Temperature and oxidation resistance of the ODS materials MA 956 and PM 2000

The objective of the present paper was to show the various macro-lmicrostructural appearances of the ODs materials MA 956 and PM 2000 at the surface and in the bulk after exposure to high temperatures in combustion chambers (gaseous environment). At the surface a chromium oxide layer forms above the alumina layer originally formed after preoxidation. At locations where the surface has been melted these two oxide layers disappear and an iron oxide showing cracks forms at the surface. Several cracks run into the material. In the bulk material due to high thermal gradients a porosity of up to 18 % in MA 956 and 2% in PM 2000 develops during operation (Kirkendall effect). With longer operation times, at higher temperatures and probably in other environments (chemical cracking of the fuel) internal oxidation or nidriding of aluminium andlor formation of chromium carbides take place.