This chapter presents the lubricating properties of different vegetable-oil-based nanofluids through a comparative evaluation between frictional test and grinding experiment. The first experiment aimed to prejudge the lubricating properties of different nanofluids with a frictional test, which simulated the interface state of grinding between the abrasive grains and the workpiece. The second aimed to test and verify the lubricating properties of the same nanofluids through a grinding experiment. The mechanism of oil-film formation of nanofluids in the grinding zone was analyzed by morphology and element analysis of the worn surface. The experimental results show that Al2O3 nanofluids have the best tribological properties. Compared with pure base oil, the friction coefficient is reduced by 20%, and the optimal friction surface morphology is obtained. The good anti-friction and anti-wear properties of nanofluids are attributed to the formation of the protective oil film formed by chemical reaction on the surface.
Top13.1 Introduction
Influence laws of different nanofluids on lubricating property are obtained through the grinding experiment in Chapter Twelve. Much research work has been done regarding both application of tribological properties of nanoparticles to machining process and their verification in the frictional wear experiment (Kulkarni, Nadakatti, Patil, & Kulkarni, 2017; Sharma, Tiwari, & Dixit, 2015; Virdi, Chatha, & Singh, 2019). However, as different nanoparticles have different physical characteristics, their tribological properties may also be different (Li, Zhang, Jia, Wang, & Hou, 2015; Zhang, Li, Jia, Zhang, & Zhang, 2015a). Zhang et al. (2015b) found that MoS2/CNT hybrid nanoparticles had better lubrication effect than single nanoparticles. The best mixture ratio of MoS2/CNT and the concentration of nanofluids were 2:1 and 6 wt.%, respectively. The research of Mao (2012) showed that compared with dry grinding, MQL grinding can significantly improve the grinding performance in improving the quality of grinding workpiece, reducing the grinding temperature and grinding force. Zhang et al. (2016) found that the hybrid nanoparticles composed of alumina and silicon carbide nanoparticles have lower Ra value and surface roughness than the pure nanoparticles due to their “physical synergistic effect”. Zhao et al. (2017) studied the stability of particle dispersion by Zeta potential method. The particle size of additive conglomerate in nanofluids was measured by dynamic light scattering. The results show that the dispersion of nanoparticles has an important influence on the friction properties of nanofluids. The results of EDS and XPS in Battez et al. (2010) study show that the antifriction behavior of nano lubricating oil on the wear surface can be attributed to the third body and friction sintering mechanism. Gara and Zou (2012) studied the effects of the type, concentration and surface roughness of nanoparticles on the friction and wear characteristics. The friction and wear tests were carried out with UMT-2 Micro Friction and wear tester. It is found that nanoparticles have a great influence on the friction and wear characteristics of lubricating oil. Kao and Lin (2009) found that the friction coefficient of nanofluid was always lower than that of no nanoparticles, although the viscosity loss would be caused by the increase of temperature. Nanoparticles provide rolling function, surface repair and increased viscosity as a lubricant. Yu et al. (2008) studied the effect of temperature on the tribological properties of copper nanoparticles on a four ball friction and wear tester. The results show that a copper protective film with low elastic modulus and low hardness is formed on the worn surface, which makes the copper nanoparticles have good tribological properties, especially at high oil temperature. Jiao et al. (2011) studied the tribological properties of modified alumina / silica composite nanoparticles as lubricant additives. The results show that their wear resistance and friction properties are better than those of pure alumina or silica nanoparticles. Due to the double effects of grinding and heating, the modifier is completely dispersed on the surface of particles, and combines with Si to form Si-O-C, and with Al to form double tooth coordination acyl alumina (Li, Ren, Jia, Liu, & Zhu, 2010). Peng et al. (2009) studied the tribological properties of diamond and silica nanoparticles prepared by oleic acid surface modification method in liquid paraffin. As liquid paraffin additives, the two nanoparticles have better antiwear and antifriction properties than pure paraffin oil at a very small concentration. Liu et al. (2017) studied the effect of nano particle size on the tribological properties of SiO2/Polyalkylene glycol nanofluids under different lubrication conditions. It is found that the mixed nano additive has better anti-wear and anti friction performance than the nano additive with uniform particle size. Gara and Zou (2013) studied the effects of surfactant, ultrasonic time, particle concentration, applied load, sliding speed and surface roughness on the friction and wear properties of nanofluids. The results show that under certain conditions, the oil-based nanofluids containing nano zinc oxide reduce the friction and wear, the application of oleic acid as dispersant reduces the friction and wear to a certain extent, and improves the dispersion and stability of the nanofluids. Han et al. (2019) pointed out that diamond nanofluids produce higher ball wear than zinc oxide nanofluids. Ran et al. (2017)'s research found that oil-based nanofluids containing nano zinc oxide can significantly reduce friction and wear. Zin et al. (2016) found that the dispersed nanostructures play an important role in protecting the surface from wear and improving the friction performance and bearing capacity of crude oil. Pavan et al. (2019) studied the properties of graphene nanosheets cutting fluid in Inconel 718 Alloy MQL grinding. The experimental results show that the grinding force, temperature, specific grinding energy and surface roughness are reduced significantly. Minh et al. (2017)'s research shows that due to its better tribological performance and cooling and lubricating effect, when using alumina nanofluids for minimum lubrication, the tool life increases by nearly 177% - 230% (depending on the type of nanofluids), and the surface roughness and cutting force decrease by nearly 35% - 60%. Kumar et al. (2017) found that the use of nanofluids greatly improved the surface finish and reduced sub surface damage. Madanchi et al. (2019) studied the effect of nanoparticles and particles on the properties of cutting fluid and tribology. The effects of two different metal oxides, Al2O3 and ZrO2, as well as the size, concentration and base solution of silica were studied. Although the lubricity of most nanoparticles has been improved, the opposite has been found in alumina. Dambatta et al. (2019) found that with the increase of nanofluid concentration, the grinding force of engineering ceramics decreased significantly, and the surface quality was improved. Lv et al. (2018) used graphene oxide/SiO2 hybrid nanoparticles water-based lubricant as cutting fluid, and compared the tribological and processing characteristics of four ball milling test devices. The results showed that the friction coefficient and wear scar diameter of hybrid nanoparticles water-based MQL are significantly lower than those of single nanoparticles water-based MQL. Furthermore, in order to improve the processing performance and reduce the oil mist concentration in the processing workshop, Lv et al. (2018) proposed a near dry processing technique called electrostatic minimum quantity lubrication. The tribology and deposition performance of nanoparticles lubricant electrostatic minimum quantity lubrication and ordinary minimum lubrication were compared processability.