Characterization of Oxide Scales Formed on Ferritic Stainless Steel 441 at 1,100 °C under water vapor

Abstract

This study focuses on the characterization of the oxide scales formed after different exposure times in the range of 2.5-20 min. A commercially available ferritic steel grade AISI 441 was exposed to wet argon at 1100°C with 5, 9 and 13% H 2 O. Raman microspectroscopy, XRD, EDS and XPS were used to fully characterize the oxide scale. For all samples exposed for over 4 min, the scale was constituted of three layers in this order: a thin top layer of spinel phases (Fe,Cr,Mn) 3 O 4 with local outgrowths; a second and main layer of Cr 2 O 3 ? (Mn,Cr) 3 O 4 ; and finally a bottom layer of SiO 2 . The uncommon presence of Fe in the top layer was also observed.

Design of stainless steel porous surfaces by oxide reduction with hydrogen

“…As seen in a previous work [11], the former oxide of Type 2 was a mix of mainly Cr 2 O 3 and some Mn-Cr spinel oxides. These oxides are thermodynamically very stable and are thus difficult to reduce.…”

“…1.b and is mainly composed of chromium and manganese oxides. That type of oxide scale has been investigated in depth and previously published [11].…”

“…Such a morphology should be more difficult to control as it is not possible to adjust the parameters drawing on the existing literature, as for Type 1. Thickening the former oxide is also difficult [11] as it reaches a steady state. Using that method to improve the amount of porosity is not as relevant.…”

“…In the first step an oxide scale is built using specific steel grade and oxidation conditions. This step has been studied in previous investigations [10,11]. In the second step, after obtaining the oxide scale on a significant thickness, samples have been reduced using an adapted reduction time to obtain satisfactory morphologies.…”

Corrosion and Oxidation Behavior of Polymer Derived Ceramic Coatings With Passive Glass Fillers on Aisi441 Stainless Steel

“…However, the corrosion and oxidation performance of the steel is not sufficient for a long-term operation at higher temperatures [1]. A non-protective (Mn,Cr) 3 O 4 spinel layer is formed at the surface when the steel is exposed to oxidation environment at T > 800°C, together with a protective Cr 2 O 3 underneath the (Mn,Cr) 3 O 4 spinel layer [2]. Some authors report that the oxide film is composed of chromia (Cr 2 O 3 ) or chromiumrich iron oxide ((Cr,Fe) 2 O 3 ) in the inner part and by a manganese-chromium spinel oxide (Mn,Cr) 3 O 4 in the outer part [3,4].…”