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in Study on Failure Analyses and Material Characterizations of a Damaged Booster Pump
> Handbook of Case Histories in Failure Analysis
Published: 01 December 2019
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001365
EISBN: 978-1-62708-215-0
.... The chlorine (chloride) increases the pitting potential within the pre-existing shrinkage cavities. The copper and nickel are possible indicators of corrosion in water circuit heat exchangers. Fig. 10 Typical results of in situ EDS analyses at the base of shrinkage voids in the impeller Mechanical...
Abstract
An investigation was conducted to determine the cause of numerous cracks and other defects on the surface of a cast ASTM A743 grade CA-15 stainless steel main boiler feed pump impeller. The surface was examined using a stereomicroscope, and macrofractography was conducted on several cross sections removed from the impeller body. Areas that appeared to have the most severe surface damage were sectioned, fractured open, and examined using SEM. The chemistry of the impeller and an apparent repair weld were also analyzed. The examination indicated that the cracks were shrinkage voids from the original casting process. Surface repair welds had been used to fill in or cover over larger shrinkage cavities. It was recommended that more stringent visual and nondestructive examination criteria be established for the castings.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001083
EISBN: 978-1-62708-214-3
... Abstract Copper alloy (C83600) impellers from two different feed pumps that supplied water to a 2-year-old boiler failed repeatedly. Examination by various methods indicated that the failures were caused by sulfide attack that concentrated in shrinkage voids in the castings. Two alternatives...
Abstract
Copper alloy (C83600) impellers from two different feed pumps that supplied water to a 2-year-old boiler failed repeatedly. Examination by various methods indicated that the failures were caused by sulfide attack that concentrated in shrinkage voids in the castings. Two alternatives to prevent future failures were recommended: changing the impeller composition to a cast stainless steel, or implementing stricter nondestructive evaluation requirements for copper alloy castings.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006760
EISBN: 978-1-62708-295-2
.... Some examples are ISO 6157, BPS-F-69, SAE 123, NAS 496, and ASTM F 788. Gas Porosity Gas porosity is indicated by rounded voids caused by precipitation of gas bubbles in molten material during casting ( Fig. 30 ). Fig. 30 Aluminum casting exhibiting gas porosity Shrinkage Porosity...
Abstract
Visual examination, using the unaided eye or a low-power optical magnifier, is typically one of the first steps in a failure investigation. This article presents the guidelines for selecting samples for scanning electron microscope examination and optical metallography and for cleaning fracture surfaces. It discusses damage characterization of metals, covering various factors that influence the damage, namely stress, aggressive environment, temperature, and discontinuities.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001779
EISBN: 978-1-62708-241-9
... the dominant failure mechanisms and that the materials and processes used to make the pumps were largely unsuited for the application. pump casing cavitation wear erosion steel shrinkage pits and voids scanning electron microscopy cavitation resistance C30 (low-carbon steel alloy) UNS G10300...
Abstract
Material samples collected from failed booster pumps were analyzed to determine the cause of failure and assess the adequacy of the materials used in the design. The pumps had been in service at a power plant, transporting feedwater from a deaerator to a main turbine boiler. Samples from critical areas of the pump were examined using optical and scanning electron microscopy, electrochemical analysis, and tensile testing. Based on microstructure and morphology, estimated corrosion rates, and particle concentrations in the feedwater, it was concluded that cavitation and erosion were the dominant failure mechanisms and that the materials and processes used to make the pumps were largely unsuited for the application.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.steel.c9001598
EISBN: 978-1-62708-232-7
.... In addition, the use of grain stabilized Pt/Rh alloy should be evaluated as a method to prevent grain growth. Wall thinning 80Pt-20Rh Pitting corrosion Creep fracture/stress rupture Background Americium and Curium (Am-Cm) were recovered in one of the Savannah River Site's (SRS) two chemical...
Abstract
The metallurgical condition of a cylindrical induction melter (CIM) vessel was evaluated after approximately 375 h of operation over a two-year span at temperatures between 1400 to 1500 deg C. Wall thinning and significant grain growth was observed in the lower portion of the conical section and the drain tube. No through-wall penetrations were found in the cylindrical and conical sections of the CIM vessel and only one leak site was identified in the drain tube. Failure of the drain tube was associated with localized overheating and creep. The observed degradation resulted from cumulative service at elevated temperature. A recommendation was made to implement a support for the conical section of the CIM and to increase the wall thickness of the drain tube. Thus, the possibility of drain tube misalignment in the induction coils and localized over heating will be minimized. In addition, the use of grain stabilized Pt/Rh alloy should be evaluated as a method to prevent grain growth.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c9001712
EISBN: 978-1-62708-234-1
... I.D. oxidation up to 3 mm, stemming from shrinkage porosity heavily spherodized, grey, primary carbonitrides O.D. surface decarburization with oxidation - 1 mm thick non-aligned creep voids throughout 1C similar to above 1F primary carbonitrides less heavily...
Abstract
A failure analysis was conducted in late 1996 on two rolls that had been used in the production of iron and steel powder. The rolls had elongated over their length such that the roll trunnions had impacted with the furnace wall refractory. The result was distortion and bowing of the roll bodies which necessitated their removal from service. The initial analysis found large quantities of nitrogen had been absorbed by the roll shell. Further research indicated nitrogen pickup accounted for 3% volumetric growth for every 1% by weight nitrogen absorption. This expansion was sufficient to account for the dimensional change observed in the failed rolls. This paper details the failure analysis and resulting research it inspired. It also provides recommendations for cast material choice in highly nitriding atmospheres.
Book Chapter
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003508
EISBN: 978-1-62708-180-1
... in the form of cracks, appearing on the faces or along edges, generally only after machining Dispersed shrinkage B 200: Cavities with generally rough walls, shrinkage B 210: Open cavity of Class B 200, sometimes penetrating deeply into the casting B 211 (a) Open, funnel-shaped cavity...
Abstract
This article focuses on the general root causes of failure attributed to the casting process, casting material, and design with examples. The casting processes discussed include gravity die casting, pressure die casting, semisolid casting, squeeze casting, and centrifugal casting. Cast iron, gray cast iron, malleable irons, ductile iron, low-alloy steel castings, austenitic steels, corrosion-resistant castings, and cast aluminum alloys are the materials discussed. The article describes the general types of discontinuities or imperfections for traditional casting with sand molds. It presents the international classification of common casting defects in a tabular form.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001396
EISBN: 978-1-62708-229-7
...-form and corrosion will develop. In addition to being present as a surface film, magnetite in a soft powdery form is frequently found in boiler tubes as a corrosion product of iron and as such is often present in the pits and scabs which arise from normal corrosion, differential aeration corrosion...
Abstract
The phenomenon of on-load corrosion is directly associated with the production of magnetite on the water-side surface of boiler tubes. On-load corrosion may first be manifested by the sudden, violent rupture of a boiler tube, such failures being found to occur predominantly on the fire-side surface of tubes situated in zones exposed to radiant heat where high rates of heat transfer pertain. In most instances, a large number of adjacent tubes are found to have suffered, the affected zone frequently extending in a horizontal band across the boiler. In some instances, pronounced local attack has taken place at butt welds in water-wall tubes, particularly those situated in zones of high heat flux. To prevent on-load corrosion an adequate flow of water must occur within the tubes in the susceptible regions of a boiler. Corrosion products and suspended matter from the pre-boiler equipment should be prevented from entering the boiler itself. Also, it is good practice to reduce as far as possible the intrusion of weld flash and other impedances to smooth flow within the boiler tubes.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.9781627083294
EISBN: 978-1-62708-329-4
Book Chapter
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003507
EISBN: 978-1-62708-180-1
... 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...
Abstract
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.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006835
EISBN: 978-1-62708-329-4
... also occur. Subsurface flaws often (but not always) originate from the as-cast ingot due to shrinkage, voids, and porosity that form during solidification. Figure 1 illustrates how rolled bar may contain porosity and pipe imperfections carried over from the cast ingot. These imperfections can serve...
Abstract
The primary purpose of this article is to describe general root causes of failure that are associated with wrought metals and metalworking. This includes a brief review of the discontinuities or imperfections that may be common sources of failure-inducing defects in the bulk working of wrought products. The article addresses the types of flaws or defects that can be introduced during the steel forging process itself, including defects originating in the ingot-casting process. Defects found in nonferrous forgings—titanium, aluminum, and copper and copper alloys—also are covered.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006775
EISBN: 978-1-62708-295-2
... nucleation and propagation. In cast alloys, the presence of both microscale interdendritic porosity and macroscale shrinkage cavities provide “holes” for crack nucleation. There is little difference in void growth from shrinkage porosity and a hole containing an unbonded inclusion. The incipient crack...
Abstract
This article focuses on characterizing the fracture-surface appearance at the microscale and contains some discussion on both crack nucleation and propagation mechanisms that cause the fracture appearance. It begins with a discussion on microscale models and mechanisms for deformation and fracture. Next, the mechanisms of void nucleation and void coalescence are briefly described. Macroscale and microscale appearances of ductile and brittle fracture are then discussed for various specimen geometries (smooth cylindrical and prismatic) and loading conditions (e.g., tension compression, bending, torsion). Finally, the factors influencing the appearance of a fracture surface and various imperfections or stress raisers are described, followed by a root-cause failure analysis case history to illustrate some of these fractography concepts.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003538
EISBN: 978-1-62708-180-1
... and macroscale shrinkage cavities provide “holes” for crack nucleation. There is little difference in void growth from shrinkage porosity and a hole containing an unbonded inclusion. The incipient crack can form in four ways: Hole formation around an often weakly bonded particle Cracking...
Abstract
This article provides a description of the microscale models and mechanisms for deformation and fracture. Macroscale and microscale appearances of ductile and brittle fracture are discussed for various specimen geometries and loading conditions. The article reviews the general geometric factors and materials aspects that influence the stress-strain behavior and fracture of ductile metals. It highlights fractures arising from manufacturing imperfections and stress raisers. The article presents a root cause failure analysis case history to illustrate some of the fractography concepts.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006765
EISBN: 978-1-62708-295-2
... by the etchant. Coarse grinding scratches must be removed; even very fine polishing scratches may not be tolerable in examining failed parts. Pullout, pitting, cracking of hard particles, smear, and other preparation artifacts must be avoided. Relief (i.e., excessive surface-height variations between...
Abstract
Metallographic examination is one of the most important procedures used by metallurgists in failure analysis. Typically, the light microscope (LM) is used to assess the nature of the material microstructure and its influence on the failure mechanism. Microstructural examination can be performed with the scanning electron microscope (SEM) over the same magnification range as the LM, but examination with the latter is more efficient. This article describes the major operations in the preparation of metallographic specimens, namely sectioning, mounting, grinding, polishing, and etching. The influence of microstructures on the failure of a material is discussed and examples of such work are given to illustrate the value of light microscopy. In addition, information on heat-treatment-related failures, fabrication-/machining-related failures, and service failures is provided, with examples created using light microscopy.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003532
EISBN: 978-1-62708-180-1
... grinding scratches must be removed; even very fine polishing scratches may not be tolerable in examining failed parts. Pullout, pitting, cracking of hard particles, smear, and other preparation artifacts must be avoided. Relief (i.e., excessive surface-height variations between structural features...
Abstract
This article provides a discussion on the metallographic techniques used for failure analysis, and on fracture examination in materials, with illustrations. It discusses various metallographic specimen preparation techniques, namely, sectioning, mounting, grinding, polishing, and electrolytic polishing. The article also describes the microstructure examination of various materials, with emphasis on failure analysis, and concludes with information on the examination of replicas with light microscopy.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006831
EISBN: 978-1-62708-329-4
... porosity (cavities) at the casting surface, appearing over more or less extended areas Surface pinholes B 124 (a) Small, narrow cavities in the form of cracks, appearing on the faces or along edges, generally only after machining Dispersed shrinkage B 200 Cavities with generally rough...
Abstract
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.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006825
EISBN: 978-1-62708-329-4
..., flakes, shrinkage cavities, laminations, and other similar discontinuities that produce reflective interfaces. X-ray or gamma-ray radiography is used to identify defects in the weld joints as well as to assess the overall soundness of the component/part. Mechanical Testing The mechanical...
Abstract
Failures in boilers and other equipment taking place in power plants that use steam as the working fluid are discussed in this article. The discussion is mainly concerned with failures in Rankine cycle systems that use fossil fuels as the primary heat source. The general procedure and techniques followed in failure investigation of boilers and related equipment are discussed. The article is framed with an objective to provide systematic information on various damage mechanisms leading to the failure of boiler tubes, headers, and drums, supplemented by representative case studies for a greater understanding of the respective damage mechanism.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0001817
EISBN: 978-1-62708-180-1
... of corrosion products or metal surfaces. For example, silver nitrate tests may be performed on residues clinging to a pitted stainless steel surface to confirm the presence of chloride ions—a common cause of pitting. Wet chemical methods are often supplemented by the use of x-ray diffraction or electron probe...
Abstract
This article describes the characteristics of tubing of heat exchangers with respect to general corrosion, stress-corrosion cracking, selective leaching, and oxygen-cell attack, with examples. It illustrates the examination of failed parts of heat exchangers by using sample selection, visual examination, microscopic examination, chemical analysis, and mechanical tests. The article explains corrosion fatigue of tubing of heat exchangers caused by aggressive environment and cyclic stress. It also discusses the effects of design, welding practices, and elevated temperatures on the failures of heat exchangers.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.marine.c9001657
EISBN: 978-1-62708-227-3
.... The vane had developed a well defined crack in the airfoil section, Figure 2 . The airfoil had also suffered a considerable amount of erosion along the leading edge area and general pitting of the concave surface. At the time of the vane removal, the engine (no. 2) had logged 5500 h of running time...
Abstract
The circumstances surrounding the in-service failure of a cast Ni-base superalloy (Alloy 713LC) second stage turbine blade and a cast and coated Co-base superalloy (MAR-M302) first stage air-cooled vane in two turbine engines used for marine application are described. An overview of a systematic approach, analyzing the nature of degeneration and failure of the failed components, utilizing conventional metallurgical techniques, is presented. The topographical features of the turbine blade fracture surface revealed a fatigue-induced crack growth pattern, where crack initiation had taken place in the blade trailing edge. An estimate of the crack-growth rate for the stage II fatigue fracture region coupled with the metallographic results helped to identify the final mode of the turbine blade failure. A detailed metallographic and fractographic examination of the air-cooled vane revealed that coating erosion in conjunction with severe hot-corrosion was responsible for crack initiation in the leading edge area.
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