Oxidation of (Cr,Ti)(2)AlC Compounds at 700-1000 degrees C for One Year in Air

Abstract

(Cr,Ti)(2)AlC compounds were synthesized by hot pressing, and oxidized at 700, 850, and 1000 degrees C in air for up to one year. They consisted of Ti-incorporated Cr2AlC phase, Ti-rich phase, and Cr-rich phase. The formed scales divided into a uniform oxide layer and oxide nodules. The uniform oxide layer consisted primarily of a thin Al2O3 scale. The oxide nodules that originated from the Ti-rich phase consisted of TiO2, which grew by both the outward diffusion of Ti4+ ions and inward diffusion of O2- ions. Chromium did not appreciably enter the oxide scale. Instead, it existed in the Ti-incorporated Cr7C3 sublayer after oxidation. (Cr,Ti)(2)AlC compounds had good oxidation resistance, because of formation of the Al2O3 barrier layer.