In-situ method to monitor surface reaction/oxidation at high temperature
The formation of external Cr2 O3 scale is important to obtain the oxidation resistance of Fe-Cr alloys at high temperatures. It is well known that the critical concentration of Cr to form protective external scale of Cr2 O3 in humid condition is higher than that in dry condition, and the cri...
| Main Authors: | , , , , |
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| Format: | Conference or Workshop Item |
| Language: | English |
| Published: |
2010
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/23104/ http://irep.iium.edu.my/23104/ http://irep.iium.edu.my/23104/1/p39.pdf |
| Summary: | The formation of external Cr2
O3 scale is important to obtain the oxidation resistance of Fe-Cr alloys at
high temperatures. It is well known that the critical concentration of Cr to form protective external scale
of Cr2
O3
in humid condition is higher than that in dry condition, and the criterion of this concentration is
expressed as Wagner’s equation. To determine this concentration experimentally, a lot of mass gain data
and metallographic surveys are required. An in-situ method of continuous monitoring of surface oxygen
potential by oxygen concentration cell using stabilized zirconia has been developed and applied to the
oxidation of Fe-Cr alloy in order to check the protectiveness of the scale. In our previous work, the
oxygen chemical potential on growing oxide scales during high temperature oxidation of Fe, Ni, and Co
were successfully measured. In this study, the surface oxygen potentials of Fe-0~17 wt% Cr alloys in Ar-
21%O2
gas as dry condition and Fe-10~22 wt% Cr alloys in Ar-20%O2
-20%H2
O gas as humid condition
were measured at 1073 K up to 20 ks.
In dry condition, the surface oxygen potentials of Fe with more than 10 wt% Cr alloys were close to
the oxygen potential of atmosphere immediately after the heating period. It indicates that protective Cr2
O3
scale formed on these alloys at early stage of oxidation. However, the surface oxygen potentials of these
same composition alloys were lower in humid condition than that in dry. By this method, the
protectiveness of scales formed on Fe-Cr alloys can be evaluated in-situ in a few hours. |
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