Atom probe tomography of thermally grown oxide scale on FeCrAl

Thermally grown Al2O3 scales formed on a FeCrAl alloy were successfully analyzed using pulsed green laser atom probe tomography. Two types of atom probe tomography specimens, the “thin oxide” type: a thin Al2O3 layer (<100 nm) with underlying metal (1 μm), and the “thick oxide” type: only with Al2O3 (1 μm), were prepared and analyzed. It was found that the thin oxide type yields poorer mass resolution due to a combined effect of laser absorption and thermal conduction effects. Application of a relatively low laser energy yields a better mass resolution and increased multiple events, however, more accurate quantification results. Although no other oxide phase than Al2O3 is expected to form, some iron–oxygen and chromium–oxygen molecular ions were recorded at the Al2O3/metal interface due to the large change in evaporation field over this zone.

► Thermally grown Al2O3 scales formed on a FeCrAl alloy were successfully analyzed.
► Specimens with a thin oxide and underlying metal yield poorer mass resolution.
► Low laser energy yields a better mass resolution.
► Fe–O, Cr–O molecular ions were found at Al2O3/metal interface; this is an ion evaporation effect.