Three‐Dimensional Multi‐Physics and Stochastic Deposition Model for Predicting the Microstructure of SPS 8YSZ Coatings

ABSTRACT

Supersonic plasma spraying (SPS) entails tightly coupled arc–plasma–particle interactions that govern the microstructural formation of thermal barrier coatings (TBCs). We present an integrated three‑dimensional (3D) unsteady multi‑physics model coupled with a stochastic particle‑deposition algorithm to quantify relationships among process parameters, in‑flight particle behavior, and final coating microstructure for 8 wt.% Y ₂ O ₃ ‑stabilized ZrO ₂ (8YSZ). The framework couples arc‑plasma dynamics, turbulent jet evolution, particle heating/melting, and multi‑particle deposition to reconstruct 3D lamellar morphology while explicitly accounting for pore‑formation mechanisms (droplet curling, satellite droplets, and incomplete interlamellar filling). Parametric studies show that increasing spraying current raises jet temperature and velocity via enhanced Joule heating and electromagnetic forcing, whereas Ar primary‑gas flow mainly affects jet kinetic energy through mass‑flux variation. Carrier‑gas flow rate, particle size, and injection position critically influence particle heating and trajectories; outward powder injection maximizes deposition efficiency and mitigates torch blockage. An optimal condition of 850 A current and 90 scfh Ar was identified. The model predicts porosity and thickness (∼8.40% and ∼211.6 µm) that agree closely with experiments (deviation ≈ 0.76%), validating the approach. The results offer quantitative guidance for SPS process optimization and microstructure design of TBCs.