Titanium and titanium alloys have high specific strength, high corrosion resistance and good biocompatibility properties. Therefore, these are suitable for many high-performance applications in aerospace and medical technology. The main shaping here is carried out by cutting processes. When cutting titanium materials, high temperatures occur due to their low thermal conductivity. In conventional processes, the presence of oxygen from the ambient atmosphere is always present. The oxygen and the high chemical affinity of titanium lead to oxidation processes on the tool and workpiece. In order to investigate the influence of oxygen on the cutting performance during milling of Ti6Al4V, investigations are carried out under air and under XHV-adequate conditions in a gas tight enclosure. The influence of the surrounding atmosphere on the wear behavior during milling is investigated. These investigations are supported by the measurement and evaluation of the process forces. Furthermore, energy-dispersive X-ray spectroscopy images provide information on the sequence of chemical processes during the cutting process.