Transient Thermal Mapping Utilizing the Sintering of Glass-Ceramics

Abstract

Thermal paints are essential for mapping the surface temperature of gas turbine engine components but can only indicate maximum temperature. A novel transient thermal history sensor that combines the capabilities of a thermocouple with those of a thermal paint is developed here, enabling the retrieval of full thermal history using a “sintering” model. The glassy ceramic thermal paint undergoes a qualitative optical transition due to sintering in response to temperature that is quantified using UV–vis spectroscopy. This provides high-resolution transient temperature measurement (±6 °C) when maximum temperature is above its glass transition temperature (T_g) of 563 °C and up to 660 °C. The glass-ceramic coating exhibits strong adhesion to Inconel 718 substrates due to matched coefficients of thermal expansion. By fabricating similar paints with distinct temperature ranges and placing them in proximity, this approach can significantly reduce the number of thermocouples needed for surface temperature mapping, thereby improving the accuracy of measurements required for engine validation.