Interaction Regimes and Deposition Mechanisms of Ceramic Particles on Porous Substrates During Cold Spraying

Refractory materials used in thermal reactors are susceptible to degradation because aggressive media penetrate their porous microstructure, while thermo-mechanical loading accelerates material damage. Cold-sprayed ceramic coatings represent a promising approach for surface protection; however, the deposition mechanisms of brittle ceramic particles on porous substrates remain insufficiently understood. This study combines cold spray experiments, computational fluid dynamics (CFD), and an energy-based analytical framework to investigate particle–substrate interactions during ceramic cold spraying. Gas flow and particle trajectories were simulated within µCT-reconstructed pore geometries using Lagrangian particle tracking, while critical impact conditions were evaluated by considering particle fragmentation and substrate damage. The combined numerical and analytical approach reveals distinct interaction regimes governed by the interplay between particle inertia, impact conditions, and the porous substrate morphology. The integrated experimental observations and theoretical analysis indicate that coating formation is governed by two complementary deposition mechanisms. Fine particles are retained by mechanical interlocking within the pore network, whereas fragmentation of larger particles is proposed to generate additional fine debris that progressively fills the remaining pore space and contributes to coating consolidation. The results further identify processing conditions that promote stable coating formation while suppressing substrate erosion. The proposed framework provides a physics-based understanding of ceramic particle deposition on porous substrates and supports the rational design and optimisation of cold spray processes for refractory surface protection.