Two diesel engine crankshafts of similar dimensions, the journal diam being approximately 7 in., failed due to cracking originating in the fillet at the junction between the crankpin and the web nearest to the flywheel. The cracks were discovered before rupture occurred. Several small cracks originated in the fillet, ran together and developed as two main crack fronts that ultimately merged into one, a typical example of a fatigue failure. Electromagnetic crack detection revealed the presence of a number of discontinuities which were located at a position that would correspond to the vertical axis of the original ingot. The crankshaft had not been stress-relieved after a welding operation had been carried out. The only satisfactory course to follow when dealing with a highly stressed part in which defects of the type in question are revealed during machining is to scrap the forging.

The causes of cracking of an as-drawn 90-10 cupronickel tube during mechanical working were investigated to determine the source of embrittlement. Embrittlement was sporadic, but when present was typically noted after the first process anneal. Microstructural and chemical analyses were performed on an embrittled section and on a section from a different lot that did not crack during forming. The failed section showed an intergranular fracture path. Examination of the fracture surfaces revealed the presence of tellurium at the grain boundaries. The source of the tellurium was thought to be contamination occurring in the casting process that became concentrated in the recycled skimmings. It was recommended that future material specifications for skimmings and for externally obtained scrap copper include a trace analysis for tellurium.

Three radiant heating element tubes from an aluminum holding furnace failed after a few months of service. One side of each of the tubes had disintegrated, leaving large holes and thinned cross sections. Microstructural analysis showed that the surface of the tube had been oxidized along the grain boundaries and had extensive precipitation inside the grains. Chemical analysis indicated that the steel used for the tubes was AISI type 316 stainless steel Specifications for the tubes had called for AISI type 310S to be used. It was recommended that other tubes made from the same batch of steel sheet be checked.

This article provides an overview of metal additive manufacturing (AM) processes and describes sources of failures in metal AM parts. It focuses on metal AM product failures and potential solutions related to design considerations, metallurgical characteristics, production considerations, and quality assurance. The emphasis is on the design and metallurgical aspects for the two main types of metal AM processes: powder-bed fusion (PBF) and directed-energy deposition (DED). The article also describes the processes involved in binder jet sintering, provides information on the design and fabrication sources of failure, addresses the key factors in production and quality control, and explains failure analysis of AM parts.

Suspension lugs fabricated from AISI 4340 steel used to facilitate loading of bombs onto the underside of military aircraft could not sustain required loads during routine proof load testing. Three failed lugs underwent visual examination, chemical analysis, metallography, hardness testing, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. It was determined that the failures were due to forging defects. Both forging laps and seams acted as stress concentrators when the lugs were loaded during proof testing.

The information provided in this article is intended for those individuals who want to determine why a casting component failed to perform its intended purpose. It is also intended to provide insights for potential casting applications so that the likelihood of failure to perform the intended function is decreased. The article addresses factors that may cause failures in castings for each metal type, starting with gray iron and progressing to ductile iron, steel, aluminum, and copper-base alloys. It describes the general root causes of failure attributed to the casting material, production method, and/or design. The article also addresses conditions related to the casting process but not specific to any metal group, including misruns, pour shorts, broken cores, and foundry expertise. The discussion in each casting metal group includes factors concerning defects that can occur specific to the metal group and progress from melting to solidification, casting processing, and finally how the removal of the mold material can affect performance.

An oil scavenge pump was found to have failed when a protective shear neck fractured during the start of a jet engine. Visual inspection revealed that the driven gear in one of the bearing compartments was frozen as was the corresponding drive gear. Spacer wear and thermal discoloration (particularly on the driven gear) were also observed. The gears were made from 32Cr-Mo-V13 steel, hardened and nitrided to 750 to 950 HV. Micrographic inspection of the gear teeth revealed microstructural changes that, in context, appear to be the result of friction heating. The spacers consist of Cu alloy (AMS4845) bushings force fit into AA2024-T3 Al alloy spacing elements. It was found that uncontrolled fit interference between the two components had led to Cu alloy overstress. Thermal cycling under operating conditions yielded the material. The dilation was directed inward to the shaft, however, because the bushing had only a few microns of clearance. The effect caused the oil to squeeze out, resulting in metal-to-metal contact, and ultimately failure.

Work rolls made of indefinite chill double-poured (ICDP) iron are commonly used in the finishing trains of hot-strip mills (HSMs). In actual service, spalling, apart from other surface degeneration modes, constitutes a major mechanism of premature roll failures. Although spalling can be a culmination of roll material quality and/or mill abuse, the microstructure of a broken roll can often unveil intrinsic inadequacies in roll material quality that possibly accentuate failure. This is particularly relevant in circumstances when rolls, despite operation under similar mill environment, exhibit variations in roll life. The paper provides an insight into the microstructural characteristics of spalled ICED HSM work rolls, which underwent failure under similar mill operating environment in an integrated steel plant under the Steel Authority of India Limited. Microstructural features influencing ICDP roll quality, viz. characteristics of graphite, carbides, martensite, etc., have been extensively studied through optical microscopy, quantitative image analysis (QIA), and electron-probe microanalysis (EPMA). These are discussed in the context of spalling propensity and roll life.

Cracking was discovered in an in-service, second-stage turbine impeller during a downtime inspection. The fabricated 4300 series low-alloy steel impeller was used in a compressor in an industrial petrochemical plant. It was also reported that a process upset had allowed a 10% NaOH solution to be ingested by the unit. Routine magnetic particle inspection revealed numerous cracks in the hub area and vane tips of the second-stage impeller Additionally, the outside surface of the backing plate showed a cyclic pattern of cracks. An overview of a conventional, systematic metallurgical approach to failure analysis to confirm that the cracking was caused by a caustic stress-corrosion cracking mechanism is presented.

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.

Materials selection is closely related to the objectives of failure analysis and prevention. This article briefly reviews the general aspects of materials selection as a concern in both proactive failure prevention during design and as a possible root cause of failed parts. Coverage is more conceptual, with general discussions on the following topics: design and failure prevention, materials selection in design, materials selection for failure prevention, and materials selection and failure analysis. Because materials selection is just one part of the design process, the overall concept of design is discussed. The article also describes the role of the materials engineer in the design and materials selection process. It provides information on the significance of materials selection in both the prevention and analysis of failures.

Stainless steel pipe (273-mm OD x 8-mm wall thickness) used in the fabrication of large manifolds developed crack-like decohesions during a routine inductive bending procedure. The imperfections, which were found near the outside diameter, were around 3 mm in length oriented in the circumferential direction and penetrated nearly 2 mm into the pipe wall. The pipes were made of titanium-stabilized austenitic stainless steel X6CrNiMoTi17-12-2. Six hypotheses were considered during the investigation, which ultimately concluded that the failure was caused by liquation cracking due to overheating.

Materials selection is an important engineering function in both the design and failure analysis of components. This article briefly reviews the general aspects of materials selection as a concern in proactive failure prevention during design and as a possible root cause of failed parts. It discusses the overall concept of design and describes the role of the materials engineer in the design and materials selection process. The article highlights the significance of materials selection in both the prevention and analysis of failures.

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.

Metallographic studies found that steel used to fabricate the U.S.S. Arizona battleship during original construction, 1913-1915 and reconstruction, 1929-1931 were consistent with the best materials available during each time period. Due to the force of the forward magazine detonation, the best steel available today would not have had any impact on the outcome. Heavy banding in steels from both periods could adversely affect the corrosion resistance under anaerobic conditions that prevail during a corrosion cycle that has developed under hard biofouling layers for over 58 years. Banding would have no effect on corrosion rate under aerobic conditions that may occur in local areas on the hull. In the part of the ship from which samples for this report were obtained, high temperatures above 1340 deg F did not occur. Hull plate samples from the submerged wreckage are not yet available. These samples will be important to confirm findings to this time and determine the remaining thickness of the hull plate and, indirectly, the integrity of the fuel oil tanks.

This article provides an overview of the classification of hydrogen damage. Some specific types of the damage are hydrogen embrittlement, hydrogen-induced blistering, cracking from precipitation of internal hydrogen, hydrogen attack, and cracking from hydride formation. The article focuses on the types of hydrogen embrittlement that occur in all the major commercial metal and alloy systems, including stainless steels, nickel-base alloys, aluminum and aluminum alloys, titanium and titanium alloys, copper and copper alloys, and transition and refractory metals. The specific types of hydrogen embrittlement discussed include internal reversible hydrogen embrittlement, hydrogen environment embrittlement, and hydrogen reaction embrittlement. The article describes preservice and early-service fractures of commodity-grade steel components suspected of hydrogen embrittlement. Some prevention strategies for design and manufacturing problem-induced hydrogen embrittlement are also reviewed.

Hydrogen damage is a term used to designate a number of processes in metals by which the load-carrying capacity of the metal is reduced due to the presence of hydrogen. This article introduces the general forms of hydrogen damage and provides an overview of the different types of hydrogen damage in all the major commercial alloy systems. It covers the broader topic of hydrogen damage, which can be quite complex and technical in nature. The article focuses on failure analysis where hydrogen embrittlement of a steel component is suspected. It provides practical advice for the failure analysis practitioner or for someone who is contemplating procurement of a cost-effective failure analysis of commodity-grade components suspected of hydrogen embrittlement. Some prevention strategies for design and manufacturing problem-induced hydrogen embrittlement are also provided.

This article describes the general root causes of failure associated with wrought metals and metalworking. This includes a brief review of the discontinuities or imperfections that may be the common sources of failure-inducing defects in bulk working of wrought products. The article discusses the types of imperfections that can be traced to the original ingot product. These include chemical segregation; ingot pipe, porosity, and centerline shrinkage; high hydrogen content; nonmetallic inclusions; unmelted electrodes and shelf; and cracks, laminations, seams, pits, blisters, and scabs. The article provides a discussion on the imperfections found in steel forgings. The problems encountered in sheet metal forming are also discussed. The article concludes with information on the causes of failure in cold formed parts.

This article presents the benefits of selecting plastics for products to be manufactured. It discusses the four key considerations for plastic part design: material, process, tooling, and design. The article provides a detailed discussion of the development sequence for plastic parts. The basis for the development sequence is twofold: first, to create the best solution for the application, and second, to minimize potential project risks through careful and thoughtful work habits.