Temperature measurements during induction skull melting of titanium aluminide

Abstract

An immersion thermocouple and a twin wavelength infrared radiation pyrometer have been used to measure the temperature of titanium aluminide during melting in an induction skull melting furnace. A molybdenum-alumina cermet thermocouple sheath has been found to survive for long enough to enable about three reliable measurements to be made. A significant drift occurred between the temperatures measured using the pyrometer and the thermocouple when melting under a partial pressure of argon, and has been attributed to the generation of fume inside the melting vessel. The drift did not occur when melting was carried out in a continuously pumped vacuum. The superheat obtained increased from ~33°C when melting 4·5 kg of TiAl with 200 kW in a vacuum to ~44°C and ~62°C when melting under argon partial pressures of 20 and 80 kPa respectively. There appears to be little benefit from increasing the applied power from 200 to 350 kW.