the use of photometers, provides best practices and recommendations for photographing structures and features of interest, and describes the capabilities of hot-stage and hot-cell microscopes.

This chapter presents various case histories that illustrate a variety of failure mechanisms experienced by the high-strength steel components in aerospace applications. The components covered are catapult holdback bar, AISI 420 stainless steel roll pin, main landing gear (MLG) lever, inboard flap hinge bolt, nose landing gear piston axle, multiple-leg aircraft-handling sling, aircraft hoist sling, internal spur gear, and MLG axle. In addition, the chapter provides information on full-scale fatigue testing, nondestructive testing, and failure analysis of fin attach bolts.

This appendix focuses on procedures, techniques, and precautions associated with the investigation and analysis of metallurgical failures that occur in service. It describes the steps of an orderly failure analysis from collecting and examining samples to performing mechanical and nondestructive tests, preparing and examining fractographs and micrographs, determining failure mode, writing the report, and developing follow-up recommendations. It also examines the fundamental mechanisms of failure, why they occur, and how to identify them by their characteristic features.

This chapter discusses the important aspects that a metallographer should understand in order to effectively reveal a microstructure. It begins by exploring etching response and how it can be a tool for revealing various microstructural features. The next part of the chapter discusses methods for revealing microstructure in the as-polished (unetched) specimen, then guidelines for selecting and using etchants when needed. The chapter discusses different types of etchants in terms of their ingredients, etching procedure, and major uses. The etchants discussed include basic etchants (nital and picral and their variations) and tint etchants for carbon and low-alloy steels and cast irons, and basic etchants for stainless steels. Finally, information is provided on different illumination methods (differential interference contrast and dark-field illumination) that can be used to highlight certain features in microstructures.

Thermal barrier coatings (TBCs) are applied using thermal spray coating (TSC) processes to components that are internally cooled and operated in a heated environment. The TSC microstructures are prone to interactions with common metallographic procedures that may result in artifacts and misinterpretation of the TSC microstructure. This article aims to aid in identifying metallographic TSC artifacts, specifically in the air plasma spray zirconia-based TBC, including both of its common constituents, the bond coating and the top coating. Artifacts that result from specific sectioning and mounting practices, as well as from different polishing times, are presented. Additionally, the article discusses the factors in optical microscopy and scanning electron microscopy that affect microstructure interpretation.