Carburization processes involved in boiler-tube failures

Lopez-Lopez, D.; Wong-Moreno, A.; Martı́nez, L.

doi:10.1016/0010-938x(93)90335-e

Cited by 6 publications

(4 citation statements)

References 7 publications

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“…Kaya [8] investigated the carburization phenomenon in two tubular materials made from Fe-Cr-Ni-based HK40 alloy after a service life of approximately 25,000 h in an ethylene pyrolysis furnace. Catastrophic failures due to carburization of 9Cr-1Mo, 13CrMo44, 321H and TP304H steels were also reported in the literature for service life well below the design life [9][10][11]. Carburization failures due to extremely high temperatures have also been reported.…”

Section: Introductionmentioning

confidence: 86%

Carburization of high-temperature steels: A simulation-based ranking of carburization resistance

Samaras

Haidemenopoulos

2015

Engineering Failure Analysis

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Section: Introductionmentioning

confidence: 86%

Carburization of high-temperature steels: A simulation-based ranking of carburization resistance

Samaras

Haidemenopoulos

2015

Engineering Failure Analysis

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“…7). The temperature of recrystallization of the 347 type of steel lies within the range of 232 ÷ 746°C, at the temperature of melting between 1400 ÷ 1425°C [18]. Matrix recovery, as a result of annihilation of the dislocations and their entanglement in the boundaries, contributes to the softening process.…”

Section: Results Of Research and Discussionmentioning

confidence: 99%

“…The lack of access to data concerning the microstructure in the as-received condition limits the possibility of analyzing the changes that run in the examined steel during the service. However, considering the applied heat treatment for this grade of steel -hyperquenching in water from the temperature of 1180 ÷ 1250°C [19], and literature data [1,2,8,10,18], it can be assumed that in the as-received condition, the investigated steel was characterized by the microstructure consisting of austenitic matrix and primary NbC precipitations. It shows that the degradation of the microstructure of the examined steels during the service mostly occurred through the precipitation of secondary carbides, i.e.…”

Section: Results Of Research and Discussionmentioning

confidence: 99%

Microstructural Aspect of Long Term Service of the Austenitic TP347HFG Steel / Wpływ Długotrwałej Eksploatacji Na Mikrostrukturę Stali TP347HFG

Golański¹,

Lis²,

Słania³

et al. 2015

Archives of Metallurgy and Materials

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The paper presents the results of research on the microstructure of austenitic creep-resisting TP347HFG steel after longterm service. The tests of the microstructure were performed using SEM and TEM. The identification of precipitates was carried out using selective electron diffraction. It has been shown that long-term service mostly contributes to the processes of precipitation of secondary NbC carbides inside grains and M23C6 carbides on grain boundaries. In the microstructure of the examined steel, also the processes of polygonization and recrystallization of the matrix were revealed.

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“…This phenomenon has been previously reported for oil fired boilers, and very low excess air is among the operational factors that are believed to contribute to the generation of carbon-rich reducing atmospheres leading to the deposition of unburned carbon particulate on the tube surfaces [8]. Carburization in the presence of coal or carbon soot is expected to be of significance only at temperatures above 800°C.…”

Section: High-temperature Carburization Of Superheater/reheater Matermentioning

confidence: 92%

Materials degradation mechanisms in coal-fired boilers

Nava¹,

Henry²

2003

Materials at High Temperatures

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INTRODUCTIONThe technical viability of advanced power plants will be critically dependent on the availability of suitable materials. Higher efficiencies can be achieved only by operating at temperatures that will exceed the capabilities of many of the conventional alloys. It is expected that maximum waterwall temperatures in high efficiency units will approach 600 to 625°C, with superheater and reheater outlet temperatures expected to go as high as 750°C. Similar or higher temperatures are expected for piping and headers. These higher operating temperatures may severely limit the serviceable lives of critical operating components due to an increase in the kinetics of oxidation/ corrosion mechanisms. Controls on emissions imposed by government regulatory agencies in the USA promoted the development of various strategies for lowering these emissions through changes in the way the fossil fuel was burned in a boiler. Staged coal firing provided a viable technology to meet stringent requirements on NO x emissions. However, it was found that during staged firing the substoichiometric firing conditions generate relatively high concentrations of total reduced sulfur species (TRS), unburned carbon, and pyrite particulate at the boiler waterwalls. Reduced sulfur species and reducing microclimates then are conducive to accelerated waterwall wastage by various sulfidation mechanisms.Higher operating waterwall temperatures will lead to accelerated scaling on the unprotected ID surface of waterwall tubing. This build-up of oxide will restrict heat transfer, and may, if metal temperatures are high enough, cause local overheating of the tube wall and premature failure. The consequent reduction in boiler availability will jeopardize the economic benefits of the higher efficiency plants. In addition, when the oxide reaches a critical thickness it will exfoliate from the surface of the tube, become entrained in the steam, and enter the turbine, where the high velocity impact of the oxide particles on critical turbine components can lead to significant losses in turbine efficiency. Although alternative materials with higher creep strength are being developed for these applications, the available data suggests that in many cases their oxidation behavior in steam is not satisfactory.Radical changes in the way the fuel is burned in the furnace of present-day steam generator have led to variations in the traditional wastage mechanisms, such as coal-ash corrosion. Standard high-temperature alloys, such as grades 304H or 310H, have been subjected to the effects of high-temperature carburization. Although the number of reported failures related to carburization to date has been small, the frequency of occurrence clearly is increasing, and the phenomenon has been acknowledged officially in a recent study of coal-ash corrosion [1].The purpose of the present report is to review recent test data that has served as the basis for the understanding of the major modes of degradation that affect current and future coal-fired power plants. Recommend...

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Carburization processes involved in boiler-tube failures

Cited by 6 publications

References 7 publications

Carburization of high-temperature steels: A simulation-based ranking of carburization resistance

Carburization of high-temperature steels: A simulation-based ranking of carburization resistance

Microstructural Aspect of Long Term Service of the Austenitic TP347HFG Steel / Wpływ Długotrwałej Eksploatacji Na Mikrostrukturę Stali TP347HFG

Materials degradation mechanisms in coal-fired boilers

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