High-temperature interaction of molten vermicular graphite cast iron with Al2O3 substrate

The wetting behavior and reactivity between molten cast iron (originally vermicular graphite cast iron, containing in wt. %: 3.70 C, 2.30 Si, 0.44 Mn, 0.054 P, 0.017 Mg, 0.015 S) and commercial polycrystalline alumina (Al₂O₃ substrate of 99.70% purity and less than 3 vol. % porosity) were investigated. The wettability test was performed under an inert flowing gas atmosphere (Ar, 850-900 hPa) at a temperature of 1450°C for 15 min using a sessile drop method combined with classical contact heating procedure.
The high temperature interaction between molten cast iron sample and Al₂O₃ substrate was continuously recorded with a high-speed high-resolution CCD camera. The results showed that the molten cast iron does not wet the Al₂O₃ substrate (θ = 131°).
After wettability test, the cross-sectioned sessile drop couple was examined using scanning electron microscopy coupled with X-ray energy dispersive spectroscopy. It was found that in the solidified cast iron drop, the graphite phase took the shape of flakes having a different dispersion degree, i.e. vermicular precipitates of graphite did not re-grow during solidification of the drop. Moreover, structural characterization of the drop/substrate interface revealed the layer of about 26 μm thick composed mainly of carbon and located at the drop-side interface while at the substrate-side interface, the reaction zone (~70 μm) formed due interaction between Al₂O₃ and molten cast iron was well distinguished.

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