High Speed Turning of AISI 4140 Steel Using Nanofluid Through Twin Jet SQL System

Application of small quantity lubrication (SQL) technology in high speed machining is being recognized as a sustainable approach for achieving suitable cooling/lubrication in machining zone. Present investigation focused on effectiveness of SQL with nanofluids in high speed turning of AISI 4140 steel with a TiN-top coated multilayered carbide insert and explored the advantages of using a twin-jet SQL system instead of a single jet one. SQL system was developed in-house with external-mix nozzles. The experiment was conducted varying the cutting velocity at two different feed rates (0.05mm/rev and 0.10mm/rev) with conventional coolant and nanofluids. Immediate improvement in machinability and the quality of turned surface was observed with twin-jet nanofluid SQL. A significant reduction of force and specific energy could be achieved by using 3vol% alumina and 1vol% multi walled carbon nano tube (MWCNT) nanofluid instead of soluble oil. The MWCNT nanofluid was found to be superior to alumina nanofluid in reduction of tensile residual stress. Such a reduction is typically an indirect indication of reduction of cutting zone temperature, which could be achieved due to enhanced level of lubricity at chip-tool interface and enhanced level of heat dissipation ability of the nanofluids. Improvement in retention of sharpness of tool cutting edges was also observed under nanofluid-SQL environment, which could have played important role in improvement of surface quality.