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Keywords

plasma spraying, suspension, coating for aerospace, digital twin, fluid mechanics, CFD, modeling, simulation, numerical method.

Abstract

Suspension plasma spraying can be used to produce coatings with a variety of fine microstructures to meet the demanding requirements of emerging industrial applications, such as new-generation thermal barriers for the aerospace industry. In this process, the liquid suspension containing submicron particles of the material to be deposited is injected into a thermal plasma jet to be fragmented and evaporated, releasing individual or agglomerated submicron particles which are then accelerated and melted, impacting and spreading out on the part to be coated to form the coating. Mastering the process requires an understanding of the complex, interdependent mechanisms governing suspension processing and coating construction.
This understanding requires simulation of the process as a function of its operating parameters by a digital twin, from plasma jet generation to coating construction. The IRCER and TREFLE laboratories at I2M have joined forces to make progress on this issue, which is of great interest to Safran, the international leader in the production of coatings for aeronautical parts. This modeling work on plasma jet formation, turbulent development, suspension treatment and deposit construction gave rise to an initial project, which is continuing with support from Safran and the Nouvelle-Aquitaine region.
The aim of this PhD will be to model the behavior of submicrometer particles within an already fragmented suspension droplet, subjected to the heat flux and shear of the plasma flow, and whose carrier liquid evaporates, deforms and recirculates, taking into account diffusion and forces on/between particles, so as to predict the number of particles resulting, their size and even their shape, as one droplet could possibly lead to the birth of several aggregates.