The Effect of Ti-6Al-4V Microstructure, Cutting Speed, and Adiabatic Heating on Segmented Chip Formation and Tool Life

Turning experiments on Ti-6Al-4V using uncoated carbide inserts at cutting speeds of 1 m/s, 1.5 m/s, and 2 m/s exhibited shorter tool life on solution-treated and aged than mill-annealed microstructures. Finite element analysis was performed to identify Johnson-Cook material model parameters that enabled matching of the measured segmented adiabatic shear banded chip geometry and periodic cutting force, in order to estimate the temperature and strain behavior inside the chip. The measured crater wear rate for both microstructures at 2 m/s are higher than predicted by analytical models, suggesting that by reaching 900°C, at least partial transformation to the β phase more aggressively diffusively absorbed the tool binder. Electron backscattered diffraction maps show that the geometry of every segment and shear band varies due to the local crystal orientations, leading to segment-to-segment variations that are greater than the variation in the average segmentation characteristics at each cutting speed.