Targeted improvement of the stability and efficiency of suspension plasma spraying by means of adapted diagnostic methods

• Applicants: Privatdozent Dr.-Ing. Georg Mauer; Dr.-Ing. Stephan Zimmermann
• Subject Area: Coating and Surface Technology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 501838742

The aim of this research project is the targeted improvement of the stability and efficiency of suspension plasma spraying with axial injection of the suspension precursor with the aid of adapted diagnostic methods. Based on the work carried out within the scope of the planned project, the process-determining mechanisms in suspension plasma spraying with central injection are to be better understood and specifically influenced with the aid of diagnostic methods. To this end, the expertise of the two applicants will be combined in such a way that the process and materials science knowledge of FZ Jülich on the one hand will be linked with the knowledge of UniBw Munich in the field of plasma generator development and plasma and particle diagnostics on the other. For the experimental investigation of measures to improve stability, a new model experiment stand (MES) with three plasma generators and an axially arranged suspension injector is to be set up using existing systems in such a way that various setting options (e.g. different plasma generators, cascaded or non-cascaded, pulse operation, etc.), as well as various spatial arrangements of these systems in relation to each other, are possible. A nozzle, in which the three plasma torches are combined, is to be designed according to cooling and fluid mechanical aspects in such a way that the suspension interacts "optimally" with the resulting plasma. In this context, operation in "idle mode" (without injection of the suspension) is also to be understood, since increased instabilities and increased cathode/anode wear occur in conventional three-generator systems with central injection (Mettech Axial III). Furthermore, good accessibility for diagnostic systems must be given in order to be able to elucidate the process-determining phenomena. The particular difficulty in adapting diagnostic methods for suspension plasma spraying lies in the high local and temporal resolution required, as well as the separation of the individual plasmas, the total plasma, and the separation of the radiation from the droplets/particles. In addition to the injection conditions and the interaction between droplets/particles and plasma, the deposition conditions are investigated simultaneously in order to be able to identify mechanisms of action on the layer properties. Here, the process stability plays a central role. Deposition efficiency is another aspect. It is expected that with the help of the adapted diagnostic methods, valuable knowledge can be gained about the interaction between the plasma jet (individual and total in the case of a merging nozzle) and the suspension and subsequently used to specifically improve the effectiveness of the process.

• DFG Programme: Research Grants