Performance evaluation of the minimum quantity lubrication with Al2O3- mixed vegetable-oil-based cutting fluid in drilling of AISI 321 stainless steel

Abstract

Abstract Due to increased awareness of ecological and health related problems, the researchers are actively searching for renewable and biodegradable cutting lubricants. Vegetable oils with solid lubricants are being explored as a potential source of environmentally helpful lubricants due to good combination of biodegradability, renewability and fabulous lubrication performance. Although sunflower oil poses good cooling capability, yet its application has not been explored extensively in drilling. Therefore, in this research work minimum quantity lubrication (MQL) technique with Al2O3-mixed vegetable-oil-based cutting fluid was implemented. The main objective of this experiment is to analyze the performance of various coolant-lubricant environments (dry, flood, pure MQL and nanofluid MQL) with regard to drilling forces, surface roughness, drill tip temperature and tool wear mechanism in the drilling of AISI 321 stainless steel by using HSS drill tools. In the MQL conditions, coolant supply rate and air pressure are fixed at 120 mL/hr and 6 bar respectively. In addition to explore the cooling capabilities of sunflower oil, nano-Al2O3 were added to the sunflower oil to prepare different concentration (0.5 wt.%, 1.0 wt.% and 1.5 wt.%) nanofluids. Results indicated that MQL drilling with Al2O3-mixed vegetable-oil-based cutting fluid achieved much better performance as compared to the dry, wet and pure MQL drilling. Thrust force, torque, surface roughness and drill tip temperature approximately reduced 44 %, 67 %, 56 % and 26 % respectively at the 30th hole under nanofluid MQL drilling (with 1.5 wt.% of aluminium oxide nanoparticles) as compared to flood conditions. Moreover, tool wear rate reduced significantly while machining under NFMQL conditions. Better results of nanofluid MQL drilling may be attributed to the fact that NFMQL is capable for producing higher cooling effect due to the lubrication characteristics of nanoparticles.