EXPERIMENTAL RESEARCH ON THE ABSORPTION OF FLUORINE IN GAMMA-TiAl DURING ELECTROSLAG REMELTING

摘要

In literature, it has been reported that the so called "halogen effect" significantly improves the oxidation resistance of gamma- TiAl. This effect is based on the formation of gaseous Al-halides which are oxidized to A1_2O_3 on the surface resulting in a protective alumina layer. To investigate the absorption of fluorine in gamma-TiAl during electroslag remelting and to enhance the oxidation resistance of the produced alloy by bulk-fluoridation, a series of tests was performed at IME. In a 400 kW lab scale furnace multiple electrodes of Ti-45Al were remelted using an active Ca-CaF_2 slag. Parameters like melt rate and Ca content in the slag were systematically varied. The ingots were sectioned and characterized by GDOS and EPMA to demonstrate the influence of the melting parameters on the efficiency of fluoridation as well as their impact on solidification structure with special regard to the distribution of fluorine.