Hoppe, S. and Kantola, T., "DuroGlide® - New Generation Piston Ring Coating for Fuel-Efficient Commercial Vehicle Engines," SAE Technical Paper 2014-01-2323, 2014, doi:10.4271/2014-01-2323.
The fundamental drivers in the development of commercial vehicle engines are improved fuel efficiency and the need to meet more stringent exhaust emissions legislation. This strategy presents significant challenges in the development of engine components, particularly piston rings. Within the power cylinder, piston rings are significant contributors to friction losses, with the ring pack contributing up to 25 percent of the total mechanical engine friction loss, and a corresponding fuel consumption of up to four percent. The challenge lies in reducing friction power loss, without compromising oil consumption, while also mastering the increasing thermo-mechanical and tribological demands that piston rings must endure due to increased power density, smoother cylinder bores, reduced lubrication, and the use of alternative fuels. In this context, the robustness of the piston ring running face, as characterized by wear resistance and scuff resistance in particular, plays an increasing role. As coatings are a crucial surface design element, they inevitably are a primary focus for addressing friction loss and increasing robustness in the piston ring/cylinder tribological system.This paper will outline the development of a new generation tetrahedral amorphous carbon (ta-C) piston ring coating called DuroGlide®, which is setting new standards in high-performance, low-friction piston ring technology. DuroGlide-coated piston rings demonstrate outstanding durability, friction, and scuff resistance compared to any ring coatings and contribute, in combination with advanced top and oil ring designs, fuel economy savings up to 1.2 percent for commercial vehicle engines. This paper demonstrates how DuroGlide provides superior wear and scuff resistance, enabling higher performance and fuel efficiency in engines where adverse lubrication conditions are most prevalent. Finally, this paper will summarize fundamental results from bench tests and engine validation for both upper compression rings and oil control rings.