is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Metz -France Abstract Machinability of high-strength steels can be improved without degrading the mechanical properties using metallurgical solutions to create or retain non-metallic inclusions. Such a metallurgical treatment usually leads, during machining, to the appearance of so-called Built-Up Layers (BULs) or transfer layers on the cutting tool. These BULs protect the tool against wear, and longer tool life or better productivity is achieved. Formation of such BULs on the cutting tool depends on many parameters i.e. tool geometry, tool material, cutting conditions. This paper proposes an experimental methodology to identify and describe BUL occurring on the tool rake face. Machining tests were carried out with a high strength free-cutting steel using an untested AlSiTiN coated carbide tool. BULs morphology and composition were determined for various cutting conditions. Temperature distributions at the tool-chip interface were measured during the cutting tests using an infrared camera. BUL appearance was then linked to the thermo-mechanical conditions at the tool-chip interface.

In the following work, we propose a metallurgical approach to the chip formation process. We focus on a turning application of high strength steel in which chips are produced by adiabatic shear bands that generate cutting force signals with high frequency components. A spectral analysis of these signals is applied and highlights peaks above 4 kHz depending on the cutting conditions. A microscopic analysis on the chip sections provided data on chip breaking and serration mechanisms. Shear band spacing and excitation frequency of the whole cutting system were calculated and gave a good correlation with cutting forces spectra.