FORCARBON

I. 3 Optimisation of the wear resistance of sliding contacts in Diesel direct injection systems for low-consumption motor vehicles

Due to the rising demands concerning economical and overall mechanical performance of combustion engines for motor vehicles, as well as the rising Diesel market share and the need for lower pollutant (especially particle) emissions, there is an increasing need for further improvement of diesel direct injection systems. At present, injection pressures ranging from 1600 to 1800 bar in combination with ultra fine mineral particles in the fuel result in significant wear of the injectors. A further increase in the injection pressure, which is required for a more homogeneous combustion and, in consequence, higher power output and lower pollutant emission, leads to higher wear which could exceed the critical wear limit of the coatings currently used. Thus, to avoid malfunction or complete failure of the injection system within the expected lifetime, higher wear resistant coatings have to be developed. Since the performance of a coated surface depends on coating/substrate properties and interaction as well as surface topology, the aim of the research work lies in an improvement of the complete system. One step is the development of more wear resistant coatings based on DLC. On the other hand, the potential of modifications of substrate material properties and surface topology is to be examined systematically. Research work will be performed using simple samples as well as components of real injectors to avoid mismatch between simple sample test and component or operating test performance. Coating development takes place in mutual co-operation between the Institute for Engineering Design and Balzers AG. Tribological and substrate material aspects are mainly covered by INA-Schaeffler KG. Component tests for validation will be performed by means of a self-tailored diesel injector wear test rig. Finally the coated units are to be tested in field by Siemens VDO.