Abstract
The oxidation behavior of two Ni-based superalloys, Inconel-625 (In-625) and Hastelloy X (Has-X) was studied at 750 ~ 1050 °C in dry air. The oxidation kinetics of both alloys followed a two-stage parabolic-rate law, indicating that diffusion is the rate-controlling step during oxidation. The steady-state rate constants (k p values) of these two alloys were nearly identical. The scales formed on the two alloys were composed of a heterophasic mixture of mostly Cr 2 O 3 and minor MnCr 2 O 4 .