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On ultra-high temperature oxidation of Cr–Cr3Si alloys: Effect of germanium

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  • Partly presented at the Plansee Seminar 2013.

Abstract

The oxidation behavior of Cr–Cr3(Si1−XGeX) alloys with the composition range Cr85GeXSi1−X (0 < X < 15) was studied at 1350 °C. Thermogravimetric measurements showed improved oxidation kinetics by alloying up to 2 at% of Ge, but a significant weight loss was observed when higher Ge was added. Phase analysis and composition of the spalled oxide scales and subscale alloy substrates revealed that eskolaite (Cr2O3) forms the protective scale, while SiO2 (cristobalite) is locally formed below the chromia scale. Addition of up to 2 at% altered the morphology of locally formed silica and subsequently affected the spallation of chromia scale. The morphological observations of the different chromia scales are discussed for all alloys oxidized at 1350 °C.

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