The Effect of High-Pressure Jet Cooling on Surface Roughness, Cutting Force and Chip Formation of Ti-6Al-4V ELI in High-Speed Turning

In the machining of difficult-to-machine metals, such as titanium-based alloys, the delivery of coolant with high pressure can increase machining efficiency and improve process stability through more efficient chip breaking and better cooling. Proper selection of machining conditions can also increase the productivity of the process by reducing cutting forces and tool wear rate. To investigate the effect of high-pressure jet cooling (HPJC) on cutting force, surface roughness, and chip formation of Ti-6Al-4V ELI in high-speed turning, Grade 5 Ti ELI turning tests were carried out under coolant pressure of 200 bar. A lower pressure of 6 bar was also used in this study to compare the results of the pressure change. In general, surface roughness increased as the feed rate increased at constant cutting speeds in experiments with both 6 bar and 200 bar coolant pressures. Even though 200 bar pressure provided a better cooling thus reduced cutting force, and tool wear rate; the surface roughness values obtained from the experiments with 200 bar were relatively worse than the experiments with 6 bar pressure. It was also seen that 200 bar coolant pressure may result in instabilities in the turning process in terms of chip geometries and formations.