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insufficient nitriding
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Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001847
EISBN: 978-1-62708-241-9
... underneath. This led to further wear and an increase in friction between the sleeve and bearing bush. Fatigue crack initiation occurred at the root fillet because of stress concentration and large frictional forces. Insufficient nitriding depth facilitated the propagation of fatigue cracks. bearing...
Abstract
An investigation was conducted to determine what caused a bearing sleeve in a locomotive turbocharger to fail. The sleeve, which is made of nitrided 38CrMoAl steel, fractured at the transition fillet between the cylinder and plate. Visual examination revealed significant wear on the external surface of the cylinder, with multiple origin fatigue fracture appearing to be the dominant fracture mechanism. Metallurgical examination indicated that the nitrided layer was not as deep as it was supposed to be and had worn away on the outer surface of the sleeve, exposing the soft matrix underneath. This led to further wear and an increase in friction between the sleeve and bearing bush. Fatigue crack initiation occurred at the root fillet because of stress concentration and large frictional forces. Insufficient nitriding depth facilitated the propagation of fatigue cracks.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.machtools.c9001574
EISBN: 978-1-62708-223-5
... was a clear indication of high temperature exposure (due to insufficient cooling) during application. The most probable cause of failure was thermal fatigue. Grain boundaries Precipitation Punches WR-95 Chromium nitride coating Thermal fatigue fracture Background The CrN coated restrike...
Abstract
A CrN coated restrike punch was made of WR-95 (similar to H-11), which was fluidized bed nitrided. The coated punch was used on hot Inconel at about 1040 deg C (1900 deg F). However, a water-soluble graphite coolant was used to maintain the punch temperature at 230 deg C (450 deg F). Visual and binocular inspection at 64+ revealed presence of cracks and complete washout of coating in the working area of the failed punch. Comparison of metallographic cross sections of used and unused punches revealed a significant microstructural transformation in case of the used punch. Presence of a yellow porous layer was clearly evident between the nitrided layer and the coating, in case of the used punch. Cracks were observed to propagate from the outer surface into the bulk. Oxidation was evident along the cracks. The microstructural transformation observed in the case of the used punch was a clear indication of high temperature exposure (due to insufficient cooling) during application. The most probable cause of failure was thermal fatigue.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.auto.c0047846
EISBN: 978-1-62708-218-1
... was removed in an effort to reduce cost and hence the shaft was subjected to increased vibration and shock loading. Insufficient fatigue limit of the shaft was revealed by fatigue testing of the shafts taken from stock in a rotating-beam machine. As a corrective measure, the fatigue limit of shafts...
Abstract
An 8640 steel shaft installed in a fuel-injection-pump governor that controlled the speed of a diesel engine used in trucks and tractors broke after few days of operation. The mechanism that drove the shaft was designed to include a slip clutch to protect the governor shaft from shock loading. It was revealed by visual examination that the fracture had initiated in the sharp corner at the bottom of a longitudinal hole which was part of a force feed lubricating system. Beach marks were observed on the fracture surfaces. It was revealed by further examination that the slip clutch was removed in an effort to reduce cost and hence the shaft was subjected to increased vibration and shock loading. Insufficient fatigue limit of the shaft was revealed by fatigue testing of the shafts taken from stock in a rotating-beam machine. As a corrective measure, the fatigue limit of shafts was increased to 760 MPA by nitriding for 10 h at 515 deg C.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001251
EISBN: 978-1-62708-235-8
..., the aluminum addition was reduced by one-half. Since then, there have been no additional rejects due to insufficient tensile and bend values. Castings Cracking (fracturing) Flanges Nonmetallic inclusions Tension tests Fe-0.22C GS C 25 (Other, general, or unspecified) fracture In a steel...
Abstract
In a steel foundry, tensile and bend specimens of castings made in a 2-ton basic arc furnace showed, at irregular intervals, regions with coarse-grained fractures where the specimens broke prematurely, so that the specified strength and toughness values could not be reached. Several cast tensile specimens and some forcibly-broken pieces of the flanges of armature yokes made of cast steel GS C 25 according to DIN 17 245 were investigated. Microscopic examination showed that the cause of damage was the superabundant use of aluminum as deoxidizer. According to recommendations, the aluminum addition was reduced by one-half. Since then, there have been no additional rejects due to insufficient tensile and bend values.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001269
EISBN: 978-1-62708-215-0
... homogenization of the carbides in the resultant hob, and lower sulfur content. Carbides Coatings Hobbing cutters Microstructural effects Sulfur Wear M2 UNS T11302 Brittle fracture Background A gear manufacturer reported recurring premature failures of titanium nitrided M2 tool steel gear...
Abstract
Recurring, premature failures occurred in TiN-coated M2 gear hobs used to produce carbon steel ring gears. Fractographic and metallographic examination, microhardness testing, and chemical analysis by means of EDS revealed that the primary cause of failure was a coarse cellular carbide network, which created a brittle path for fracture to occur longitudinally. As the cellular carbide network must be dispersed and refined during hot working of the original bar of material, the hobs were not salvageable. Minor factors contributing to the hob failures were premature wear resulting from lower matrix hardness and high sulfur content of the material, which contributed to lower ductility through increased nucleation sites. It was recommended that the hob manufacturer specify a minimum amount of required reduction for the original bar of tool steel material, to provide for sufficient homogenization of the carbides in the resultant hob, and lower sulfur content.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.marine.c9001621
EISBN: 978-1-62708-227-3
...-range cyclic stresses (for example, bending in a shaft) are enough to cause continued fatigue crack growth. In a small number of cases, however, the long-range stresses in the body of the component are insufficient to cause continued propagation. 4 In those cases, the result is shallow, nonpropagating...
Abstract
A crankshaft flange from a marine diesel engine illustrated a less-common case of fretting-fatigue cracking. The crankshaft was from a main engine of a sea-going passenger/vehicle ferry. The afterface of the flange was bolted to the flange of a shaft driving the gearbox. Cracks observed were sharp, transgranular, and not associated with any decarburization or other microstructural anomalies in the steel. Cracking of this main engine crankshaft flange was very likely a consequence of fatigue cracking initiated at fretting damage. The cause of the fretting was from loosening of the bolts.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001846
EISBN: 978-1-62708-241-9
..., and journal surface. The excessive heat also softened the induction-hardened case on the journal surface, decreasing its fatigue strength. Fatigue crack initiation occurred at the root fillet of the groove because of stress concentration. rotary shaft bearing sleeve fracture insufficient lubrication...
Abstract
The main shaft in a locomotive turbocharger fractured along with an associated bearing sleeve. Visual and fractographic examination revealed that the shaft fractured at a sharp-edged groove between two journals of different cross-sectional area. The dominant failure mechanism was low-cycle rotation-bending fatigue. The bearing sleeve failed as a result of abrasive and adhesive wear. Detailed metallurgical analysis indicated that the sleeve and its respective journal had been subjected to abnormally high temperatures, increasing the amount of friction between the sleeve, bearing bush, and journal surface. The excessive heat also softened the induction-hardened case on the journal surface, decreasing its fatigue strength. Fatigue crack initiation occurred at the root fillet of the groove because of stress concentration.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.chem.c0091362
EISBN: 978-1-62708-220-4
...) supported the conclusion that failure of the nozzle weld was the result of intergranular corrosion caused by the pickup of interstitial elements and subsequent precipitation of chromium carbides and nitrides. Carbon pickup was believed to have been caused by inadequate joint cleaning prior to welding...
Abstract
A nozzle in a wastewater vaporizer began leaking after approximately three years of service with acetic and formic acid wastewaters at 105 deg C (225 deg F) and 414 kPa (60 psig). The shell of the vessel was weld fabricated from 6.4 mm (0.25 in.) E-Brite stainless steel plate and measured 1.5 m (58 in.) in diameter and 8.5 m (28 ft) in length. Investigation (visual inspection, chemical analysis, radiography, dye-penetrant inspection, and hydrostatic testing of all E-Brite welds, 4x images, 100x/200x images electrolytically etched with 10% oxalic acid, and V-notch Charpy testing) supported the conclusion that failure of the nozzle weld was the result of intergranular corrosion caused by the pickup of interstitial elements and subsequent precipitation of chromium carbides and nitrides. Carbon pickup was believed to have been caused by inadequate joint cleaning prior to welding. The increase in the weld nitrogen level was a direct result of inadequate argon gas shielding of the molten weld puddle. Two areas of inadequate shielding were identified: improper gas flow rate for a 19 mm (0.75 in.) diam gas lens nozzle, and contamination of the manifold gas system. Recommendations included changes in the cleaning and welding process.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.mech.c9001254
EISBN: 978-1-62708-225-9
... with aluminum gave rise to the conclusion that the damage was caused by precipitation of aluminum nitride onto the primary and austenitic grain boundaries, subsequent determinations were made of aluminum and nitrogen content and the following values were found: They are arranged according to decreasing...
Abstract
The specified elongation of 10% could not be achieved in several hollow pinion gear shafts made of cast Cr-Mo steel GS 35 Cr-Mo 5 3 that were heat treated to a strength of 90 kp/sq mm. The steel was melted in a basic 3 ton arc furnace and deoxidized in the furnace and in the pan with a total of 7 kg aluminum. Fracture of a tensile specimen occurred with low elongation and, apparently, also with low reduction of area. In some places it was coarse grained conchoidal. It was found that the exceptionally low elongation of the cast specimens was due to excessive deoxidation by aluminum.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.steel.c9001255
EISBN: 978-1-62708-232-7
... off neck. In the centre of the fracture is a darkly tinted excentric flaw ( Fig. 2 ). Such internal cracks occur when a cast or forged work piece is heated up too quickly and insufficiently thoroughly for the anneal. The thermal expansion of the outer zone puts the central core under tensile stress...
Abstract
Several back up rolls of 1400 mm barrel diam from a broad strip mill broke after a relatively short operating time as a result of bending stresses when the rolls were dismantled. The fracture occurred in the conical region of the neck at about 600 mm diam. The rolls were shaped steel castings with 0.8 to 1.0% C, 1% Mn, 1% Cr, 0.5% Mo and 0.4% Ni and were heat treated to a tensile strength of 950 N/sq mm. Because the bending stress on mounting was only 42 N/sq mm in the fracture cross section, it was evident at the outset that material defects had promoted the fracture. In the case of this roll and the other broken rolls, the cracking and fracture were promoted by various casting defects. Investigation of the rolls showed that both the breaking off of the neck and the disintegration of the barrel edges was caused by material defects, more exactly casting defects. The fractures on the other rolls examined were so badly rusted or contaminated that they were incapable of yielding any information.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003573
EISBN: 978-1-62708-180-1
...; the valve spring may have broken because corrosion had weakened it. The spring may have had insufficient strength and taken a set, allowing the valve to drop into the path of the piston, or the engine may have been raced beyond its revolutions per minute limit many times, causing coil clash and subsequent...
Abstract
Distortion failure occurs when a structure or component is deformed so that it can no longer support the load it was intended to carry. Every structure has a load limit beyond which it is considered unsafe or unreliable. Estimation of load limits is an important aspect of design and is commonly computed by classical design or limit analysis. This article discusses the common aspects of failure by distortion with suitable examples. Analysis of a distortion failure often must be thorough and rigorous to determine the root cause of failure and to specify proper corrective action. The article summarizes the general process of distortion failure analysis. It also discusses three types of distortion failures that provide useful insights into the problems of analyzing unusual mechanisms of distortion. These include elastic distortion, ratcheting, and inelastic cyclic buckling.
Book Chapter
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006797
EISBN: 978-1-62708-295-2
... head with the piston, but the failure analyst must go beyond this immediate cause in order to recommend proper corrective measures. The valve may have stuck open because of faulty lubrication; the valve spring may have broken because corrosion had weakened it. The spring may have had insufficient...
Abstract
Distortion often is observed in the analysis of other types of failures, and consideration of the distortion can be an important part of the analysis. This article first considers that true distortion occurs when it was unexpected and in which the distortion is associated with a functional failure. Then, a more general consideration of distortion in failure analysis is introduced. Several common aspects of failure by distortion are discussed and suitable examples of distortion failures are presented for illustration. The article provides information on methods to compute load limits, errors in the specification of the material, and faulty process and their corrective measures to meet specifications. It discusses the general process of material failure analysis and special types of distortion and deformation failure.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006791
EISBN: 978-1-62708-295-2
... and contacts operating in the mixed- and boundary-lubrication regimes, due to insufficient lubrication supply, inadequate viscosity, incorrect internal clearances, incorrect installation, or misalignment. Adhesive wear also can cause rapid and sometimes catastrophic failures ( Ref 2 ). This can occur in metal...
Abstract
Friction and wear are important when considering the operation and efficiency of components and mechanical systems. Among the different types and mechanisms of wear, adhesive wear is very serious. Adhesion results in a high coefficient of friction as well as in serious damage to the contacting surfaces. In extreme cases, it may lead to complete prevention of sliding; as such, adhesive wear represents one of the fundamental causes of failure for most metal sliding contacts, accounting for approximately 70% of typical component failures. This article discusses the mechanism and failure modes of adhesive wear including scoring, scuffing, seizure, and galling, and describes the processes involved in classic laboratory-type and standardized tests for the evaluation of adhesive wear. It includes information on standardized galling tests, twist compression, slider-on-flat-surface, load-scanning, and scratch tests. After a discussion on gear scuffing, information on the material-dependent adhesive wear and factors preventing adhesive wear is provided.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003555
EISBN: 978-1-62708-180-1
... scale-forming alloys appear to be much more resistant to carburization than the chromia scale-formers ( Ref 16 ). Nitridation Nitridation of alloys in ammonia environments is well known in ammonia and heat treating industries ( Ref 17 ). Nitridation attack by N 2 is known in the powder metal...
Abstract
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.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0001814
EISBN: 978-1-62708-180-1
... nitric acid) pin, both the cam and the pin were heavily decarburized. (c) The chamfered cam holes were quite rough. 6.5×. The as-rolled surface decarburization had not been removed before heat treatment, and the surfaces were not cleaned-up after heat treatment. Failures of Nitrided Parts...
Abstract
This article describes the characteristics of tools and dies and the causes of their failures. It discusses the failure mechanisms in tool and die materials that are important to nearly all manufacturing processes, but is primarily devoted to failures of tool steels used in cold-working and hot-working applications. It reviews problems introduced during mechanical design, materials selection, machining, heat treating, finish grinding, and tool and die operation. The brittle fracture of rehardened high-speed steels is also considered. Finally, failures due to seams or laps, unconsolidated interiors, and carbide segregation and poor carbide morphology are reviewed with illustrations.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006818
EISBN: 978-1-62708-329-4
... and the pin were heavily decarburized. (c) The chamfered cam holes were quite rough. Original magnification: 6.5×. The as-rolled surface decarburization had not been removed before heat treatment, and the surfaces were not cleaned up after heat treatment. Failures of Nitrided Parts Although not used...
Abstract
This article discusses failure mechanisms in tool and die materials that are very important to nearly all manufacturing processes. It is primarily devoted to failures of tool steels used in cold working and hot working applications. The processes involved in the analysis of tool and die failures are also covered. In addition, the article focuses on a number of factors that are responsible for tool and die failures, including mechanical design, grade selection, steel quality, machining processes, heat treatment operation, and tool and die setup.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.conag.c9001471
EISBN: 978-1-62708-221-1
... in the region of the origin of the fracture. This latter region was also examined at high magnification with a view to detecting the presence of any embrittling constituents such as cementite films at grain boundaries or precipitated nitrides but none were seen. The chemical composition of the material...
Abstract
A crane hook was stamped S.W.L. 3 tons and, while its main dimensions were in approximate accordance with those specified in B.S. 482 for a hook of this capacity, its shape in some respects was not exactly in conformity with that recommended. At the time of fracture, the load being lifted was slightly under 10 cwts. Fracture occurred away from the normal wearing surface where the hook makes contact with the lifting slings. There was no evidence that fracture was preceded by any appreciable deformation locally or in the region of the failure. A sulphur print, taken on a cross section of the hook adjacent to the plane of fracture, showed the hook was made from a killed steel free from major segregation. Microscopic examination showed the material to be a mild steel in the normalized condition, the carbon content being of the order of 0.25%. Bend tests showed the material at the intrados of the hook would deform in a ductile manner both under slow and impact-loading conditions if in the form of an unnotched test piece, but if notched, it failed in a brittle manner under impact, though not under slow loading.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0001810
EISBN: 978-1-62708-180-1
...-load ratings are based on results of laboratory rolling-contact fatigue tests that have been conducted under conditions as near ideal as possible. Any departure from these reasonably ideal conditions, such as misalignment, vibration, shock loading, insufficient or inefficient lubrication, extremes...
Abstract
Rolling-element bearings use rolling elements interposed between two raceways, and relative motion is permitted by the rotation of these elements. This article presents an overview of bearing materials, bearing-load ratings, and an examination of failed bearings. Rolling-element bearings are designed on the principle of rolling contact rather than sliding contact; frictional effects, although low, are not negligible, and lubrication is essential. The article lists the typical characteristics and causes of several types of failures. It describes failure by wear, failure by fretting, failure by corrosion, failure by plastic flow, failure by rolling-contact fatigue, and failure by damage. The article discusses the effects of fabrication practices, heat treatment and hardness of bearing components, and lubrication of rolling-element bearings with a few examples.
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
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.
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
..., nitriding, carburizing, anodic hard coating Excessive case thickness, microcracks, embrittled material at stress raisers Machining Tool marks, grinding cracks Welding Weld-metal defects, hydrogen-induced cracking, inclusions, improper structure The primary purpose of this article...
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.
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