Extraordinarily-High-Speed (EHS) Turning of Alloy 718 by Mixed Alumina Ceramic Tool (Al2O3/TiC) and Clarification of the Speed-Dependent Tool Wear Mechanism

In this paper, extraordinarily-high-speed (EHS) turning of Alloy 718 is investigated using a mixed alumina ceramic (Al2O3/TiC) tool. Although ceramic tools have been applied to high-speed turning of nickel-based alloys, previous studies have been limited to cutting speeds of 500 m/min or less. On the other hand, previous studies have suggested that cutting temperature saturation may occur in an extraordinarily-high-cutting-speed range. Therefore, cutting force, cutting temperature, and tool wear measurements are conducted over a wide cutting speed range from 100 to 1700 m/min to investigate the cutting temperature behavior and the corresponding tool wear characteristics in each speed range. As a result, the occurrence of cutting temperature saturation is confirmed for Alloy 718 in the EHS cutting regime. Furthermore, it is also found that the tool wear progression saturates in the temperature saturation region. Comprehensive analyses of cutting temperature, tool wear, cutting-edge profiles, and SEM/EDS observations clarify the speed-dependent tool wear mechanism. These findings suggest that the EHS turning can significantly improve cutting efficiency without sacrificing tool life.