Search Results for Chemical analysis

Identification of alloys using quantitative chemical analysis is an essential step during a metallurgical failure analysis process. There are several methods available for quantitative analysis of metal alloys, and the analyst should carefully approach selection of the method used. The choice of appropriate analytical techniques is determined by the specific chemical information required, the condition of the sample, and any limitations imposed by interested parties. This article discusses some of the commonly used quantitative chemical analysis techniques for metals. The discussion covers the operating principles, applications, advantages, and disadvantages of optical emission spectroscopy (OES), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray spectroscopy, and ion chromatography (IC). In addition, information on combustion analysis and inert gas fusion analysis is provided.

This article describes some of the common elemental composition analysis methods and explains the concept of referee and economy test methods in failure analysis. It discusses different types of microchemical analyses, including backscattered electron imaging, energy-dispersive spectrometry, and wavelength-dispersive spectrometry. The article concludes with information on specimen handling.

This article addresses some established protocols for characterizing thermoplastics and whether they are homogeneous resins, alloyed, or blended compositions or highly modified thermoplastic composites. It begins with a discussion on characterizing mechanical, rheological, and thermal properties of polymer. This is followed by a section describing molecular weight determination using viscosity measurements. Next, the article discusses the use of cone and plate and parallel plate geometries in melt rheology. It then reviews the processes involved in the analysis of thermoplastic resins by chromatography. Finally, the article covers three operations of thermoanalysis, namely differential scanning calorimetry, thermogravimetric analysis, and thermomechanical testing.

Chemical analysis is a critical part of any failure investigation. With the right planning and proper analytical equipment, a myriad of information can be obtained from a sample. This article presents a high-level introduction to techniques often used for chemical analysis during failure analysis. It describes the general considerations for bulk and microscale chemical analysis in failure analysis, the most effective techniques to use for organic or inorganic materials, and examples of using these techniques. The article discusses the processes involved in the chemical analysis of nonmetallics. Advances in chemical analysis methods for failure analysis are also covered.

This article describes testing and characterization methods of ceramics for chemical analysis, phase analysis, microstructural analysis, macroscopic property characterization, strength and proof testing, thermophysical property testing, and nondestructive evaluation techniques. Chemical analysis is carried out by X-ray fluorescence spectrometry, atomic absorption spectrophotometry, and plasma-emission spectrophotometry. Phase analysis is done by X-ray diffraction, spectroscopic methods, thermal analysis, and quantitative analysis. Techniques used for microstructural analysis include reflected light microscopy using polarized light, scanning electron microscopy, transmission electron microscopy, energy dispersive analysis of X-rays, and wavelength dispersive analysis of X-rays. Macroscopic property characterization involves measurement of porosity, density, and surface area. The article describes testing methods such as room and high-temperature strength test methods, proof testing, fracture toughness measurement, and hardness and wear testing. It also explains methods for determining thermal expansion, thermal conductivity, heat capacity, and emissivity of ceramics and glass and measurement of these properties as a function of temperature.

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.

This article focuses on wet chemical methods that have stood the test of time in laboratories around the world. It begins with a description of the appropriateness of classical wet methods. This is followed by sections on sampling procedures, basic chemical equilibria, and wet analytical chemistry. Mechanical methods and nonoxidizing acids and/or acid mixtures for dissolving solid samples for wet chemical analysis are then reviewed. Qualitative methods that are used to identify materials by wet chemical reaction are also included. The article provides information on various methods for the separation of chemical mixtures and on the types of gravimetry and titrimetry. Strategies for removing inclusions are also included to aid in their compositional understanding. The article also briefly describes the processes involved in chemical surface studies and partitioning of oxidation states. It ends by presenting some examples of the applications of classical wet methods.

Phosphating is used in the metalworking industry to treat substrates like iron, steel, galvanized steel, aluminum, copper, and magnesium and its alloys. This article provides an overview of the types, uses, and theory of phosphate coatings and their formation. It also discusses the composition of phosphating baths, phosphate layers, and their analysis, as well as the process hardware necessary to realize these treatments. A summary of the different types of phosphate layers is tabulated, and the chemical formulas for a number of different phosphate compounds that are theoretically possible in crystalline phosphate layers are illustrated. The article presents four chemically important phosphating steps, namely, cleaning, activation or conditioning, phosphating, and posttreatment plus standard rinsing. It describes the physical and chemical properties by gravimetric analysis, chemical analysis, structure and morphology, thermal analysis, and alkaline resistance.

This article commences with a discussion on the characteristics of stress-corrosion cracking (SCC) and describes crack initiation and propagation during SCC. It reviews the various mechanisms of SCC and addresses electrochemical and stress-sorption theories. The article explains the SCC, which occurs due to welding, metalworking process, and stress concentration, including options for investigation and corrective measures. It describes the sources of stresses in service and the effect of composition and metal structure on the susceptibility of SCC. The article provides information on specific ions and substances, service environments, and preservice environments responsible for SCC. It details the analysis of SCC failures, which include on-site examination, sampling, observation of fracture surface characteristics, macroscopic examination, microscopic examination, chemical analysis, metallographic analysis, and simulated-service tests. It provides case studies for the analysis of SCC service failures and their occurrence in steels, stainless steels, and commercial alloys of aluminum, copper, magnesium, and titanium.

This article outlines the basic steps to be followed and the range of techniques available for failure analysis, namely, background data assembling, visual examination, microfractography, chemical analysis, metallographic examination, electron microscopy, electron microprobe analysis, X-ray techniques, and simulations. It also describes the steps for analyzing the data, preparing the report, preservation of evidence, and follow-up on recommendations.

This article describes the characteristics of tubing of heat exchangers with respect to general corrosion, stress-corrosion cracking, selective leaching, and oxygen-cell attack, with examples. It illustrates the examination of failed parts of heat exchangers by using sample selection, visual examination, microscopic examination, chemical analysis, and mechanical tests. The article explains corrosion fatigue of tubing of heat exchangers caused by aggressive environment and cyclic stress. It also discusses the effects of design, welding practices, and elevated temperatures on the failures of heat exchangers.

This article provides an introduction to the molecular fluorescence spectroscopy, and discusses the theory of fluorescence and its application to chemical analysis. It provides information on fluorescence that occurs in organic compounds and inorganic atoms and molecules. The article describes the instruments used in the spectroscopy, namely, radiation sources, sample holders, wavelength selectors, detectors, computers, and ratiometric instruments. The practical considerations include solvent effects, corrected spectra, wavelength calibration, temperature, and scattered light. The article also discusses the uses of some special techniques used in molecular fluorescence spectroscopy.

This article presumes the reader has a basic understanding of the operation and principles of scanning electron microscopy (SEM). The emphasis of this article is specifically on the application of SEM to the study of metallic and nonmetallic fracture surfaces, where the typical objectives of SEM examination of a fracture surface may include the following: identification of characteristic fracture features to aid in identifying fracture mechanism(s); characterization of material anomalies that may have influenced the fracture; qualitative or semiquantitative chemical analysis of component material(s); and qualitative or semiquantitative analysis of deposits or corrosion products on or near fracture surfaces.

This article is a pictorial representation of commonly observed microstructures in iron-base alloys (carbon and alloy steels, cast irons, tool steels, and stainless steels) that occur as a result of variations in chemical analysis and processing. It reviews a wide range of common and complex mixtures of constituents (single or combination of two phases) that are encountered in iron-base alloys and the complex structure that is observed in these microstructures. The single-phase constituents discussed in the article include austenite, ferrite, delta ferrite, cementite, various alloy carbides, graphite, martensite, and a variety of intermetallic phases, nitrides, and nonmetallic inclusions. The article further describes the two-phase constituents including, tempered martensite, pearlite, and bainite and nonmetallic inclusions in steel that consist of two or more phases.

The characterization, testing, and nondestructive evaluation of ceramics and glasses are vital to manufacturing control, property improvement, failure prevention, and quality assurance. This article provides a broad overview of characterization methods and their relationship to property control, both in the production and use of ceramics and glasses. Important aspects covered include the means for characterizing ceramics and glasses, the corresponding rationale behind them, and relationship of chemistry, phases, and microconstituents to engineering properties. The article also describes the effects that the structure of raw ceramic materials and green products and processing parameters have on the ultimate structure and properties of the processed piece. The effects that trace chemistry and processing parameters have on glass properties are discussed. The article describes mechanical tests and failure analysis techniques used for ceramics.

This article discusses the capabilities and limitations of various material characterization methods that assist in the selection of a proper analytical tool for analyzing particulate materials. Commonly used methods are microanalysis, surface analysis, and bulk analysis. The techniques used for performing microanalysis include scanning electron microscopy and electron probe X-ray microanalysis. The article describes surface analysis techniques, including Auger electron spectroscopy, X-ray photoelectron spectroscopy, and ion-scattering spectroscopy. Bulk analysis techniques, such as X-ray powder diffraction, inductively coupled plasma atomic emission spectroscopy, atomic absorption spectroscopy, and atomic fluorescence spectrometry, are also discussed.

This article reviews the failure analysis process with specific reference to the considerations that should be addressed when a casting has failed. It describes the failure analysis methodology for three failed cast components: an aluminum bracket, a bronze suction roll, and a steel automotive spindle. The article discusses failure analysis investigation by obtaining casting background information, planning the evaluation and selecting the appropriate casting for analysis, conducting a preliminary examination, conducting the proper material evaluations, and thoroughly evaluating the test data. It concludes with information on case studies that show how the methodology is adapted for differing materials, failure mechanisms, and failure circumstances.