Fraunhofer Institute for Mechanics of Materials IWMDevelopment of innovative ta-C-based coatings and lubricants for the holistic tribological optimization of all critical engine components (valve train, piston ring, cylinder wall, connecting rod) in order to significantly reduce friction losses in combustion engines and thus lower energy consumption and CO₂ emissions by up to 40%.
High-performance carbon coatings for friction-optimized engine components (PROMETHEUS)
Completed research project
Project description
Approximately 40% of energy losses in combustion engines are caused by friction between moving engine components (pistons and cylinders, valve train, connecting rods and crankshaft, roller bearings). These friction losses lead to increased fuel consumption, higher CO₂ emissions, and a shorter component service life. Previous research projects (PEGASUS II, CHEOPS) addressed tribological measures in isolation: individual coatings, lubricants, and surface structures for specific engine parts. The additive principle often did not lead to the theoretically expected friction reductions.
The PROMETHEUS project researched and developed a systemic approach to reducing friction losses:
- Holistic consideration of all engine components in context
- Multiscale tribo-optimization for the integration of lubrication, coating, surface topography, and engine design
- Numerical tribology at the component and engine level
Key technical solutions are:
- ta-C:X coatings (doped diamond-like carbon) with optimized tribochemical interaction in engine oil additives
- Innovative engine oils with new additive packages for ta-C contacts
- Surface geometries (surface roughness, microstructuring) tailored to sliding and rolling contacts
- Engine geometry adjustments (e.g., piston ring designs) taking tribological optimizations into account
Fraunhofer IWM's work packages were:
- Experimental tribology and lubricant tests under engine conditions (high temperatures, varying loads, high sliding speeds)
- Atomistic and continuum mechanical simulation of lubricant-coating interactions
- Surface analysis: characterization of tribofilms, wear mechanisms, and tribochemical processes
- Nanoanalysis of the superlubrication mechanism
- Tribological optimization for demonstrator engine components
Fraunhofer IWM and IWS published a universal mechanism of superlubrication (frictionless sliding with μ < 0.01) in ta-C/organic lubricant systems in Nature Communications (2019) – a key result for PROMETHEUS.
Transfer of project results into the following R&D services provided by Fraunhofer IWM for companies:
- Development of high-performance coatings for engine components (piston rings, valves, bearing shells)
- Tribosimulation at the system level: Numerical prediction of friction and energy losses in engine components and identification of friction reduction potential
