THE REACTIVE ELEMENT EFFECT IN COMMERCIAL ODS FECRAL ALLOYS

Two commercial oxide dispersion strengthened alumina-forming FeCrAl alloys, Inco alloy MA956 and Kanthal alloy APM, were studied in order to look at the effect of reactive elements on their oxidation behaviour. MA956 has a distribution of Y(2)O3-Al2O3 particles, while APM has a ZrO2-Al2O3 distribution. Isothermal oxidation at 1000 degrees C and 1200 degrees C showed a reduced oxidation rate for both alloys compared to that of an undoped FeCrAl alloy. In short-term cyclic tests at 1200 degrees C, both alloys exhibited excellent scale adhesion. Using scanning transmission electron microscopy with X-ray energy dispersive spectroscopy, both Y and Zr, respectively, were found to segregate to the oxide grain boundaries and the metal-scale interface after oxidation at 1000 degrees C and 1200 degrees C. These experimental observations are discussed with regard to a new theory to explain the reactive element effect.