The mechanism of early oxidation stages of Fe20Cr5Al-type alloys at 1123 K

Abstract

Fe20Cr5Al-type alumina forming alloys are known as α alumina-forming materials at relatively high temperatures (≥1273 K). This paper reports on the oxidation mechanism of commercial and synthetic Fe20Cr5Al alloys, at a considerably lower temperature, 1123 K. Some of the alloys were implanted with oxygen or yttrium ions prior to the oxidation exposure.

Two-stage-oxidation, secondary ion mass spectrometry, secondary electron microscopy and lowangle X-ray diffraction were used as experimental tools. Results showed that even prolonged exposures are not sufficient to ensure that the scale consists essentially of α-Al₂O₃. Mechanisms involved from the observed scale morphology, microstructure and phase composition are discussed