Influence of thermal conductivity on wear when machining titanium alloys

We study failure of coated carbide tools due to thermal loading. The study emphasizes the role of thermo-physical properties of the tool material in enhancing wear resistance of the tool. We show that heat conduction in the tool active zone is a function of the so called thermodynamic forces. Due to coupling between thermal and mechanical states within the active volume of the tool material, three distinct thermal zones evolve. The first, which is located on the rake face close to the primary shear zone, exhibits a severe drop in its ability of thermal conduction. The second zone, located at the tool tip is characterized by a predominant thermo mechanically induced conduction anisotropy. The anisotropic behaviour, forces heat to partially flow toward the thermally dead zone whence contributing to the intense thermal energy accumulation within the affected material volume. The third zone is one where the thermally triggered degradation of conduction takes place. Heat flow, in light of the existence of these zones, evolves such that, the tip of the tool will be almost thermally congested. The congestion is thought to be the mechanism that renders the energy needed to activate wear mechanisms available. (C) 2008 Elsevier Ltd. All rights reserved.