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Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.pulp.c0045911
EISBN: 978-1-62708-230-3
... amounts of sodium, calcium, potassium, aluminum, and sulfur, alkali, alkali earth, and other contaminants that completely permeated even the thin oxides on the fracture surfaces. Additional investigation of the purity of the steam itself as reported by the power plant showed that corrosion and cracks were...
Abstract
Within the first few months of operation of an 8 km (5 mile) long 455 mm (18 in.) diam high-pressure steam line between a coal-fired electricity-generating plant and a paper mill, several of the Inconel 600 bellows failed. The steam line operated at 6030 kPa (875 psi) and 420 deg C (790 deg F). Metallographic sections, energy-dispersive x-ray spectra, chemical analyses, tensile tests, and Auger microscope analyses showed the failed bellows met the specifications for the material. However, investigation also showed entire oxide thickness was contaminated with relatively large amounts of sodium, calcium, potassium, aluminum, and sulfur, alkali, alkali earth, and other contaminants that completely permeated even the thin oxides on the fracture surfaces. Additional investigation of the purity of the steam itself as reported by the power plant showed that corrosion and cracks were ultimately caused by the steam. While under normal operation, the steam's purity posed no problem to the material, during boiler cleaning operations, the generating plant had allowed contamination to get into the steam line.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001109
EISBN: 978-1-62708-214-3
... to approximately 9 months. Several corroded grate bars were examined metallographically and by electron microscopy to determine the causes of the accelerated corrosion. Chemical and X-ray diffraction analyses were also conducted, along with simulation tests to assess the role of alkali chlorides in the corrosion...
Abstract
Grate bars in the traveling grate indurators in several taconite processing units suffered excessive corrosion following a conversion from acid to fluxed pellet production procedures. The campaign life of the HH grade cast stainless steel bars was reduced from more than 7 years to approximately 9 months. Several corroded grate bars were examined metallographically and by electron microscopy to determine the causes of the accelerated corrosion. Chemical and X-ray diffraction analyses were also conducted, along with simulation tests to assess the role of alkali chlorides in the corrosion process. The basic cause of degradation was found to be hot corrosion caused by the deposition of alkali sulfates and chlorides. However this degradation may have been aggravated by thermal cycling and abrasion. The source of the salt was impurities in the flux. Two potential solutions were proposed: modification of the processing parameters to reduce the salt deposition and / or change of bar materials to a more resistant alloy.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c0048331
EISBN: 978-1-62708-229-7
... of the rupture. A red and white deposit was found on the sides and bottom of the tube in the rupture area. The deposit was produced by attack of the steel by the alkali acid sulfate and had thinned the tube wall. It was concluded that rupture of the tube had occurred due to thinning of the wall by coal-ash...
Abstract
The top tube of a horizontal superheater bank in the reheat furnace of a steam generator ruptured after seven years in service. The rupture was found to have occurred in the ferritic steel tubing (2.25Cr-1Mo steel (ASME SA-213, grade T-22)) near the joint where it was welded to austenitic stainless steel tubing (type 321 stainless steel (ASME SA-213, grade TP321H)). The surface temperature of the tube was found to be higher than operating temperature in use earlier. The ferritic steel portion of the tube was found to be longitudinally split and heavily corroded in the region of the rupture. A red and white deposit was found on the sides and bottom of the tube in the rupture area. The deposit was produced by attack of the steel by the alkali acid sulfate and had thinned the tube wall. It was concluded that rupture of the tube had occurred due to thinning of the wall by coal-ash corrosion. The thinned tubes were reinforced by pad welding. Type 304 stainless steel shields were welded to the stainless steel portions of the top reheater tubes and were held in place about the chromium-molybdenum steel portions of the tubes by steel bands.
Series: ASM Handbook
Volume: 11B
Publisher: ASM International
Published: 15 May 2022
DOI: 10.31399/asm.hb.v11B.a0006909
EISBN: 978-1-62708-395-9
...., alkalis and acids), ionizing radiation, and biological degradation, along with the combined effects of mechanical stress, temperature, and moisture (including environmental stress corrosion). The article also includes information on the use of accelerated testing for predicting material property...
Abstract
Accelerated life testing and aging methodologies are increasingly being used to generate engineering data for determining material property degradation and service life (or fitness for purpose) of plastic materials for hostile service conditions. This article presents an overview of accelerated life testing and aging of unreinforced and fiber-reinforced plastic materials for assessing long-term material properties and life expectancy in hostile service environments. It considers various environmental factors, such as temperature, humidity, pressure, weathering, liquid chemicals (i.e., alkalis and acids), ionizing radiation, and biological degradation, along with the combined effects of mechanical stress, temperature, and moisture (including environmental stress corrosion). The article also includes information on the use of accelerated testing for predicting material property degradation and long-term performance.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001324
EISBN: 978-1-62708-215-0
... surfaces were all similar in appearance, and a primary crack origin could not be identified. A secondary crack brought to fracture in the laboratory showed brittle, cleavage features rather than classic, tensile overload features. This suggested that the material was embrittled. Alkalies Caustic...
Abstract
A type 430Ti stainless steel flue gas expansion joint cracked because of caustic-induced stress-corrosion cracking. Energy-dispersive X-ray spectroscope analysis of the fracture surface deposits revealed the presence of sodium and potassium—caustics in hydroxide form. Primary fracture surfaces were all similar in appearance, and a primary crack origin could not be identified. A secondary crack brought to fracture in the laboratory showed brittle, cleavage features rather than classic, tensile overload features. This suggested that the material was embrittled.
Image
Published: 01 January 2002
Fig. 23 General shifts in fracture mechanism fields for metallic and nonmetallic (ionic or covalent) bonding. (a) fcc metals, cleavage at low temperatures does not occur as in the bcc. (b) Refractory bcc metals. (c) Alkali halides. (d) Refractory oxides. Source: Ref 39
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Image
Published: 15 January 2021
Fig. 24 General shifts in fracture mechanism fields for metallic and nonmetallic (ionic or covalent) bonding. (a) Face-centered cubic metals; cleavage at low temperatures does not occur as in the body-centered cubic (bcc). (b) Refractory bcc metals. (c) Alkali halides. (d) Refractory oxides
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Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c9001405
EISBN: 978-1-62708-234-1
..., although their microstructures may not show any significant differences, and it seems probable that this behavior may be related to the amount and continuity of the grain-boundary carbides. Alkalies Boilers Carbides Caustic cracking Electron microscopy Steam boilers Steam boiler steel...
Abstract
During microscopic examination of a number of cases of caustic cracking, a certain feature has been recognized that appeared to be associated only with caustic cracking. This was a preferential attack on the carbide envelopes and lamellae of the pearlite grains. Evidence suggests that the intergranular path of caustic cracks in steam boilers may be due largely to the presence, probably on a submicroscopic scale, of carbides at the grain boundaries, thus rendering these regions susceptible to preferential attack. It is known that some steels are more liable to develop caustic cracks than others, although their microstructures may not show any significant differences, and it seems probable that this behavior may be related to the amount and continuity of the grain-boundary carbides.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003551
EISBN: 978-1-62708-180-1
... (solids, S, + liquid, L, type of reaction), but atmosphere corrosion also occurs under specific circumstances (under reducing or oxido-reducing conditions), as, for example, under attack from carbon monoxide or alkalis and other condensable gases (S + gas, G, type of reaction). Corrosion of technical...
Abstract
This article provides a discussion on the structural ceramics used in gas turbine components, the automotive and aerospace industries, or as heat exchangers in various segments of the chemical and power generation industries. It covers the fundamental aspects of chemical corrosion and describes the corrosion resistance characteristics of specific classes of refractories and structural ceramics. The article also examines the prevention strategies that minimize corrosion failures of both classes of materials.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001798
EISBN: 978-1-62708-241-9
.... The second possible reason is that perfect macromolecular structure is corrupted. In this case, 3D macromolecular network is normally formed during curing process, but is destroyed and fractured during storage by strong acids, alkalis, and so on. The third possible reason is that imperfect macromolecular...
Abstract
The crosslinked epoxy resin encapsulant protecting an electromagnetic valve coil failed during long-term storage and was examined to determine the cause. The investigation included fault-tree analysis, FTIR and EDX spectroscopy, and differential scanning calorimetry with thermogravimetric analysis. Based on test data, the epoxy resin had not been properly cured and was hydrolyzed in its compromised state because of humidity. Hence, the depolymerized material gradually softened to the point where the effect of creep caused it to flow, ultimately causing the failure.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001400
EISBN: 978-1-62708-235-8
... to stress corrosion cracking in mild steel are alkalies (hydroxides), nitrates and occasionally hydrogen sulphide or ammonia. We are informed that this particular process for the removal of CO 2 employed monoethanolamine solution. The substance is alkaline and may well act as inorganic alkalies...
Abstract
Following the discovery numerous cracks at many of the welded seams of a mild steel CO2 absorber vessel, a sample for examination was removed from the worst affected area where repairs had been effected. A 12 in. long circumferential crack was visible. Specimens were taken to cover the several locations of cracking which, in all cases, were found to be similar and of the intergranular type filled with oxide or corrosion product. The association of the cracks with the weld seams indicated that contraction stresses from welding were primarily responsible. Failure of the absorber vessel was found to be due to stress corrosion. Although the active agent present was not positively identified, the aqueous solution of monoethanolamine was thought to be the most probable. The origin of the stresses was not elucidated but the association of the cracks with the welded seams indicated inherent residual stresses as being primarily responsible. Tests carried out tend to suggest that stress relief was not carried out. For the replacement plant, consideration of stress relieving or the use of an alternative material was advised.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.bldgs.c9001457
EISBN: 978-1-62708-219-8
... of 30 p.p.m., this being subsequently treated with a proprietary tannin extract, without—as far as is known—addition of alkali. It is considered, therefore, that the agent responsible was probably chlorides. The stresses, in all probability, were those developed by tightening the nuts. Whether...
Abstract
The cover of a feed cock fitted to an economic boiler suddenly blew off and the plug lifted sufficiently to permit the escape of water. It was found that all four of the studs securing the cover had fractured. In each case fracture had occurred at the end of one of the screwed portions adjacent to the shank. The fractures were of a short nature, with no evidence of progressive cracking by fatigue, nor was there any sign of stretching prior to failure. The fractured faces and the shanks of the studs were of rusted appearance. Microscopic examination of the material showed it to be an austenitic nickel-chromium stainless steel, stabilized by titanium and of the free machining type. Multiple transgranular cracking characteristic of failure from stress-corrosion cracking, was present to an extensive degree. It was considered probable that there had been slight leakage of water from the valve over a period and evaporation resulted in a solution which favored failure from stress-corrosion cracking. If corrosion resistant studs were desired, those of bronze or Monel metal are to be preferred.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c9001177
EISBN: 978-1-62708-234-1
... are chlorides such as calcium and magnesium chloride, but also highly concentrated alkali solutions such as potassium or sodium hydroxide. The process takes place very slowly at room temperature, but is strongly accelerated by raising the temperature, Stresses are effective even if they lie far below the yield...
Abstract
A solution containing 50 to 70% calcium chloride (pH 7.5 to 8.5) was concentrated by evaporation in a brick-lined vessel by passing steam at a pressure of 15 atmospheres through a system of heating coils made of austenitic stainless steel X 10 Cr-Ni-Mo-Ti 18 12 (Material No. 1.4573). After five months one of the coils, which consisted of tubes having a wall thickness of 3.4 mm, developed a leak. Tightly closed cracks were seen on the outer surface of the tube. Further tests with color penetration process revealed multiple branched cracks. Longitudinal section showed that the cracks had started from the outside surface of the tube. Electrolytic etching further showed that they had propagated mainly across the grains. It was concluded that this was a typical case of transcrystalline stress corrosion.
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
... order of estimated life). Hot Corrosion Hot corrosion is a complex process involving both sulfidation and oxidation ( Ref 27 ). Hot corrosion is a form of accelerated oxidation that affects alloys and coatings exposed to high-temperature gases contaminated with sulfur and alkali metal salts ( Ref...
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 Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001061
EISBN: 978-1-62708-214-3
... of the failures. Minimizing residual stresses through use of welding procedures that include appropriate preweld and interpass temperatures and postweld stress relief heat treatment at 650 deg C (1200 deg F) was recommended to prevent further failures. Alkalies, environment Heat-affected zone Papermaking...
Abstract
Schedule 80 low-carbon steel pipes used to transfer kraft liquor in a Kamyr continuous pulp digester failed within 18 months after installation. Visual and metallographic examinations established that the cracking initiated on the internal surfaces of the equalizer pipes in the welds and heat-affected zones (HAZs). Fracture/crack morphology was brittle and primarily intergranular and deposits at crack tips were primarily iron oxides with significant amounts of sodium compounds. On these bases, the cracking was characterized as intergranular stress-corrosion cracking (IGSCC). Corrosion-related deterioration was not found, indicating that the material was generally suitable for the intended service. High residual tensile stresses in the welds and HAZS, resulting from field welding under highly constrained conditions using inadequate weld procedures, were the most probable cause of the failures. Minimizing residual stresses through use of welding procedures that include appropriate preweld and interpass temperatures and postweld stress relief heat treatment at 650 deg C (1200 deg F) was recommended to prevent further failures.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001827
EISBN: 978-1-62708-241-9
... and the air can lead to deposition of alkali metal sulfates on the blade or vane surfaces, resulting in hot corrosion attack [ 2 ]. Overview of Gas Turbine Engine Hot Parts The areas of the gas turbine where the temperature is the highest and which are therefore, most subject to high-temperature...
Abstract
Gas turbines and other types of combustion turbomachinery are susceptible to hot corrosion at elevated temperatures. Two such cases resulting in the failure of a gas turbine component were investigated to learn more about the hot corrosion process and the underlying failure mechanisms. Each component was analyzed using optical and scanning electron microscopy, energy dispersive spectroscopy, mechanical testing, and nondestructive techniques. The results of the investigation provide insights on the influence of temperature, composition, and microstructure and the contributing effects of high-temperature oxidation on the hot corrosion process. Preventative measures are also discussed.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001310
EISBN: 978-1-62708-215-0
... of salts in the corrosion deposit. In addition to ammonia, a number of environments can cause cracking, such as oxygen and carbon dioxide with ammonia, hydrogen sulfide, air contaminated with sulfur and nitrogen oxides, nitrates, phosphates, alkalis, chlorides, hydrogen fluoride, and nitric acid ( Ref 1...
Abstract
Leaks developed in 22 admiralty brass condenser tubes. The tubes were part of a condenser that was being used to condense steam from a nuclear power plant and had been in operation for less than 2 years. Analysis identified three types of failure modes: stress-corrosion cracking, corrosion under deposit (pitting and crevice), and dezincification. Fractures were transgranular and typical of stress-corrosion cracking. The primary cause of the corrosion deposit was low-flow conditions in those parts of the condenser where failure occurred. Maintenance of proper flow conditions was recommended.
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.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.bldgs.c9001702
EISBN: 978-1-62708-219-8
... macroscopic scan of deteriorating areas of the bridge concrete, including areas under loosened aggregate grains, was done to determine the presence of significant alkali-silica reaction (ASR) products. The examination was done using ultra-violet light and a standard uranyl acetate solution indicator. None...
Abstract
The Rocky Point Viaduct, located near Port Orford, OR, was replaced after only 40 years of service. A beam from the original viaduct was studied in detail to determine the mechanisms contributing to severe corrosion damage to the structure. Results are presented from the delamination survey, potential and corrosion mapping, concrete chemistry, and concrete physical properties. The major cause of corrosion damage appears to have been the presence of both pre-existing and environmentally-delivered chlorides in the concrete.
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
... by the combination of large cathode and a small anode, as develops in such cases. The solution of magnetite by caustic alkali results in the formation of sodium ferroate and ferrite, in accordance with the following equation 3 :— Fe 3 O 4 + 4 NAOH = Na 2 FeO 2 ( Ferroate...
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.
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