Oxidation of selected alloys during 25,000 h in superheated steam at 482 and 538/sup 0/C

Griess, J.C.; Maxwell, W.A.

doi:10.2172/5491716

Cited by 5 publications

(6 citation statements)

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“…1) at the temperature of 591 and 595 8C for 7700 hours. Thus the effect of heat flux to give a thicker oxide as observed by Maxwell et al [14] can neither be supported nor refuted. If comparing with the specimen without heat flux, after longer exposure times, the inner pit thickness increases.…”

Section: Thickness Of the Pitsmentioning

confidence: 89%

Investigation on steam oxidation behaviour of TP347H FG Part 1: Exposure at 256 bar

Jiang

Montgomery²,

Larsen³

et al. 2005

Materials and Corrosion

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The stainless steel TP347H FG is a candidate material for the final stage tubing of superheater and reheater sections of ultra supercritical boilers operated at steam temperatures up to 620 8C in the mild corrosion environments of coal-firing. A series of field tests has been conducted with the aforementioned steel in coal-fired boilers and this paper focuses on the steam oxidation behaviour for specimens tested at various metal temperatures for exposure times of 7700, 23000 and 30000 hours as investigated by light optical and scanning electron microscopy. The oxide present on the specimens is a duplex oxide, where the outer layer consists of two sub-layers, an iron oxide layer and an iron-nickel oxide layer; the inner layer is chromium rich chromium-iron-nickel oxide. Microstructure examination showed that for all these samples the varying grain size of subsurface metal affected the oxide thickness, where the larger the metal grain size, the thicker the oxidation scale. This gave the appearance of uneven inner oxides with a varying pit thickness. Comparison of the pit thickness measurement and oxide composition reveals that the oxidation rate is fast during the initial oxidation stage, but the subsequent growth of oxide from further exposure is slower due to the formation of a healing layer consisting of chromium rich oxide near original alloy grain boundaries. At a temperature region above 600 8C a thin oxide rich in chromium and manganese is sometimes formed. In addition precipitation of secondary carbides in the bulk metal also occurs at this temperature region.

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Section: Thickness Of the Pitsmentioning

confidence: 89%

Investigation on steam oxidation behaviour of TP347H FG Part 1: Exposure at 256 bar

Jiang

Montgomery²,

Larsen³

et al. 2005

Materials and Corrosion

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“…During the laboratory tests, cycling also took place in order to weight and/or remove samples from the rig but these averaged only 2-3 times every 1000 h. Cyclic steam oxidation testing carried out in the laboratory by different groups has also resulted in earlier spallation onset when compared to isothermal exposures [5,22,23]. Heat fluxing is also a cause of increased metal loss as shown by Griess et al [24]. The second important difference between the samples was the scale morphology and thickness after longer exposure.…”

Section: Uncoated P92mentioning

confidence: 99%

Comparison between field and laboratory steam oxidation testing on aluminide coatings on P92

Agüero

González

Gutiérrez

et al. 2011

Materials & Corrosion

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Steam oxidation has become an important issue for steam power plants as operating temperatures increase from the current 550 to 600-650 8C. For the last 10 years several groups have been carrying out steam oxidation testing of both uncoated substrates and coatings in the laboratory. On the other hand, field testing results are very scarce. In this paper, a comparison of laboratory steam oxidation testing with field test results carried out by Alstom at the Kraftwerk Westfalen power station located in Hamm, Germany will be presented. Both slurry deposited aluminide coatings and uncoated P92 steel have been included in the study. Under steam (atmospheric pressure) and isothermal conditions in the laboratory at 650 8C, spallation of oxides formed on ferritic steels occurs after significantly longer time when compared to exposure to real operating conditions. Oxide spallation results in serious damage in steam power plants by obstructing heat exchanger tubes, erosion of valves and turbine blades, etc. Moreover, the thickness of the oxide scales formed under field testing conditions is significantly higher after similar exposure. On the other hand, aluminide coated P92, which exhibit thickness through cracks, have shown to be stable in the laboratory for up to 60 000 h at 650 8C under steam, without evidence of crack propagation. However, field test results indicate that some degree of crack propagation occurs but without causing substrate attack up to 21 700 h of exposure. Moreover, the aluminium oxide observed in both laboratory and field tested specimens is different.

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“…Petersburg, Florida, in which a variety of materials were exposed to superheated steam at 482 and 53&°C (900 and 1000°F) in a once-through loop. Two reports concerning preliminary data from this prcgran* have been issued; one summarized data for the first 12,000 h 1 and the other for the first 25,000 h. 2 The plates to be joined were machined to produce a 75° included angle with a 0.38-mm (0.015-in.) root face.…”

Section: Introductionmentioning

confidence: 99%

Oxidation of selected alloys during 25,000 h in superheated steam at 482 and 538/sup 0/C

Abstract: NTlS price codes-Printed Copy: A03 Microfiche A01 This report was prepared as an account of work sponsored by an agency of the United StatesGovernment.

Cited by 5 publications

References 0 publications

Investigation on steam oxidation behaviour of TP347H FG Part 1: Exposure at 256 bar

Investigation on steam oxidation behaviour of TP347H FG Part 1: Exposure at 256 bar

Comparison between field and laboratory steam oxidation testing on aluminide coatings on P92

Long-term oxidation of selected alloys in superheated steam at 482 and 538/sup 0/C

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