This article presents the different hardness test methods used to measure the effectiveness of surface carbon control in carburized parts of steel. Common test methods include Rockwell hardness measurements, superficial Rockwell 15N testing, and microhardness testing. The article provides information on the microscopic method used to detect smaller variations in carbon content, and reviews consecutive cuts analysis and spectrographic analysis that are used to accurately evaluate the carbon concentration profile of carburized parts. It describes procedures of and precautions to be undertaken during shim stock analysis, which is used to measure the atmosphere carbon potential. The article includes a discussion on the electromagnetic nondestructive tests that are used to evaluate the case depth of case-hardened parts.

Case depth is the normal distance from the surface of the steel to the start of the core. Measurement of case depth is highly sensitive to the type of case hardening, original steel composition, quenching condition, and even to the testing method. This article describes the various methods of measuring case depth in steels, including chemical methods such as the combustion analysis and spectrographic analysis, microhardness test method, macroscopic and microscopic visual methods, and nondestructive methods. It contains a table that provides approximate equivalent hardness numbers for steel.

Control of temperature and furnace atmospheres has become increasingly critical to successful heat treating. Temperature instrumentation and control systems used in heat treating include temperature sensors, controllers, final control elements, measurement instruments, and set-point programmers. This article describes these items and discusses the classifications and control of furnace atmospheres. The article also describes the surface carbon control devices available for the wide variety of furnace atmospheres and evaluation of carbon control. Finally, the article provides a set of guidelines for safety procedures that are common to all industrial heat treating furnace installations.

During the melting and solidification of cast irons, certain trace (minor) elements may unintentionally accumulate to an extent that they have a detrimental effect on the microstructure of castings. This article discusses the residual elements, trace elements, and tramp elements in cast irons. Elements that influence the matrix structure of cast irons are commonly classified as ferrite-promoting elements or pearlite-promoting elements. The article describes the effects of minor elements on microstructure and properties of cast irons. It discusses the use of a combination of tools to control the effects of minor elements on the structure and properties of cast irons. The article concludes with information on allowable levels of trace and tramp elements in cast irons.

This article provides information on basic chemical equilibria, wet analytical chemistry, and the appropriateness of classical wet methods. It focuses on nonoxidizing acids and oxidizing acids. The article includes information on the qualitative methods used to identify materials by wet chemical reaction. Gravimetry, in which a chemical species is weighed; titrimetry, which involves volume measurement of a liquid reactant; and a host of separation techniques, which require diverse forms of laboratory manipulation, are discussed. The article briefly describes the partitioning of oxidation states as well as those applications in surface studies and rapid material identification in which chemical techniques have proved useful.

Several qualitative, semiquantitative, and quantitative tests are available to estimate and control metal cleanliness, particularly inclusion concentration of aluminum alloys. This article provides a description of a few of the metal cleanliness assessment techniques, such as chemical analysis, pressure filter tests, electric resistivity tests, reduced-pressure test, and ultrasonic technique. Detection methods based on the certain principles and the types of impurities in chemical analysis are discussed.

Germanium is a semiconducting metalloid element found in Group IV A. Germanium is used in the field of electronics, infrared optics, and in the fields of gamma ray spectroscopy, catalysis, and fiber optics. This article discusses the sources, manufacturing, and processing of germanium, and focuses on the chemical properties of various germanium compounds, including germanium halides, germanates, germanides, germanes, inorganic, and organogermanium compounds. It also tabulates the physical, thermal, electronic, and optical properties of germanium, and explains the economical aspects and specifications of germanium. The article describes the analytical and test methods of germanium, including gravimetric method, titrimetric method, and spectral method. It provides a short note on toxicology, and concludes with the uses of germanium in different fields.

This article is a compilation of abbreviations, symbols, and tradenames for terms related to the properties, selection, processing, and applications of the most widely used nonmetallic engineering materials.

This article describes the characterization techniques, mechanical tests, and nondestructive evaluation methods that are commonly used for metal-matrix composites. It also tabulates typical methods of particle size and size distribution measurement, as well as mechanical test specifications for aluminum-matrix composites.

Inert gas fusion is a method of determining the quantitative content of gases in ferrous and nonferrous materials where gases, such as hydrogen, nitrogen, and oxygen, are physically and chemically adsorbed by the materials and later removed and swept by from the fusion area by an inert carrier gas. This article describes the operating principles and sample selection of inert gas fusion. It explains the mechanisms involved in the introduction of fusion gas, separation and detection of fusion gas by thermal-conductive and infrared detection methods. Additionally, the article explains the methods used for analyzing trace amounts of nitrogen, oxygen, and hydrogen in the carrier mediums, providing examples that aid in solving several problems.

This article provides a background of friction-bearing failures due to overheating. The failures of locomotive axles caused by overheated traction-motor support bearings are discussed. The article also describes liquid-metal embrittlement (LME) in steel. It examines the results of various axle studies, with illustrations and concludes with information on the simulation of the LME mechanism.

This article is a compilation of definitions of terms related to materials characterization techniques.

Thermal analysis is used to analyze solidification processes by recording the temperature as a function of time during cooling or heating of a metal or alloy to or from a temperature above its melting point. This article describes the use of cooling curves for analyzing a solidification process, such as the solidification temperature, structure analysis, fraction of phases and heat of fusion with focus on solidification of cast iron, and the use of cooling curves to control and adjust the casting conditions. It discusses deviations from equilibrium that occur due to kinetic effects during solidification. The article also illustrates the evaluation of fraction of solid formed during the precipitation of austenite from heat balance.

This article reviews nondestructive testing (NDT) and inspection techniques, namely liquid penetrant, magnetic particle, ultrasonics, X-ray, eddy current, visual and radiography that are commonly used to detect and evaluate flaws or leaks in an engineering system. This article compares the merits and limitations of these techniques and describes the various uses of NDT, including leak detection, metrology, structure or microstructure characterization, stress-strain response determination, and rapid identification of metals and alloys.

This article is a compilation of terms and definitions related to materials characterization.

This article focuses on the heat removal stages involved in quenching, and on the experimental setup used for measuring temperature and detecting sound signals with the help of illustrations and curves. The quenching process generates acoustic signals, which are the consequences of the phase transformation of steel and of the boiling process at the interface during the cooling process. The sound-pressure signal is captured by the hydrophone through sound-emission measurements that occur during steel quenching in different quenching media. The analysis of the results offers an interesting approach to evaluation and, more importantly, to monitoring, controlling, and optimizing the entire quenching process.

Planning of experiments does not consist merely of identifying a few key parameters and then selecting a specific plan. Selection of the proper experimental plan depends on the purpose of the experiment, physical restrictions on the taking of measurements, and other restrictions imposed by time, economic considerations, and materials and personnel availability. This article presents recommendations that should be followed in outlining the methods of conducting and analyzing an experiment to ensure successful results. It discusses restricted type of experiments, in which the experimenter varies the parameters, or factors, under study and then observes the effects of this action. These include factorial experiments, blocked factorial experiments, and fractional factorial experiments. The article describes the estimation of experimental errors and provides information on randomized designs and block designs. It also presents the methods for determining optimum conditions or levels.

This article discusses the general principles, optical systems, and emission sources of optical emission spectroscopy for elemental analysis. Changes in the energy of the valence or outer shell electrons result in the atomic lines used in emission spectroscopy. Each possible combination of electron configurations produces a spectroscopic term that describes the state of the atom. Atomic emission is analytically useful only to the extent that the emission from one atomic species can be measured and its intensity recorded independent of emission from other sources. Emission sources are often designed to minimize molecular emission. Each of the four types of emission sources; arcs, high-voltage sparks, glow discharges, and flames; has a set of physical characteristics with accompanying analytical assets and liabilities. The article also discusses the applications of each type of emission source.

Distortion failure occurs when a structure or component is deformed so that it can no longer support the load it was intended to carry. Every structure has a load limit beyond which it is considered unsafe or unreliable. Estimation of load limits is an important aspect of design and is commonly computed by classical design or limit analysis. This article discusses the common aspects of failure by distortion with suitable examples. Analysis of a distortion failure often must be thorough and rigorous to determine the root cause of failure and to specify proper corrective action. The article summarizes the general process of distortion failure analysis. It also discusses three types of distortion failures that provide useful insights into the problems of analyzing unusual mechanisms of distortion. These include elastic distortion, ratcheting, and inelastic cyclic buckling.

Distortion often is observed in the analysis of other types of failures, and consideration of the distortion can be an important part of the analysis. This article first considers that true distortion occurs when it was unexpected and in which the distortion is associated with a functional failure. Then, a more general consideration of distortion in failure analysis is introduced. Several common aspects of failure by distortion are discussed and suitable examples of distortion failures are presented for illustration. The article provides information on methods to compute load limits, errors in the specification of the material, and faulty process and their corrective measures to meet specifications. It discusses the general process of material failure analysis and special types of distortion and deformation failure.