Cutting force modeling during turning Inconel 718 using unitary Al2O3 and hybrid MWCNT + Al2O3 nanofluids under minimum quantity lubrication

Higher cutting forces and higher cutting zone temperatures during the machining of nickel alloys have a significant impact on the tool life, dimensional accuracy, and surface finish. Therefore, the development of a reliable model that can predict the cutting forces will be extremely valuable and represents a key issue. This study develops a cutting force model by reviewing the traditional analytical mechanics of oblique cutting for evaluating the performance of unitary and hybrid nanofluids during turning Inconel 718 under minimum quantity lubrication. The cutting forces are modeled using Merchants' model, considering the mechanics of oblique cutting in the normal plane. The model prerequisites, the chip thickness ratio, and the normal shear angle are obtained by developing empirical models. This study found that the trend observed for the predicted forces agreed well with the experimental results. The predicted forces using Merchants' model, namely cutting and feed forces by 10-15% and radial forces by 20-25%, were underestimated compared to the experimental results. However, by including the regressor coefficients and constants in the model based on the experimental data, the model's accuracy is enhanced with a correlation coefficient of 0.95 and a %error of less than 10%. Lower cutting forces were observed with hybrid MWCNTs + Al2O3 nanofluids against unitary Al2O3 nanofluids. Cutting forces decreased with the cutting speed and increased with the feed and depth of cut. However, this effect was more prominent with the unitary Al2O3 nanofluid. Also, the tangential cutting force was significantly affected by the depth of cut, followed by feed, and cutting speed. Smooth breaking of chip edges with MWCNTs + Al2O3 nanofluids and severe workpiece microparticle deposition with irregular serrations on the chip free surface were observed for unitary Al2O3 nanofluids.