Insights on in situ MgAl2O4 Formation Mechanism and its Correlation with the Corrosion Resistance of Spinel-containing Refractory Castables
1 Federal University of São Carlos, Materials Microstructural Engineering Group, GEMM (FIRE Associate Laboratory) 13565-905 São Carlos/Brazil
2 Saint-Gobain do Brasil, Refractories Technical Department, 13280-000 Vinhedo/Brazil
Revision 02.11.2013, 26.11.2013
Volume 6, Issue 1, Pages 79 - 83
Abstract
The in situ formation of magnesium-aluminate spinel (MgAl2O4) is usually followed by a positive volumetric change and a resulting pore generation after the reaction. However, when compared to castables containing synthesized spinel grains, in situ spinel-forming castables usually show excellent corrosion performance in both laboratorial tests and industrial applications, even presenting such expansive reaction and apparently a more porous microstructure. Considering this scenario, the objective of the present work is to shed some light on these two main questions: a) what does really rule the in situ spinel formation in refractory castables, and b) if this phase formation reaction is followed by expansion and pore generation, why do spinel-forming castables present excellent corrosion resistance in industrial applications. The results suggested that the faster Mg2+ migration during the spinel formation led to vacancy accumulation and, consequently, to pore generation, as a direct result of the Kirkendall effect. Nonetheless, its performance is less affected by such mechanism then by the location of CA6 crystals in its microstructure (as these castables are usually bonded with CAC), which results in a suitable physicochemical protection of both, the tabular alumina aggregates and the matrix.
Keywords
spinel castables, in situ formation, corrosion resistance
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