MAVO TriboMan. Integrated approach for friction reduction of power train components by manufacturing integrated surface modification

The effective reduction of friction losses in combustion engines requires the combined approach of different techniques. In addition, tribological phenomena on different length scales have to be addressed. Joining the forces of the Fraunhofer Gesellschaft a multi-million Euro project called TriboMan was started two years ago. Tribological optimization was focused on the ring-liner contact, bearings and the valve train. The research includes materials development as well as casting, machining, surface modification of Powertrain components and the testing of their tribological behaviour. Numerous tests with hypereutectic AlSi alloys for liners showed that after proper running-in the near-surface material takes on a nanocrystalline structure. Therefore, the Si content of the alloy was reduced to refine the grain structure. This process was supported by the addition of strontium. After casting the liners an energetically controlled finishing operation was applied to condition the material further. A selection of liners was laser-textured to stimulate micro-hydrodynamic effects. This technique was also applied to the piston pin and parts of the valve train. Finally diamond-like carbon was used to coat the piston rings. The received engine parts were tested on-line with respect to friction losses and wear. Surface science methods were applied to analyze the tribological effects on different length scales.