Beschreibung
Titanium and titanium alloys have high specific strength, excellent corrosion resistance and excellent biocompatibility. Therefore, the use of titanium materials is widespread in high-performance applications such as aerospace and biomedical industries. However, titanium and titanium alloys such as Ti-6Al-4V are considered as difficult to machine. This is attributed to their low thermal conductivity, unfavourable chip formation with typically segmented chips, and high thermomechanical load on the cutting tool. In addition, titanium alloys have a high chemical affinity for surrounding elements such as oxygen. Tool wear, surface and subsurface properties of the workpiece are significantly affected by the presence of oxygen and the resulting chemical interactions. Among other things, chemical reactions such as oxidation occur due to the high temperatures and presence of oxygen. In this work, the chip formation of Ti-6Al-4V at different cutting speeds in continuous orthogonal cutting under different atmospheres is investigated. A conventional air atmosphere, a pure argon atmosphere and a silane-doped argon atmosphere were used. The oxygen content of the silane-doped argon atmosphere corresponds to an extremely high vacuum (XHV), which is practically oxygen-free. It was found that by using an XHV-adequate atmosphere, a significant reduction in chip segmentation occurs. In addition, the feed force is up to 26% lower under silane-doped argon atmosphere compared to cutting under air. This can be attributed to up to 23% reduced coefficient of friction in the secondary shear zone. In addition, the maximum tool temperature at a cutting speed of vc = 60 m/min was reduced by up to 310 °C as a result of using an XHV-adequate atmosphere.
