A section of type 304 stainless steel pipe from a stand by system used for emergency injection of cooling water to a nuclear reactor failed during precommissioning. Leaking occurred in only one spot. Liquid penetrant testing revealed a narrow circumferential crack. Metallographic examination of the cracked area indicated stress-corrosion cracking, which had originated at rusted areas that had formed on longitudinal scratch marks on the outer surface of the pipe. The material was free from sensitization, and there was no significant amount of cold work. It was recommended that the stainless steel be kept rust free.

Several hundred leaks were reported in the type 304 stainless steel pipelines, vessels, and tanks of a chemical plant at a tropical location within a few weeks after startup. Investigation of the failure involved a site visit, metallographic examination and analysis of the material, analysis of hydrotest waters, and microbiological examination of slime that had formed in certain pipework sections. It was determined that the failure resulted from microbially induced corrosion promoted by the use of poor-quality hydrotest water and uncontrolled hydrotesting practice. Use of appropriate hydrotesting procedures was recommended to prevent similar failures.

Corrosive wear is defined as surface damage caused by wear in a corrosive environment, involving combined attacks from wear and corrosion. This article begins with a discussion on several typical forms of corrosive wear encountered in industry, followed by a discussion on mechanisms for corrosive wear. Next, the article explains testing methods and characterization of corrosive wear. Various factors that influence corrosive wear are then covered. The article concludes with general guidelines for material selection against corrosive wear.

This paper summarizes several cases of metallurgical failure analysis of surgical implants conducted at the Laboratory of Failure Analysis of IPT, in Brazil. Investigation revealed that most of the samples were not in accordance with ISO standards and presented evidence of corrosion assisted fracture. Additionally, some components were found to contain fabrication/processing defects that contributed to premature failure. The implant of nonbiocompatible materials results in immeasurable damage to patients as well as losses for the public investment. It is proposed that local sanitary regulation agencies create mechanisms to avoid commercialization of surgical implants that are not in accordance with standards and adopt the practice of retrieval analysis of failed implants. This would protect the public health by identifying and preventing the main causes of failure in surgical implants.

This investigation characterizes five surgical stainless steel piercings and one niobium piercing that caused adverse reactions during use, culminating with the removal of the jewelry. Chemical composition shows that none of the materials are in accordance with ISO standards for surgical implant materials. Additionally, none of the stainless steel piercings passed the pitting-resistance criterion of ISO 5832-1, which implies that [%Cr + 3.3(%Mo)] > 26. Under microscopic examination, most of the jewelry revealed the intense presence of linear irregularities on the surface. The lack of resistance to pitting corrosion associated with the poor surface finishing of the stainless steel jewelry may induce localized corrosion, promoting the release of cytotoxic metallic ions (such as Cr, Ni, and Mo) in the local tissue, which can promote several types of adverse effects in the human body, including allergic reactions. The adverse reaction to the niobium jewelry could not be directly associated with the liberation of niobium ions or the residual presence of cytotoxic elements such as Co, Ni, Mo, and Cr. The poor surface finish of the niobium jewelry seems to be the only variable of the material that may promote adverse reactions.

This article briefly reviews the factors that influence the occurrence of intergranular (IG) fractures. Because the appearance of IG fractures is often very similar, the principal focus is placed on the various metallurgical or environmental factors that cause grain boundaries to become the preferred path of crack growth. The article describes in more detail some typical mechanisms that cause IG fracture. It discusses the causes and effects of IG brittle cracking, dimpled IG fracture, IG fatigue, hydrogen embrittlement, and IG stress-corrosion cracking. The article presents a case history on IG fracture of steam generator tubes, where a lowering of the operating temperature was proposed to reduce failures.

Several cases of embrittlement failure are analyzed, including liquid-metal embrittlement (LME) of an aluminum alloy pipe in a natural gas plant, solid metal-induced embrittlement (SMIE) of a brass valve in an aircraft engine oil cooler, LME of a cadmium-plated steel screw from a crashed helicopter, and LME of a steel gear by a copper alloy from an overheated bearing. The case histories illustrate how LME and SMIE failures can be diagnosed and distinguished from other failure modes, and shed light on the underlying causes of failure and how they might be prevented. The application of LME as a failure analysis tool is also discussed.

This article briefly reviews the various metallurgical or environmental factors that cause a weakening of the grain boundaries and, in turn, influence the occurrence of intergranular (IG) fractures. It discusses the mechanisms of IG fractures, including the dimpled IG fracture, the IG brittle fracture, and the IG fatigue fracture. The article describes some typical embrittlement mechanisms that cause the IG fracture of steels.

Mechanical springs are used in mechanical components to exert force, provide flexibility, and absorb or store energy. This article provides an overview of the operating conditions of mechanical springs. Common failure mechanisms and processes involved in the examination of spring failures are also discussed. In addition, the article discusses common causes of failures and presents examples of specific spring failures, describes fatigue failures that resulted from these types of material defects, and demonstrates how improper fabrication can result in premature fatigue failure. It also covers failures of shape memory alloy springs and failures caused by corrosion and operating conditions.

This article focuses on the mechanisms of microbially induced or influenced corrosion (MIC) of metallic materials as an introduction to the recognition, management, and prevention of microbiological corrosion failures in piping, tanks, heat exchangers, and cooling towers. It discusses the degradation of various protective systems, such as corrosion inhibitors and lubricants. The article describes the failure analysis of steel, iron, copper, aluminum, and their alloys. It also discusses the probes available to monitor conditions relevant to MIC in industrial systems and the sampling and analysis of conditions usually achieved by the installation of removable coupons in the target system. The article also explains the prevention and control strategies of MIC in industrial systems.

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 focuses on the mechanisms of microbiologically influenced corrosion as a basis for discussion on the diagnosis, management, and prevention of biological corrosion failures in piping, tanks, heat exchangers, and cooling towers. It begins with an overview of the scope of microbial activity and the corrosion process. Then, various mechanisms that influence corrosion in microorganisms are discussed. The focus is on the incremental activities needed to assess the role played by microorganisms, if any, in the overall scenario. The article presents a case study that illustrates opportunities to improve operating processes and procedures related to the management of system integrity. Industry experience with corrosion-resistant alloys of steel, copper, and aluminum is reviewed. The article ends with a discussion on monitoring and preventing microbiologically influenced corrosion failures.

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.

Bearing in mind the three-legged stool approach of device design/manufacturing, patient factors, and surgical technique, this article aims to inform the failure analyst of the metallurgical and materials engineering aspects of a medical device failure investigation. It focuses on the device "failures" that include fracture, wear, and corrosion. The article first discusses failure modes of long-term orthopedic and cardiovascular implants. The article then focuses on short-term implants, typically bone screws and plates. Lastly, failure modes of surgical tools are discussed. The conclusion of this article presents several case studies illustrating the various failure modes discussed throughout.

This article describes some of the welding discontinuities and flaws characterized by nondestructive examinations. It focuses on nondestructive inspection methods used in the welding industry. The sources of weld discontinuities and defects as they relate to service failures or rejection in new construction inspection are also discussed. The article discusses the types of base metal cracks and metallurgical weld cracking. The article discusses the processes involved in the analysis of in-service weld failures. It briefly reviews the general types of process-related discontinuities of arc welds. Mechanical and environmental failure origins related to other types of welding processes are also described. The article explains the cause and effects of process-related discontinuities including weld porosity, inclusions, incomplete fusion, and incomplete penetration. Different fitness-for-service assessment methodologies for calculating allowable or critical flaw sizes are also discussed.