Reducing frictional power losses and improving the scuffing resistance in automotive engines using hybrid nanomaterials as nano-lubricant additives

What is it about?

The purpose of this work was to investigate a new nano-additive for improved internal combustion engine oils designed for increased fuel economy and a cleaner environment. The friction and wear characteristics of nano-lubricants containing hybrid nano-materials of Al2O3 and TiO2 were been evaluated under reciprocating test conditions to simulate a piston ring/cylinder liner contact. Al2O3/TiO2 nanoparticles were suspended in a commercially available lubricant in various concentrations. The Al2O3 and TiO2 nanoparticles had sizes of 8-12 nm and 10 nm, respectively. The morphology and microstructure of the tribofilms produced during frictional contact were investigated via FE-SEM, EDS and a 3-D surface profiler. In the best case, there was a reduction of frictional power losses for the simulated piston ring assembly by 40-51% compared to a commercially available lubricant. The nano-additive composition in that case was 0.05 wt.% Al2O3+0.05 wt.% TiO2. Moreover, the wear rate of piston ring decreased by 17% after a sliding of 50 km due to the delamination of Al2O3 and TiO2 nanoparticles on worn surfaces. In that case, they acted as a solid lubricant to reduce both wear and scuffing. These results present a promising and straightforward approach to automotive fuel economy and an increased life span for engine parts.

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Why is it important?

The findings of this study lead to the conclusion that Al2O3/TiO2 hybrid nano-lubricants can contribute to an improvement in the efficiency of engines and fuel economy in automotive engines via the reduction of frictional power losses. The following conclusions can be drawn: 1- The morphology of the worn surfaces of the ring and liner indicates that a protective film formation on the worn surfaces takes the form of a solid lubricant or an ultra-thin lubricating coating, which is responsible for the minimization of frictional power losses, as well as the anti-wear and anti-scuffing ability provided by Al2O3/TiO2 hybrid nanoparticles and the oil additive package (Phosphorus active element of ZDDP) in the fully formulated base engine oil (5W-30). 2- The frictional power losses for the piston ring assembly were reduced by 40-51% for the Al2O3/TiO2 hybrid nano-lubricants, as compared with the commercial lubricant (5W-30). This could lead to an improved performance and fuel economy of an automotive engine. 3- The friction coefficient decreased by 47.61% under the boundary lubrication regime for the use of the Al2O3/TiO2 hybrid nano-lubricants as compared with the engine oil without nanoparticles. Moreover, the use of oleic acid alone in engine oil contributes to a friction coefficient reduction by 18% due to chemical reaction on worn surfaces. 4- The surface roughness of the piston ring and liner while using 0.1 wt.% optimum concentrations for Al2O3/TiO2 hybrid nano-lubricants decreased by 64.7% and 40%, respectively, compared with the commercial lubricant. 5- The wear rate of the piston ring decreased by 17% due to the delamination mechanism by the Al2O3/TiO2 hybrid nanoparticles for worn surfaces leading to a reduced metal contact between worn surfaces.