Influence of subsurface microstructure on the running-in of an AlSi alloy

The friction and wear behavior of a lubricated AlSi11Cu3 disk in contact with a 100Cr6 pin was studied by a radionuclide-assisted pin-on-disk tribometer. It is well known that shear forces change chemistry and microstructure of the near-surface material, thereby influencing friction and wear. To better understand the influences of the microstructure on the running-in behavior, disks with different silicon phase morphologies were tested under constant stressing conditions. Topography, chemistry and microstructure of pin and disk were characterized before and after tribological testing by white light interferometry, X-ray photoelectron spectroscopy, Auger electron spectroscopy and focused ion beam microscopy. Wear of pins was measured with a radionuclide technique to resolve ultra-low wear rates. To characterize near-surface deformations, Ga ion markers were implanted and Auger electron spectroscopy was applied to follow their shear-induced displacements. To monitor subsurface shear, the deformation of columnar markers was analyzed. The results were discussed using Godet׳s third body model. Furthermore, the results allowed to us extend the model to systems operated under ultra-low wear rates.