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2007
Journal Article
Titel
Thermal shock and corrosion behavior of coated crucibles for induction melting of titanium
Abstract
The fabrication of short fibres of titanium by melt extraction has been investigated in close collaboration of the Fraunhofer-Institutes lKTS, EPM and IWS, Dresden. The inductive melting of titanium means a complex demand on melting tanks and the refractory materials respectively. The goal of the ceramic research was to develop a crucible with a high resistance to metal corrosion and thermal shock. Shrinking-free concretes were used to fabricate the tank, which were coated by thermal spraying and/or engobing. With regard to the thermodynamic evaluations and the material expertise the coatings based on systems such as Y-Ti-O, Mg-Al-O, but also hexagonal and gas phase deposited boron nitride, TiB2, and TiC or ZrO2. To develop engobing it was necessary to optimize the coating procedure, the drying, and the co-firing without crack formation or spelling. The corrosion test involves the sessile drop test and the melt corrosion test by inductive heating. Thermal stresses in the wall of the tank and the formation of eutectic melts in the system CaO - Y2O3 - Al2O3 limit the time of the melt extraction at 1730 degrees C to 20 minutes.