In Situ Integration of High-Temperature Thin-Film Sensor for Precise Measurement of Heat Flux and Temperature on Superalloy Substrate

For the normal operation and cooling design of the hot-section components in an aerospace engine, in situ heat flux and temperature monitoring have become important in the development of the aerospace industry. This article presents the high-temperature thin-film sensors on a superalloy substrate for heat flux and temperature measurement, consisting of the insulation layer, sensitive structure, and thermal resistance layer. For the insulation between the sensitive structure and substrate, multilayer homogeneous Al2O3 films are adopted, which can operate at 1000 °C. The thermopile array is rectangular with a linewidth of
$80 \mu \text{m}$
, so the area occupied by the sensor is reduced. Besides, Pt/Pt-13Rh is utilized as the material of thermopile because of the small resistance compared to ceramic material. As a result, the precision of the sensor is guaranteed, especially at high temperatures. Additionally, a SiO2 film is used as a thermal resistance layer due to its low thermal conductivity and good thermal stability. The sensitivity of the heat flux sensors with 37, 74, and 111 pairs of thermocouples is 3.30, 4.77, and
$6.13 \mu \text{V}$
/(kW/
$\text{m}^{{2}}{)}$
, respectively, and for the temperature sensor, the sensitivity is 0.01 mV/°C. The fabricated heat flux sensor remains stable after cycling tests and the response time and recovery time are 10.18 and 9.04 ms.