Studies on the Platinum Thick Film Sensor Conformally Written by Laser Micro-Cladding: Formability, Microstructure, and Performance

In this paper, laser micro-cladding technology (LMC) was conducted to prepare high-temperature Pt thick film sensors in situ. The formability, microstructure, sintering mechanism, and electrical properties of the LMCed Pt thick films were first studied systematically. Results indicated that with the increase of laser power density, the sintering degree of the Pt thick film increased obviously, improving its adhesion strength and reducing its resistivity. However, when the laser power density exceeded the threshold, holes or grooves were formed in the Pt film, leading to the degeneration of its properties. A Pt thick film with good adhesion strength, excellent conductive networks, and the minimum resistivity (46 ± 2 μΩ·cm) was obtained at a laser power density of 1.37 × 106 W·cm-2. Then, Pt thick film temperature sensors (including Pt thermal resistance temperature (RTD) and Pt-Pt10%Rh thermocouple sensors) were conformally prepared by LMC. Their temperature-sensing performance became stable after the initial high-temperature calibration, with a linearity of 0.9985 for the RTD with a TCR of 2.46 × 10-3/°C (at 920 °C) and a linearity of 0.9905 for the thermocouple with a Seebeck coefficient of 9.7 μV/°C, both of which are better than that made by direct DC magnetron sputtering deposition. Therefore, this work provides a novel feasible way to conformally integrate high-performance Pt film sensors in situ.