A Thin-Film Heat Flux Sensor With an Insulation Layer Using Chemical Vapor Deposition for High-Temperature Bearings

Thermal barrier coatings offer extended and stable services for high-temperature bearings where heat flux density is a vital parameter for coating monitoring. As the electrical insulation between the sensing element and the alloy substrate of the bearing is a prerequisite for a thin-film sensor, a high-temperature chemical vapor deposition (CVD) was developed to deposit alpha -Al2O3 in situ on the surface of GH3536 alloy in this work. An ITO/In2O3 thermopile was then prepared on the CVD-Al2O3 insulation layer to develop a thin-film heat flux sensor. Compared to traditional physical vapor deposition (PVD), CVD reduces the insulation loss of the insulation film caused by the annealing process. During the electrical insulation test at 1000 (degrees) C, the film resistance reached 1.5 M Omega . Experimental results show that the heat flux density of 300 kW/m(2) can be measured at 1040 (degrees) C for the developed sensor, with a sensitivity of 22.59 mu V/(kW/m(2)) and a response frequency of 6.83 kHz. It provides a reliable method for measuring heat flux density on the thermal barrier coating of the high-temperature bearing.