An HK-40 alloy tubing weld in a reformer furnace of a petrochemical plant failed by leaking after a shorter time than that predicted by design specifications. Leaking occurred because of cracks that passed through the thickness of the weldment. Analysis of the cracked tubing indicated that the sulfur and phosphorus contents of the weld metal were higher than specified, the thickness was narrower at the weld, and the mechanical resistance of the weld metal was lower than specified. Cracking initiated at the weld root by coalescence of creep cavities. Propagation and expansion was aided by internal carburization. Quality control of welding procedures and filler metal was recommended.

In a HyL III heat exchanger's radiant pipes, metal dusting reduced the pipe thickness from 8.5 to 3 mm in just nine months, leaving craters on the inner surface. The pipes are fabricated from HK 40 alloy. The heated gas (400 to 800 deg C) consisted of CO, CO2, and H2, with a 4:1 CO/CO2 ratio. Metallographic investigations revealed that the surface of the attacked pipes consisted of (Cr, Fe) carbide. The metal dusting was the result of a decomposition process (CO to CO2 + C) that deposited C on the pipe surface. Because of the high temperature, the C subsequently diffused through the surface oxide layer (Cr2O3), triggering a succession of reactions that led to pitting and the formation of craters.

Two steam-methane reformer furnaces were subjected to short-time heat excursions because of a power outage, which resulted in creep bulging in the Incoloy 800 outlet pigtails, requiring complete replacement. Each furnace had three cells, consisting of 112 vertical tubes per cell, each filled with a nickel catalyst. The tubes were centrifugally cast from ASTM A297, grade HK-40 (Fe-25Cr-20Ni-0.40C), heat-resistant alloy. The tube was concluded after metallurgical inspection to have failed from creep rupture (i.e., stress rupture). A project for detecting midwall creep fissuring was instigated as a result of the failure. It was concluded after laboratory radiography and macroexamination that if the fissure were large enough to show on a radiograph, either with or without the catalyst, the tube could be expected to fail within one year. The set up for in-service radiograph examination was described. The tubes of the furnace were radiographed during shut down and twenty-four tubes in the first furnace and 53 in the second furnace showed significant fissuring. Although, radiography was concluded to be a practical technique to provide advance information, it was limited to detecting fissures caused by third-stage creep in tubes because of the cost involved in removing the catalysts.

A sample tube was removed from a reformer furnace for life assessment after 69,000 h of service. Sections were cut from the tube, which was a spindle cast A297 Grade HK 40 (25 Cr, 20 Ni, 0.4 C) austenitic steel of 122.5 mm OD and 10.5 mm nominal wall thickness. They were examined metallographically on transverse sections and on longitudinal sections through the butt welds joining the separate cast segments of the tube. Creep damage was mainly concentrated within the inner one third of the wall thickness. The use of damage assessment parameters in evaluating the reformer tube remaining life showed the welds to be inadequate, and to have a strength and creep resistance below those of the base metal.

A pair of steam generators operating at a pressurized water reactor site were found to be leaking near a closure weld. The generators were the vertical U-tube type, constructed from ASTM A302 grade B steel. The shell material exhibited high hardness values prior to confirmatory heat treatment, indicating high residual stresses in the area of the weld. All cracks were transgranular and were associated with pits on the inside surfaces of the vessels. It was concluded that the cracking was caused by a low-cycle corrosion fatigue phenomenon, with cracks initiating at areas of localized corrosion and propagating by fatigue. The cause of the pitting/cracking was related to the unit's copper species in solution.

Important clues about the probable cause of a gun tube explosion were obtained from a fractographic and metallographic examination of the fragments. The size, distribution, and surface markings of fragments may be used to localize the explosion and deduce its intensity. Microstructural features such as voids, adiabatic shear, and structural surface alterations also indicate the explosion intensity and further allow a comparison of the tube structure near and away from the explosion zone. These, and other metallurgical characteristics, are illustrated and discussed for cases of accidental and deliberately caused explosions of large caliber gun tubes.

The failure of a reformer tube furnace manifold has been examined using metallography. It has been shown that the cause of failure was thermal fatigue; the damage was characterized by the presence of voids produced by creep mechanisms operating during the high temperature cycle under high local stress. The study indicates that standard metallographic procedures can be used to identify failure modes in high temperature petrochemical plants.

Various aluminum bronze valves and fittings on the essential cooling water system at a nuclear plant were found to be leaking. The leakage was limited to small-bore socket-welded components. Four specimens were examined: three castings (an ASME SB-148 CA 952 elbow from a small-bore fitting and two ASME SB-148 CA 954 valve bodies) and an entire valve assembly. The leaks were found to be in the socket-weld crevice area and had resulted from dealloying. It was recommended that the weld joint geometry be modified.

Because of the tough engineering environment of the railroad industry, fatigue is a primary mode of failure. The increased competitiveness in the industry has led to increased loads, reducing the safety factor with respect to fatigue life. Therefore, the existence of corrosion pitting and manufacturing defects has become more important. This article presents case histories that are intended as an overview of the unique types of failures encountered in the freight railroad industry. The discussion covers failures of axle journals, bearings, wheels, couplers, rails and rail welds, and track equipment.

High temperature corrosion may occur in numerous environments and is affected by factors such as temperature, alloy or protective coating composition, time, and gas composition. This article explains a number of potential degradation processes, namely, oxidation, carburization and metal dusting, sulfidation, hot corrosion, chloridation, hydrogen interactions, molten metals, molten salts, and aging reactions including sensitization, stress-corrosion cracking, and corrosion fatigue. It concludes with a discussion on various protective coatings, such as aluminide coatings, overlay coatings, thermal barrier coatings, and ceramic coatings.

This article discusses the effect of using unsuitable alloys, metallurgical discontinuities, fabrication practices, and stress raisers on the failure of a pressure vessel. It provides information on pressure vessels made of composite materials and their welding practices. The article explains the failure of pressure vessels with emphasis on stress-corrosion cracking, hydrogen embrittlement, brittle and ductile fractures, creep and stress rupture, and fatigue with examples.

This article describes the failure characteristics of high-pressure long-distance pipelines. It discusses the causes of pipeline failures and the procedures used to investigate them. The use of fracture mechanics in failure investigations and in developing remedial measures is also reviewed.

This article discusses pressure vessels, piping, and associated pressure-boundary items of the types used in nuclear and conventional power plants, refineries, and chemical-processing plants. It begins by explaining the necessity of conducting a failure analysis, followed by the objectives of a failure analysis. Then, the article discusses the processes involved in failure analysis, including codes and standards. Next, fabrication flaws that can develop into failures of in-service pressure vessels and piping are covered. This is followed by sections discussing in-service mechanical and metallurgical failures, environment-assisted cracking failures, and other damage mechanisms that induce cracking failures. Finally, the article provides information on inspection practices.

This article is dedicated to the fields of mechanical engineering and machine design. It also intends to give a nonexhaustive view of the preventive side of the failure analysis of rolling-element bearings (REBs) and of some of the developments in terms of materials and surface engineering. The article presents the nomenclature, numbering systems, and worldwide market of REBs as well as provides description of REBs as high-tech machine components. It discusses heat treatments, performance, and properties of bearing materials. The processes involved in the examination of failed bearings are also explained. Finally, the article discusses in detail the characteristics and prevention of the various types of failures of REBs: wear, fretting, corrosion, plastic flow, rolling-contact fatigue, and damage. The article includes an Appendix, which lists REB-related abbreviations, association websites, and ISO standards.

High-temperature corrosion can occur in numerous environments and is affected by various parameters such as temperature, alloy and protective coating compositions, stress, time, and gas composition. This article discusses the primary mechanisms of high-temperature corrosion, namely oxidation, carburization, metal dusting, nitridation, carbonitridation, sulfidation, and chloridation. Several other potential degradation processes, namely hot corrosion, hydrogen interactions, molten salts, aging, molten sand, erosion-corrosion, and environmental cracking, are discussed under boiler tube failures, molten salts for energy storage, and degradation and failures in gas turbines. The article describes the effects of environment on aero gas turbine engines and provides an overview of aging, diffusion, and interdiffusion phenomena. It also discusses the processes involved in high-temperature coatings that improve performance of superalloy.

Overload failures refer to the ductile or brittle fracture of a material when stresses exceed the load-bearing capacity of a material. This article reviews some mechanistic aspects of ductile and brittle crack propagation, including a discussion on mixed-mode cracking, which may also occur when an overload failure is caused by a combination of ductile and brittle cracking mechanisms. It describes the general aspects of fracture modes and mechanisms. The article discusses some of the material, mechanical, and environmental factors that may be involved in determining the root cause of an overload failure. It also presents examples of thermally and environmentally induced embrittlement effects that can alter the overload fracture behavior of metals.

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.