Carburization behavior of FeCrAl alloy APMT and the critical role of pre-oxidation

The carburization behavior of bare and pre-oxidized APMT has been assessed after long-term graphite exposure at 1000 degrees C. Bare coupons formed a thick scale after graphite exposure due to carbon interaction and chromiumrich carbides were detected, as predicted from thermodynamic calculations. Pre-oxidation of APMT was conducted in air, and oxidation kinetics were measured through thermogravimetry. The oxide layer formed at 800 degrees C failed to prevent carburization. However, increasing the pre-oxidation temperature to 1200 degrees C produced an oxide layer with good resistance to carbon diffusion indicating that the alpha-alumina formed at high temperatures is key in preventing carburization of the material.