A New Theoretical Approach to the Thermodynamic Calculation of High-Temperature Oxidation of NiCr Alloys

Yu. Ya. Andreev and A. A. Shumkin

Moscow State Institute of Steel and Alloys, Leninskii pr. 4, Moscow, 117936 Russia

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Received April 12, 2005

Abstract — In calculations, not only the Gibbs formation energy of nickel and chromium oxides and thermodynamic activities of the alloy components, but also the Gibbs surface energy of a Ni–Cr alloy is taken into account. The method is based on the adsorption model of the alloy oxidation, according to which the adsorption of an alloy component with the smaller surface energy, namely, nickel, at the alloy–oxide film interface bound-ary shifts the dynamic equilibrium between the alloy and oxide-film components toward the formation of NiO. For the oxidation of Ni–Cr alloys, which are solid solutions with an fcc lattice, at 1123 to 1473 K, concentration boundaries of the chromium content in the alloy are calculated for the case of the prevailing formation of Cr₂O₃ oxide, which determines the high heat resistance of Ni–Cr alloys.