An optical technique based on silicate glass sintering for temperature mapping

Thermal paints have been used for decades by the gas turbine engine community to map surface temperature with low resolution. A novel thermal paint based on the sintering of a lead-silicate glass powder was developed that can map maximum temperature with high resolution (±5°C) over a 60°C range beginning at the glass transition temperature ($T_g$). The paint exhibited excellent adhesion to nickel-based superalloy components due to similar coefficients of thermal expansion between the superalloy and glassy ceramic coating. An optical transition was qualitatively and quantitatively observed using scanning electron microscopy, ultraviolet-visible (UV-VIS) reflectance spectroscopy, and visual inspection. UV-VIS reflectance spectroscopy was used to confirm the optical transition observed by the naked eye and quantitatively assess the transition of the thermal paint with high resolution. This technique for obtaining high resolution experimental temperature maps can aid the performance, efficiency, and reliability of gas turbine engines.