Abstract: Nitriding a workpiece of aluminum or aluminum alloy by laser treatment in an atmosphere rich in nitrogen is disclosed. Laser treatment is applied for a period of less than one second at a laser power density of at least 0.1.times.10.sup.6 W/cm.sup.2 to form a hard workpiece surface layer comprising aluminum nitride. A workpiece surface pretreatment, prior to exposure to the laser beam, forms a smutty surface layer having a low content of impurities. A preferred embodiment includes utilizing an aluminum alloy containing an amount of at least 5 weight percent silicon and less than 2.1 weight percent magnesium.