Prediction of friction and heat flow in machining incorporating thermophysical properties of the coating–chip interface

This paper deals with an experimental and analytical investigation into the thermodynamically activated effects influencing the behaviour of the multi-layered coated tool rake face during orthogonal cutting of ferromagnetic and paramagnetic steels. Temperature measurements on the tool rake face using a thermocouple-based technique and identification of the contact zone by means of computer image processing were carried out. New methodology for assessing friction and the amount of thermal energy generated when machining with a coated tool insert with natural and restricted contact coupled with a metallic chip, using thermophysical properties of the sliding materials is developed in this study. The dependence of the material properties on the contact temperature makes the predictive models more realistic. It was proven, based on the heat flux analysis, that the use of advanced coatings with an intermediate Al2O3 layer could substantially improve the heat flow into the chip at distinctly lower temperatures than other commercially available coatings. The data obtained can be used for the optimisation of tool selection with respect to friction and heat transfer and for maintaining the recommended contact temperature.