Tribological enhancement of piston skirt conjunction using graphene-based coatings

Piston skirt to cylinder liner conjunctions are amongst the major contributors to frictional power losses of Internal Combustion Engines (ICEs). Efforts have been made to mitigate the frictional losses of these conjunctions by incorporating different technologies such as texturing and application of novel coatings. Any potential technology needs to provide adequate wear resistance as well as frictional reduction in order to be practically applicable. In this paper, the piston skirt of a gasoline engine is deposited by three different variants of Graphene Oxide (GO) coatings deposited using an Electro-Phoretic Deposition (EPD) method. Their tribological performance is benchmarked against uncoated steel and graphite coated aluminium skirts. These coatings are experimentally characterised in terms of asperity level friction, topography and wear resistance. The conjunction and system level performance of these coatings considering both boundary and viscous friction and system dynamics are then evaluated using a multi-physics tribo-dynamic model. Results show that by incorporating an appropriate GO coating, the frictional power loss of the piston skirt to cylinder liner conjunction can be improved by up to 14% whilst maintaining the wear resistance of the coating at the level of an uncoated steel surface.