Phenomenon of Whiskers Formation in Al2O3-C Refractories

Pure alumina (Al2O3) and carbon-bonded alumina (Al2O3-C) are used to investigate their interaction with iron (Armco) at 1625 degrees C, applying the sessile drop method. The investigations are conducted inside a heating microscope for 1 h under argon atmosphere with low oxygen partial pressure. No whiskers formation is observed from the experiments with pure Al2O3 and molten iron. In the case of Al2O3-C/Fe system, several phenomena including the decarburization of Al2O3-C, Al2O3-C dissolution in molten iron, Al2O3 layer formation on the iron droplet, and Al2O3 whiskers formation are observed. To clarify the possible influence of iron on Al2O3 whiskers formation, blank Al2O3-C samples without the presence of iron are heated and held in a half-sealed platinum crucible at 1550 degrees C for 2 h. Thereby, the Al2O3 whiskers formation is detected. Finally, the experimental investigations are supported with thermodynamic simulations.