A study of the effect of CO2 cryogenic coolant in end milling of Ti-6Al-4V

Abstract Titanium alloys, like Ti-6Al-4V, are widely used in the aerospace industry for the excellent resistance/weight ratio. The machinability of the Ti-6Al-4V is poor due to the high temperature close to the cutting edge and high cutting pressure on the cutting edge; consequently it limits the tool life and the productivity. In order to overcome to such issues, cryogenic machining has been adopted from many years. Liquid nitrogen and liquid carbon dioxide are the most common gases for cryogenic machining, and several researchers worked on turning and indexable milling cutters. In this paper the liquid carbon dioxide (CO2) machining with solid end mills have been investigated. The end mills have internal holes in order to use CO2 through the spindle. The aim is to investigate the difference against conventional coolant and the effect of dimension and position of the internal channels, in terms of tool wear and tool life. Thanks to different internal channel design, the intention is to better understand the mechanism of cryogenic machining using CO2; several attempts were done from the researchers from the entire world, but significant variation in results has been found. The tool has been tested in straight pass and down side milling; the workpiece material is Ti-6Al-4V.