TEM Investigation of the Microstructure of the Scale Formed on a FeCrAlRE Alloy at 900 A degrees C: The Effect of Y-rich RE Particles
Artikel i vetenskaplig tidskrift, 2010

Three oxide features: the thin and smooth protective oxide, reactive element (Ti-, Zr- or Y-rich) particles, and patches of thick oxide surrounding the Y-rich reactive element particles, were observed on a commercial FeCrAlRE alloy, Kanthal AF, exposed at 900 A degrees C. The microstructural development of the patches of thick oxide was investigated on samples exposed for 24 or 168 h in either dry O-2 or O-2 + 40% H2O. Analytical transmission electron microscopy in combination with site-precision TEM sample preparation by FIB/SEM was used. In all patches a thin but continuous inward growing alpha-Al2O3 layer was formed under a thick outward growing alumina layer, which initially consisted only of gamma-Al2O3. In dry O-2, transformation of gamma-Al2O3 (in the outer layer) to alpha-Al2O3 had started during 24 h and a considerable amount of gamma-Al2O3 had transformed after 168 h. The transformation originated immediately above the inward growing alpha-Al2O3. No such transformation occurred in O-2 + H2O. The possible effects of the Y-rich RE particles, as well as the effects of water vapour, on the oxidation were discussed.

adherence

alumina scales

High

oxidation resistance

o-2

Y

kanthal af

h2o

Microstructure

EDX

Al2O3

FeCrAl alloy

TEM

40-percent

oxide scales

minor additions

reactive element

Phase transformation

RE

Water vapour

temperature oxidation

FIB/SEM

dry

transient oxidation

Författare

Fang Liu

Chalmers, Teknisk fysik, Mikroskopi och mikroanalys

Mikael Götlind

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Jan-Erik Svensson

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Lars-Gunnar Johansson

Chalmers, Kemi- och bioteknik, Oorganisk miljökemi

Mats Halvarsson

Chalmers, Teknisk fysik, Mikroskopi och mikroanalys

Oxidation of Metals

0030-770X (ISSN) 1573-4889 (eISSN)

Vol. 74 11-32

Ämneskategorier

Kemiteknik

DOI

10.1007/s11085-010-9195-5