Embedded temperature and heat flux sensors for advanced health monitoring of turbine engine components

MesoScribe Technologies has developed a process for producing embedded, conformal, thick film sensors based on Direct Write technology. Thermocouple and heat flux sensors can be fabricated directly onto engineering components and embedded into functional coatings. This provides for a variety of vital advantages: reliability, robustness and survivability in extremely harsh environments, cost effective implementation, and fabrication onto surfaces that are large, conformal (non-flat) and flexible. Embedded thermocouples and heat flux sensors were deposited onto superalloy substrates and subjected to a number of high temperature tests including isothermal furnace heating, cyclic burner rig testing, and continuous flame impingement. Initial testing yields Seebeck coefficients within 3% of commercial thermocouples. Results also demonstrate that embedded Type K thermocouples survive over 200 thirty minute burner rig cycles with surface temperatures exceeding 1150°C. Embedding thermocouples at different depths within the TBC allows for simultaneous temperature measurements within the temperature gradient. In addition, over 20 hours of continuous flame impingement have been recorded with stable output. Embedded thermocouples were also tested at NASA GRC using a 3.5 kW CO₂ high heat flux laser which also allows extraction of thermal conductivity. The test comprised of 75 thirty minute cycles with a surface temperature of 1150°C and metal interface temperature of 930°C for a total duration of 41 hours. This very first test showed the capability of the embedded TC in terms of performance and durability. This paper will summarize the harsh environment test results as well as provide an overview of the capabilities of Direct Write technology to instrument propulsion and space structures.