Physics based modelling of interface temperatures in machining with multilayer coated tools at moderate cutting speeds

A new thermal model is presented for turning with tools with multilayer coatings. In the previous paper [Int. J. Mach. Tools Manuf. 43 (2003) 1311] devoted to the thermal problems in dry turning of steels with tools treated with multilayer coatings with an intermediate Al₂O₃ layer new analytical models for estimating the heat partition to the chip and the average interface temperature were derived and the predictions were compared with experimental results. In this paper, a physics based modelling concept has been applied to both the individual layer and the composite layer approach to develop an estimate of the average and the maximum steady-state chip-tool interface temperatures in orthogonal turning. Different approaches for determining the heat partition coefficient for sliding bodies of defined thermal properties were tested. Experiments using the work and the tool as the thermocouple pair have verified that the proposed models accurately predict the temperatures for uncoated and coated tools for a range of cutting speeds. As a result a new computational algorithm, for predicting with reasonable accuracy the average and peak values of the temperatures at the chip-coating/substrate interface at cutting speeds up to 200 m/min, has been recommended.