Development of simulative approaches for the specific design of the properties of plasma sprayed coatings

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Kirsten Bobzin

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+49 241 80 95329

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Subproject A10 deals with the prediction of the properties of plasma-sprayed coatings using simulations. For this purpose, the entire process chain (Figure 1) of plasma spraying from the plasma generator to the coating structure is addressed. These simulations are used to analyse, understand and control the influences of the often non-linear process parameters on the coating properties. The aim is to predict the coating properties as precisely as possible. In the first phase, basic simulation models of the process chain of atmospheric plasma spraying were developed. The particle state in the plasma jet resulting from these models, such as the particle velocity and temperature, were simulated and validated using particle diagnostics. In addition, the degree of melting of particles and the heat transfer within spherical particles in the plasma jet were predicted. However, the integration of disturbances, the consideration of complex particle geometries and the resulting prediction of effective coating properties were not yet possible at the end of the first phase. These goals were subsequently pursued in the second phase of the project. Here, the disturbances such as nozzle wear, electrode wear and injector wear as well as turbulence in the plasma jet an it’s effects on the coating properties were investigated. At the same time, the simulations were extended to include complex particle morphologies and a 3D-model of the particle impact was developed (Figure 2). Similarly, the effects of disturbances and different injector geometries on the process were investigated with the help of high-resolution diagnostics methods. In the planned third phase, the following research objectives will now be pursued:

  • Predictive simulations of the process chain with binary gas compositions and investigation of the effects on process stability.

  • Implementation of phase transformation and crack initiation in the particle impact model to increase the precision in the prediction of coating properties.

  • Compensation of the effect of turbulence using simulation aided adjustments of the flow conditions in the plasma free jet and experimental investigation of these effects.

  • Prediction of modified process parameters to compensate for the observed long-term disturbances.

These measures shall allow to increase the predictive precision of the simulations and thus to control the process chain of plasma spraying. Furthermore, occurring disturbance variables are to be compensated either by direct measures or by the developed methodology for parameter modifications.

In collaboration with A13 (N), the modelling of the particle impact will also be carried out using the smoothed particle hydrodynamics (SPH) method (Figure 3). Similarly, together with A12, the simulation predictions will be applied to heating and insulation layers by predicting thermo-mechanical and electrical layer properties. In addition, the predictions developed in A12 using artificial intelligence are compared with the predictions of the simulation chain. Based on these investigations, the differences with respect to the disturbances are addressed. The thermal barrier coatings resulting from A10 shall also be used in the casting and moulding processes of B01 and B08 in order to precisely control the heat transfer in these applications.

 
  Process chain of the APS simulation and its corresponding sub models Copyright: © SFB 1120 Figure 1: Process chain of the APS simulation and its corresponding sub models   a) Modelled coating build-up b) Determination of the coatings’ effective heat conductivity Copyright: © SFB 1120 Figure 2: a) Modelled coating build-up b) Determination of the coatings’ effective heat conductivity
 
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Figure 3: Particle impacted modelled using the SPH method