Performance assessment of nano-Al₂O₃ enriched coconut oil as a cutting fluid in MQL-assisted machining of AISI-1040 steel

To address the negative consequences of conventional mineral-based cutting fluids, manufacturing industries strive to utilize less harmful and environmentally friendly cutting fluids. The non-toxicity and biodegradability of vegetable oils present them as a suitable replacement for cutting fluids based on mineral oil. However, vegetable oil possesses inferior oxidation and thermal stability at elevated temperatures due to which nanoparticles are blended with vegetable oil to improve the lubrication and cooling characteristics. In this perspective, the influence of nano-suspended coconut oil (CO) has been investigated during the turning of AISI-1040 steel. The various wt% concentrations of nano-Al2O3 ranging from 0.25 to 1.50% were added in CO to prepare the nanofluid. Then, the machining operation was performed under dry cutting, flood cooling with conventional mineral-based oil, minimum quantity lubrication with pure coconut oil (CO-MQL), and MQL with nanofluids (NF-MQL). The performance was evaluated through tool wear, cutting temperature, surface integrity, cutting tool vibration, and microhardness. The findings revealed that NF-MQL significantly reduces tool wear in comparison with other selected cutting environments. The 53%, 38%, and 25% reduction in flank wear and 37%, 31%, and 17% reduction in crater wear depth in correlation with dry cutting, flood cooling, and CO-MQL demonstrate the superiority of NF-MQL in increasing the tool life. NF-MQL also results in superior surface finish quality with an improvement of 54%, 32%, and 28%, reduction in cutting temperature by 55%, 38%, and 20%, minimizing the tool vibration by 68%, 45%, and 24% in comparison with dry cutting, flood cooling, and CO-MQL cutting environments.