Cold spray deposition is fundamentally governed by high-velocity impacts of individual solid particles. However, the deformation, rebound, jetting, and bonding processes occurring over micro- and nanoscales remain difficult to resolve using cold spray. In particular, it remains unclear whether the critical velocity criterion defined for metal-metal cold spray systems is applicable to metal-ceramic deposition systems.
In this study, laser ablation particle acceleration and observation (LAPAO) is employed to systematically investigate the supersonic impact and adhesion behavior of individual Al microparticles on Al₂O₃ ceramic substrates. Unlike metal-metal impacts, no unique critical velocity separating adhesion from rebound is observed. Adhesion and rebound coexist stochastically over a broad impact-velocity range, with no evident dependence on particle size. Ejection generated during impact originated from the ceramic substrate. Post-impact characterization reveals that bonding is primarily controlled by mechanical interlocking between the deformed Al particle and the locally fractured brittle Al₂O₃ substrate. Because the formation of an effective interlock depends strongly on local ceramic microstructural heterogeneity and fracture morphology, the adhesion process is inherently stochastic. Substantial particle deformation and substrate fracture cannot guarantee successful bonding without the formation of valid mechanical interlocking structures.

cold spray,single particle,high-velocity impact,metal-ceramic bonding,mechanical interlock