Abstract
KEYWORDS – bearing, polymer, microcapsules, seizure, wear
ABSTRACT
Engine components, specifically crankshaft bearings, in modern high speed diesel engines face increasing demands with regards to peak cylinder pressures and the resulting higher loads. Combined with ever thinner oil films, the seizure and wear resistance of engine bearings play a crucial role in modern engine development.
To attend to these demands, a next generation high-performance polymer coating with lubricant-filled microcapsules has been developed. The microcapsules are designed to rupture during nascent scuff and high wear events and release the contained lubricant on demand, just when it is needed to prevent seizure. A clear tendency for the novel polymer coating to provide better recovery from scuffing events was measured, allowing for continuing safe operation of the bearings, and thus reducing the seizure risk. Testing shows that microcapsules improved the recovery rate after seizure events to 66% whereas conventional polymer overlays show a recovery rate of 25%. As an additional benefit, the microcapsule-filled polymer coatings provide a wear improvement of more than 20%. Simultaneously, they maintain the exceptional fatigue performance and stop/start capability expected of polymer overlay coatings. The developed bearing material is especially targeted at high-speed diesel applications as a possible replacement of conventional sputter overlays.
Microcapsules have been used for the first time in an engine bearing overlay and open an entirely new development path as they can be filled with a broad range of tribologically active agents. The present paper reviews the development of the novel polymeric overlay with lubricant-filled microcapsules for improved seizure resistance and details rig test as well as engine test results.