Segregation at the Al2O3-FeCrAl interface during high-temperature oxidation

Impurity segregation at the Al2O3-metal interface of Fe-Cr-Al and Fe-CrAl-Y alloys oxidized at 1100 degrees C was studied using Auger electron spectroscopy (AES). A strong sulfur segregation of the order of a monolayer was found at the contact oxide-metal interface on the yttrium-free alloy, while almost no sulfur was detected at the interface on the yttrium-containing alloy, These results are in agreement with the AES studies of surface segregation on the same alloys during heating at 900 degrees C in ultra-high vacuum. It is suggested that stresses in the alumina scale and underlying metal during oxidation may provide the driving force for impurity segregation at the contact oxide-metal interface.