Modern Piston Ring Coatings and Liner Technology for EGR Applications

Exhaust gas recirculation (EGR) is an upcoming technology for heavy duty (HD) engines in order to face the strict environmental laws in the USA from 2002 and EURO IV from 2004 in Europe. This paper is dedicated to describe modern power cylinder technologies to combat EGR driven needs. In detail, the paper introduces the market situation for heavy duty engines using EGR in Europe and the US. The main technical issues of EGR technology for HD engines are outlined. Since with EGR up to 30 % and more of the exhaust gases will be recirculated through the engine inlet pipe back into the cylinder the paper will discuss the major influences of EGR onto the engine's tribology. Thereby, the paper mainly focuses onto modern piston ring coating technology such as hard particle reinforced chrome plating, HVOF spraying and PVD. The paper introduces these technologies to the reader and will outline the specific coating characteristics. A focal point is set onto the key parameters of these coating technologies in order to optimize the coating performance. Furthermore, some material solutions for liners appropriate to be used in EGR engines are described. The paper presents both wear rig test analyses and engine test results.