Dry sliding wear behavior of hot extruded Al–Si–Pb alloys in the temperature range 25–200 °C

The wear behavior of hot extruded Al–Si–Pb alloys was investigated under dry conditions in a temperature range 25–200 °C using a pin-on-disc type wear testing machine. The results show that the microstructure and mechanical properties can be greatly improved and porosity can be significantly decreased by hot extrusion. These factors contribute to great increase in wear resistance of hot extruded Al–Si–Pb alloys. Optical observation and X-ray photoelectron spectroscopy (XPS) analysis reveal that at room temperature the almost constant wear rate and lowest level in coefficient of friction at high load levels for Al–Si–Pb alloys with more than 15 wt.% lead are due to a film of lubricant covering almost the entire worn surface. This film is a mixture of different constituents containing Al, Fe, Si, O and Pb, in which Pb exists in the form of Pb4SiO6. In the case of Al–Pb–Si alloy with 15% lead worn at 100 °C, X-ray analysis reveal that constant wear rate and lowest level in coefficient of friction are caused by a film of lubricant with a main constituent of Pb4Al2(SiO3)7. At 200 °C, no film of lubricant was formed on the worn surface of Al–Pb–Si alloy with 15% lead.