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Processing of Ti alloy is often accompanied with large frictions and high temperature. Nanofluids prepared by adding nanoparticles show good lubrication performance due to the excellent antifriction and antiwear of nanoparticles. The physicochemical properties of nanoparticles are important factors that influence the lubrication performance of nanofluid minimum quantity lubrication (NMQL). An experimental study on Ti alloy (Ti-6Al-4V) milling was conducted to explore the lubrication performance of minimum quantity lubrication (MQL) using different nanofluids. Cottonseed oil was used as the base oil, and the tribological properties of several typical nanoparticles (i.e., Al2O3, MoS2, SiO2, carbon nanotubes, SiC, graphite) were studied. The lubrication performance was evaluated by milling parameters, including milling force, surface roughness (Ra, RSm, Rmr), friction coefficient, microstructures of debris and workpiece surface, and energy spectra of the workpiece surface. Results demonstrated that the milling process based on Al2O3 nanofluid achieved the minimum milling force and friction coefficient, whereas the milling process based on SiO2 nanofluid had the minimum surface roughness value (Ra). Furthermore, the physicochemical properties of nanoparticles and the viscosity of nanofluid were analyzed. Spherical Al2O3 and SiO2 nanoparticles improved the lubrication effect of base oil mostly. The Al2O3 nanoparticles exhibited high hardness, which was conducive to reducing milling force. SiO2 nanofluid demonstrated high viscosity, which could improve workpiece surface quality. [ABSTRACT FROM AUTHOR]

To solve the limited cooling capacity of drip cooling technique in current clinical grinding orthopedic surgery, this paper carried out a nanoparticle jet minimum quantity cooling grinding experiment by using hydroxyapatite, SiO2, Fe2O3, carbon nanotubes nanofluids. The mass fraction of each nanofluids was 2%, 4%, 6%, 8%, 10%, respectively. Grinding temperature during the grinding process was measured, and results show that the temperature peak of bone micro-grinding isn't always proportional to the mass fraction of nanofluids. The measured temperature peak shows an inversely proportional relationship with the mass fraction of nanofluids within a certain mass fraction range, but a proportional relationship beyond this mass fraction range. Such a critical mass fraction varies when using different types of nanoparticles. Combined with heat transfer enhancement of nanofluids, the influence law of nanofluids type and concentration on grinding temperature was disclosed from the rheological properties of nanofluids and the micromechanisms of nanoparticles in the grinding zone. The bigger the mass fraction, the more easily it displays rheological properties. As for hydroxyapatite, whose length-diameter ratio is high and for SiO2 and CNTs, whose hardness values are high, they more easily display shear thinning and shear thickening, and the effect of rheological properties on temperature is obvious. [ABSTRACT FROM AUTHOR]

The present research investigated the lubrication performances of AlO/SiC nanofluid minimum-quantity lubrication (MQL) grinding in accordance with recent technologies used in conducting minimum-quantity lubrication grinding with nanofluids. The mean grain size of the AlO and SiC nanoparticles (NPs) was set to 50 nm, and the difficult grinding Ni-based alloy was used as the workpiece material in the experiment. Grinding force was measure by using a three-component dynamometer and then used to calculate grinding force ratio ( R). Workpiece surface roughness was measured by a roughness tester. Five groups of NPs were mixed with synthetic lipids at a mass fraction of 6 %. The lipids were then used as the grinding fluid for the nanofluid MQL grinding. Results showed that, compared with pure SiC NPs, pure AlO NPs obtained lower R = 0.3, lower specific grinding energy ( U = 75.93 J/mm), and lower surface roughness ( Ra = 0.386 μm), indicating better lubrication performance. The mixed NP consisting of AlO and SiC NPs achieved even lower R and surface roughness than pure NPs because of the 'physical synergistic effect.' The optimal ratio of the effect of mixed NPs was explored based on this finding. The AlO/SiC (2:1) mixed NPs obtained the smallest R = 0.28 and specific grinding energy ( U = 60.68 J/mm), thus indicating the best lubrication performance. Therefore, 2:1 is the optimal ratio for mixed NPs. [ABSTRACT FROM AUTHOR]

The effect of nanoparticle concentration on the lubricating property of nanofluids for minimum quantity lubrication (MQL) grinding was experimentally investigated based on the status of nanofluid MQL. Different concentrations of nanofluids with molybdenum disulfide (MoS 2 ), carbon nanotubes (CNTs), and their mixtures (MoS 2 -CNTs) were prepared. Difficult-to-cut Ni-based alloy was used as the workpiece material to explore the effect of mass fraction of nanofluids on grinding force ratio ( G ) and workpiece surface quality. The statistical analysis of grinding force ratio and surface roughness ( Ra ) were performed using one-way analysis of variance followed by Tukey’s post-hoc test with confidence intervals (CI) of 95%. Results showed that given the same mass fraction, MoS 2 -CNTs achieved lower G [ G Mix (8%) = 0.274] and surface roughness ( Ra = 0.328 μm) than MoS 2 and CNTs. These characteristics were attributed to the physical collaboration of the mixed nanoparticles. For the same nanoparticle, G decreased initially, reaching the lowest value at 8% [ G Mix (8%) = 0.274], and then increased with the increase in mass fraction of nanofluids because of the influence of agglomeration. Ra, increased gradually with the increase in viscosity of nanofluids. Autocorrelation analysis shows that MoS 2 -CNT nanofluid MQL achieved the lowest autocorrelation initial value ( R Mix = 0.64) when τ = 0. This result confirms that MoS 2 -CNT nanofluid MQL could improve machining precision and surface quality. Among different concentrations of nanofluids, the high-frequency continuous oscillation of the autocorrelation curve of the 8% MoS 2 -CNTs indicated improved workpiece surface quality. Combined friction coefficient, Ra , and autocorrelation analytical results show that 8% MoS 2 -CNTs was the optimum concentration for nanofluid MQL in the experiment. Autocorrelation analysis of the profile curves reveals the microstructural information of the workpiece surface and, combined with Ra analysis, provides a better method of analyzing the surface quality of a workpiece. [ABSTRACT FROM AUTHOR]