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A hybrid lubricant with improved thermal and tribological properties was developed by blending multiwalled carbon nanotubes (MWCNTs) with alumina-based nanoparticles into cutting fluid at fixed volumetric proportions (10:90). The hybrid cutting fluid was prepared in different volumetric concentrations (0.25, 0.75, and 1.25 vol%), and the tribological properties and contact angles were measured using pin-on-disc tribometry and goniometry, respectively. The study showed a reduction in wear and friction coefficient with increasing nanoparticle concentration. The cutting fluid performance was investigated using minimum quantity lubrication (MQL) in the turning of AISI 304 stainless steel. Regression models were developed for measuring the temperature and tool flank wear in terms of cutting speed, feed, depth of the cut, and nanoparticle concentration using response surface methodology. The developed hybrid nanolubricants significantly reduced the tool flank wear and nodal temperature by 11% and 27.36%, respectively, as compared to alumina-based lubricants. Friction 7(2): 153-168 (2019) | https://mc03.manuscriptcentral.com/friction Friction 7(2): 153-168 (2019) | https://mc03.manuscriptcentral.com/frictionFriction 7(2): 153-168 (2019)

SU-8, an epoxy-based negative photoresist polymer, is highly suitable for making micro-electromechanical systems (MEMS) structures. Despite fabrication advantages, its bulk mechanical and tribological properties are the main limitations for application as MEMS material. Carbon filler materials such as graphene, graphite and multi-walled carbon nanotube (MWCNT) are added to SU-8 for tribological and mechanical property enhancements. SU-8/(5 wt%) graphite composite has performed better for the steady-state coefficient of friction at all loads including for the speed effect. SU-8/(5 wt%) MWCNT has shown excellent wear resistance. At 10 wt% graphite content, SU-8/graphite is superior in tribological performance to other composites tested.

In this study, SU-8 and its composites are fabricated by blending 10 wt.% hexagonal boron nitride (h-BN) fillers with/without lubricants, such as 10 wt.% base oil (SN150) and 20 wt.% perfluoropolyether (PFPE). The thickness of SU-8 and its composites coating is fabricated in the range ~100-105 μm. Further, SU-8 and its composites are characterized by a 3D optical profilometer, atomic force microscopy, scanning electron microscopy, a thermal gravimetric analyzer, a goniometer, a hardness tester, and an optical microscope. Under a tribology test performed at different normal loads of 2, 4, and 6 N and at a constant sliding speed of 0.28 m/s, the reduction in the initial and steady-state coefficient of friction is obtained to be ~0.08 and ~0.098, respectively, in comparison to SU-8 (~0.42 and ~0.75), and the wear resistance is enhanced by more than 103 times that of pure SU-8. Moreover, the thermal stability is improved by ~80-120 °C , and the hardness and elastic modulus by ~3 and ~2 times that of pure SU-8, respectively. The SU-8 composite reinforced with 10 wt.% h-BN and 20 wt.% PFPE demonstrated the best thermo-mechanical and tribological properties with a nano-textured surface of high hydrophobicity.

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Brakes are very important component in any vehicle, used to stop the motion of it either by applying mechanical or hydraulic pressure on brake pads. By engaging and disengaging of braking action, the surface of brake components (or) materials is ruined after some time. Therefore, it is important to study and develop a new composition of brake materials which provides optimum coefficient of friction along with increasing wear resistance to the materials. Hence, new combination has been formulated for fabrication of brake composite material using powder metallurgy method which consist of copper-tin alloy mixed with silicon carbide as a base materials, aluminium oxide as an abrasive material with varying volume percentage of graphite and talc powder as a friction modifiers. The pin-on-disc test was performed on brake composite material to analyse their tribological properties namely friction and wear. From tribo-test, it was observed that all composites give the friction coefficient in the range of ∼0.33–0.51 and the loss of materials in the range of ∼79–131 mg. Further, the mechanical, thermal stability and surface characterization were also carried out on brake composites using universal testing machine, vicker’s hardness tester, thermogravimetric analyser and scanning electron microscope respectively. These results reveal a very marginal change in hardness, increase in compressive strength by increase of talc concentration to the matrix, uniform distribution of reinforcement into the matrix and multi stage degradation of material loss in thermograph.

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