High-temperature oxidation of Al₂O₃-forming heat-resistant alloys with small amounts of sulfur and reactive elements at 1373 and 1473K

Abstract

High-temperature oxidation behavior of Fe-20Cr-4Al alloys with small amounts of sulfur and reactive elements (Y, Hf) were studied for 360ks in air at 1373 and 1473K by mass change measurements, observation of surface appearance of the alloys, X-ray diffraction, scanning electron microscopy and electron probe X-ray microanalysis. Small amounts of yttrium to the alloy showed the increased oxidation resistance. On the other hand, oxide scales on the 900 and 1900ppmHf alloys spalled the entire surface after oxidation at 1473K for 360ks. These results may be attributed to their thermal stability and the differential free energies of yttrium and hafnium sulfides.