Laser surface cladding of Si 3N 4 powder layer on AA6061 aluminum alloy was carried out using a 2 kW CW Nd YAG laser. Subsequent laser surface melting of the layers gave a surface metal matrix composite (MMC). The microstructure and phase identification of the modified layer were examined using scanning electron microscopy (SEM) and X ray diffractometry (XRD) respectively. Cavitation erosion and electrochemical corrosion tests were also performed in 3.5% NaCl solution at 23℃. Finally the cavitation erosion mechanisms of the laser surface cladding modified layers were studied by surface morphology analysis.