The promoted formation of an α-Al2O3 scale on a nickel aluminide with surface Cr2O3 particles

A concept has been proposed that spreading particles of oxide (e.g., Cr2O3) with the same crystallographic structure as α-Al2O3 onto an alumina-forming aluminide can promote the growth of α-Al2O3 at high temperatures. This is in agreement with experimental observation that a Ni2Al3 experiences a θ-to-α Al2O3 transformation while the Cr2O3-treated one only grows α-Al2O3 during oxidation in air at 1000 °C. The θ-α phase transformation bypassing by the surface Cr2O3 particles decreases the oxidation rate of the aluminide and prevents the phase-transformation-induced negative effects of the formation of microcracks in the alumina scale and cavities at the scale/metal interface.