Enhanced Internal Oxidation as Reason for Breakdown of Protective Chromia Scales on FeCr-Alloys in Water Vapour Containing Gases

The oxidation behaviour of binary Fe-Cr alloys containing 10 and 20 mass % Cr, respectively, was studied in Ar-20%O2, Ar-7%H2O and in Ar-4%H2-7%H2O at temperatures between 800 and 1050°C. Thermogravimetric analyses in combination with analytical studies using SEM/EDX and Raman Spectroscopy revealed, that in atmospheres in which water vapor is the source of oxygen, Cr exhibits a higher tendency to become internally oxidized than in the Ar-O2 gas. Contrary to previous studies which showed the presence of water vapor to affect transport processes in the surface oxide scale, the present results reveal that the presence of water vapor also affects the transport processes in the alloy. The enhanced internal oxidation, which is likely the result of water vapor increasing the solubility and/or the diffusivity of oxygen in the alloy, explains the frequently observed effect that Fe(Ni)Cr alloys with intermediate Cr contents (e.g. 10-20%, depending on temperature) exhibit protective oxidation in dry gases but breakaway type oxidation in steam. The temperature dependence of the change from protective to non-protective behaviour in Ar-H2O differs quantitatively, but not qualitatively from that in Ar-O2.

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Long-Term, Cyclic Oxidation Behaviour of Alumina- and Chromia-Forming Alloys

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.237-240.1107 ◽

2005 ◽

Vol 237-240 ◽

pp. 1107-1114 ◽

Cited By ~ 5

Author(s):

Renata Bachorczyk Nagy ◽

Richard J. Fordham

Keyword(s):

Corrosion Resistance ◽

Physical Properties ◽

Oxide Scale ◽

Water Vapour ◽

Oxidation Resistance ◽

Cyclic Oxidation ◽

Oxidation Behaviour ◽

Reactive Elements ◽

Funded Project

The oxidation resistance behaviour of a number of surface-treated FeCrAl commercial alloys and some model alloys of well-defined composition, incorporating a range of reactive elements in trace amounts, has been studied under thermal cyclic conditions in air with and without additions of water vapour. Additions of reactive elements such as Zr, La, Y, Hf modify the oxidation resistance behaviour of FeCrAl-alloys by improving the scale adherence and consequently may extend the lifetime of FeCrAl steels. The presence of the water vapour can affect oxidation in a number of different ways. Our results may indicate that high content of water vapour can cause the lives of such alloys to be decreased. This work forms part of a larger European-funded project to evaluate physical properties, microstructural features, oxidation/corrosion resistance and lifetime improvement. The correlation between alloy parameters and lifetime; as well as the modeling of oxide scale behaviour as function of cycling conditions is also studied.

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The Effect of Gas Flow Rate on the Oxide Scale Morphology of a 10%Cr-Ferritic Steels in Ar-H2O and Ar-H2-H2O Mixtures

Materials Science Forum ◽

10.4028/www.scientific.net/msf.522-523.155 ◽

2006 ◽

Vol 522-523 ◽

pp. 155-162 ◽

Cited By ~ 2

Author(s):

J. Zurek ◽

M. Michalik ◽

Lorenz Singheiser ◽

W.Joe Quadakkers

Keyword(s):

Oxide Scale ◽

Water Vapour ◽

Flow Rate ◽

Gas Flow ◽

Oxidation Process ◽

Oxidation Behaviour ◽

Gas Flow Rate ◽

Flow Conditions ◽

Water Vapour Content ◽

Equilibrium Oxygen

The oxidation behaviour of a Ferritic 10%Cr steel in Ar-H2O mixtures was investigated at 650°C. The studies aimed at elucidating the effect of water vapour content as well as the gas flow rate on the mechanisms of oxide scale formation. An important observation of the present investigation is, that H2 produced by the reaction of water vapour with the steel, can play a significant role in the oxidation process. It affects the possibility to form an external haematite layer and may alter the oxide scale growth rate. The extend by which the H2 affects the oxidation behaviour depends on the gas flow conditions, the water vapour content and the exposure time. To confirm these observations a number of specimens were oxidized in Ar-H2-H2O mixtures. This atmosphere guarantees a very low equilibrium oxygen partial pressure, in which H2 formed by reaction of the gas with the metal, does not substantially alter the thermodynamic properties of the gas.

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Influence of Water Vapor on Oxide Scale Morphology of Incoloy800HT at 850°C

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.875.36 ◽

2018 ◽

Vol 875 ◽

pp. 36-40 ◽

Cited By ~ 3

Author(s):

Anusara Srisrual ◽

Kasidet Pitaksakorn ◽

Piyorose Promdirek

Keyword(s):

Raman Spectroscopy ◽

Water Vapor ◽

Oxide Scale ◽

Surface Finishing ◽

Scale Morphology ◽

Spinel Oxide ◽

Thermal Oxide ◽

Influence Of Water ◽

Oxide Phases ◽

Oxygen Gas

This paper aims to report the influence of water vapor on thermal oxide scale grown on incoloy800HT at 850°C. Alloy was prepared in coupons with a surface finishing up to 1200 SiC abrasive paper. Oxidization was performed in tubular furnace at 850°C during 50 hours. The oxidizing gases were varied as a dry oxygen gas and a wet oxygen gas. Thermal oxide morphology was characterized by scanning electron microscopy (SEM). Oxide phases were identified by X-ray diffraction (XRD) and Raman spectroscopy techniques. The oxide multilayers were revealed in all the oxidized samples. Oxide spallation was obviously detected on the samples oxidized under a dry oxygen gas, whereas, the spallation was not detected on the samples oxidized under a wet oxygen gas. Moreover, by water vapor mixing gas, the alloy surface presented a finer oxide. XRD and Raman spectroscopy provided the coincident oxide identification results. The corundum oxide of (Fe,Cr)2O3and the spinel oxide of (Fe,Cr)3O4were identified as a typical thermal oxide, however, the oxides were different in stoichiometry. The existence of water vapor promoted a Cr2O3corundum oxide, whereas, a Fe3O4spinel oxide was hindered from the outer oxide layer. Hence, water vapor not only clearly influenced on oxide scale morphology but also affected on stoichiometry of (Fe,Cr)2O3and (Fe,Cr)3O4solid solution.

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Broadening coefficients of water vapor lines induced by pressure of hydrogen, temperature dependence

Оптика атмосферы и океана ◽

10.15372/aoo20161004 ◽

2016 ◽

Keyword(s):

Water Vapor ◽

Temperature Dependence

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The effect of water vapor in increasing growth stresses in the oxide scale on martensitic steam plant alloys

Materials at High Temperatures ◽

10.3184/096034005782750446 ◽

2005 ◽

Vol 22 (1) ◽

pp. 139-146 ◽

Cited By ~ 4

Author(s):

Alexander Donchev ◽

Harald Fietzek ◽

Vladislav Kolarik ◽

Daniel Renusch ◽

Michael Schütze

Keyword(s):

Water Vapor ◽

Oxide Scale ◽

Growth Stresses ◽

Effect Of Water ◽

Steam Plant

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Water vapor transport in the lower mesosphere of the subtropics: a trajectory analysis

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-7273-2008 ◽

2008 ◽

Vol 8 (23) ◽

pp. 7273-7280 ◽

Cited By ~ 8

Author(s):

T. Flury ◽

S. C. Müller ◽

K. Hocke ◽

N. Kämpfer

Keyword(s):

Water Vapor ◽

Trajectory Analysis ◽

Microwave Radiometer ◽

Rotational Transition ◽

Transport Processes ◽

Water Vapor Transport ◽

Transition Line ◽

Wind Fields ◽

Large Variability ◽

Northern India

Abstract. The Institute of Applied Physics operates an airborne microwave radiometer AMSOS that measures the rotational transition line of water vapor at 183.3 GHz. Water vapor profiles are retrieved for the altitude range from 15 to 75 km along the flight track. We report on a water vapor enhancement in the lower mesosphere above India and the Arabian Sea. The measurements took place on our flight from Switzerland to Australia and back in November 2005 conducted during EC- project SCOUT-O3. We find an enhancement of up to 25% in the lower mesospheric H2O volume mixing ratio measured on the return flight one week after the outward flight. The origin of the air is traced back by means of a trajectory model in the lower mesosphere and wind fields from ECMWF. During the outward flight the air came from the Atlantic Ocean around 25 N and 40 W. On the return flight the air came from northern India and Nepal around 25 N and 90 E. Mesospheric H2O measurements from Aura/MLS confirm the transport processes of H2O derived by trajectory analysis of the AMSOS data. Thus the large variability of H2O VMR during our flight is explained by a change of the winds in the lower mesosphere. This study shows that trajectory analysis can be applied in the mesosphere and is a powerful tool to understand the large variability in mesospheric H2O.

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Difference oxidation behaviors of Ni8Al and Ni25Cr coatings in air with water vapor at 650∘

Modern Physics Letters B ◽

10.1142/s0217984921502742 ◽

2021 ◽

pp. 2150274

Author(s):

Dingjun Li ◽

Wenlang Huang ◽

Xiaohu Yuan ◽

Taihong Huang ◽

Chao Li ◽

...

Keyword(s):

Water Vapor ◽

High Velocity ◽

Cyclic Oxidation ◽

Oxidation Behaviour ◽

Fuel Spray ◽

High Velocity Oxygen Fuel ◽

Service Environment ◽

Generator Unit ◽

Oxygen Fuel ◽

Oxidation Behaviors

The oxidation behaviour of Ni8Al and Ni25Cr coatings produced by high velocity oxygen fuel spray (HVOF) which were deposited on Fe-based alloys (CB2) was investigated. We simulated the service environment of the steam generator unit, and put the samples in a thermostatic tube furnace at 650[Formula: see text] in air with 20 wt.% water vapor for 1000 hours of cyclic oxidation. The formation mechanism are explained using SEM, XRD, and EDX. There were no spallations and obvious cracks in both coatings. Ni25Cr coating generated a better protection oxides scale than that scale on Ni8Al. The behavior and mechanism of the oxide scale formation had an important influence in coatings and we have discussed these phenomenons in the study.

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