Assessment of cryo-MQL environment for machining of Ti-6Al-4V

Titanium alloys are highly resistant to aggressive environment, possess high strength and have lightweight as well as exceptional fatigue endurance. Even with excellent properties, in the industrial scenario, titanium alloys are considered as one of the difficult-to-cut materials. Therefore, a hybrid lubrication/cooling environment is proposed by combining minimum quantity lubrication (MQL) and cryogenic environments for turning of Ti-6Al4V alloys at heavy machining conditions. Cryo-MQL includes simultaneous application of MQL and liquid nitrogen from two different nozzles at the machining region for better lubrication and cooling. Feed and cutting forces, workpiece surface roughness and microhardness, sliding-sticking regions contact length and tool morphology was assessed for three distinct lubrication/cooling environments; dry, MQL, and cryo-MQL. The assessment indicates a significant improvement in machining performance; cryo-MQL environment shows reduction in machining forces and workpiece surface roughness by 27 % and 46 % over dry environment. Morphology of the tool rake surface shows significant reduction in sliding-sticking regions contact length. Elemental composition confirms the reduction of workpiece material adhesion on the tool rake surface compared to dry and MQL environment.