Abstract
Laser post treatment is a well known procedure in order to homogenize the geometry, the microstructure and aspect of the surface of thermal sprayed coatings. Furthermore the properties of coatings, as for example corrosion resistance can be improved, as a sealing layer is induced by remelting. High power laser sources as CO2-, Nd:YAG as well as diode laser are used for this aim. They allow a very deep remelting zone in a depth-range between 0,2-2 mm. Contemporarily the hard phases as well carbides in the coating degenerate due to the very high heat input and the wear resistance of the coating decreases. Short-pulse laser are very advantageous for processing surfaces in a very narrow band (under 50 µm). Applications are nowadays developed for the surface treatment of aluminium cylinder running surfaces and of titanium implants. The short-pulse laser post processing can be a very profitable methods to improve the behaviour of coatings without damaging hard phases. Investigations on remelting of PTA- and thermal sprayed coatings with a Nd:YAG-short-puls laser and with an excimer laser are reported in this paper. Surface quality as for example roughness of PTA-coatings with tungsten carbides (NiCrBSi+60%WSC) could be improved and a slight surface sealing layer was induced. Depending on the adopted laser system, different surface roughness profiles can be reached. In further investigations the suitability of the method was proven for thermally sprayed coatings of NiCrBSi
