Öz In machining processes, MQL method is substantially preferred in terms of sustainable production because of lower usage of cutting fluid and better cutting performance in comparison with traditional techniques. On the other hand, it is also critical that the cutting fluid used is not hazardous to human and environmental health. In the present study, we aimed to investigate the cutting performance of AISI O2 steel in the presence of the cutting fluid containing various amounts of environmentally friendly Nano hexagonal boron nitride (Nano h-BN) based ethylene glycol (EG) by minimum quantity lubrication (MQL) method. Nano h-BN at 1% and 2% percentage by volume was added to the ethylene glycol and sonication was carried out for one hour for both prepared cutting fluids. Based on the experimental results using prepared cutting fluids, the highest cutting tool life was obtained in tests using 2% h-BN containing cutting fluid with 2.4 m cutting length. The improvement in tool life was approximately 46% using 2% h-BN containing cutting fluid compared to using 1% h-BN containing cutting fluid in milling tests. 2% h-BN containing cutting fluid compared to dry conditions in terms of tool life, the increase was approximately 78%. The improvement in surface roughness value measured on milled surface of workpiece material was approximately 60% using 2% h-BN containing cutting fluid compared to dry conditions. Compared to using 1% h-BN containing cutting fluid the improvement in surface roughness values was approximately 46%. A reduction in the cutting forces measured by the increased h-BN ratio in the prepared ethylene glycol based cutting fluid has occurred. As a result of SEM images and EDS analysis of worn tools, it was observed that the dominant wear mechanism was abrasion in all applied tests.
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