In this work, improved both global and local levels has been made on understanding the tribological mechanisms at the chip-tool-workpiece interface in dry machining of a AISI 1045 steel with a TiN coated carbide tool. In the first part, several friction tests have been performed to study the sensitivity of friction parameters on the tribological behavior at pin-workpiece interface. Thus, evolutions of the apparent friction coefficient, of heat flux and of heat flux partition ratio have been identified. To better understand these phenomena, a metallographic study was performed on the samples of the workpiece.It has enabled the achievement of metallurgical transformations in terms of surface area of the room : the refinement of grains (plastic deformation) friction at low speeds and white layers (thermal curing)for high speeds. These results show that the initial state of the steel (ferritic-pearlitic microstructure) has been changed, In fact, two phenomena have been observed. The first phenomenon has been observed for low sliding velocities. In this range of the sliding velocities, the grains have been crushed because of the large plastic deformations. The second phenomenon has been observed by increasing the friction velocity. In fact, the white zones have been identified at the surface layer and which have presented a different structure compared to the initial state of the steel. A 3D A.L.E. numerical model, simulating the friction test, enables to extract local information from the contact area, especially the contact pressure, the contact temperature and the average local sliding velocity. An adhesive friction model and a heat partition coefficient model depending on average local sliding velocity have been identified. These friction models can be utilized in a FEM of the cutting process in order to improve the understanding of the material flow and temperature distribution around cutting tools. In the second part, pin wear in the friction tests and tool wear in machining tests have been performed. To compare the phenomena observed at the tool-chip interfaces during the wear tests in machining with the phenomena observed at the pin-workpiece during the wear tests of friction, similarities of faces have been observed at different scales of analysis on the pins and on the cutting tool inserts.
