Clogging and Lump Formation During Atmospheric Plasma Spraying with Powder Injection Downstream the Plasma Gun

Abstract

This study aimed to numerically and experimentally investigate lump formation during atmospheric plasma spraying with powder injection downstream the plasma gun exit. A first set of investigations was focused on the location and orientation of the powder port injector. It turned out impossible to keep the coating quality while avoiding lumps by simply moving the powder injector. A new geometry of the powder port ring holder was designed and optimized to prevent nozzle clogging, and lump formation using a gas screen. This solution was successfully tested for applications with Ni-5wt.%Al and ZrO 2 -7wt.%Y 2 O 3 powders used in production. The possible secondary effect of plasma jet shrouding by the gas screen, and its consequence on powder particles prior to impact was also studied.