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On ultra‐high temperature oxidation of Cr–Cr 3 Si alloys: Effect of germanium
Author(s) -
SoleimaniDorcheh A.,
Donner W.,
Galetz M. C.
Publication year - 2014
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201307423
Subject(s) - chromia , spallation , materials science , germanium , alloy , oxide , thermogravimetric analysis , metallurgy , cristobalite , atmospheric temperature range , phase (matter) , kinetics , analytical chemistry (journal) , silicon , chemical engineering , chemistry , thermodynamics , physics , quartz , chromatography , quantum mechanics , neutron , engineering , organic chemistry
The oxidation behavior of Cr–Cr 3 (Si 1− X Ge X ) alloys with the composition range Cr 85 Ge X Si 1− 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 (Cr 2 O 3 ) forms the protective scale, while SiO 2 (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.