Development of NiCr∕NiSi Thin-Film Thermocouple Sensor for Workpiece Temperature Measurement in Chemical Explosive Material Machining

Temperature plays a vital role in the machining industry today. With increasing cutting speeds being used in machining operations, the thermal aspects of cutting have become more important. A nickel-chrome versus nickel-silicon thin-film thermocouple system has been established for measuring instantaneous workpiece temperature in chemical explosive material machining. The thin-film thermocouples have been directly deposited inside high-speed steel cutters by means of multiple arc ion plating and the thickness of the thermocouple junction is only a few micrometers. The research effort has been concentrated on developing solutions to the insulating problem between the thin-film thermocouples and the high-speed steel cutters. SiO2 insulating films have been deposited on the high-speed steel substrates by microwave electron cyclotron resonance plasma source enhanced radiofrequency (rf) reactive magnetron sputtering. Static and dynamic calibrations of the NiCr∕NiSi thin-film thermocouples are presented. The results of the testing indicate that the thin-film thermocouples have good linearity, little response time, and perform excellently when machining in situ.