On the ‘rocket’ effect during plasma arc spraying

Abstract

A particle's surface is not heated uniformly during plasma arc spraying: the side of the surface that faces the torch is hotter than the opposite side. If the particle temperature is high enough for substantial evaporation to occur, the imbalance of the vapour pressure gives rise to a net recoil force accelerating the particle toward the substrate. Estimations show that if particle loss of mass due to evaporation , the suggested effect is as important for particle dynamics as aerodynamic drag. (M is the particle mass, Ud is the particle speed and is the speed of the evaporating atom, m is its mass, and T is the particle surface temperature.)