High-temperature oxidation of Fe-Cr alloys in air

Author: Goncharov O.   Kanunnikova O.  

Publisher: MAIK Nauka/Interperiodica

ISSN: 0020-1685

Source: Inorganic Materials, Vol.43, Iss.5, 2007-05, pp. : 515-519

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Abstract

The scales formed on the Fe-Cr (19, 29.5, and 46.8 at % Cr) and Fe70Cr15B15 alloys in the initial stages of oxidation in air at 1470 K have been analyzed using depth profiling. The results demonstrate that the Cr/(Fe + Cr) ratio in the scales on the Fe-Cr alloys is close to 30 at %, independent of the bulk chromium concentration. The top scale layers on the Fe-Cr alloys consist predominantly of M2O3 (M = Cr, Fe) solid solutions and CrO2, the intermediate layers are composed of (Fe, Cr)3O4 and FeO, and the internal oxidation and nitridation layers consist of chromium oxides and nitrides. The top scale layers on the oxidized Fe70Cr15B15 alloy contain, in addition, boron oxides, and the internal nitridation product is BN instead of chromium nitrides.