Experiments and modeling of rapid solidification of plasma-sprayed yttria-stabilized zirconia

Thermal barrier coatings (TBCs) are widely used to increase the working temperature and improve the high-temperature corrosion resistance of base materials. Thermal spraying methods such as air plasma spraying (APS) are convenient techniques to deposit TBCs. This work examines the rapid solidification of APS-deposited yttria-stabilized zirconia (YSZ), by modeling the non-equilibrium solidification of a single molten particle. The model solves the so-called hyperbolic equations for heat and mass transfer to predict interface undercooling and velocity as a function of time, and also predicts the morphology of the solidification front (and thus the microstructural characteristics of rapidly solidified YSZ) as a function of interface velocity. Results are presented of a single particle solidifying onto a steel substrate, and onto a previously deposited particle. The numerical results are also compared to experimental data of the microstructure of a YSZ splat deposited by APS, to validate the model.