Numerical simulation of unsteady ArH2 plasma spray impact on a moving substrate

Abstract

Plasma spraying is used to manufacture thermal barriers composed of a bond coat and a thin ceramic layer on a metallic part. Following the process conditions and material structure, the ceramic layer is a porous medium. The coupling between morphology and properties of ceramics provides high insulation with a thin layer. Due to the small time and space scales (ranges of μs and μm for ceramic droplet spreading and solidification), it is difficult to experimentally measure all the parameters governing the deposition. This work has focused on the plasma flow interaction with a moving substrate in order to quantify the heat transferred to the substrate and to estimate the flow structure in the impingement zone of ceramic particles for different stand-off distances. Previous studies have addressed the plasma torch flow by numerical simulation considering the experimentally measured arc tension time evolution as a boundary condition. This simulation provides unsteady temperature and velocity profiles at the torch exit which have been used as unsteady boundary conditions for the Large Eddy Simulation turbulence modeling. The CFD code takes into account the fluid compressibility, heat transfers with the substrate, turbulent flow, unsteady flow exhausted from the torch, ambient air engulfment in the plasma and solid target motion through penalty methods.