Temperature Measurement on Tool Surfaces by Wear Resistant PVD Sensor Coatings

Abstract

In manufacturing technology, sensors are important elements for monitoring process parameters and for recording data in the Industrie 4.0. Thin sensors manufactured by means of physical vapor deposition (PVD) offer a way to combine wear and corrosion protection on the one hand and the integration of a temperature sensor function on the other hand. For the analysis of the performance of PVD sensor coatings based on the thermoelectric effect, no standardized methods and procedures are state of the art. In this paper a measuring setup is presented, which allows reference measurements using a calibrated thermocouple and a thermographic camera besides the potential difference measurement of the sensor coating. Two measuring modes, which allow a continuous and a discontinuous measurement, are presented. The measuring methodology was evaluated using the PVD sensor coating Al2O3+Ni+NiCr+Al2O3. This multilayer sensor coating was deposited using an industrial coating unit and was tested with regard to the sensor properties. The deposition technology used for the sensor coating results in an interface without defects between the two sensor layers with a smooth transition. This provides a suitable electrical contact and a promising compound adhesion. The results show a suitable and detailed measurement of temperature and potential differences by means of calibrated measurement methods and the sensor coating. The measured results are reproducible and show a linear relationship between the potential difference and the surface temperature.