C. Courty et al., EFFECTS OF CARBON AND MANGANESE IMPURITIES ON CERIUM INCORPORATION INIRON-OXIDES SCALES, Journal de chimie physique et de physico-chimie biologique, 93(9), 1996, pp. 1509-1524
Comparison of oxidation results (T=700 degrees C - pO(2)=0.04 Pa) obta
ined on ceria-coated Fe-Mn, Fe-C and Fe-Mn-C steels, shows that it is
the Mn-C combination which hinders the cerium incorporation in iron ox
ide scales. Carbon and manganese alone have no detrimental effect on t
he cerium incorporation into an iron oxide scale as a CeFeO3 compound.
The CeFeO3 formation is attributed to an oxidation-reduction process
between the CeO2 coating and the FeO nuclei at the beginning of the ox
idation test. On ceria-coated Fe-Mn-C steel, carbon and manganese impu
rities, together, have a strong influence on the oxidation rate and on
the rare-earth element location. After the coated steel oxidation, ce
rium is located at the scale-gas interface as a CeO2 phase. Cerium is
not incorporated inside the iron oxide scale. This is due to the iron-
manganese carbides presence inside the steel grain boundaries. The car
bide oxidation prevents the formation of CeFeO3 due to the manganese a
nd carbon oxide evaporation at the beginning of the reaction. After th
e coating spallation, no contact between the reducing FeO nuclei and t
he oxidant CeO2 phase is then permitted any more to produce the CeFeO3
phase.