Oxidation of FeCrAlY Fibers at Low Oxygen Potentials

Abstract

The oxidation of Fe-15Cr-5Al-0.3Y (wt.%) coupons and 22-lm-diameter fibers has been studied in a helium atmosphere containing *150 ppm oxygen at temperatures of 750-950°C. Thermogravimetric analysis was used to follow kinetics, and oxide scales were analyzed with scanning-electron microscopy, electron-microprobe analysis, and photostimulated luminescence. The observed kinetics behavior of the coupons and fibers is attributed to effects of both transitional aluminas and aluminum depletion in the alloy. Distinct differences are observed with the fibers as compared to the coupons at 900 and 950°C, but similar behavior is observed at 850°C. Pre-oxidation treatments of the fibers at 1,100°C in air formed a thin layer of a-Al 2 O 3 and slowed oxidation dramatically at 850°C. The fibers showed aluminum depletion and formed mixed alumina-chromia scales, which appeared adherent and protective.