Influence of Test Conditions on the Lubricated Friction and Wear Behaviour of Al-25Zn-3Cu Alloy

The friction and wear properties of Al-25Zn-3Cu alloy were investigated over a range of oil flow rate, pressure and sliding speed using a pin-on-disc machine, after examining its microstructure and mechanical properties. The results obtained were compared with those of a conventional-bearing material (SAE 65 bronze). It was observed that the microstructure of the Al-25Zn-3Cu alloy consisted of aluminium-rich alpha, eutectoid alpha + eta and theta phases, while the microstructure of the SAE 65 bronze revealed copper-rich alpha, and eutectoid alpha + delta phases. It was found that the friction coefficient, temperature and wear volume of both the alloys decreased sharply with increasing oil flow rate and attained almost constant levels beyond a certain range of oil flow rate. It was also found that the friction coefficient and the wear volume of the alloys decreased with increasing pressure, but was observed to be almost independent of the sliding speed. The Al-25Zn-3Cu alloy exhibited higher wear resistance as compared to that of the bronze under all the test conditions. Smearing type of adhesion appeared to be the most effective wear mechanism for the Al-25Zn-3Cu alloy, while abrasion dominated one for the SAE 65 bronze.