Thermally Sprayed Sensor Coatings for Spatially Resolved Temperature Detection

Abstract In injection moulding, knowledge about the cavity surface temperature and its distribution is vital for process understanding and part optimization. The measurement of cavity surface temperatures in moulding processes is often infeasible due to the harsh process environments and the limited amount of space. Therefore, a multi-layer coating system was developed for future measurement of the temperature of the injection moulding tool surfaces. A temperature-sensitive semiconducting TiOx/Cr2O3 coating is applied between two Al2O3 isolation coatings and electrically contacted with NiCr conductor paths outside the isolation coatings. The current study focuses on a proof of concept by correlating the coating’s electrical resistances with occurring temperatures using the modified Arrhenius equation. Furthermore, the reproducibility of measurements is investigated in the temperature range of T = 80 to 320 °C, which corresponds to the conditions during injection moulding processes. Conducting paths and measurements spots in the multi-layer coating system are designed precisely by ultrashort pulsed laser ablation. Parameters are developed for each individual layer of the coating system without negatively affecting underlying layers. Investigations are conducted focusing on minimal measurement area size resulting in geometries less than A = 1 mm2.