Friction in Turning Titanium Alloy Ti-6Al-1.5Cr-2.5Mo-0.5Fe-0.3Si under Minimum Quantity Lubrication (MQL) Condition

High cutting force, high cutting temperature and severe adhesion will be produced in the machining process of Ti-6Al-1.5Cr-2.5Mo-0.5Fe-0.3Si. Furthermore, there are critical needs to reduce the use of cutting fluid in machining process. This paper presents a friction force model under MQL condition. An experiment of turning titanium alloy was presented to test and analyze MQL effects. The mainly results were: (1) MQL can reduce the friction at the chip-tool interface when cutting parameters and matching parameters of MQL were chosen properly. (2) Degrees of serrated chips and chip morphology affected by different lubrication conditions were different.