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.

This article introduces the wafer-level fault localization failure analysis (FA) process flow for an accelerated yield ramp-up of integrated circuits. It discusses the primary design considerations of a fault localization system with an emphasis on complex tester-based applications. The article presents examples that demonstrate the benefits of the enhanced wafer-level FA process. It also introduces the setup of the wafer-level fault localization system. The application of the wafer-level FA process on a 22 nm technology device failing memory test is studied and some common design limitations and their implications are discussed. The article presents a case study and finally introduces a different value-add application flow capitalizing on the wafer-level fault localization system.

This chapter provides a comprehensive overview over all phenomena related to Voltage Contrast (VC) mechanisms in SEM and FIB. The multiple advantages, possibilities, and limits of active and passive VC failure localization are systemized and discussed. The knowledge of all facts influencing the VC generation (capacitance, leakage, doping, and circuitry) is very helpful for successful failure localization.

This chapter describes some of the most effective tools for investigating boiler tube failures, including scanning electron microscopy, optical emission spectroscopy, atomic absorption spectroscopy, x-ray fluorescence spectroscopy, x-ray diffraction, and x-ray photoelectron spectroscopy. It explains how the tools work and what they reveal. It also covers the topic of image analysis and its application in the measurement of grain size, phase/volume fraction, delta ferrite and retained austenite, inclusion rating, depth of carburization/decarburization, scale thickness, pearlite banding, microhardness, and hardness profiles. The chapter concludes with a brief discussion on the effect of scaling and deposition and how to measure it.

This chapter discusses the use of electron microscopy in metallographic analysis. It explains how electrons interact with metals and how these interactions can be harnessed to produce two- and three-dimensional images of metal surfaces and generate crystallographic and compositional data as well. It discusses the basic design and operating principles of scanning electron microscopes, transmission electron microscopes, and scanning transmission electron microscopes and how they are typically used. It describes the additional information contained in backscattered electrons and emitted x-rays and the methods used to access it, namely wavelength and energy dispersive spectroscopy and electron backscattering diffraction techniques. It also describes the role of focused ion beam milling in sample preparation and provides information on atom probes, atomic force microscopes, and laser scanning microscopes.

Structural members in a radar antenna system are held together by cadmium-plated high-strength steel bolts, several of which had fractured along the fillet near the head. Investigators determined that the bolts did not seat properly, making contact only at the periphery, which subjected them to high stress concentrations in the fillet region. They also concluded that the intergranular nature of the fracture, as revealed by scanning electron fractography, pointed to hydrogen embrittlement as a contributing factor. This chapter provides a summary of the investigation along with a recommendation to consider adding spring washers to the assembly.

This chapter discusses the key findings of an investigation into the failure of an aircraft engine fuel pump. It explains how investigators came to the conclusion that metal slivers from a heavily worn spring may have interrupted the flow of lubricant to one of the slipper pads, causing adhesive wear and the welding of slipper pad material onto the surface of a mating cam plate. Excessive friction between the slipper pads and cam plate, in turn, created a torsional overload that caused the camshaft to break. The chapter presents SEM images showing the wear pattern on one of the springs along with photographs of the damaged slipper pads and cam plate. It also includes an image of a copper flake found in one of the pistons and discusses the results of qualitative x-ray chemical analysis.

An adaptor and a bolt were overloaded during a flight causing them to fracture. This chapter recounts the circumstances that led to the failure and the investigation that followed. It includes images of the fracture surfaces which show that both components failed quickly due to overload conditions. It also recommends the use of twin suspension hooks to make attachment points more stable under difficult flight conditions.

This chapter discusses the failure of an aircraft control cable and the investigation that followed. It explains how visual examination showed that the failure occurred in a heavily worn section that runs over a pulley. Further examination under a stereoscope and in a SEM found that 40 out of 49 wires had thinned and broke apart, and that the remaining nine wires failed in tension evidenced by cup and cone fracture and the presence of dimples on the fracture surface. Based on their findings, investigators concluded that cable snapped because of excessive thinning due to contact wear.

An aircraft fuel pump failed just after takeoff, resulting in engine flameout. Investigators discovered that one of the seven pistons broke into several pieces, causing the quill shaft to fracture. An examination of the fracture surfaces revealed severe rubbing on the quill shaft and beach marks on the piston along with a nick on the opposite side of the barrel. In addition, the metal around the corresponding hole in the rotor had plastically deformed and the slipper pad was gone. Based on the investigation, the failure most likely occurred due to a problem with the spring guides or a jammed slipper pad. The chapter provides several recommendations to avoid such failures in the future.

A design modification intended to reduce dowel bolt failures in an aircraft engine proved ineffective, prompting an investigation to determine what was causing the bolts to break. As the chapter explains, failure specimens were examined under various levels of magnification and subjected to chemical analysis and low-cycle fatigue tests. Based on their findings, investigators concluded that the bolts failed due to fatigue compounded by excessive clearances and poor surface finishes. The chapter provides a number of recommendations addressing these issues and related concerns.

Helicopter control mechanisms were failing at a higher than normal rate on high-altitude flights in mountainous regions. All of the failures occurred at or near attachment points on pressurized tubes, causing a pressure drop and partial loss of function. Visual and SEM examinations revealed cracks along the inner surface of the tubes, some of which had propagated through the thickness of the wall. Cracks emanating from weld toes were also visible. Based on their observations, investigators concluded that the tubes were subjected to excessive flexural load, causing cracks due to fatigue. They also provide recommendations for avoiding such failures in the future.

This chapter describes an investigation that was conducted to determine why quill shafts were failing prematurely in gear boxes on aircraft engines. The investigation focused on the splines in a splined bore. Visual examination showed that the splines were heavily worn and covered with red powder on one end. Investigators also observed blueing, an effect of overheating. Based on these observations and the results of SEM imaging, it was concluded that the splines in the spline bore were wearing out for lack of lubrication.

Several hydraulic pumps that failed in service on a particular type of aircraft were received for analysis. Hydraulic testing was not an option, so the pumps were disassembled and their plungers and cylinders were cleaned and examined. Based on their observations, investigators concluded that cavitation erosion damaged the plungers, causing them to seize.

One of the rotor bearings in an electric motor failed, producing excessive vibrate. The bearing was removed and disassembled, revealing craters and bruises on the inner ring raceway and balls along with evidence of melting and burning of metal. Scanning electron microscopy revealed metal particles near the craters, and energy-dispersive x-ray analysis showed that slivers recovered from the grease had the same composition as the bearing raceway and balls. Based on these observations, it was concluded that the bearing failed due to electrostatic discharge, which would have led to seizure if it continued. The report recommends the use of electrically conductive grease and proper grounding practices.

This chapter discusses field, visual, physical, and metallurgical examinations of gear failures. Physical examinations reviewed include nondestructive testing, including magnetic-particle inspection, tooth characteristic studies, surface hardness testing, ultrasonic testing, nital etching, profilometer measurements, and dimensional checking. Metallurgical examinations reviewed include the cross-sectional hardness survey, macroscopic examination, carbon gradient traverse, chemical analysis, case hardness traverse [microhardness], microscopic examination, and scanning electron microscopy.