Rake Face Temperature When Machining with Coated Cutting Tools

Infrared thermography through transparent cutting tools has been used to measure the chip-tool interface temperature. It is of interest to extend this technique to study changes in interface temperature when tool coatings are used. An initial attempt is made here to measure the chip-tool interface temperature distribution when cutting Ti6Al4 V with a TiN coated YAG tool. The TiN coating thickness is kept low at about 100 nm to minimize the temperature difference between the front (chip-TiN interface) and the back (TiN-YAG interface) faces of the coating. The transparency of the YAG tool allows near infrared radiation emitted by the back face of the TiN coating to be imaged. A novel method is used to measure the emissivity of the TiN/YAG interface. Using this method, and the available blackbody calibration of the temperature vs. intensity response of the imaging system, the images are converted into temperature maps. The performance of the coated tool is also evaluated in terms of machining force and tool wear characteristics. Coatings that remain intact during the experiments will reduce ambiguity in interpretation of the results.