ABSTRACT
In the oxidation of alloys phenomena at the interface oxide/metal are important for the nucleation, adherence and morphology of oxide scales. Such phenomena can be observed by AES and LEED in the initial stages of oxidation or after laying bare the interface by fracture or spallation of the oxide. Three studies are reported:
In the system Fe-Al-Ti-C the formation of a thin epitaxial layer of Ti(C,O) beneath the alumina layer favours the nucleation of (α-Al2O3 and improves its adherence.
Initial formation of epitaxial CrN layers in the oxidation of Fe-20Cr in N2-H2O-H2 mixtures leads to an increased roughness and porosity of the Cr2O3 layer, the oxidation rate is enhanced compared to oxidation in the absence of N2.
Processes causing void formation beneath oxide scales are favoured and accelerated by sulphur segregation from the alloy to the surface of the voids and cavities, no sulphur segregation was observed at coherent chromia/or alumina/metal interface.
