Arc welding methods can be classified into shielded metal arc welding, flux-cored arc welding, submerged arc welding, gas metal arc welding, gas tungsten arc welding, plasma arc welding, plasma-metal inert gas (MIG) welding, and electroslag and electrogas welding. This article provides information on process capabilities, principles of operation, power sources, electrodes, shielding gases, flux, process variables, and advantages and disadvantages of these arc welding methods. It presents information about the arc welding procedures of hardenable carbon and alloy steels, cast irons, stainless steels, heat-resistant alloys, aluminum alloys, copper and copper alloys, magnesium alloys, nickel alloys, and titanium and titanium alloys.

Microjoining methods are commonly used to fabricate medical components and devices. This article describes key challenges involved during microjoining of medical device components. The primary mechanisms used in microjoining for medical device applications include microresistance spot welding (MRSW) and laser welding. The article illustrates the fundamental principles involved in MRSW and laser welding. Most multicomponent medical devices implement microjoining techniques to join various forms of materials and geometries. The article presents examples of various microjoining methods used in medical device applications, including pacemaker and nitinol microscopic forceps.

Quenching and partitioning (Q&P) steel is a term used to describe a series of C-Si-Mn, C-Si-Mn-Al, or other steels subjected to the quenching and partitioning heat treatment process. This article discusses the Q&P steel's chemical compositions and mechanical properties, and provides an overview of the important background and product characteristics with a focus on the automotive sheet steel application. It schematically represents the continuous annealing process, consequent phase-transformation behaviors, and forming-limit curves of Q&P steels. The article describes the parameters associated with resistance spot welding, laser welding, and metal active gas welding. It also provides useful information of retained austenite volume fraction measured by x-ray diffraction and electron backscatter diffraction. The article also examines microstructure evolution during tensile testing at different strain levels using electron backscatter diffraction.

Acoustical holography is the extension of holography into the ultrasonic domain. The basic systems for acoustical holography are the liquid-surface type and the scanning type. This article discusses the applications for acoustical holography, including inspection of large composite parts, through-transmission breast imaging system, inspection of welds in thick materials, and inspection of sleeve-bearing stock. It describes the basic system for liquid-surface acoustical holography and scanning acoustical holography. A comparison between these techniques is also provided.

This article discusses the inspection/reference standards that are absolutely critical for proper application of ultrasonic inspection systems. Many of the standards and specifications for ultrasonic inspection require the use of standard reference blocks. The article lists the variables that should be considered when selecting standard reference blocks and describes the three types of standard blocks ordinarily used for calibration or reference: area-amplitude blocks, distance-amplitude blocks, and blocks of the type sanctioned by the International Institute of Welding. It reviews the determination of area-amplitude and distance-amplitude curves of a straight-beam pulse-echo ultrasonic inspection system. The article discusses the three principal conventional manual ultrasonic sizing techniques: 6 dB drop technique, maximum-amplitude technique, and 20 dB drop technique. It provides information on the dimension-measurement applications of ultrasonic inspection methods.

This article addresses the cobalt and cobalt-base alloys most suited for aqueous environments and those suited for high temperatures. The performance of cobalt alloys in aqueous environments encountered in commercial applications is discussed. The article provides information on the environmental cracking resistance of the cobalt alloys. Three welding processes that are used for hardfacing with the high-carbon Co-Cr-W alloys, namely, oxyacetylene, gas tungsten arc, and plasma-transferred arc are also discussed. The article examines the effects of various modes of high-temperature corrosion. It describes the applications and fabrication of cobalt alloys for high-temperature service.

In terms of component design, casting offers a great amount of flexibility. This article discusses the parameters that can drive the geometry of casting design from a process standpoint. It provides information on the design of junctions and addresses considerations of secondary operations in design. The article describes the factors that control casting tolerances and provides specific tips for designing castings with uniform wall thickness and unequal sections, designing thin sections, designing for economical coring, designing for functional packaging, and core design principles. The choice of whether a component is best manufactured as welded, assembled, fabricated, forged, machined, or cast is based on the component geometry, production costs, and requirements in application. The article addresses these issues and provides a framework for analyzing all manners of manufacturing as possible conversion candidates. It concludes with a discussion on different metalcasting design projects.

Metal-induced embrittlement is a phenomenon in which the ductility or the fracture stress of a solid metal is reduced by surface contact with another metal in either the liquid or solid form. This article summarizes some of the characteristics of liquid-metal- and solid-metal-induced embrittlement. This phenomenon shares many of these characteristics with other modes of environmentally induced cracking, such as hydrogen embrittlement and stress-corrosion cracking. The discussion covers the occurrence, failure analysis, and service failures of the embrittlement. The article also briefly reviews some commercial alloy systems in which liquid-metal-induced embrittlement or solid-metal-induced embrittlement has been documented and describes some examples of cracking due to these phenomena, either in manufacturing or in service.

Ultrasonic inspection is a nondestructive method in which beams of high-frequency acoustic energy are introduced into a material to detect surface and subsurface flaws, to measure the thickness of the material, and to measure the distance to a flaw. This article provides a detailed account of ultrasonic flaw detectors, including ultrasonic transducers and types of search units and couplants. The article describes pulse-echo and transmission inspection methods and data interpretation. The general characteristics of ultrasonic waves and the factors influencing ultrasonic inspection are also addressed. The article concludes with a review of the advantages and disadvantages of ultrasonic inspection compared with other methods applications of the technique.

Corrosion is the electrochemical reaction of a material and its environment. This article addresses those forms of corrosion that contribute directly to the failure of metal parts or that render them susceptible to failure by some other mechanism. Various forms of corrosion covered are galvanic corrosion, uniform corrosion, pitting, crevice corrosion, intergranular corrosion, selective leaching, and velocity-affected corrosion. In particular, mechanisms of corrosive attack for specific forms of corrosion, as well as evaluation and factors contributing to these forms, are described. These reviews of corrosion forms and mechanisms are intended to assist the reader in developing an understanding of the underlying principles of corrosion; acquiring such an understanding is the first step in recognizing and analyzing corrosion-related failures and in formulating preventive measures.

Laser-ultrasonics is a particular implementation of ultrasonic nondestructive inspection in which ultrasound is generated and detected by lasers. This article discusses the various mechanisms that ensure ultrasound generation and explains the possibility to get the equivalent of phase-array by numerical processing of an array of previously acquired laser-ultrasonic signals. The article describes the ultrasound generation by thermoelastic mechanism and ablation or vaporization. It illustrates the principle of optical detection of ultrasound with confocal Fabry-Perot interferometer and photorefractive two-wave mixing interferometer. The article concludes with information on the industrial applications of laser-ultrasonics, including thickness measurement, flaw detection, and material characterization.

This article reviews the corrosion behavior in various environments for seven important nickel alloy families: commercially pure nickel, Ni-Cu, Ni-Mo, Ni-Cr, Ni-Cr-Mo, Ni-Cr-Fe, and Ni-Fe-Cr. It examines the behavior of nickel alloys in corrosive media found in industrial settings. The corrosive media include: hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, hydrobromic acid, nitric acid, organic acids, salts, seawater, and alkalis. The modes of high-temperature corrosion include oxidation, carburization, metal dusting, sulfidation, nitridation, corrosion by halogens, and corrosion by molten salts. Applications where the corrosion properties of nickel alloys are important factors in materials selection include the petroleum, chemical, and electrical power industries. Most nickel alloys are much more resistant than the stainless steels to reducing acids, such as hydrochloric, and some are extremely resistant to the chloride-induced phenomena of pitting, crevice attack, and stress-corrosion cracking (to which the stainless steels are susceptible). Nickel alloys are also among the few metallic materials able to cope with hot hydrofluoric acid. The conditions where nickel alloys suffer environmentally assisted cracking are highly specific and therefore avoidable by proper design of the industrial components.

This article provides a detailed account of x-ray diffraction (XRD) residual-stress techniques. It begins by describing the principles of XRD stress measurement, followed by a discussion on the most common methods of XRD residual-stress measurement. Some of the procedures required for XRD residual-stress measurement are then presented. The article provides information on measurement of subsurface stress gradients and stress relaxation caused by layer removal. The article concludes with a section on examples of applications of XRD residual-stress measurement that are typical of industrial metallurgical, process development, and failure analysis investigations undertaken at Lambda Research.

Eddy-current inspection is based on the principles of electromagnetic induction and is used to identify or differentiate among a wide variety of physical, structural, and metallurgical conditions in electrically conductive ferromagnetic and nonferromagnetic metals and metal parts. This article discusses the advantages and limitations of eddy-current inspection, as well as the development of the eddy-current inspection process. It reviews the principal operating variables encountered in eddy-current inspection: coil impedance, electrical conductivity, magnetic permeability, lift-off and fill factors, edge effect, and skin effect. The article illustrates some of the principal impedance concepts that are fundamental to understanding of and effective application of eddy-current inspection. It discusses various types of eddy-current instruments, such as the resistor and single-coil system, bridge unbalance system, induction bridge system, and through transmission system. The article concludes with a discussion on the inspection of aircraft structural and engine components.

X-ray diffraction (XRD) residual-stress analysis is an essential tool for failure analysis. This article focuses primarily on what the analyst should know about applying XRD residual-stress measurement techniques to failure analysis. Discussions are extended to the description of ways in which XRD can be applied to the characterization of residual stresses in a component or assembly and to the subsequent evaluation of corrective actions that alter the residual-stress state of a component for the purposes of preventing, minimizing, or eradicating the contribution of residual stress to premature failures. The article presents a practical approach to sample selection and specimen preparation, measurement location selection, and measurement depth selection; measurement validation is outlined as well. A number of case studies and examples are cited. The article also briefly summarizes the theory of XRD analysis and describes advances in equipment capability.

This article discusses the characteristics, composition limits, and classification of wrought tool steels, namely high-speed steels, hot-work steels, cold-work steels, shock-resisting steels, low-alloy special-purpose steels, mold steels, water-hardening steels, powder metallurgy tool steels, and precision-cast tool steels. It describes the effects of surface treatments on the basic properties of tool steels, including hardness, resistance to wear, deformation, and toughness. The article provides information on fabrication characteristics of tool steels, including machinability, grindability, weldability, and hardenability, and presents a short note on machining allowances.

Nondestructive testing (NDT), also known as nondestructive evaluation (NDE), includes various techniques to characterize materials without damage. This article focuses on the typical NDE techniques that may be considered when conducting a failure investigation. The article begins with discussion about the concept of the probability of detection (POD), on which the statistical reliability of crack detection is based. The coverage includes the various methods of surface inspection, including visual-examination tools, scanning technology in dimensional metrology, and the common methods of detecting surface discontinuities by magnetic-particle inspection, liquid penetrant inspection, and eddy-current testing. The major NDE methods for internal (volumetric) inspection in failure analysis also are described.

This article aims to identify and illustrate the types of overload failures, which are categorized as failures due to insufficient material strength and underdesign, failures due to stress concentration and material defects, and failures due to material alteration. It describes the general aspects of fracture modes and mechanisms. The article briefly reviews some mechanistic aspects of ductile and brittle crack propagation, including discussion on mixed-mode cracking. Factors associated with overload failures are discussed, and, where appropriate, preventive steps for reducing the likelihood of overload fractures are included. The article focuses primarily on the contribution of embrittlement to overload failure. The embrittling phenomena are described and differentiated by their causes, effects, and remedial methods, so that failure characteristics can be directly compared during practical failure investigation. The article describes the effects of mechanical loading on a part in service and provides information on laboratory fracture examination.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of AISI/SAE alloy steels (4xxx steels) and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the brittle fracture, ductile fracture, impact fracture, fatigue fracture surface, reversed torsional fatigue fracture, transgranular cleavage fracture, rotating bending fatigue, tension-overload fracture, torsion-overload fracture, slip band crack, crack growth and crack initiation, crack nucleation, microstructure, hydrogen embrittlement, sulfide stress-corrosion failure, stress-corrosion cracking, and hitch post shaft failure of these steels. The components considered in the article include tail-rotor drive-pinion shafts, pinion gears, outboard-motor crankshafts, bull gears, diesel engine bearing cap bolts, splined shafts, aircraft horizontal tail-actuator shafts, bucket elevators, aircraft propellers, helicopter bolts, air flasks, tie rod ball studs, and spiral gears.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of titanium alloys and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the fracture surface, fatigue crack growth, intergranular fracture, crack propagation, ductile overload fracture, dimpled rupture, microvoid coalescence, and quasi-cleavage fracture of these alloys.