High Temperaturc Oxidation of Fe-20Cr-4Al Alloys with Small Additions of Rare Karth Elements (Y, La. Gd)

摘要

The oxidation behavior of Fe-20Cr-4Al, Fe-20Cr-4Al-0. 021 La, Fe-20Cr-4Al-0.050La. Fe-20Cr-4Al-0.05Ti-0.003Y, Fe-20Cr-4Al-0.05Ti-0.021Y, Fe-20Cr-4Al-0. 05Ti-0.005Gd and Fe-20Cr-4Al-0.05Ti-0.007Gd alloys was studied for 18. Oks at 1473 and 1573K in O_2 by mass change measurements. X-ray diffraction and scanning electron microscopy. The mass changes of Fe-20Cr~4Al alloy showed negative values at the both temperatures of oxidation. The result suggested that spall ing of the oxide on the Fe-20Cr-4Al alloy occurred over the entire surface during cooling. The mass change of the other alloys showed positive values at both temperatures of oxidation and increased in the order of Fe-20Cr-4Al-0.05Ti-0.021Y < Fe-20Cr-4Al-0.05Ti-0.005Gd < Fe-20Cr-4Al-0.050La< Fe-20Cr-4Al-0.05Ti-0. 007Gd < Fe-20Cr-4Al-0. 021La < Fe-20Cr-4Al-0.05Ti-0.003Y after oxidation at 1573K. The oxides on all the alloys were mainly α-Al_2O_3 The oxide on the Fe-20Cr-4Al alloy had a convoluted morphology, and many microvoids were observed into the oxide after oxidation at 1473K. Oxide scales on the alloys with rare earth elements had good adherence, and they were almost planar. The oxide adherence of these alloys may be correlated to their oxide morphologies.