THE EFFECT OF IMPLANTED YTTRIUM ON THE OXIDATION BEHAVIOR OF FE-20CR-5AL ALLOY AT 1373-K IN AIR

The influence of implanted yttrium on the oxidation behaviour of an Fe -20Cr-5Al alloy was studied at 1373 K in air under isothermal and ther mal cycling conditions in order to verify previous results obtained at 1473 K which indicated no beneficial effect of this addition. The imp lanted yttrium substantially improved the scale resistance to spalling , only slightly affected the scale growth rate, and altered the scale morphology. On unimplanted material developed ridged scales, while ytt rium promoted the formation of buckled oxide layers, the higher the do se the more buckled the scale. After spalling of the scale from yttriu m implanted material due to prolonged thermal cycling ridges were grow ing instead of buckles. These and previous results showed that the eff iciency of the implanted yttrium depends on its amount in the substrat e and on the reaction temperature as well and that there is no simple correlation between the scale thickness and its resistance to spalling .