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Cássio Barbosa, Jôneo Lopes do Nascimento, José Luiz Fernandes, Ibrahim de Cerqueira Abud
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silicate and oxide inclusions
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Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.steel.c9001645
EISBN: 978-1-62708-232-7
... that the brittle oxides that formed stringers were alumina, and the other macroinclusions were complex silicates. Both the alumina and silicate inclusions were deleterious to contact-fatigue properties. Microstructurally, the carburized regions of the broken roller and of inner-race samples contained high-carbon...
Abstract
An extensive metallurgical investigation was carried out on samples of a failed roller bearing from the support and tilting system of a basic oxygen furnace converter used in the steel melting shop of an integrated steel plant. The converter bearing was fabricated from low-carbon, carburizing grade steel and had failed in service within a year of fitting to a repaired shaft. Microscopic observations of both the broken roller and inner-race samples revealed subsurface cracking and preponderance of brittle oxide and other macroinclusions. Electron probe microanalysis studies confirmed that the brittle oxides that formed stringers were alumina, and the other macroinclusions were complex silicates. Both the alumina and silicate inclusions were deleterious to contact-fatigue properties. Microstructurally, the carburized regions of the broken roller and of inner-race samples contained high-carbon tempered martensite. Microhardness measurements revealed that. Although the core hardness of the roller and the inner-race samples were similar, the surface hardness of the roller was approximately 8.5 HRC units harder than that of the inner-race. SEM observations of the roller fracture surface revealed striations indicative of fatigue, and EDS analyses corroborated a high incidence of silicate inclusions at crack sites. The study suggests that the failure of the bearing occurred because the hardness difference between the roller bearing and the inner-race surfaces resulted in wear of the inner-race. The wear led to shaft misalignment and play during service. The misalignment, coupled with the presence of inclusions, caused fatigue failure of the roller bearing.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.aero.c9001489
EISBN: 978-1-62708-217-4
... of the chemical composition obtained from (c) an inclusion and (d) the matrix. IV. Chemical Analysis of Inclusions The results of EDS in an STEM and gas chromatography quite conclusively showed that the inclusions were oxides, silicates, or aluminates. The information collected from the EDS analysis...
Abstract
The cause of the fatigue failure in the retaining ring of the compressor region of an aero-engine turbine was found to be the presence of a high concentration of nonmetallic inclusions. The results of chemical analysis were used to estimate the phases present. The most frequently observed inclusions were spinel solid solutions of the type MO middot; N2O3, where M = Fe, Mn, or Mg and N = Cr or Al. The detrimental inclusions were corundum, calcium aluminates, cristobalite, and silicates. The most detrimental phases were traced on the surfaces of the specimens fractured using impact loading; the comparison is being made with the polished surfaces and the tensile specimen fracture surfaces. The inclusions in the failed retaining ring were compared with the ones in a similar component obtained from a used engine. In the case of the latter, a large number of fine and elongated (Mn, Cr, Fe)S inclusions were present along with spinels. The nondeformable, rigid oxide particles are considered more undesirable than the sulfides as far as fatigue life of the component is concerned. It has been reported that the presence of sulfides may eliminate the stresses due to oxides.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.rail.c9001607
EISBN: 978-1-62708-231-0
... near the surface of individual wire strands in the rope. The inclusions were identified as Al-Ca-Ti silicates in a large number of stringers, and some oxide and nitride inclusions were also found. The wire used in the rope did not conform to the composition specified for AISI 316 grade steel, nor did...
Abstract
Wire ropes, pulleys, counterweights, and connecting systems are used for auto tensioning of contact wires of electric railways. A wire rope in one such auto tensioning system suffered premature failure. Failure investigation revealed fatigue cracks initiating at nonmetallic inclusions near the surface of individual wire strands in the rope. The inclusions were identified as Al-Ca-Ti silicates in a large number of stringers, and some oxide and nitride inclusions were also found. The wire used in the rope did not conform to the composition specified for AISI 316 grade steel, nor did it satisfy the minimum tensile strength requirements. Failure of the wire rope was found to be due to fatigue; however, the ultimate fracture of the rope was the result of overload that occurred after fatigue failure had reduced the number of wire strands supporting the load.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c0047118
EISBN: 978-1-62708-235-8
... primarily of aluminum oxide or silicates rich in aluminum oxide. Inclusions of this type could not be found in the interior of the cross section; only oxide and sulfide inclusions of normal size were found in the interior. Conclusions The inclusions consisted of pieces of fireclay from channel brick...
Abstract
An automobile manufacturer rejected several 1035 steel stub axles because of what appeared to be short longitudinal cracks in the surfaces of the pins. The cracks were found when six axles were examined for defects by magnetic-particle inspection. However, metallographic examination showed that these lines were not cracks but slag inclusions at and immediately below the surface. Analysis (visual inspection, metallographic examination, and 100x/500x magnetic-particle inspection) supported the conclusions that the inclusions consisted of pieces of fireclay from channel brick that were flushed into the ingot mold. Although no true cracks were present, rejection of the stub axles was nevertheless justified. Slag streaks could reduce the strength of the stub axles and lead to the formation of fatigue fractures during operation. No recommendations were made.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.mech.c0047315
EISBN: 978-1-62708-225-9
... sulfides, oxides, phosphides, and silicates. A large inclusion, believed to be manganese sulfide, was found along a prior-austenite grain boundary located on the surface of crack 2 at an inside corner. Sizable areas of iron sulfide were identified in the surface of crack 4. No evidence of ductility...
Abstract
A sand-cast gray iron flanged nut was used to adjust the upper roll on a 3.05 m (10 ft) pyramid-type plate-bending machine. The flange broke away from the body of the nut during service. Analysis (visual inspection and 150x micrographs of sections etched with nital) supported the conclusions that brittle fracture of the flange from the body was the result of overload caused by misalignment between the flange and the roll holder. The microstructure contained graphite flakes of excessive size and inclusions in critical areas; however, these metallurgical imperfections did not appear to have had significant effects on the fracture. Recommendations included carefully and properly aligning the flange surface with the roll holder to achieve uniform distribution of the load. Also, a more ductile metal, such as steel or ductile iron, would be more suitable for this application and would require less exact alignment.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.marine.c9001591
EISBN: 978-1-62708-227-3
... at 500times;, for the transverse plane. The dark gray inclusions are silicates, whereas the light gray inclusions are sulfides. The elongated and rounded particles of a large silicate and several sulfides are shown in Fig. 5 . The composition of the sulfide particles determines its plasticity. Manganese...
Abstract
On 14 April 1912, at 11:40 p.m., Greenland Time, the Royal Mail Ship Titanic on its maiden voyage was proceeding westward at 21.5 knots (40 km/h) when the lookouts on the foremast sighted a massive iceberg estimated to have weighed between 150,000 to 300,000 tons at a distance of 500 m ahead. Immediately, the ship’s engines were reversed and the ship was turned to port (left) in an attempt to avoid the iceberg. In about 40 sec, the ship struck the iceberg below the waterline on its starboard (right) side near the bow. The iceberg raked the hull of the ship for 100 m, destroying the integrity of the six forward watertight compartments. Within 2 h 40 min the RMS Titanic sank. Metallurgical examination and chemical analysis of the steel taken from the Titanic revealed important clues that allow an understanding of the severity of the damage inflicted on the hull. Although the steel was probably as good as was available at the time the ship was constructed, it was very inferior when compared with modern steel. The notch toughness showed a very low value (4 J) for the steel at the water temperature (-2 deg C) in the North Atlantic at the time of the accident.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001120
EISBN: 978-1-62708-214-3
... A, plate III. The microcleanliness ratings were as follows: Type A inclusions (sulfides) None detected Type B inclusions (alumina) None detected Type C inclusions (silicates) None detected Type D inclusions (globular oxides) Fields: 1 heavy: 1 1 2 thin Figure 3...
Abstract
A segment from a premium-quality H13 tool steel die for die casting of aluminum failed after only 700 shots. The segment was subjected to visual, macroscopic, hardness, and metallographic testing. The investigation revealed that failure occurred as a result of fatigue at an electrical-discharge-machined surface where the resulting rehardened layer had not been removed. This rehardened layer had cracked, providing a source for fatigue initiation.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001615
EISBN: 978-1-62708-235-8
... showing the lateral crack The first stage forgings and undeformed shank/raw bar stock were cleaned properly and prepared for macrostructure examination. The macrostructure of the first stage forging contained numerous oxide (globular) and sulfide (elongated) inclusions in the central portion ( Fig...
Abstract
Carbon steel axle forgings were rejected due to internal cracks observed during final machining. To determine the cause of the cracks, the preforms of the forging were analyzed in detail at each stage of the forging. The analysis revealed a large central burst in the intermediate stage of the forging preform, which subsequently increased in the final stage. A high upset strain during forging, especially in the final stage, accentuated the center burst by high lateral flow of the metal. It was concluded that the center burst of the axle forging resulted from a high concentration of nonmetallic inclusions in the central portion of the raw bar stock rather than the usual problem of improper forging temperature. Strict control over the inclusion content in the raw material by changing the vendor eliminated the problem.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001206
EISBN: 978-1-62708-235-8
... precipitates in the ferritic zones around the cracks ( Fig. 7 ) are vitreous silicates, based on their behavior in polarized light. This form of selective oxidation is favored by the scarcity of oxygen in narrow cracks. In the extensions of the cracks, ferritic bands are often recognizable (see Fig. 5...
Abstract
A number of seamless pipe nipples of 70 mm diam and 3.5 mm wall thickness made of steel type 35.8 were oxyacetylene welded to collectors of greater wall thickness with a round bead. X-ray examination showed crack initiation in the interior of the nipples close to the root of the weld seam. The cracks only appeared where the originally deposited bead was remelted in the regions of overlap. Given the construction and welding technique used, it would have been preferable to make the nipples of a steel lower in sulfur content. However, by taking advantage of all the potential in shaping and welding technology, it should be possible to prevent crack formation with steel type 35.8 of normal composition.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006787
EISBN: 978-1-62708-295-2
... 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...
Abstract
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.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001323
EISBN: 978-1-62708-215-0
... aggravated by the presence of silicon and sulfur (silicates and sulfates). It was recommended that the tubes be replaced with Inconel 600 or 601, as a practical option until the carryover problem could be solved. Alkalies, environment Boiler tubes Environmental effects Inconel 600, 601 Sodium...
Abstract
Original carbon steel and subsequent replacement austenitic stainless steel superheater tube U-bend failures occurred in a waste heat boiler. The carbon steel tubes had experienced metal wastage in the form of caustic corrosion gouging, while the stainless steel tubes failed by caustic-induced stress-corrosion cracking. Sodium was detected by EDS in the internal deposits and the base of a gouge in a carbon steel tube and in the internal deposits of the stainless steel tube. The sodium probably formed sodium hydroxide with carryover moisture and caused the gouging, which was further aggravated by the presence of silicon and sulfur (silicates and sulfates). It was recommended that the tubes be replaced with Inconel 600 or 601, as a practical option until the carryover problem could be solved.
Book Chapter
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001819
EISBN: 978-1-62708-241-9
... of the longitudinal section of the austenitic stainless steel pump axis. Many nonmetallic inclusion particles (sulfide, oxide, and silicate particles) can be seen. The microstructure of the same material can be observed in Fig. 6 (transverse section) and Fig. 7 (longitudinal section): austenitic twinned grains...
Abstract
The shafts on two centrifugal pumps failed during use in a petroleum refinery. Light optical microscopy and scanning electron microscopy were used to analyze the damaged materials to determine the cause of failure. The results showed that one shaft, made of duplex stainless steel, failed by fatigue fracture, and the other, made of 316 austenitic stainless steel, experienced a similar fracture, which was promoted by the presence of nonmetallic inclusion particles.
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
... (such as pickling and electroplating) and would not be helpful in removing hydrogen introduced during steelmaking. Excessive gas contents in ingots are most serious when oxide inclusions are present. Inclusions provide sites for the agglomeration of gas; thus, molten alloys are often treated to reduce...
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.
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
... defect that also appears as a linear discontinuity. They occur from a crack, a heavy cluster of nonmetallic inclusions, or a deep lap (a lap that intersects the surface at a large angle). A seam can also result from a defect in the ingot surface, such as a hole, that becomes oxidized and is prevented...
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.
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
...; generally spherical and often coated with oxide Cold shot G 113 Spherical metallic inclusions inside blowholes or other cavities or in surface depressions (see A 311). Composition approximates that of the alloy cast but nearer to that of a eutectic Internal sweating, phosphide sweat G 120...
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
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001835
EISBN: 978-1-62708-241-9
... fracture stress concentration metallographic analysis silicate and oxide inclusions stress analysis low-temperature fracture toughness Fe-0.34C-0.7Mn-0.34Cr (chromium alloy steel) Introduction Wind power generation has rapidly spread in recent years as one of the clean energy resources...
Abstract
Wind turbine blades are secured by a number of high-strength bolts. The failure of one such bolt, which caused a turbine blade to detach, was investigated to determine why it fractured. Based on the results of a detailed analysis, consisting of stress calculations, chemical composition testing, metallurgical examination, mechanical property testing, and fractographic analysis, it was determined that the bolt failed by fatigue accelerated by stress concentration at low temperatures. The investigation also provided suggestions for avoiding similar failures.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001601
EISBN: 978-1-62708-235-8
... remelted. The inclusion ratings of this grade of steel, based on ASTM E 45, are as follows: Sulfides Alumina Silicates Globular oxides Thin Thick Thin Thick Thin Thick Thin Thick 1.5 0.5 2.5 1.0 1.5 1.5 0.5 • The dissolved oxygen, nitrogen, and hydrogen in the steel...
Abstract
Flow forming technology has emerged as a promising, economical metal forming technology due to its ability to provide high strength, high precision, thin walled tubes with excellent surface finish. This paper presents experimental observations of defects developed during flow forming of high strength SAE 4130 steel tubes. The major defects observed are fish scaling, premature burst, diametral growth, microcracks, and macrocracks. This paper analyzes the defects and arrives at the causative factors contributing to the various failure modes.
Book Chapter
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003509
EISBN: 978-1-62708-180-1
... include: Underbead cracks Gas porosity Inclusions—slag, oxides, or tungsten metal Incomplete fusion Inadequate penetration Solidification cracks, liquation cracks Failure to meet strength, ductility, or toughness requirements is another cause for rejection of weldments. Details...
Abstract
This article briefly reviews the general causes of weldment failures, which may arise from rejection after inspection or failure to pass mechanical testing as well as loss of function in service. It focuses on the general discontinuities observed in welds, and shows how some imperfections may be tolerable and how the other may be root-cause defects in service failures. The article explains the effects of joint design on weldment integrity. It outlines the origins of failure associated with the inherent discontinuity of welds and the imperfections that might be introduced from arc welding processes. The article also describes failure origins in other welding processes, such as electroslag welds, electrogas welds, flash welds, upset butt welds, flash welds, electron and laser beam weld, and high-frequency induction welds.
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
... G 112 (a) Metallic inclusions of the same chemical composition as the base metal; generally spherical and often coated with oxide Cold shot G 113 Spherical metallic inclusions inside blowholes or other cavities or in surface depressions. Internal sweating, phosphide sweat...
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.a0006826
EISBN: 978-1-62708-329-4
... and sulfur treatments for sulfide, alumina, and silicate inclusions ( Ref 19 ). Hard inclusions in the workpiece material can abrade the cutting tool material ( Ref 20 ). Inclusions, porosity, and oxide films in powder metallurgy steels can reduce their machinability, but closing the pores, increased...
Abstract
The first part of this article focuses on two major forms of machining-related failures, namely machining workpiece (in-process) failures and machined part (in-service) failures. Discussion centers on machining conditions and metallurgical factors contributing to (in-process) workpiece failures, and undesired surface layers and metallurgical factors contributing to (in-service) machined part failures. The second part of the article discusses the effects of microstructure on machining failures and their preventive measures.
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