Abstract
Recently we successfully developed a new suspension plasma spray (SPS) system by using a twin-cathode plasma spray gun. The system consists of three plasma torches (central main torch with cathode nozzle and anode, and two sub-torches on the sides with anode nozzle and cathode). The system is characterized by using only argon (Ar) as the plasma gas and low input power, which makes it a gas and power consumption SPS system, compared to the other available SPS systems. This study will discuss the unique features of the axial injection spraying and its effect on the coating formation by the new system. The axial injection showed a significant potential during suspension feeding. It keeps the liquid suspension on the plasma core zone; therefore, the liquid encountered the highest heat and momentum transfers. This enhances the precious control of the coating microstructure through controlling of the droplet size and splat size. It was possible to control the droplet size and therefore the coating microstructure through axial injection and controlling the solid load content on the suspensions. Furthermore, gas atomization control and adjustment showed a strong potential on controlling the mist distribution on the plasma plume and coating formation during axial injection suspension plasma spraying.
