This article covers the three most popular techniques used to characterize the very outermost layers of solid surfaces: Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Some of the more important attributes are listed for preliminary insight into the strengths and limitations of these techniques for chemical characterization of surfaces. The article describes the basic theory behind each of the different techniques, the types of data produced from each, and some typical applications. Also discussed are the different types of samples that can be analyzed and the special sample-handling procedures that must be implemented when preparing to do failure analysis using these surface-sensitive techniques. Data obtained from different material defects are presented for each of the techniques. The examples presented highlight the typical data sets and strengths of each technique.

Laser surface mapping of a canister closure weld provided data that was used to generate three-dimensional images of the weld failure. These images were invaluable in that they allowed people who did not have access to the canister to see the anomaly in great detail. This aided in the scientific examination while reducing exposure to the radiologically contaminated canister. Precise measurements from the surface maps provided useful information about the location of weld features that were used in the examination of the weld failure. Laser surface mapping proved to be a powerful addition to the nondestructive examination tools available for surface phenomena.

A batch of bimetal foil/epoxy laminates was rejected because of poor peel strength. The laminates were manufactured by sintering a nickel/phosphorus powder layer to a copper foil, cleaning, then chromate conversion coating the nickel-phosphorus surface, and laminating the nickel-phosphorus side of the clad bimetal onto an epoxy film, so that the end product contained nickel-phosphorus sandwiched between copper and epoxy, with a chromate conversion layer on the epoxy side of the nickel-phosphorus. Peel testing showed abnormally low adhesion strength for the bad batch of peel test samples. Comparison with normal-strength samples using XPS indicated an 8.8% Na concentration on the surface of the bad sample; the good example contained less than 1% Na on the surface. After 15 min of argon ion etching, depth profiling showed high concentrations of sodium were still evident, indicating that the sodium was present before the chromate conversion treatment was performed. A review of the manufacturing procedures showed that sodium hydroxide was used as a cleaning agent before the chromate conversion coating. Failure cause was that apparently the sodium hydroxide had not been properly removed during water rinsing. Thus, recommendation was to modify that stage in the processing.

Eddy current inspection was performed on a vertical evaporator unit (that contained 180 tubes) used in a chemical processing plant. It was advised that the tube material was type 316 stainless steel. The shell-side fluid was condensate and gaseous methylene chloride, while the tube-side fluid was contaminated liquid methylene chloride. More than 100 tubes exhibiting severe outer surface pitting and cracklike indications near each tube sheet were revealed during eddy current inspection. It was observed that the indications correlated with rust-stained, pitted, and cracked areas on the outer surfaces. The cracking was revealed by metallographic examination to have initiated from the outer surface, frequently at pits, and penetrated the tube wall in a transgranular, branching fashion. The crack features were characteristic of chloride stress-corrosion cracking. A change in tube material was recommended to avoid future failures and loss of service.

An eddy current survey of the copper evaporator (chiller) tubes in an absorption air-conditioning unit revealed two tubes in the evaporator bundle with indications typical of longitudinal cracks. Significant necking down and grain distortion at the fracture surfaces was revealed by metallographic examination. The fracture features were found to be characteristic of an overload failure in a ductile material. The ruptured tubes were concluded as a result of examination to have failed as a result of excessive internal pressure. The source of the excessive internal pressure was assumed to be a freeze-up of the tube side water that occurred during interruption of the tube side flow or misoperation of the unit.

The quantitative characterization of fracture surface geometry, that is, quantitative fractography, can provide useful information regarding the microstructural features and failure mechanisms that govern material fracture. This article is devoted to the fractographic techniques that are based on fracture profilometry. This is followed by a section describing the methods based on scanning electron microscope fractography. The article also addresses procedures for three-dimensional fracture surface reconstruction. In each case, sufficient methodological details, governing equations, and practical examples are provided.

This article provides information on the chemical characterization of surfaces by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS). It describes the basic theory behind each of these techniques, the types of data produced from each, and some typical applications. The article explains the strengths of AES, XPS, and TOF-SIMS based on data obtained from the surface of a slightly corroded stainless steel sheet.