Modeling and visualization of plasma spraying of functionally graded materials and its application to the optimization of spray conditions

This paper presents a simulation and visualization system for plasma spraying of functionally graded materials (FGM). The recently modified CFD code, LAVA-P, that incorporates a well-verified model for plasma gas flow and chemistry is employed. The particle movement and its trajectory are described within a Lagrangian formulation by considering drag as the major driving force, and the particle melting, evaporation, and resolidification are considered using a recently developed model for particle-flame interaction. In addition to the noncontinuum and variable property effects associated with high-temperature plasma, the effects of particle evaporation on particle momentum and heat transfer are also taken into account. Calculations are performed for NiCrAlY and ZrO₂ powders for a wide range of size distributions. The influences of power levels and flow rate of H₂ on plasma flow field and, hence, on the particle velocity and temperature are investigated. The predicted velocity and temp erature fields agree well with the measurements under similar spraying conditions. With the help of a special in-house built process animation and visualization algorithm, the powder injection conditions, such as the number of injectors, injector location, and injection velocity, are investigated and can be optimized to obtain coatings with a specified distribution of different species.