Oxidation Behavior of Nb-20Mo-15Si-5B-20Cr and Nb-20Mo-15Si-5B-20Ti Alloys Up to 1300℃

摘要

Nb-20Mo-15Si-5B-20Cr (Cr alloy) and Nb-20Mo-15Si-5B-20Ti (Ti alloy) alloys have been subjected to oxidation in air for 24 hours in a range of temperatures from 700 to 1300℃. As cast structures contain Nb_(ss), Nb_5Si_3, and Nb_3Si in both alloys but Cr alloy also contains NbCr_2. Cr alloy exhibits better oxidation resistance than Ti alloy. Oxidation characterization has been carried out for samples heated in 700-1300℃ temperature range. Large number of oxides of Nb, Mo, Si, Cr, and Ti has been observed as characterized by XRD, x-ray mapping, and EDS on SEM. The scale in immediate contact with the alloy substrate has been found to usually contain Mo oxides. Swollen oxide/metal mixture appears at 900, 1200 and 1300℃ for Ti alloys and between 1100 and 1300℃ for Cr alloy.