Friction Behavior of Different DLC Coatings by using Various Kinds of Oil

The requirements on engine components are becoming tougher. On the one hand, the load of the components is increasing due to the optimization of the engines to make them more efficient. New materials and/or coatings and surface treatments are needed to fulfill the new requirements. On the other hand, changes of oil additives and the introduction of alternative fuels are challenging the engine materials as well. In addition, there is a high demand to reduce the friction of the engine for improved fuel consumption. One-way to support this is the application of friction reduced coatings and/or surface treatments. DLC coatings seem to be a promising candidate. But what differentiates DLC coatings on the market and within different lubrication conditions in regards to friction? Standard valve train bucket tappets coated with different DLC coatings will be compared regarding friction to uncoated steel bucket tappets by using a special self build test rig. The friction results of the test in the lab will be compared to those of the cylinder head tests. Further the structure of the DLC coatings and the chemistry of the oils will be discussed.