Surface nanocrystallization by sandblasting and annealing for improved mechanical and tribological properties

A sandblasting and annealing process was utilized to modify the surface structure of aluminium. The modified surface structure was examined by x-ray diffraction (XRD) profile analysis and transmission electron microscopy (TEM). It was demonstrated that the grain size of the sandblast-annealed surface layer was in the range 50-70 nm. Mechanical and tribological properties of the nanocrystalline surface were investigated using micro-indentation, nano/micro-scratch, scanning Kelvin probe (SKP), and atomic force microscope (AFM) techniques. It was observed that the micro-hardness and wear resistance of the surface were considerably increased due to the formation of a nanocrystalline layer. In addition, a close correlation between the electron work function (EWF) and the adhesive force was observed; higher EWF corresponded to lower adhesive force and thus lower friction under light loads.