Performance study and application of thin film thermocouple based on diamond-like carbon protective coating

Abstract Advancements in smart manufacturing necessitate precise measurement of cutting temperatures to optimize machining quality. Thin-film thermocouples (TFTCs) have garnered significant attention due to their rapid response characteristics and minimal process interference. This study proposes a diamond-like carbon (DLC) protective coating for TFTCs, fabricating a multi-layered structure comprising an insulating SiO 2 layer, functional NiCr/NiSi bilayer, and DLC protective layer on tungsten carbide YG8 substrates via magnetron sputtering. Comprehensive characterization revealed uniform microstructure with dense surface morphology and elemental composition aligned with Type-K thermocouple standards. The static calibration shows that the TFTCs have a Seebeck coefficient of 40.6 μV/°C, a linear fit correlation coefficient of 0.999, and a repeatability error of up to 6.93% over the range of 30-310°C, which is a stable performance. The dynamic response time of 1.208 μs provides a microsecond dynamic response capability. Integrating it into the turning tool enables real-time temperature detection and the output temperature data curve is smooth and free of noise. The DLC-protected TFTCs have excellent performance in terms of sensitivity and response speed, providing an effective solution for high-precision temperature monitoring in complex processing environments.