A new cold spray process for a combustion-free spraying is studied experimentally and by modeling and simulation. The high particle velocity at the front of the substrate is achieved by using the shock tube technology. The particles have been injected downstream of the nozzle throat into a supersonic nozzle flow. The shock tube of 6.5 m length and 56 mm inner diameter provides the necessary reservoir conditions for the nozzle flow. The measurements of the particle velocity made by a laser Doppler anemometry (LDA) setup showed that the maximum velocity amounts to 1220 m/s for stainless steel particles of 15 µm diameter. The CFD-Code (Fluent) is first verified by a comparison with available numerical and experimental data for gas and gas-particle flow fields in a long Laval-nozzle. The good agreement implied the great potential of the new dynamic process concept for cold gas coating applications. Then the flow fields in the short Laval nozzle designed and realized by the Shock Wave Laboratory (SWL) have been investigated. The gas flow for experimentally obtained stagnation conditions has been simulated. The gas-particle flow without and with the influence of the particles on the gas flow has been calculated by the Surface Engineering Institute (IOT) and compared with experiments. The influence of the injection parameters on the particle velocities has been investigated as well.

The process parameters of atmospheric plasma spraying (APS) influence the coating formation and properties of partially yttria stabilized zirconia (PYSZ) thermal barrier coatings (TBCs). Simulations can be used to investigate this dependency and to design the coating process for a targeted production of TBCs. A whole process simulation was realized by modeling the linked sub-processes: plasma torch, plasma free jet, powder particles characteristics and coating formation. The coating formation can be described by model approaches with different physical assumptions and geometric scales. One approach is the simulation of single powder particles hitting the substrate surface. An alternative macroscale FEM-model-approach is applied in the coating formation simulation. A group of particles is pooled in a splash dependent on the pre-calculated particle distribution in front of the substrate. A third modeling approach is applied to calculate effective mechanical and thermodynamical properties of coatings dependent on the experimentally obtained or calculated microstructure of the PYSZ-TBC, which is based on different homogenization methods. The application of three simulation approaches in the whole process simulation of APS is discussed, advantages and disadvantages are elucidated. Results based on simulation and experiments are presented for a variation of process parameters. Missing links in the multiscale approach are detected to make suggestions for future modeling and simulation work.