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in Failure Analysis of Fire Tube Sleeve of Heater Treater
> Handbook of Case Histories in Failure Analysis
Published: 01 December 2019
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001088
EISBN: 978-1-62708-214-3
... and that a low-carbon steel welding procedure had been used. This resulted in incipient cracks in the stainless steel weld metal near the toes of the component-to-shaft welds. The hardnesses of the heat-affected zones were as high as 58 HRC, and they were grain coarsened. The parting of the shaft was determined...
Abstract
A 25 mm (1 in.) diam carrier shaft failed suddenly during operation. The shaft failed near the toe of the 4.8 mm (316 in.) frame-to-shaft 60 deg and 120 deg submerged metal arc (SMA) tack welds after an unknown time in service. Material specifications called for the shaft to be made from SAE 1018 cold-rolled carbon steel. Carrier assembly components were made from type 300 stainless steel, and all nuts, spacers, and washers were to be SMA tack welded to the stainless steel frame. Chemical analyses (OES, SEM/EDS) showed the shaft to actually be made from SAE 1050 high-carbon steel and that a low-carbon steel welding procedure had been used. This resulted in incipient cracks in the stainless steel weld metal near the toes of the component-to-shaft welds. The hardnesses of the heat-affected zones were as high as 58 HRC, and they were grain coarsened. The parting of the shaft was determined to have been caused by an impact failure mechanism, with the origin at the incipient cracks in the weld metal. Additionally, the coarsened heat-affected zones were found to be hydrogen embrittled. The primary cause of the failure was the use of an unspecified material.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001850
EISBN: 978-1-62708-241-9
.... Microstructural and EDS analysis yielded evidence of overheating, revealing voids, scale, grain boundary oxidation, decarburization, and grain coarsening on the inner surface of the pipe, which also suggest the initiation of creep. Based on the information gathered during the investigation, the blow pipe...
Abstract
After about a year of uninterrupted service, one of the blow pipes on a blast furnace developed a bulge measuring 300 x 150 x 12 mm. The conical shaped section was removed from the furnace and examined to determine why it failed. The investigation consisted of visual inspection, chemical analysis, microstructural characterization, and mechanical property testing. The pipe was made from nonresulfurized carbon steel as specified and was lined with an alumina refractory. Visual inspection revealed cracks in the refractory lining, which corresponded with the location of the bulge. Microstructural and EDS analysis yielded evidence of overheating, revealing voids, scale, grain boundary oxidation, decarburization, and grain coarsening on the inner surface of the pipe, which also suggest the initiation of creep. Based on the information gathered during the investigation, the blow pipe was exposed to high temperatures when the liner cracked and subsequently bulged out due to creep.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c0091048
EISBN: 978-1-62708-235-8
... residual stresses, a mixed microstructure, inclusions, and gross grain coarsening. These synergistic factors resulted from extreme heat input during fillet welding. Recommendations included altering the welding variables such as current, voltage, and travel speed to substantially reduce the heat input...
Abstract
A welded ferritic stainless steel heat exchanger cracked prior to service. The welding filler metal was identified as an austenitic stainless steel and the joining method as gas tungsten arc welding. Investigation (visual inspection, SEM images, 5.9x images, and 8.9x/119x images etched with Vilella's reagent followed by electrolytic etching in 10% oxalic acid) supported the conclusion that the heat exchanger cracked due to weld cold cracking or postwelding brittle overload that occurred via flexure during fabrication. The brittle nature of the weld was likely due to a combination of high residual stresses, a mixed microstructure, inclusions, and gross grain coarsening. These synergistic factors resulted from extreme heat input during fillet welding. Recommendations included altering the welding variables such as current, voltage, and travel speed to substantially reduce the heat input.
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in Investigation on Bulging of Blow Pipe in a Blast Furnace
> Handbook of Case Histories in Failure Analysis
Published: 01 December 2019
and grain coarsening, ( d ) matrix structure shows formation of voids at the grain boundaries, and ( e ) microstructure away from the bulged zone shows banded ferrite–pearlite matrix
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in Thermal Fatigue Failure of a CrN-Coated Restrike Punch
> ASM Failure Analysis Case Histories: Machine Tools and Manufacturing Equipment
Published: 01 June 2019
Fig. 1 Photograph showing transformed microstructure (a) with crack (350×), (b) grain coarsening (600×).
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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
... with grain boundary coarsening (indicating grain boundary precipitation) 1 , 2 was observed ( Figure 1b ). EDS of the yellow layer indicated an increase in N and O peaks. In case of the unused part, no yellow layer was observed and the microstructure with respect to grain size, composition, etc., appears...
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.steel.c0046998
EISBN: 978-1-62708-232-7
...-grain microstructure of the alloy (ASTM grain size 4 to 7, but predominantly 5 to 7). Discussion Extreme grain coarsening was observed in the corroded region of the failed tube at the approximate midpoint of the 3-mm (0.120-in.) wall thickness (third micrograph of specimen 1, as shown in Fig. 1...
Abstract
One of 14 vertical radiant tubes (RA 333 alloy) in a heat-treating furnace failed when a hole about 5 x 12.5 cm (2 x 5 in.) corroded completely through the tube wall. The tube measured 183 cm (72 in.) in length and 8.9 cm (3 in.) in OD and had a wall thickness of about 3 mm (0.120 in.). Failure occurred where the tube passed through the refractory hearth (floor) of the furnace. Although the furnace atmosphere was neutral with respect to the work, it had a carburizing potential relative to the radiant tubes. Analysis (visual inspection, 250x spectroscopic examination of specimens etched with mixed acids, metallographic examination, and chemical analysis) supported the conclusions that the premature failure of the tube by perforation at the hearth level resulted from (1) corrosion caused by sulfur contamination from the refractory cement in contact with the tube and (2) severe local overheating at the same location. Recommendations included replacing all tubes using a low sulfur refractory cement in installation and controlling burner positioning and regulation more closely to avoid excessive heat input at the hearth level.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001818
EISBN: 978-1-62708-241-9
...-base superalloy metal loss wall thinning grain coarsening stereomicroscopy temperature Incoloy 800 (nickel-base superalloy) UNS N08800 Introduction and Background Information The fire tube sleeve of the Heater Treater ruptured while the unit was operating under normal conditions where...
Abstract
A sleeve-shaped fire shield that operates inside one of two burner trains in an oil and gas processing unit ruptured after 15 y of service. A detailed analysis was conducted to determine how and why the sleeve failed. The investigation included visual inspection, chemical and gas analysis, mechanical property testing, stereomicroscopy, and metallographic examination. The fire sleeves are fabricated from 3-mm thick plate made of Incoloy 800 rolled into 540-mm diam sections welded along the seam. Three such sections are joined together by circumferential welds to form a single 2.8 m sleeve. The findings from the investigation indicated that internal oxidation corrosion, driven by high temperatures, was the primary cause of failure. Prolonged exposure to temperatures up to 760 °C resulted in sensitization of the material, making it vulnerable to grain boundary attack. This led to significant deterioration of the grain boundaries, causing extensive grain loss (grain dropping) and the subsequent thinning of sleeve walls. Prior to failure, some portions of the sleeve were only 1.6 mm thick, nearly half their original thickness.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001257
EISBN: 978-1-62708-235-8
... ammonium chloride solution according to Heyn. 1× The uncracked pipe showed a ferritic-pearlitic structure in micro-section. Except for grain coarsening and a partially spear-like formation of ferrite (Widmannstätten structure), no major changes had occurred in the vicinity of the weld seam due...
Abstract
A steel socket pipe conduit NW 150 cracked open during pressure testing next to the weld seam almost along the entire circumference. The crack occurred in part in the penetration notch and in part immediately adjacent to it. While the uncracked pipe showed the light etch shading of a low-carbon steel in which the zone heated during welding was delineated only slightly next to the seam, the other pipe was etched much darker, i.e., higher in carbon, and the heated zone appeared to stand out darkly against the basic material. The overlapping weld was defect-free and dense. The uncracked pipe consisted of soft steel that obviously was made for this purpose, while the cracked pipe consisted of a strongly-hardenable steel which contained not only more carbon and manganese than customary but also a considerable amount of chromium. Therefore, the damage was caused by a mix-up of materials that allowed an unsuitable steel to be used for the weldment.
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
... austenite, untempered martensite, grain coarsening, surface decarburization or localized burning associated with the TiN coating at the surface. The cellular carbide networking is indicative of insufficient hot working to disperse, refine and homogenize the carbide structures formed when producing...
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
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001756
EISBN: 978-1-62708-241-9
... of overheating like grain coarsening, grain boundary thickening, or dissolution of the strengthening precipitates, etc. The samples also revealed solution-treated and aged structures which were similar to that noticed in the samples sectioned from the other locations in the blades. Micro examination...
Abstract
The failure of HP turbine blades in a low bypass turbofan engine was analyzed to determine the root cause. Forensic and metallurgical investigations were conducted on all failed blades as well as failed downstream components. It was found that one of the blades fractured in the dovetail region, causing extensive damage throughout the turbine. Remedial measures were suggested to prevent such failures in the future.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.auto.c0046981
EISBN: 978-1-62708-218-1
... operating temperature in a corrosive environment. When the microstructure near the stem surface was examined, it was apparent that carbide spheroidization had occurred. Also, there was a coarsening of the carbide network within the austenite grains. The microstructure indicated that the underhead region...
Abstract
The exhaust valve of a truck engine failed after 488 h of a 1000 h laboratory endurance test. The valve was made of 21-2 valve steel in the solution treated and aged condition and was faced with Stellite 12 alloy. The failure occurred by fracture of the underhead portion of the valve. Analysis (visual inspection, electron probe x-ray microanalysis, hardness testing, 4.5x fractograph) supported the conclusions that failure of the valve stem occurred by fatigue as a result of a combination of a nonuniform bending load, which caused a mild stress-concentration condition, and a high operating temperature in a corrosive environment. When the microstructure near the stem surface was examined, it was apparent that carbide spheroidization had occurred. Also, there was a coarsening of the carbide network within the austenite grains. The microstructure indicated that the underhead region of the valve was heated to about 930 deg C (1700 deg F) during operation. The cause of fatigue fracture, therefore, was a combination of non-uniform bending loads and overheating. No recommendations were made.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001346
EISBN: 978-1-62708-215-0
... in solution. Tubes that operate in the temperature range below 480 °C (896 °F) should not form carbides in several years. High temperatures would also induce age hardening and grain coarsening. The total effect would be to deplete the chromium content of the alloy, particularly at the grain boundaries...
Abstract
Alloy UNS N08800 (Alloy 800) tubes of the steam superheating coils of two hydrocracker charge heaters in a refinery failed prematurely in service. Failure analysis of the tubes indicated that the failures could be attributed to thermal fatigue as a result of temperature fluctuations as well as restriction to movement. Fatigue cracks initiated intergranularly from both the flue gas and steam sides. Enhanced general and grain boundary oxidation coupled with age hardening of the alloy led to the formation of incipient intergranular cracks that acted as sites for the initiation of the fatigue cracks.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c0060154
EISBN: 978-1-62708-234-1
... in the ruptured area gave the following evidence that the header metal had not been subjected to gross overheating in service: The header metal still had a general grain structure that would be classified as being of fine size, while severe grain coarsening would have occurred if the header metal had been...
Abstract
One of the coils in the radiant section of a primary reformer furnace used in an ammonia plant was found leaking. The bottom of one of seven outlet headers (made of ASME SA-452, grade TP316H, stainless steel) was revealed during examination to be ruptured. It was revealed by metallurgical examination that it had failed as a result of intergranular fissuring and oxidation (creep rupture). The ruptured area revealed that the header had failed by conventional long-time creep rupture as a result of exposure to operating temperatures probably between 900 and 955 deg C. Three samples from different sections (ruptured area, slightly bulged but nonruptured area and visually sound metal) were inspected. The presence of pinhead-size intergranular fissures throughout the cross sections of the latter two samples was observed. An ultrasonic attenuation method was employed to investigate the remaining headers. All headers were revealed by ultrasonic readings to be in an advanced stage of creep rupture and no areas were found to be fissured to a degree that they needed immediate replacement. As a conclusion, the furnace was deemed serviceable and it was established that in the absence of local hot spots, the headers would survive for a reasonable period of time.
Image
Published: 01 January 2002
Fig. 33 AISI 1040 steel bar austenitized at 913 °C (1675 °F) for 30 min, then cooled slowly in a furnace. White areas are ferrite; dark areas are pearlite. Mixed grain size due to heating into the coarsening range is also observed. Source: Ref 4
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Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c0045988
EISBN: 978-1-62708-235-8
... and exhibited a coarsened grain size of ASTM 4. Conclusions Transgranular-cleavage (brittle) fracture occurred across rivet holes in the clamp strap closest to one edge of the pin retainer. Coarse grain size (ASTM 2 to 3) was responsible for the brittle fracture. Excessively high temperature during...
Abstract
During installation, a clamp-strap assembly, specified to be type 410 stainless steel-austenitized at 955 to 1010 deg C (1750 to 1850 deg F), oil quenched, and tempered at 565 deg C (1050 deg F) for 2 h to achieve a hardness of 30 to 35 HRC, and used for securing the caging mechanism on a star-tracking telescope, fractured transversely across two rivet holes closest to one edge of the pin retainer in a completely brittle manner. Comparison with a non-failed strap using microscopic examination, spectrographic analysis, and slow-bend tests showed that both fit the 410 stainless steel specs, but hardness and grain size were different. Reheat treatment of full-width specimens showed that coarse grain size (ASTM 2 to 3) was responsible for the brittle fracture, and excessively high temperature during austenitizing caused the large grain size in the failed strap. The fact that the hardness of the strap that failed was lower than the specified hardness of 30 to 35 HRC had no effect on the failure because that of the non-failed strap was even lower. Recommendation was that the strap should be heat treated as specified to maintain the required ductility and grain size.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001479
EISBN: 978-1-62708-229-7
... — a process which is facilitated by the presence of a tensile stress. By penetration in this manner, especially when the grains of the steel have coarsened, a small amount of molten metal is enabled to result in rapid and severe loss of cohesion and ultimate failure in the manner seen giving fractures having...
Abstract
Several ruptures took place in the front wall tubes of a water tube boiler. Some rupture samples showed ductile failure while others showed brittle failure. Specimens taken from the rupture where a thick edge had been produced, i.e., with little evidence of prior plastic deformation, showed a coarse microstructure indicative of gross overheating. The examination indicated that failure in the main resulted from gross overheating arising from water starvation as could have been due to a number of causes. The ruptures in some tubes were of the type commonly found in overheated tubes, the material being drawn out to a feather edge at the time of rupture. Other ruptures in the same and other tubes were of a more brittle type, this being associated with penetration of material by molten copper derived from scale.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001031
EISBN: 978-1-62708-214-3
... caused ductility loss and grain-boundary separation. The excessive oxygen content in the liner was attributed to diffusion from an oxygen-rich environment that had resulted from nonuniform mixing of propellants. The internal oxygen embrittled the alloy and reduced its thermal conductivity, which resulted...
Abstract
Pinhole defects were found in a main combustion chamber made from NARloy-Z after an unexpectedly short time in service. Analysis indicated that the throat section of the liner had been exposed to very severe environmental conditions of high temperature and high oxygen content, which caused ductility loss and grain-boundary separation. The excessive oxygen content in the liner was attributed to diffusion from an oxygen-rich environment that had resulted from nonuniform mixing of propellants. The internal oxygen embrittled the alloy and reduced its thermal conductivity, which resulted in a higher hot-gas wall temperature and associated degradation of mechanical properties.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001107
EISBN: 978-1-62708-214-3
... (1700 °F) ( Fig. 6 ). Carbon adsorption and diffusion into the metal matrix induce the formation of chromium carbides, first intergranularly and then within the grains. Excessive formation and coarsening of these carbides lead to matrix consumption and subsequent transformation to ferrite and graphite...
Abstract
A 150 mm (6 in.) diam, 1.6 mm (0.065 in.) thick alloy 800 1iner from an internal bypass line in a hydrogen reformer was removed from a waste heat boiler because of severe metal loss. Visual and metallographic examinations of the liner indicated severe metal wastage on the inner surface, along with sooty residue. Patterns similar to those associated with erosion/corrosion damage were observed. Microstructural examination of wasted areas revealed a bulk matrix composed of massive carbides, indicating that gross carburization and metal dusting had occurred. X-ray diffraction analysis showed that the carbides were primarily chromium based (Cr 23 C 7 and Cr 7 C 3 ). The sooty substance was identified as graphite. Wasted areas were ferromagnetic and the degree of ferromagnetism was directly related to the degree of wastage. Three actions were recommended: (1) inspection of the waste heat boiler to determine the extent of metal damage in other areas by measuring the degree of ferromagnetism, (2) replacement of metal determined to be magnetic, and (3) closer monitoring of temperatures in the region of the reformer furnace outlet.
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