Protecting layers against carburizing atmospheres are of great importance for high temperature alloys. Very good results have been obtained with a model alloy FeAl0.5Ti. For a single crystal sample of this alloy, the composition and growth of the protecting layers were studied by AES and LEED. Excellent epitaxial fit was observed for a titanium oxycarbide layer growing on (100) and (110) oriented samples at high temperatures by surface segregation of C and Ti in oxygen containing atmosphers. At the same time Al segregated to the surface and diffused through this carbide layer. Reaction with oxygen led to the formation of an epitaxial Al 2 O 3 layer on top of the carbide. Both layers were very dense and well adherent even for high quenching rates. Only very small amounts of carbon impurity were able to penetrate through the dense Al 2 O 3 layer and were captured by the oxycarbide layer.
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Viefhaus et al. (1987) studied this question.