Machined Surface Analysis in High-Speed Dry Milling of Ti-6Al-4V Alloy with Coated Carbide Inserts

An experimental investigation was conducted to analyze the machined surface in high-speed dry milling of Ti-6Al-4V alloy using coated carbide inserts, with white light interferometer, scanning electron microscope (SEM), and X-ray diffraction (XRD) employed. The effect of cutting force and the workpiece temperature rise on the machined surface under different cutting speeds was discussed. As cutting speed increases above 150 m/min, the mean cutting forces decrease remarkably, but the corresponding higher temperature will be harmful to the machined surface. A deformed layer is detected by SEM with grains orientation along the feed direction from the sub-surface microstructure. The 3D surface topography and XRD patterns confirm the intense deformation of the machined surface and show a crystallographic texture modification. However, no phase transformation was observed. The β phases seem to experience more deformation and volume shrinkage in the near surface with the increase in cutting speed. And the observed variations of the machined surface with the cutting speed should be attributed to the elevated workpiece temperature rise under dry milling.