Performance Evaluation of Various Vegetable Oils and Distilled Water as Base Fluids Using Eco-friendly MQL Technique in Drilling of AISI 321 Stainless Steel

Due to rising attention towards environmental and ecological issues caused by mineral oil-based lubricants in machining operations, the developing of an environmental favourable lubricant has become inevitable. As environmental favourable cutting fluids, vegetable oils have acquired great attention in machining operations due to their good biodegradability, non-toxicity and less environmental pollutant properties. Nowadays, the minimum quantity lubrication (MQL) technique is explored as alternative technique to conventional flood cooling technique. However, very limited work is done to investigate the effect of MQL technique using vegetable oils as the base oil for machining of hard materials. Moreover, systematic comparison of different vegetable oils as the base oil will be of great significance to the manufacturing industry. Therefore, in this study, the performance of six vegetable oils viz. castor, coconut, soybean, canola, palm and sunflower oil, and distilled water has been investigated during drilling of stainless steel (AISI 321) using minimum quantity lubrication technology. The main objective of this study is to compare the performance of various cooling strategies viz. dry, flood and seven MQL conditions with respect to drilling characteristics (thrust force, torque, surface roughness, coefficient of friction (COF), chip morphology and wear mechanism) in the drilling of stainless steel (AISI 321) by using HSS drill tools. Experimental findings showed that MQL drilling conditions have given excellent drilling performance by improving drilling characteristics than dry and flood drilling. Among the MQL fluids, sunflower oil provided better lubrication and improved the drilling characteristics followed by palm, canola, soybean, coconut, castor oil and distilled water. Sunflower oil had a thrust force, torque, surface roughness and coefficient of friction of 1425 N, 22.8 Nm, 4.356 µm and 4.000 µ, which reduced by 21.27%, 25.49%, 30.72% and 5.35%, respectively than that under flood drilling at 30th hole. The better lubrication performance of sunflower oil may be attributed to the rich presence of saturated-fatty acids. In addition, vegetable oils based MQL technique is more worthy to improve the cooling capabilities and promote sustainability in the manufacturing sector by saving resources and extending environmental benefits.