– The thesis shows that it is possible to choose lead-free materials with better tribological performance, and that environmental pollution due to hazardous lead from engine bearing bearings therefore can be avoided. My results provide valuable contributions for developers of bearing materials, says Daniel Gebretsadik, PhD in Machine Elements at Luleå University of Technology.
Lead-based components are phased out
Conventional engine bearing materials contain a considerable amount of lead (Pb). However, new rules prohibit the use of lead for when manufacturing vehicle components, and consequently new lead-free engine bearing materials will eventually replace the conventional bearing materials. Additionally, it is necessary to select materials that can be used in engines with a start-stop system where bearing material properties become very important.
In the thesis, the tribological characteristics of some new lead-free materials are studied to see if they can replace conventional bearing materials in a good way. The results showed that some lead-free materials even have better tribological performance than conventional bearing materials.
Good tribological performance
– A bronze-based bearing alloy coated with a polyamide-imide based outer layer containing solid lubricants had superior friction, wear and anti-seizure properties, although its abrasive wear resistance in the presence of contaminant abrasive particles in engine oil is poorer than conventional bearing materials. The tribological compatibility with different engine oil formulations is also something we looked at more closely.
Scania CV AB, the Austrian Excellence Center for Tribology (AC2T) and Luleå University of Technology, has funded the research.