Numerical Analysis of Quenching Stress in Thermal Spray Process Using SPH Method

Thermal spray is an important surface treatment technique used in many industrial applications. Thermal spray processes involve molten droplets sprayed onto substrates. Heat transfer between the droplet and the substrate at different temperatures results in sharp temperature gradients and a phase change. Quenching stresses arise as a combined effect of phase change and the thermal mismatch between materials. It is important to characterize quenching stress for predicting material durability. However, such characterization is challenging due to the complex physics involved. In this study, the smoothed particle hydrodynamics method is used to predict the quenching stress in the thermal spray process for different droplet materials, including yttrium-stabilized zirconia (YSZ), stainless steel (SS), aluminum (Al), and alumina (Al₂O₃) impinging on various substrate materials. The present numerical model is validated against the experiments and previous numerical studies for splat behavior, time evolution of substrate temperature, and quenching stress. A parametric study investigates the main contributing factors to quench stress. The parametric study reveals that elevated substrate temperatures reduce thermal gradient, thus quenching stress. Compared to the differences in droplet material, the quenching stress shows increased sensitivity to the substrate material. Additionally, materials with high thermal diffusivity, such as SS, exhibit lower quenching stress due to their ability to dissipate heat quickly. Conversely, materials with lower thermal diffusivity, such as YSZ, show higher quenching stress because of slower heat dissipation. These findings provide critical insights into optimizing thermal spray processes to minimize quenching stress and enhance material durability.