Carbon nanotubes/silicon nitride nanocomposites for gasoline lubricated high pressure pumps

High pressure gasoline direct injection systems are able to considerably reduce both the fuel consumption and the harmful emissions, but the current metallic components should be replaced by new advanced materials with enhanced tribological properties. In this work, multi-walled carbon nanotubes (MWCNTs)/silicon nitride (Si3N4) nanocomposites have been tested in a high-pressure 3-piston prototype pump for gasoline using both a cam/pusher self-mated system, and a nanocomposite cam/steel AISI 52100 pusher configuration. Si3N4 sliding systems were also tested as reference material. MWCNTs nanocomposite cams in combination with steel pushers present an outstanding performance at high rotation speeds and delivery pressures, showing mechanical efficiencies beyond 0.95, low cyclic variations, and torque oscillations 75% lower than the other tested material combinations. MWCNTs favour the formation of surface dimples where debris are entrapped, and promote tribochemical reactions with the steel pushers, enhancing the mechanical efficiency.