For many years, the standards to meet in the automotive sector - regarding exhaust gas emissions and therefore fuel efficiency of the whole power train - have been raised. One approach to fulfill the requirements for GDI (Gasoline Direct Injection) engines is in¬creasing the pressure used to inject the fuel into the combustion chamber. However, from a tribological point of view the development to higher pressures leads to problems inside the fuel pumps. Gasoline lubricated metal-to-metal contacts under high pressures, tend to lead to severe adhesive wear and eventually system failure. Under the same conditions, non-oxide engineering ceramics like SiC and Si3N4 should bear a high potential for friction and wear reduction compared to metallic components due to their lower adhesion and higher strength.
To investigate the potential of ceramic materials for media lubricated high-pressure gaso¬line injection pumps in particular, model experiments under reciprocating sliding con¬ditions were conducted. In addition to the commercially available engineering ceramics SiC and Si3N4, proprietary developed ceramic composites were tested. These composites consist of mixtures of silicon carbide and silicon nitride with varying fractions and were densified by hot isostatic pressing (HIP). The tribological experiments were run in a pellet/plate geometry, forming a flat-on-flat contact immersed in an isooctane bath. With the current test setup a stroke length of 5 mm in combination with a normal force of 200 N was feasible. First results have shown interesting effects for the newly developed composites as well as distinct frictional behavior for the different commercially available ceramics.