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 CO 2 -, 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

Coating-substrate adhesion in cold spray is a paramount property, the mechanisms of which are not yet well elucidated. These mechanisms are governed by metallurgical and morphological phenomena occuring when cold-sprayed particles impinge on the substrate. To go into these mechanisms, due to the intrinsic characteristics of the cold spray process, i.e. the low-temperature and high velocity of the particles, direct observation and control of inflight particles and related phenomena (especially when impinging) cannot be done easily. For this reason, an experimental simulation of the particle-substrate reactions at the particle impingement was developed. This simulation is based on original filter impact experiments from laser shock acceleration of plates/foils (fliers). These were applied to the Cu-Al metallurgically-reactive system to simulate Cu cold-sprayed onto Al. The velocity of the plate was selected in the range of actual cold spray velocities. Relevant Cu-Al interaction phenomena were featured and studied as a function of filter impact conditions, i.e., primarily, shearing, plastic deformation, phase transformation (including rapid melting/solidification and formation of intermetallics). These phenomena were shown to be similar to those involved in cold spray. This was ascertained by a parallel study of cold-sprayed Cu coating of Al using SEM, TEM, EPMA, and an energy balance and diffusion calculations. In addition, this simulation can be used to feed FE modeling of cold spray particle impingement on the substrate. Preliminary results are discussed from modeling using the “RADIOSS®” code. More generally, laser shock flier impact experiments were demonstrated to result in a powerful tool capable of simulating cold spray coating-substrate interface mechanisms. Major assets rest on their high significance, reproducibility, flexibility and potential for substituting for direct laborious cold spray optimization testing.