Search

The tribological behavior of traditional oil-in-water (O/W) lubricants (1.0 wt.%) and nano-TiO2 additive lubricants (1.0–9.0 wt.%) during micro rolling of titanium foils were analyzed. In this study, the surface morphologies of titanium foils under various lubrication conditions were assessed, and the corresponding lubrication mechanisms were revealed. The tribological behavior of nano-TiO2 additive lubricants during micro rolling of titanium foils was also explored through a series of characterization methods. The utilization of nano-TiO2 additive lubricants in micro rolling reduces the surface roughness of titanium foils. Moreover, it effectively inhibits the generation of indentations and cracks during rolling processes, enhancing the surface quality of rolled specimens. Additionally, owing to the synergism of rolling, tribo-film, mending and polishing effects of the nanoparticles, both the rolling force and surface roughness were minimized by using lubricants containing 3.0 wt.% TiO2 nanoparticles. Overall, an optimal concentration (3.0 wt.%) of TiO2 nanoparticles in water-based nanolubricants was obtained with enhanced tribological properties and lubrication performance during micro rolling of titanium foils. [ABSTRACT FROM AUTHOR]

Water-based nanolubricants with different concentrations of TiO2 nanoparticles were prepared and the wettability and viscosity were evaluated. The results show that the addition of TiO2 nanoparticles improves the lubrication performance during microrolling of ultrathin stainless steel foils. In addition, the viscosity decreases dramatically with the increase in the concentration of nanoparticles, which was related to the change of dispersing agent concentration. Microrolling tests were performed to explore the lubrication conditions during microrolling of ultrathin stainless-steel strips, and the results showed that the refined surface quality of the rolled strips was achieved with 3.0 wt% TiO2. The improvement in surface quality can be attributed to the synergism of the rolling effect, polishing effect, protection film, and mending effect of TiO2 nanoparticles. [ABSTRACT FROM AUTHOR]

In this work, the effects of the developed oil-in-water (O/W) based nanolubricants containing TiO 2 nanoparticles (NPs) on the tribological behaviour of oxidised high-speed steel (HSS) were studied, using pin-on-disc tests. The pin was made of HSS and, prior to the wear test, was oxidised to form a scale layer on the surface. The results show that the TiO 2 NPs in the O/W lubricant can achieve an excellent reduction of the coefficient of friction (COF) and improve the anti-wear properties of pins with oxidised surfaces. The TiO 2 NPs in the nanolubricant were found to have the filling and tribo-sintering effects. The NP aggregation around the contact area was observed with higher TiO 2 NP concentrations in the nanolubricant, revealing a larger NP aggregation area. Based on the results and analysis, the mechanism about the effects of the TiO 2 NPs in the O/W based nanolubricant on the wear and COF were well explained. [ABSTRACT FROM AUTHOR]

A ball-on-disk tribometer was employed to evaluate the lubrication performance and mechanisms of innovative TiO 2 nano-additive water-based lubricants. Two experimental methods were applied to determine the optimal mass fraction of TiO 2 . In the method I, lubricants were added onto the worn disk tracks at a predetermined time interval. In the method II, the disks were immersed in the lubricants continuously during the whole process of tribological tests. The results both indicate that the water-based lubricants can significantly reduce the coefficient of friction (COF). The 0.8 wt% TiO 2 lubricant demonstrates excellent tribological properties including the lowest COF and the strongest wear resistance under all lubrication conditions. The lubrication mechanisms are attributed to the rolling and mending effects of the TiO 2 nanoparticles. [ABSTRACT FROM AUTHOR]

Oil-in-water (O/W) emulsion is widely applied as a lubricant during hot rolling process. For reducing environmental impact caused by O/W emulsion, a novel nano-TiO 2 additive O/W lubricant with improved stability and reduced coefficient of friction (COF) is developed. Little research, however, has been focused on the growth behaviour of oxide scale formed on the workpiece surface and its effects on the tribological property of nano-TiO 2 additive O/W lubricant. In the current work, oxidation tests of high strength steel were conducted to investigate the growth behaviour of oxide scale and obtain different surface morphologies of the oxide scale. Ball-on-disk tribological tests under a temperature of 80 °C were carried out to investigate the effects of surface morphology of oxide scale on the tribological behaviour under nano-TiO 2 additive O/W lubrication. The performance of the new developed lubricant was evaluated by hot rolling process. The growth mechanism of oxide scale and the modified oxide scale growth model were proposed. Tribological results indicate that oxide scale plays an important role in the tribological behaviour of nano-TiO 2 additive O/W lubricant. A reduction in surface roughness can result in a decrease of COF, while the COF will increase if the surface roughness reduces too much because some of the nano-TiO 2 particles cannot go through the contact area to play a positive role in lubrication. [ABSTRACT FROM AUTHOR]

The characters of grain boundaries in oxide layers formed on substrates influence adhesion and friction behaviour, surface fracture and wear during high temperature steel processing. In this work, an electron backscattered diffraction (EBSD) analysis was conducted to investigate the role of surface grain boundary and orientation in magnetite (Fe 3 O 4 )/haematite (α-Fe 2 O 3 ) scale during hot rolling, and further evaluate their effects on tribological properties of water-based nanoparticles lubrication. The results demonstrate that Fe 3 O 4 (100) plane is strongly sensitive to the surface characteristics as the minimisation of surface energy. Coincident site lattice (CSL) boundaries in microstructure is in presence of Σ3 in the Fe 3 O 4 and Σ13b in the Fe 2 O 3 of the substrates subjected to a thickness reduction of 28% and cooling rate of 28 °C/s. This is due in great part to the changes in crystal slip systems. These low-Σ CSL boundaries in oxide scale offer obstacles to the propagation of cracks, where some of nanoparticles collected would be trapped at the interface and thereby may cause high wear rates. A lubrication mechanism is proposed to explain the grain boundary effect on nanoparticles lubrication, and further to determine the dependence of frictional behaviour on surface energy, crystallographic preferred orientation (microtexture) and crystal structure. These results provide an intriguing new insight into the application of water-based lubricant with graphite nanoparticles. [ABSTRACT FROM AUTHOR]