Effectiveness of coolant on sustainable drilling and hole quality of titanium alloy

The present research investigated the effects of input parameters such as feed rate, cutting speed and coolant type on sustainability and hole quality during the drilling of Ti-6Al-4V alloy. Several output parameters such as surface roughness, burr height, chip thickness ratio, thrust force, torque and peak power consumption were measured and analysed. Higher cutting speeds (2000 r/min) and lower feed rates (0.04 mm/rev) are recommended to be used to reduce drilling torque (0.77 Nm), thrust force (695 N) and power consumption (0.07 kW). However, it should be noted that increasing cutting speed (2000 r/min) can increase tool tip temperature which is detrimental, particularly for low thermal conductivity materials such as titanium alloys. In addition to that, the effect of tool wear also cannot be negated, as increased tool wear generates more heat in the cutting zone which was not effectively removed due to the poor thermal conductivity of titanium. Liquid nitrogen and chilled air had the greatest influence on temperature reduction at the cutting zone, however, its poor penetration and lubrication properties diminished hole quality. Minimum quantity lubrication conditions proved to strike a balance between good hole quality and enhancing sustainable machining by lowering torque, force and power consumption.