Injection of high-melting low thermal conductivity ceramics externally orthogonal to the DC plasma jet plays a vital role in determining the in-flight state of the particles and the process downstream. Studies have shown that over and under injection of particles can influence the particle state as much as the extremes of plasma forming torch parameters.  Hence it is important to understand particle injection and their influence on the process downstream.

In this study we explore the behavior of particles in-flight under different injection conditions. A series of experiments were conducted using a 7MB torch with N₂-H₂ plasma, where the carrier gas flow to inject YSZ was varied systematically and the resulting in-flight particle state was captured using an array of particle and plume sensors. This was repeated for widely varying total mass flow of plasma gases, different feedstock morphologies, different powder feedrates and plasma gases. A set of experiments were performed where deposits were made on insitu coating property sensor (ICP) with and without optimizing the particle injection in order to understand the role of injection optimization.