Machinability Assessment of Hybrid Nano Cutting Oil for Minimum Quantity Lubrication (MQL) in Hard Turning of 90CrSi Steel

Abstract

Friction and very high temperature are still the major challenges in hard machining technology and they greatly affect cutting efficiency. The application of the MQL (minimum quantity lubrication) method, using nanoparticles in order to improve the cooling lubrication performance of the base cutting oil, has proven to be a promising solution. Hence, this work aimed to investigate the effectiveness of Al2O3/MoS2 hybrid nanofluid and Al2O3 and MoS2 mono nanofluids in the hard turning of 90CrSi steel (60–62 HRC) under an MQL environment. The Box-Behnken experimental design was used for three input variables, including nanoparticle concentration, air pressure, and air flow rate. Their influences on surface roughness and cutting forces were studied. According to the obtained results, it was shown that the application of hybrid nano cutting oils in MQL contributes to achieving better hard machining performance than the use of mono nanofluids. In particular, a lower cutting temperature is reported and the values of surface roughness Ra, back force Fp, and cutting force Fc were smaller and more stable under Al2O3/MoS2 hybrid nanofluid MQL than those under Al2O3 and MoS2 mono nanofluid MQL due to an improvement in cooling lubrication characteristics. Thus, this work provides a novel approach to study hybrid nanofluids for MQL hard machining.