Ferreira, M., Silva, A., Praça, M., and Costa, S., "Polymeric Coated Lead Free Bronze Bearings for High Durability in Medium Duty Diesel Engines," SAE Technical Paper 2014-36-0405, 2014, doi:10.4271/2014-36-0405.
Lead free bronze substrate associated with a lead free electroplated coating has been the standard bearing material technology for medium size Diesel engines. However the increasing engine demands are driving this technology to the limit. With the increase of Peak Cylinder Pressure (PCP) to improve power density and reduce CO2 emissions, the bearings are subjected to higher loads which usually reduce their durability. The new operating conditions are more prone to wear and eventually scuffing occurrences. Therefore materials with higher scuffing and wear resistance without a significant cost increase are demanded.To meet the requirements of highly loaded Medium Duty Diesel (MDD) applications, a lead free material based on a high resistant bronze substrate associated with a polymeric coating was developed. The polymer is sprayed onto the substrate and cured on a high temperature to provide performance improvement and adequate thickness control.The solution brought the necessary wear and scuffing resistance with increased Load Carrying Capacity (LCC) when compared to the current electroplated lead free material. Other bearing surface features - e.g. conformability - were not compromised by adopting this technology.This paper will demonstrate the results of bench and engine tests emphasizing the distinct advantages of this technology.