Stephan-Scherb, C.; Nützmann, K.; Kranzmann, A.; Klaus, M.; Genzel, C.:
Real time observation of high temperature oxidation and
sulfidation of Fe-Cr model alloys. Materials and Corrosion = Werkstoffe und Korrosion 69 (2018), p. 678-689
10.1002/maco.201709892
Abstract:
Insights into early damage mechanisms during high-temperature gas corrosion
provide important aspects for the prediction of the long-term stability of hightemperature
materials exposed to a hot and corrosive environment. The current work
presents a real time study concerning the combined oxidation and sulfidation of
ferritic model alloys in a hot SO2 containing atmosphere using energy dispersive
X-ray diffraction. The applied high temperature reactor allows the transmittance of
high energetic X-rays in order to collect X-ray diffraction pattern of the sample
surface in situ during the reaction with the reactive environment. The results revealed
that the first phases crystallizing on iron with 2 wt% chromium and with 9 wt%
chromium are oxides. The aging experiments at T = 650° C with 0.5% SO2 and 99.5%
Ar were followed in situ and caused an external mixed oxide-sulfide layer on top of
iron with 2 wt% chromium. On the higher alloyed material the external scale consists
of iron oxides and the inner scale of mixed (Fe,Cr)-oxides and chromium-sulfides.
The oxide content continuously increases parallel to an increase of the sulfide
amount. Thus, the initially formed (Fe,Cr)-oxides do not have a protective character
and support the transport of sulfur through the growing oxide scale.