Simulation Supported Process Development for the Deposition of MCrAlY Coatings by Means of the AC-HVAF Process

• Applicant: Professorin Dr.-Ing. Kirsten Bobzin
• Subject Area: Coating and Surface Technology ; Production Automation and Assembly Technology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 437084607

The research project presented is a continuation of the previous project. The overall objective is to develop a simulation model for modeling the Activated-Combustion-High-Velocity-Air-Fuel process (AC-HVAF) based on the application of MCrAlY coatings. In the previous project, a complete three-dimensional simulation model of the AC-HVAF spray gun was successfully developed, which takes into account both the distribution of compressed air throughout the entire spray gun system and the integration of the mixing chamber. The model was validated by comparing the simulated and measured particle velocity of the SprayWatch 4S particle diagnostic system. The simulation model was used to determine correlations between the process parameters and the particle in-flight characteristics. Consequently, a suitable process parameter window for the fabrication of low-porosity and low-oxide MCrAlY coatings could be identified. Using these parameters, CoNiCrAlY coatings with very low porosity were produced with the coarse powder fraction. However, due to a high proportion of fine powder in the coarse powder fraction, -63 +11 µm, oxide lamellae are still recognizable in the coatings. The coatings were produced using commercially available powders specifically developed for plasma spraying and the high-velocity oxygen fuel process. In the previous work, it was shown that the particle size has a significant influence on the oxide content in the coating. However, no MCrAlY powders with a particle size distribution tailored specifically to the HVAF process are yet available. In the continuation of the project, the surface temperature of the powder particles is to be predicted using the simulation model. By discretizing the powder particles in the simulation, the temperature gradient from the surface to the core can be determined. This enables prediction of the oxidation of the particle surface during the coating process. On the one hand, process parameters with the slightest oxidation are to be predicted. On the other hand, the model shall predict ranges of particle size distributions that are favorable for the HVAF process. Subsequently, the results will be investigated experimentally.

• DFG Programme: Research Grants