In nuclear fusion reactors, the first wall is the name given to the surface which is in direct contact with the plasma. A part of it is the divertor which is a device that removes fusion products from the plasma and impurities that have entered into it from the vessel lining. It is covered with water cooled tiles which have to withstand high temperatures and high heat fluxes. Moreover, resistance to neutron bombardment, low tritium absorption and low hydrogen permeation are additional demands. One materials concept under research is the application of a Reduced Activation Ferritic Martensitic Steel (RAFM) as a structural material with a tungsten protective coating. Since there is a considerable thermal mismatch between, a functional graded materials (FGM) concept was proposed. As the formation of undesired intermetallic Fe-W phases as well as oxidation should be avoided, cold gas spraying was chosen as manufacturing process. Two powder blends of EUROFER97 RAFM steel and a fine tungsten powder cut on the one hand and a coarser one on the other hand were tested in different ratios. The coatings were characterized with respect to their porosity and surface structure. Furthermore, the deposition efficiencies for steel and tungsten were determined each. It turned out, that the deposition process is a complex mixed situation of bonding and erosion mechanisms as the deposition windows of these very different materials obviously diverge. Thus, a lower working gas temperature and pressure was advantageous in some cases. Unexpectedly, the coarser tungsten powder in general enabled to achieve better results.

In this work, the effects of plasma spray process variables are systemized in various process schemes. On this basis, different approaches to improving process reliability are described and assessed paying particular attention to in-flight particle diagnostics. A new test applying spray bead analysis is introduced and the first results are presented.

With a view to the development of thermal barrier coatings on turbine blades, such coatings were developed on the basis of Y2O3-stabilized ZrO2 and optimized with respect to their reproducibility. Particular attention was given to the spray efficiency and, in particular, the coating porosity. The porosity was measured by Hg porosimetry, which proved to be a reliable method of characterization. The plasma gas flows play an important role for a high reproducibility of the coating properties. High reproducibility of the porosity and spray efficiency was achieved for low argon flows, for which the influences of all the other parameters, such as electric arc current, meandering and sample cooling during plasma spraying or the cathode operating time of the burner, were of minor relevance for the coating properties. The spray efficiency is clearly influenced by the given powder rate and the carrier gas flow for the type of burner used. The change of the grain fraction in the plasma jet was examined for two different powders. Finally, thermal cycling tests were carried out and evaluated for pre-optimized thermal barrier coating samples.

The new Triplex-burner was used to develop 7 wt% Y 2 O 3 stabilised ZrO 2 thermal barrier coatings and to optimise the process parameters with respect to reproducibility. The investigations were focused on spray efficiency and coating porosity. Porosity levels and porosity distribution were measured with mercury intrusion, which turned out to be a very reliable characterisation technique. High reproducibility could be achieved in particular for low argon fluxes: the deviation of the porosity levels was below about 4%. Paper text in German.