All companies involved in aviation industry face severe global competition. Thereby in particular maintenance, repair and overhaul (MRO) companies deal with difficult challenges for a modern production. Already today a clear trend for high flexibility, reduced process times and costs is visible. To face these challenges different options for thermal spraying processes will be presented. Thereby modern gun technologies and system concepts can achieve an up to 70% reduced total process time. However, by only optimizing hardware the needs of a modern production could not be fulfilled. Also established standards like quality management or development structures need to be adapted. For example the mostly used sample based quality management shows several disadvantages like time-delayed failure detection and a high rework rate. Here a well balanced concept based on the three pillars: particle monitoring, parameter monitoring and a reduced sample based quality management could achieve an efficient quality management with rework rates below 4%. Finally the positive aspects of modern Design of Experiment (DoE) strategies for coating development are presented. By using DoE times and efforts for developing could be reduced by 60%. A model based target value optimization could even enable a calculation of process parameters.

Suspension plasma spraying (SPS) offers the manufacture of unique microstructures which are not possible with conventional powder feedstocks. Due to the considerably smaller size of the droplets and also the further fragmentation of these in the plasma jet, the attainable microstructural features like splat and pore sizes can be downsized to the nanometer range. Our present understanding of the SPS deposition process including injection, suspension plasma plume interaction, and deposition is outlined in this report. The conclusions drawn are based on microstructure analysis in combination with enthalpy probe and particle temperature and velocity and measurements. Measurements with a water-cooled stagnation probe provide valuable information on the interaction of the carrier fluid with the plasma plume. The examples presented include segmented thermal barrier coatings for turbine components, LSM cathode deposits for SOFCs, and TiO 2 layers for photovoltaic Gratzel cells.

Normally the conventional thermal spray processes as the atmospheric plasma spraying (APS) have to use easily flowable powders in a size range between 10 and 100 µm. In contrast the suspension plasma spraying (SPS) makes it possible to process nano sized particles directly. Due to the use of nano materials new microstructures and properties could be generated. One point is the possibility to influence the porosity level, its size range and micro crack densities in a wide band. Microstructure features like the porosity and cracks serve as scattering centres and lead to changes of optical properties. Furthermore the thermal conductivity is affected by the porosity level. In this work yttria partially stabilized zirconia coatings were generated by the SPS and APS process. The influence of the different microstructures on the thermal conductivity, the hemispherical reflectance and transmittance for wavelengths between 0.3 to 2.5 µm has been investigated. Due to the higher porosity and crack level of the SPS coatings the thermal conductivity and hemispherical transmittance was significant reduced.