Abstract

High temperature oxidation behaviour of chromium-rich iron based alloys containing high carbides fractions

Author(s): Patrice Berthod, Moussa Ba, Ahmed Dia

Six alloys based on {Fe-30wt.%Cr} and containing from2.5 to 5.0 wt.%C, were synthesized by foundry way then tested in oxidation at high temperature. The obtained types of microstructures were hypo-eutectic, eutectic or hyper-eutectic, this depending on the carbon content. The alloys were all composed of ametallic Fe(Cr)matrix and of high fractions of carbides (mainly Cr7C3). Polished samples were exposed to air during 50h at 1000, 1100 and 1200°C. The oxidized surfaces and affected sub-surfaces were analyzed. The bulk microstructures were also characterized to specify the microstructures at high temperature. The oxides were composed of an outer thick (Fe,Cr)2O3 scale and of a thin inner layer of Cr2O3. In the sub-surface a thin carbide-free zone generally has appeared just under the oxide scale.All alloys seemhaving correctly resisted against oxidation at 1000 and 1100°C, but the three carbon-richest ones (4 to 5 wt.%C) obviously suffered catastrophic oxidation.


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