Segregation at the Al2O3-FeCrAl Interface During High-Temperature Oxidation

Impurity segregation at theAl₂O₃-metal interface of Fe-Cr-Aland Fe-Cr-Al-Y alloys oxidized at 1100°C was studiedusing Auger electron spectroscopy (AES). A strong sulfursegregation of the order of a monolayer was found at the contactoxide-metal interface on the yttrium-free alloy, whilealmost no sulfur was detected at the interface on theyttrium-containing alloy. These results are in agreement with the AES studies of surface segregation onthe same alloys during heating at 900°C inultra-high vacuum. It is suggested that stresses in thealumina scale and underlying metal during oxidation may provide the driving force for impuritysegregation at the contact oxide-metalinterface.