Investigation of flow behaviour and lubrication capabilities of $$\hbox {MoS}_{2}$$

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Flow behaviour of lubricants largely depends on their rheological properties which in turn strongly influence their lubrication capabilities and ultimately the machine life. Modern chemistry plays a great role in the synthesis of nano-additives that help in enhancing the rheological and tribological properties of the lubricants. In the present study, the rheological and tribological studies of $$\hbox {MoS}_{2}$$ nanofluids are presented in order to determine their flow behaviour and lubrication capabilities. For studying the effect of $$\hbox {MoS}_{2}$$ nanoparticles on the flow behaviour and lubrication capabilities of lubricants, two commercially available blended synthetic engine oils of SAE grades 5W-40 were selected. $$\hbox {MoS}_{2}$$ nanoparticles were synthesized by hydrothermal methods. Surface modification of the synthesized $$\hbox {MoS}_{2}$$ nanoparticles was performed before blending them with the base lubricants in 0.1, 0.15 and 0.2% concentrations. Standard ASTM and IS procedures were used to determine physicochemical properties and tribo-performance behaviour of oils, respectively. The rheological parameters of $$\hbox {MoS}_{2}$$ nanofluids were determined using a rheometer. The study reveals that tested $$\hbox {MoS}_{2}$$ nanofluids behaved as non-Newtonian lubricants with shear thinning behaviour at all tested temperatures and exhibited viscoelastic behaviour at small-shear rates. As a result of this anti-wear property showed a significant enhancement up to 20% for 0.2% $$\hbox {MoS}_{2}$$ indicating better anti-wear properties of $$\hbox {MoS}_{2}$$ nanofluids. However, a marginal reduction in friction for the tuning of 4% observed for 0.2 wt% of $$\hbox {MoS}_{2}$$ nanoparticles in the tested lubricants indicates that finished products have little scope to improve anti-friction properties under the influence of the already present additives.