Nitrieren von Aluminiumlegierungen mit UV-Laserstrahlung

Abstract

The irradiation of aluminium alloys with excimer lasers at energy densities above plasma threshold leads to a substantial increase of pressure and temperature in the ns regime, as well as to plasma formation on the substrate surface. Following a single laser pulse, the thickness of the melted surface layer will increase through heat conduction to a depth of up to 20 μm. At the same time, alloying with the background gas (or plasma) is also possible. The quenching rates of the following solidification process reaches to about 10 7 to 10 11 K/s, thereby following the accepted rules of rapid quenching. Through gas alloying with excimer lasers, it is possible to produce solid-bonded and crack-free layers containing AIN, up to 20 microns in thickness for technical aluminium alloys, in which the finely dispersed AIN-crystals are evenly distributed. In nitrogen atmospheres however, the remelted layers of AlSi cast alloys will, for example, have an increase in surface hardness due to dispersion hardening, solid solution hardening and grain refinement. The AIN-concentration in the surface area is about 80Vol.-%, and will result in a decrease of the friction coefficient at dry sliding friction tests simultaneously decreasing the wear rate by up to a third, as opposed to an untreated alloy.