Abstract
The study of nanoparticles as additives for metalworking fluids (MWFs) with applications in the metal removal processes, or machining, has received increasing attention due to the possible enhancements on tribological properties. In this study, low-cost and environmentally friendly nanoparticle additives of halloysite clay nanotubes (HNTs) were dispersed in metalworking fluids utilized for milling processes. Concentrations of 0.01, 0.05, 0.10 wt. % were incorporated into a mineral oil (MO) and a semi-synthetic fluid (SF) by ultrasonication. The anti-wear properties of metalworking nanofluids were characterized with a T-05 block-on-ring tribotester at a contact pressure of 0.5 GPa. Surface roughness of worn block materials was obtained with an optical 3D surface measurement system. Results showed that at a concentration of 0.10 wt. % HNTs block mass loss was lowered by 24% for the MO + HNTs nanofluids. For the SF + HNTs, a reduction of 63% and 32% in wear mass loss and coefficient of friction (COF), respectively, were found at the same concentration. The tribological enhancing mechanism for the applied contact pressure was proposed to be due to a reduction of the area of contact and nanoparticle sliding between surfaces with no HNT deposition, evidenced by energy dispersive spectrometry (EDS). Furthermore, surface roughness studies of worn blocks showed smoother surfaces with lower groove density with the addition of nanoparticle additives. The results of this study demonstrate that HNTs can improve the lubricity of metalworking cutting fluids used for machining processes, enhancing tool life and providing better surface finish of products.
Highlights
Metalworking fluids (MWFs) are used in metal removal processes such as cutting, milling, and grinding to reduce friction between the tool and the workpiece, increase tool life by reducing wear, and improve surface finish [1,2,3,4]
halloysite clay nanotubes (HNTs) nanofluids nanofluids exhibited exhibited the the best best tribological tribological behavior behavior with with much much every lower wear mass loss compared to. This was likely due to the higher viscosity lower wear mass loss compared to mineral oil (MO) + HNT nanofluids
Two metalworking fluids (MWFs) filled with low concentrations of HNT additives were prepared and
Summary
Metalworking fluids (MWFs) are used in metal removal processes such as cutting, milling, and grinding to reduce friction between the tool and the workpiece, increase tool life by reducing wear, and improve surface finish [1,2,3,4]. HNTs are non-toxic even at high concentrations, and are much less expensive compared to other tubular-like nanoparticles such as carbon nanotubes (CNTs) [22] Due to these characteristics they have been studied for diverse applications, such as for preparing colloids with biopolymers providing tunable properties [29], for drug transport and delivery [28], as nanocontainers of additives for paper preservation [30], for obtaining inorganic reverse micelles for the entrapment of antibacterial agents [31], and for capturing hydrocarbon and aromatic oils [32]. Our group demonstrated that HNTs dispersed in metal-forming lubricants tested under extreme pressure conditions are able to increase the load-carrying capacity, scuffing load, and seizure load (load for lubricant film breakdown) under contacts pressures of 3.5–3.9 GPa [33] At this high contact pressure the tribological enhancing mechanism of HNTs was due to a possible exfoliation of their outer sheets and deposition on the surfaces. The proposed tribological enhancing mechanism of this study was determined by energy dispersive spectrometry (EDS)
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