Tribological study of crankshaft bearing systems: Comparison of forged steel and cast iron counterparts under start–stop operation

The current work investigates the tribological functionality of crankshafts bearing systems focusing on the variation of shaft materials and their surface conditions. Tribological tests were carried out with a ring-on-disc test configuration representing the bearing-shaft contact under start–stop motion. Forged steel and cast iron shaft materials were sliding against an Al based bearing alloy. The surfaces in contact were analyzed by light and electron microscopy subsequently. The performance of forged steel depends on the overall roughness of the surface, whereas the tribological functionality of cast iron is mainly determined through its microstructure and the occurrence of metal flaps with burrs. The results prove the significance of proper surface finishing of forged steel and cast iron shaft materials in order to minimize wear in journal bearing systems. For both shaft materials good sliding performances with respect to optimized surface finishing can be noted. •The tribological functionality of forged steel and cast iron is examined.•Abrasive processes of forged steel are linked with the Ra parameter.•Rpk and Rvk parameters are needed to describe the abrasive behavior of cast iron.•Metal burrs in case of cast iron cause abrasive wear of the bearing material.•Removal of metal burrs boosts the triboligical performance of cast iron.