Characterization of a Suspension Plasma Spray (SPS) torch with axial injection for Thermal Barrier Coating (TBC) application

For many years now, the aeronautical industry has been using thermal barrier coatings in the hot parts of their jet engines, such as the combustion chamber. The thermal barriers in use today are mainly produced by EBPVD (Electron Beam Physical Vapor Deposition) process. Nevertheless, new processes have been studied for a few years as an alternative to EBPVD, in particular the SPS (Suspension Plasma Spray) process. In the case of the SPS process, two types of suspension injection are possible: radial or axial. In a common way it is the radial injection which is used, thanks to its flexibility of implementation on a very large variety of plasma torches. In the case of axial injection, the torch must be adapted. This is the case of the Axial III Plus torch, which uses three couple’s anode-cathode to generate a plasma, with the center of this set the injection of the suspension, it is called ASPS (Axial Suspension Plasma Spray). This study presents the diagnosis and characterization of the plasma jet and injection of an Axial III Plus torch and the influence of this on the microstructure of thermal barrier coating application.