Hard machining has gained much attention to be an alternative solution for many traditional finish grinding operations due to high productivity, ease to adapt to complex part contours, the elimination of cutting fluids, good surface quality, and the reduction of machine tool investment. However, the enormous amount of heat generated from the cutting zone always requires the high-grade inserts and limits the cutting conditions. The MQL technique with nanofluids assisted for hard machining helps to improve the cutting performance while ensuring environmentally friendly characteristics. This paper focuses on the development of MQL technique by adding Al2O3 and MoS2 nanoparticles to the base fluids (soybean oil and water-based emulsion) for the hard turning of 90CrSi steel (60÷62 HRC). The analysis of variance (ANOVA) is used to evaluate the performance of MQL parameters in terms of cutting forces and surface roughness. The study reveals that a better performance of coated carbide inserts is observed by using MQL with Al2O3 and MoS2 nanofluids. In addition, the fluid type, nanoparticles and nanoparticle concentration have a strong effect on cutting performance. The interaction influence among the investigated variables is also studied in order to provide the technical guides for further studies using Al2O3 and MoS2 nanofluids.

Machining difficult-to-cut materials is one of the increasingly concerned issues in the metalworking industry. Low machinability and high cutting temperature generated from the contact zone are the main obstacles that need to be solved in order to improve economic and technical efficiency but still have to ensure environmental friendliness. The application of MQL method using nano cutting fluid is one of the suggested solutions to improve the cooling and lubricating performance of pure-MQL for machining difficult-to-cut materials. The main objective of this paper is to investigate the effects of nanofluid MQL (NFMQL) parameters including the fluid type, type of nanoparticles, air pressure and air flow rate on cutting forces and surface roughness in hard milling of 60Si2Mn hardened steel (50–52 HRC). Analysis of variance (ANOVA) was implemented to study the effects of investigated variables on hard machining performance. The most outstanding finding is that the main effects of the input variables and their interaction are deeply investigated to prove the better machinability and the superior cooling lubrication performance when machining under NFMQL condition. The experimental results indicate that the uses of smaller air pressure and higher air flow rate decrease the cutting forces and improve the surface quality. Al2O3 nanoparticles show the better results than MoS2 nanosheets. The applicability of soybean oil, a type of vegetable oil, is proven to be enlarged in hard milling by suspending nanoparticles, suitable for further studies in the field of sustainable manufacturing.

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.

Cutting fluids used in the metal machining industry have exerted serious impacts on the environment and human health. In addition, the very high cutting heat and forces in machining-hardened steels have been a growing concern in the metal cutting field. Hence, new, eco-friendly cooling and lubricating techniques are necessary to study and develop. Minimum quantity lubrication (MQL) and minimum quantity cooling lubrication (MQCL) using nano cutting fluids have been proven as alternative solutions for machining difficult-to cut materials while retaining an environmentally friendly characteristic. Accordingly, this paper aims to analyze and evaluate the hard turning efficiency of 90CrSi (60 ÷ 62 HRC) steel using MQL and MQCL conditions, using Al2O3 and MoS2 nano cutting fluids. The 2k-p experimental design and analysis of variance (ANOVA) were used to study the influence of input parameters including fluid type, lubrication method, nanoparticle type, nanoparticle concentration, cutting speed and feed rate on surface roughness. The obtained results showed that the machinability of CNMG120404 TM T9125 carbide tools was improved and the highest machinable hardness was increased from 35 HRC to 60 ÷ 62 HRC (rising by approximately 71.4 ÷ 77.1%) by using the nanofluid MQL and MQCL methods. Furthermore, MQCL gives better performance than MQL, and the Al2O3 nanofluid exhibits the better result in terms of surface roughness values than the MoS2 nanofluid. Feed rate displays the strongest influence on surface roughness, while fluid type, nanoparticle concentration and cutting speed show low impacts. From these results, technical guidance will be provided for further studies using Al2O3 and MoS2 nano cutting fluids for MQL and MQCL methods, as well as their application in machining practice.

Minimum quantity lubrication (MQL) has gained significant attention in various research fields and industrial applications for its advantages of being environmentally friendly and suitable for sustainable production. The effectiveness of MQL is increasing significantly by using nano cutting fluid, which can be produced by suspending nanoparticles in the based cutting fluid. This study aims to investigate the effects of MoS2 nanoparticle concentration, cutting speed, and feed rate on MQL hard turning of 90CrSi steel in terms of surface roughness and surface microstructure. The Box–Behnken experimental design was used to analyze the influence of input parameters and their interaction effects as well as to find the optimal set of variables. The obtained results prove the improvement of the machinability of carbide tools due to higher cooling and lubricating performance created by MoS2 nanofluid MQL, which contributes to improve the surface quality and reduce the manufacturing cost. There is an interaction effect between nanoparticle concentration and feed rate which has a strong influence on surface roughness.