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RESEARCH PRODUCT

Influence of the mode of introduction of a reactive element on the high temperature oxidation behavior of an alumina-forming alloy. Part I: Isothermal oxidation tests

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Several routes of yttrium introduction were applied to test the high temperature oxidation performance of a FeCrAl alloy. Isothermal oxidation tests were described in a previous paper (Part I of this paper in this journal, 2004, 55, 352). Cyclic oxidation tests were performed in air under atmospheric pressure on blank specimens, Y 2 O 3 sol-gel coated-, Y 2 O 3 metal-organic chemical vapor deposited (MOCVD)-, yttrium ion implanted-alloys, as well as on a steel containing 0.1 wt.% of yttrium as an alloying element. For the 20 hours cycles, all the samples, except FeCrAl-0.1Y, exhibit weight losses after a few cycles, indicating drastic spallation of the oxide scales. The MOCVD coated specimen has the highest weight loss. The oxidation kinetics of the FeCrAl-0.1Y alloy obey a parabolic law, indicating that the alumina scale formed on its surface is protective even after more than 1200 hours of oxidation (>50 cycles). The 100 hours cycle oxidation tests give similar results. The FeCrAl-0.1 Y alloy exhibits the best oxidation behavior with very little spallation after more than 2000 hours (85 days) of oxidation at 1100 °C (20 cycles). Most of the other samples exhibit severe oxide scale spallation followed by an increase of their oxidation rate related to the formation of non-protective iron oxides.