CPL - Chalmers Publication Library
| Utbildning | Forskning | Styrkeområden | Om Chalmers | In English In English Ej inloggad.

The effect of water vapor on the initial stages of oxidation of the FeCrAl alloy Kanthal AF at 900 degrees C

Helena Götlind (Institutionen för kemi- och bioteknik) ; Fang Liu (Institutionen för teknisk fysik, Mikroskopi och mikroanalys) ; Jan-Erik Svensson (Institutionen för kemi- och bioteknik, Oorganisk miljökemi) ; Mats Halvarsson (Institutionen för teknisk fysik, Mikroskopi och mikroanalys) ; Lars-Gunnar Johansson (Institutionen för kemi- och bioteknik, Oorganisk miljökemi)
OXIDATION OF METALS 67 (5-6): 251-266 JUN ( 0030-770X ). p. 251-266. (2007)
[Artikel, refereegranskad vetenskaplig]

The effect of water vapor on the initial stages of oxidation of the FeCrAl alloy Kanthal AF is reported. Polished samples were exposed isothermally at 900 degrees C for 1, 24, 72 and 168 h in a well-controlled environment consisting of dry O-2 or O-2 + 40% H2O. The samples were investigated using a combination of gravimetry and several surface-analytical techniques, including XRD, SEM, EDX, FIB, AES and TEM. The presence of water vapor significantly accelerates oxidation during the first 72 h. A two-layered oxide forms in both the dry and wet environments. The bottom layer consists of inward-growing alpha-Al2O3 while the outer layer initially consists of outward-growing gamma-Al2O3. A straight and narrow Cr-enriched band is present at the top of the lower (alpha-Al2O3) oxide, corresponding to the original sample surface. In dry O-2, the top (gamma-Al2O3) layer is converted into a mixture of gamma-Al2-x (Mg,Fe) (x) O-3-(x/2),O- MgAl2O4 and alpha-Al2O3. This transformation does not occur in O-2 + H2O. The initial acceleration of oxidation by H2O is attributed to the stabilization of the outward-growing gamma-alumina layer by the hydroxylation of the gamma-Al2O3 surface. A schematic mechanism of the early stages of oxidation of FeCrAl alloys is presented, emphasizing the influence of water vapor.

Nyckelord: HIGH-TEMPERATURE OXIDATION; ALUMINA SCALES; DRY O-2; GROWTH; DEPENDENCE; BEHAVIOR; FOILS



Denna post skapades 2008-01-14. Senast ändrad 2017-10-03.
CPL Pubid: 66029

 

Institutioner (Chalmers)

Institutionen för kemi- och bioteknik (2005-2014)
Institutionen för teknisk fysik, Mikroskopi och mikroanalys (2005-2012)
Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)

Ämnesområden

Kemi

Chalmers infrastruktur