THE EFFECTS OF REACTIVE ELEMENT (Y, Hf) ADDITIONS ON THE ADHERENCE OF ALUMINA TO AN Fe-20Cr-4Al ALLOY WITH SULFUR

摘要

The effects of reactive element (10, 300 and 3700 ppmY, 500, 1900 and 4300 ppmHf) additions on the adherence of alumina to an Fe-20Cr-4A1 alloy with sulfur (185 ppmS) were studied in air or oxygen at 1373 K for 18, 360 and 1800 ks by mass-change measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Oxide scales on the 185 ppmS and the 10 ppmY alloys spalled slightly after oxidation for 360 ks, and spalled from the entire surface after oxidation for 1800 ks. On the other hand, spalling of oxide scales from the other alloys practically did not occur after any oxidation time. Mass gains decreased for alloys with small additions of reactive elements, and then increased with increasing content of reactive elements. Oxide scales on the 185 ppmS alloy showed a slightly convoluted morphology, however, surface morphologies of oxide scales on the other alloys with reactive elements, except the 500 ppmHf, were almost planar after oxidation for 1800 ks.