Temperature monitoring of the tool-chip interface for PCBN tools using built-in thin-film thermocouples in turning of titanium alloy

Abstract

Measurement of the temperature at the tool-chip interface is still a significant challenge especially for machining difficult-to-machine material like titanium alloys. In this paper, a versatile PCBN tool, starting with the existing tool shape, was devised by embedding thin-film thermocouples (TFTCs) into tool interior to monitor the temperature at the tool-chip interface while machining titanium alloy bar. A simplified process was developed to fabricate TFTC array with a degree of spatial resolution (100 μm). A diffusion bonding technique was realized between PCBN plates to achieve reliable sensor protection with shorter sintering time and lower sintering temperature while metallic interlayer like titanium film was adopted. The sensors exhibit an excellent linear response with a sensitivity of about 13 μV/℃. Dry cutting including interrupted and continuous cutting was implemented with the fabricated PCBN insert. Results show that TFTCs embedded into PCBN insert not only have a good transient perception by comparing with commercial sensors but also can stably monitor cutting temperature as close as 300 μm to tool-chip interface under different cutting conditions. The devised PCBN tool presented in this paper will also be helpful for the improvement of machining processes and better understanding of the tool-chip contact phenomena.