An investigation of friction and wear properties of Zn-40Al-2Cu-2Si alloy under inadequate and continuous lubrication conditions

SUMMARY An Investigation of Friction and Wear Properties of Zn-40Al-2Cu-2Si Alloy Under Inadequate and Continuous Lubrication Conditions In this study, four ingots of Zn-40Al-2Cu-2Si alloy were produced by permanent mould casting. Two of the ingots were subjected to T6 heat treatment which consists of solution treatment, water quenching and artificial ageing. After examining microstructure and some mechanical properties of the alloy in both as-cast and in heat treated states, its friction and wear properties were investigated under inadequate and continuous lubrication conditions using a bloek-on-disk test machine. It was observed that the microsrtucture of Zn-40Al-2Cu-2Si alloy consisted of aluminium-rich a, zinc-rich i\, copper-rich s and silicon particles. The heat treatment produced fine precipitates in the microstructure but had no considerable effect on the silicon particles. It was also determined that the heat treatment increased the hardness and tensile strength of this alloy. It was found that under inadequate lubrication condition the friction coefficients of the wear samples of the alloy decreased with increasing pressure up to approximately 3 MPa above which the trend reversed. However the friction coefficients showed irregular variations with speed. It was also observed that the temperature of the wear samples increased with increasing both pressure and speed. Wear loss of the alloy increased exponentially with pressure, but show a linear increase with speed. Above the pressure of 4 MPa the increase in wear loss of the Zn-40Al-2Cu-2Si alloy with speed became exponential. Under continuous lubrication condition, the friction coefficients of the wear samples decreased with increasing pressure and speed but their temperatures increased with these parameters. It was also found that the wear loss of the alloy samples increased with increasing pressure and running speed. The wear samples of Zn-40Al-2Cu-2Si alloy in either the as-cast and in the heat treated conditions exhibited much superior wear resistance than SAE 660 bronze, especially at pressures above 4 MPa. As a result this work it was concluded that the T6 heat treatment does not increase only hardness and tensile strength of the Zn-40Al-2Cu-2Si alloy but also increase its friction coefficient, temperature during wear and wear resistance. Key Words: Zn-40Al-2Cu-2Si alloy, Inadequate lubrication, Continuous lubrication, Friction and Wear. VI