Development of High Strength Aluminum-Zinc-Silicon Alloy
Bearing with Polymer Overlay 2019-01-0179
Recent automotive engine developments have made great progressive in protecting the global environment and in meet exhaust gas regulations and fuel economy regulations. As a result, engine bearings tend to be used under severe conditions such as higher specific load onto the bearings and low viscosity of lubricating oil. Aluminum alloy bearings are widely adopted as main bearings and con-rod bearings in gasoline and compact diesel engines for passenger cars, and generally Al-Sn-Si alloys without an additional overlay are used. Although these Al-Sn-Si alloy bearings have good anti-seizure properties and excellent running-in-properties, the material strength under high temperature conditions is not sufficient because of the low melting point of Sn phase contained in the alloy, and this could potentially result in damage to the bearing as seizure and fatigue under such conditions.In such cases, Cu-Pb-Sn bearing alloys with lead-based overlay are usually applied, but Al-Zn-Si alloy bearings with bismuth overlay are also going to be applied from the view of superior corrosion resistance and low cost. This means that there is a demand for an aluminum bearing alloy which may be able to replace Cu alloy bearings.
Based on the above background, a further high strength Al-Zn-Si alloy bearing provided with a polymer overlay has been developed. Fatigue tests have verified that the developed bearing has better fatigue strength compared to conventional Al-Zn-Si alloy bearings with bismuth overlay, and it would be comparable to conventional copper-lead alloy bearings. Engine bench tests have demonstrated that this bearing has superior performance for use in automotive diesel engines.