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- Jonsson, Torbjörn, 1970, et al.
(författare)
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The influence of KCl on the corrosion of an austenitic stainless steel (304L) in oxidizing humid conditions at 600 ºC: A microstructural study
- 2009
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 72:3, s. 213-239
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Tidskriftsartikel (refereegranskat)abstract
- The effect of KCl on the corrosion behavior of the austenitic stainless steel 304L was studied at 600 A degrees C in 5% O(2) + 40% H(2)O + N(2). The breakdown of the protective oxide was investigated. This was done through a detailed microstructural characterization of the oxide scales formed after 1, 24 and 168 h. The oxidized samples were investigated by SEM/EDX, FIB and STEM/EDX. The presence of KCl(s) causes a breakdown of most of the protective scale, even though it is not in direct contact with KCl(s) particles, starting after just 1 h exposure. A fast growing porous oxide formed in direct contact with (former) KCl(s) particles and an about 2 mu m thick scale covered most of the surface. Only some regions were covered by a thin scale. K(2)CrO(4) particles were randomly distributed all over the scale after 1 h exposure. The particles are situated above the oxide scale and are not in direct contact with the subjacent metal. The thin scale contains lower Cr levels than has been observed in corresponding scales formed in the absence of KCl. The breakdown of the protective scale is suggested to be caused primarily by the formation of K(2)CrO(4), depleting the protective oxide in chromium. In addition, chromia evaporation contributes to chromia depletion and breakdown of the protective scale. Very little or no transition metal chlorides were found after breakaway oxidation. Cl is suggested to play a minor role in the initial breakdown of the protective scale. The presence of KCl particles caused local rapid oxidation, which results in an outward growing Fe and Fe-Cr rich porous oxide.
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- Pettersson, Carolina, 1980, et al.
(författare)
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High Temperature Oxidation of the Austenitic (35Fe27Cr31Ni) Alloy Sanicro 28 in O-2 + H2O Environment
- 2010
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 74:1-2, s. 93-111
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigates the high temperature oxidation of alloy Sanicro 28 (35Fe27Cr31Ni) in 5% O-2 and in 5% O-2 + 40% H2O. Polished steel coupons were isothermally exposed in a tube furnace at 600, 700 and 800 A degrees C for up to 168 h. The samples were investigated by gravimetry, grazing angle X-ray diffraction (XRD), Auger electron spectroscopy (AES), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy/energy dispersive X-rays (STEM/EDX). The results show that the material forms a protective scale in both environments. The scale is duplex. The inner part of the scale consists of corundum type chromium-rich (Cr (x) Fe1-x )(2)O-3, and the outer layer consists of spinel type oxide. Chromia is lost from the protective oxide by vaporization of CrO2(OH)(2) in O-2 + H2O environment. The capacity of Sanicro 28 to suffer chromia vaporization without forming a rapidly growing iron-rich oxide is attributed to its high Cr/Fe ratio. The spinel formed at the oxide/gas interface could in addition be beneficial for oxidation behavior in wet oxygen because it may slow down chromia evaporation.
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