Abstract

Surface micro-texturing prior spraying is aimed to force the specific and controlled columnar structure of Thermal Barrier Coatings (TBC) and then improving their thermal insulation properties. In this paper numerical modelling aimed at better understanding the Thermal Barrier Coatings (TBC) build-up mechanism is provided with Suspension Plasma Spraying (SPS) process considered as an experimental reference for numerical analysis. The flat substrates were micro-textured and numerical models of substrates with such topography; as well as a model of plasma jet hitting against such textured substrate were created. Numerical modeling also included advanced turbulent flow models; such as transition SST model and Reynolds Stress Model (RSM); as well as a volumetric heat source model that generates plasma from plasma gases while maintaining the thermophysical plasma properties throughout the process. Mathematical equations determining the process were solved by means of Ansys-Fluent 2020R1 package. The geometric and numerical model considered the generation of plasma inside the SG-100 plasma torch and the plasma flow with its highly nonlinear thermophysical characteristics; including the turbulent phenomena as well as the plasma jet interaction with the micro-textured substrate. The motivation for this investigation was to determine the influence of substrate micro-texture geometry on the behavior of the plasma jet in a substrate boundary layer. It opens the possibility of predicting the feedstock particles movement and deposition on the substrate; which is essential in understanding the coating build-up mechanism as a whole. The analysis discussed in this papier are carried out to determine the properties of the plasma flow in the substrate boundary layers which enables the discussion on the flow of fine powder particles in contact with the substrate surface.

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