A High Strength Aluminum Solution for Polymer Coated Bearings

Aluminum-tin (Al-Sn) and aluminum-tin-silicon (Al-Sn-Si) alloy lined bimetals have traditionally been utilized in rod and main bearing applications in light duty gasoline engines due to their combination of strength and soft-phase properties, such as embeddability and conformabilty. The load carrying capability of Al-Sn-Si alloys can be further increased by applying a polymer overlay, but recent advances in engine design, to improve efficiency and reduce CO₂ emissions, have resulted in maximum specific load requirements beyond the performance limits of current Al-Sn-Si-Cu products. In these instances, the usual option would be to specify a lead-free bronze-based bearing solution, which has increased strength, but necessitates greater weight and brings a significant cost disadvantage over aluminum products. To address these problems, we have developed a novel high strength aluminum lined bimetal for use with a polymer coating, which offers a significant advantage in load carrying capability over traditional Al-Sn-Si-Cu alloys. The novel high strength developed alloy employs an Al-Mn-Mg substrate, which is roll bonded to a steel backing. Bearing rig testing has demonstrated a significant improvement in fatigue performance over the highest rated Al-Sn-Si bearing alloy and an acceptable level of seizure and wear performance. Initial particle tolerance test results are encouraging. A 900-hour thermal shock engine test established the potential of the development alloy to perform satisfactorily in an application which typically uses a more costly bronze-based bearing solution.