Experimental investigation to study the effect of synthesized and characterized monotype and hybrid nanofluids in minimum quantity lubrication assisted turning of bearing steel

A minimum quantity lubrication system using biodegradable cutting fluids has facilitated the excellent machining performance and is observed as more sustainable. In the view of enhancement of machining performance, the utilization of nanofluids with a minimum quantity lubrication system as a cutting fluid delivered noteworthy outcomes. For the present experimental investigation, the monotype nanofluids (copper oxide and zinc oxide) and a hybrid nanofluid (copper oxide/zinc oxide) were synthesized by using a two-step method. Scanning electron microscopy and energy dispersive X-ray analysis were performed to characterize the synthesized nanoparticles. A vegetable oil was utilized as a base fluid and three types of nanofluids were prepared by the addition of a surfactant (butenol). Also, ultrasonication has been performed to avoid the agglomeration of nanoparticles into the base fluid. The thermal conductivity evaluation of prepared nanofluids was carried out by using a hot wire method. The effects of three nanofluids were investigated by considering three machining input variables (cutting speed, feed rate and depth of cut) on response variables (surface roughness and cutting zone temperature) during bearing steel turning under nanofluid minimum quantity lubrication cooling conditions. The multi-objective optimization was performed by using grey relational analysis and found that the hybrid nanofluid (copper oxide/zinc oxide) was noted as the highly effective cooling condition as equated to copper oxide and zinc oxide monotype nanofluid. The hybrid nanofluid (copper oxide/zinc oxide) shows a 65% and 60% reduction in surface roughness on comparing with copper oxide and zinc oxide nanofluids, respectively. Also, the minimization of cutting zone temperature was observed under the hybrid nanofluid (copper oxide/zinc oxide) by 11% and 13% on equating with copper oxide and zinc oxide nanofluids, respectively.