An experimental and analytical study of the air plasma spraying of Tribaloy 800

摘要

The plasma spray process is composed of three separate processes: the plasma generation, the plasma/particle interaction and the formation of the coating. The characteristics of the particles prior to impact, such as velocity and particle state (i.e. partly or fully molten), are probably the most important factors influencing the microstructure and properties of the coating. In this work, we have attempted to predict the temperature, state and velocity of Tribaloy 800 particles by means of numerical modelling. A commercial code is used for the numerical solution of the incompressible Navier-Stokes equations to simulate the plasma flow, and an in-house code for the particle properties. In the fluid flow calculations a mass fraction conservation equation is used to take interdiffus ion effects between the plasma and surrounding air into account. For the calculation of particle velocities, trajectories and thermal histories, allowance has been made for non-continuum effects, particle vaporisation and the effects of variable plasma properties in the particle boundary layer.