Effects of cooling conditions and grinding depth on sustainable surface grinding of Ti-6Al-4V: Taguchi approach

In this research, the effects of coolant types, cooling techniques, and grinding depth on the surface properties of the Ti-6Al-4V after surface grinding with white alumina wheel were investigated. Three coolant types namely sunflower oil, formulated sunflower oil-based emulsions and soluble cutting oil were applied to the grinding zone using two cooling techniques: wet cooling and minimum quantity lubrication. The grinding was undertaken at grinding depths of 0.005, 0.010 and 0.015 mm. An L₉ orthogonal array was used to design the experiments and undertaken the evaluation of the variable interrelationships. Surface hardness and surface morphology of the ground surfaces were determined using Vickers Macro-hardness tester and Zeiss Axio Zoom V16 optical microscope, respectively. Results from the signal-to-noise ratio analysis revealed that cooling technique has the most influence while the grinding depth has the least influence on the surface hardness of ground Ti-6Al-4V. The optimal parametric setting which gives the highest surface hardness of Ti-6Al-4V was identified from the main effect plots and were sunflower oil (SO), MQL₂ at a flow rate of 0.65 L/h and a grinding depth of 0.015 mm. Analysis of variance demonstrated that the individual contributions of coolant types, cooling techniques and grinding depths to surface hardness were 24.11%, 52.47% and 14.15%, respectively. The morphological investigations established that better surface finish was achieved through the application of sunflower oil-based emulsions in MQL cooling technique at a grinding depth of 0.005 mm.