Numerical Modeling and Analysis of Suspension Plasma Spraying with Axial Injection

The aerospace industry's demand for improved thermal barrier coatings (TBCs) has driven significant advances in coating technologies, with suspension plasma spraying (SPS) emerging as a leading method. Recent innovations in axial injection plasma spray systems have further expanded the capabilities of SPS, enabling higher flow rates, longer stand-off distances, and the use of suspensions with higher solid loading. This study develops a comprehensive 3D numerical model to investigate an axial suspension plasma spraying process using an advanced three-torch plasma system. We model the suspensions as multi-component droplets, composed of ethanol and yttria-stabilized zirconia particles. The plasma jet is simulated employing the Joule effect method, which includes a volumetric heat source in the energy equation while ignoring electromagnetic field. Our study further examines the influence of key operating parameters such as gas composition, torch power, and suspension solid concentration. Additionally, particle characteristics (size, velocity, and temperature distributions) at impact with the substrate, which ultimately control coating quality, are analyzed by tracking particle trajectories, secondary breakup of the suspension droplets, and their interactions with the plasma.