The oxidation of iron at 950°C in oxygen/water vapour mixtures
TL;DR: In this article, the presence of steam has been found to accelerate the oxidation in oxygen of mild steel and two grades of pure iron of varying purity, and the effect was found to be greater on round test pieces than on flat rectangular ones.
About: This article is published in Corrosion Science.The article was published on 1969-01-01. It has received 81 citations till now. The article focuses on the topics: Oxide & Hydrogen.
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TL;DR: In this paper, the effect of water vapour on the formation of a more porous scale is discussed. But, while there is experimental evidence for altered mechanical behaviour, there is very little data on relevant mechanical properties.
505 citations
TL;DR: In this article, the authors studied high temperature oxidation in air of Fe13Cr-x Al alloys containing up to 4.5 Al in the temperature range 680-980°C.
132 citations
TL;DR: In this article, a hot-stage, environmental scanning electron microscope has been used to observe the in situ development of oxide whiskers, pyramids, and pits in the oxidation of copper and nickel at elevated temperatures.
Abstract: A hot-stage, environmental scanning electron microscope has been used to observe the in situ development of oxide whiskers, pyramids, and pits in the oxidation of copper and nickel at elevated temperatures. The effects of oxidation temperature, metal deformation, and the presence of water vapor on these irregular oxidation features were studied. In each case, the feature results from the presence of a central screw dislocation which provides ledges for the extension of the oxide lattice, but the specific geometries are decided by factors such as surface diffusion along the dislocation core, the rate of the molecular dissociation step, and the balance of surface energy and dislocation line tension forces.
130 citations
TL;DR: In this paper, a number of alloys and coatings that form α-Al2O3 scales under oxidizing conditions were investigated at 1100 °C in dry air and air containing fixed partial pressures of water vapor.
Abstract: Oxidation studies were performed at 1100 °C in dry air and air containing fixed partial pressures of water vapor on a number of alloys and coatings that form α-Al2O3 scales under oxidizing conditions. The alloys investigated included RENE N5, PWA 1484, diffusion aluminide coatings (with and without Pt modification) on RENE N5, and a Ni-8 wt pct Cr-6 wt pct Al model alloy. The water vapor affected the oxidation of the alloys in three important ways: (1) The scales spalled more profusely during cyclic oxidation in wet air than in dry air, particularly for those alloys with alumina scales, which are only moderately adherent under dry conditions. The results were consistent with the mechanism previously proposed (Reference 1), whereby the water molecules decrease the fracture toughness of the alumina/alloy interface. (2) Thicker oxides are formed during oxidation in wet air than dry air. This effect comes primarily from accelerated transient oxidation during exposure in wet air. (3) Spinel was found to form on top of the alumina scales during long-term exposure. This phenomenon occurred in all atmospheres but was much more pronounced for exposures in wet atmospheres. Mechanisms for the preceding observations are proposed.
89 citations
TL;DR: In this article, it is proposed that water vapor causes stress corrosion cracking at the Al2O3-alloy interface during cyclic oxidation, which increases the degradation rate by a factor of 2.
Abstract: Cyclic oxidation tests have been performed at 1100 °C in wet and dry air on a number of alloys and coatings that form α-Al2O3 scales upon exposure to oxidizing conditions. The alloys that were investigated included PWA 1480, PWA 1484, CMSX 4, diffusion aluminide coatings on PWA 1480 and PWA 1484, and Co-24Cr-10.5Al-0.3Y. In cases where some cracking and spalling of the alumina scales occurred in dry air, the presence of water vapor caused the degradation rate to be increased by a factor of 2. When no cracking or spalling of the alumina occurred in dry air, as was the case for low sulfur alloys, water vapor had no effect on the oxidation behavior. It is proposed that water vapor causes stress corrosion cracking at the Al2O3-alloy interface during cyclic oxidation.
86 citations
References
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TL;DR: In this article, ausammenfassung Wahrend Wasserdampf und Kohlendioxyd the Oxydationsgeschwindigkeit von Eisen und Eisenlegierungen erhohen, haben diese Gase keinen Einfluss auf die Oxydation des Nickels.
187 citations
TL;DR: A comprehensive survey of the literature with regard to the subject of hydrogen embrittlement in metals can be found in this paper, where the authors present a detailed critical analysis of the characteristics and mechanisms of hydrogen brittleness in the body-centered-cubic metals (including steel, titanium, alphazirconium and alpha-uranium).
159 citations
TL;DR: In this article, the authors discuss the mechanische Haftung zwischen Zunder and Metall durch einen Fliessvorgang der Zunderschicht aufrechterhalten wird.
76 citations
TL;DR: In this paper, a new mechanism of high temperature oxidation of iron is proposed, where diffusion of lattice vacancies in the iron is shown to influence the type of oxide that forms.
Abstract: A new mechanism of high temperature oxidation of iron is proposed. Diffusion of lattice vacancies in the iron is shown to influence the type of oxide that forms. It was found that with thi...
52 citations
TL;DR: In this article, the authors conducted a series of experiments in Sauerstoff, Luft, CO2 and Wasserdampf and found that the results tended to be lower then those corresponding to the ideal parabola.
Abstract: Die Versuche wurden durchgefuhrt in Sauerstoff, Luft, CO2 und Wasserdampf sowie in Luft mit bis 15% Wasserdampf; die Versuchsdauer betrug bis 200 min. Fur die Oxydation von Reineisen und Stahl in Sauerstoff und Luft ergab sich ein parabolisches Zeitgesetz, das jedoch bei langerer Versuchsdauer unter dem der idealen Parabel entsprechenden Wert sank. In Wasserdampf wurde Reineisen bei 850° C linear oxydiert, bei hoheren Temperaturen lag das Zeitgesetz zwischen einer Geraden und einer Parabel. Der Weichstahl verhielt sich ahnlich, doch war hier die Abweichung bei hoheren Temperaturen weniger ausgepragt. In CO2 ergab sich fur beide Probenarten ein lineares Zeitgesetz. Ganz allgemein wurde Reineisen doppelt so schnell oxydiert wie Stahl; die Oxydationsgeschwindigkeit nahm in der Reihenfolge Sauerstoff — Wasserdampf — Kohlendioxid ab.
Bei parabolischer Oxydation bestand der Zunder immer aus drei Schichten, bei linearer Oxydation nur aus einer (Wustit).
In Luft mit Wasserdampf ergab sich immer ein parabolischer Verlauf, ohne das ein deutlicher Einflus des Wasserdampfzusatzes (2,5 bis 15 % zu erkennen gewesen ware.
Scaling rate of pure iron and mild steel in oxygen, water vapour and carbon dioxide at temperatures ranging from 850 to 1000° C
The tests were carried out in oxygen, air, CO2 and water vapour as well as in air with up to 15 per cent water vapour. The duration of the tests was up to 200 minutes. The oxidation of pure iron and steel in oxygen and air, as a function of time, was found to follow a parabolic law; with tests of long duration, however, the results tended to be lower then those corresponding to the ideal parabola. In water vapour, pure iron was found to oxidize at 850° C at a linear rate; at higher temperatures, the curve followed an alignment between straight line and parabola. Mild steel showed similar characteristics except that the deviation at higher temperatures was less marked. In CO2 the curve was linear with both samples. Generally speaking, the oxidation rate of pure iron was found to be twice as high as that of steel. The oxidation rate decreased in the sequence: oxygen, water vapour, carbon dioxide.
With parabolic oxidation, the scale always consisted of three layers; with linear oxidation, it consisted of one layer only (Wustit).
In air with water vapour content, the curve was parabolic in all cases although no distinct influence of the water vapour addition 2.5 to 15 per cent.) was recognizable.
9 citations