Copper nanofluids under minimum quantity lubrication during drilling of AISI 4140 steel

A significant quantity of power consumed in drilling process is converted into heat energy due to friction between the surfaces of tool and work piece. This extreme heat generated affects the performance of cutting tool which, leads to poor surface finish on drilled surfaces. The cutting fluid plays a vital function in improving the tool life and surface finish since it acts as a coolant and lubrication. In this research, the experiments have been carried out with difference combination of three operating parameters such as cutting speed, machining environment and feed rate using minimal quantity lubrication technique in drilling of AISI 4140 steel. The conventional coolant (CC) in flood lubrication condition, coconut oil and copper nanofluid are used as the levels of machining environments. The surface roughness and flank wear are observed as the responses and analysed using an integrated technique Average S/N ratio-based response surface methodology (ASN-RSM). The experimental results of copper nanofluid are compared with CC and coconut oil. The surface roughness, tool wear and chip morphology are also evaluated under conventional coolant, coconut oil and nanofluid. The confirmation tests are executed with the near optimal setting obtained from ASN-RSM technique and results are compared with the initial setting. It was observed that copper nanofluid-based optimal setting predicted using ASN-RSM has reduced the surface roughness and flank wear by 71% and 53% respectively over the responses obtained at coconut oil based initial setting. It is confirmed that copper nanofluid has a significant contribution in reducing surface roughness and flank wear.