Roman Morgenstern

Reduced Friction Losses and Wear by DLC Coating of Piston Pins

A Diamond Like Carbon (DLC) coating is well known to offer superior wear and friction behaviour. This combination of properties makes DLC suitable for many different areas of tribology. This paper concerns itself with usage in the power cylinder environment of automotive diesel engines. To estimate the potential of DLC coatings applied to piston pins in internal combustion engines, linearly reciprocating sliding wear examinations have been performed on uncoated and DLC coated component segments versus different counterpart materials as present in the power cylinder environment, including: piston (aluminium alloy), bushing (brass), piston pin (steel) and connecting rod (steel). Evaluation criteria for the tests include friction and wear performance in dry and lubricated conditions. Test results show how the DLC coatings offer impressive wear reductions for each of the different counterpart materials used. Furthermore, special emphasis is given to the analysis of the friction behaviour. As expected, the coefficient of friction (COF) decreased for aluminium and steel counterparts when the piston pin segments were DLC coated. However, for the combination of DLC with brass the COF increased in the dry condition. This surprising outcome is explained with SEM and EDX investigations of the wear traces. The tests at elevated temperature with lubrication show an inverse relationship with respect to friction criteria when compared with the dry room temperature tests for the DLC with brass combination. Examined engine tests confirm the results of the non-engine wear test rig, showing that DLC coatings applied on piston pins also exhibit properties and good potential to decrease frictional losses and fuel consumption in modern engines.Copyright

Transient micromechanical deformation and thermomechanical fatigue damage in AlSi based piston alloys under superimposed high cycle mechanical and low cycle thermal loading

Abstract Presently, AlSi based alloys, consisting up to 12 element systems, are used in the manufacture of automotive pistons for diesel engines. The pistons combustion wall is subject to complex superimposed transient mechanical and thermal loading with peak operating temperature representing a homologous temperature range Thom of 0.8 to 0.9. Using a special superimposed thermomechanical bench test apparatus, engine-like TMF loading has been reproduced and a number of semi in-situ experiments have been carried out to evaluate key microstructure damage mechanisms. The evolution of microstructural damage at the interface between hard Si inclusions and the softer Al matrix has been documented using scanning electron microscopy. The deformation characteristics at the Si/Al interface have been recreated using FEA techniques incorporating non-linear elasto-viscoplastic properties for the matrix material. Comparisons of bench test fatigue lives for transient superimposed high frequency and microstructural TMF loading for two different thermal cycles are then compared to isothermal mechanical load histories.

Transient microstructural thermomechanical fatigue and deformation characteristics under superimposed mechanical and thermal loading, in AlSi based automotive diesel pistons

Presently AISi based alloys, consisting up to 12 element systems, are used in the manufacture of automotive pistons for light vehicle (LVD) and heavy (HD) duty diesel engines. The pistons combustion wall is subject to complex superimposed transient mechanical and thermal loading with peak operating temperature representing a homologous temperature range of 0.8–0.9 Thom.

Minimierung von Verschleiß und Reibungsverlusten durch neue Kolbenbolzenbeschichtung

Diamantahnliche Kohlenstoffschichten (DLC = Diamond Like Carbon) zeichnen sich durch sehr vorteilhaftes Reib- und Verschleisverhalten aus. Federal-Mogul Nurnberg GmbH hat an beschichteten und unbeschichteten Serienkolbenbolzen vergleichende linear-abrasive Verschleisuntersuchungen gegenuber verschiedenen Gegenkorperwerkstoffen durchgefuhrt und ausgewertet. Zudem wurden diese Ergebnisse anhand von verschiedenen Motorlaufen bewertet. Sowohl durch die ausermotorische Prufung als auch durch die Motorergebnisse konnte das enorme Potenzial von DLC-Schichten zur Verschleis- und Reibverlustminimierung sowie zur Reduzierung der Fressneigung sehr gut aufgezeigt werden.