Numerical Simulation of Suspension Plasma Spraying with Axial Injection

Two-dimensional simulation is performed for an annular-shaped plasma torch using argon gas under different operating currents and torch-substrate distances. The mathematical model is based on the conservation equations of mass, momentum, and total energy for gasdynamics and the steady-state Maxwell's equations for electrodynamics. Suspension carrying zirconium particles are axially injected into plasma flow and their trajectories and heating histories are analyzed with the Lagrangian method. A simplified model is used to simulate the evaporation of suspension droplets and the emergence of solid particles. The numerical results show that current stream lines are sharply curved downstream of the torch. In-flight particles are strongly heated in the area where the current streams are curved. An increase in operating currents results in shortening the length of current stream lines and moving the curved area further upstream. The numerical results also indicate that the particle impacting positions on a substrate get closer to its center as the operating current gets larger and the torch-substrate distance becomes shorter. Furthermore, the numerical results suggest that setting an operating current to higher values, which leads to an increase in particle impacting velocity, is suitable for impacting particles with molten state on the substrate.