Optimizing the Piston/Bore Tribology: The Role of Surface Specifications, Ring Pack, and Lubricant

The present study looks into different possibilities for tribological optimization of the piston/bore system in heavy duty diesel engines. Both component rig tests and numerical simulations are used to understand the roles of surface specifications, ring pack, and lubricant in the piston/bore tribology. Run-in dynamics, friction, wear and combustion chamber sealing are considered. The performance of cylinder liners produced using a conventional plateau honing technology and a novel mechanochemical surface finishing process - ANS Triboconditioning® - is compared and the importance of in-design “pairing” of low-viscosity motor oils with the ring pack and the cylinder bore characteristics in order to achieve maximum improvement in fuel economy without sacrificing the endurance highlighted. A special emphasis is made on studying morphological changes in the cylinder bore surface during the honing, run-in and Triboconditioning® processes. It is demonstrated that the Triboconditioning® treatment, while in certain aspects resembling the run-in process, provides a greater effect depth and results in a beneficial tribological performance profile. In particular, the Triboconditioning® treatment of cylinder liners allows significant reduction in top ring wear when low viscosity motor oil is used for improved energy efficiency.