Concentration profiles in the underlying alloy during the oxidation of iron-chromium alloys
Abstract Compositional changes in Fe-27.4, 37.4 and 59.5% Cr alloys during the formation of Cr 2 O 3 -rich scales have been measured by electron probe microanalysis and calculated by solution of the appropriate transport equations. Agreement between corresponding results is within the limits of experimental error. Chromium concentration profiles have also been calculated for Fe-14.0 and Fe-18.0% Cr by a similar method, allowance being made for the formation of γ-phase at the surface of the alloy. The chromium concentration at the alloy/oxide interface never falls below the limiting value for thermodynamic stability of a Cr 2 O 3 scale. Chemical transformation of the Cr 2 O 3 scales from within is therefore not possible and the failure of such scales on Fe-14.0 and Fe-18.0% Cr is attributed to mechanical causes.