Optimization of Cold Gas Dynamic Spray Coatings Using Agglomerated Al–Zn–TiO₂ Powders on Steel

Cold gas dynamic spraying (CGDS) of multi-component agglomerated powders offers a promising method for producing protective coatings without melting or oxidation. This study investigates Al–Zn–TiO₂ composite powders prepared via both wet agglomeration with binders and dry mechanical mixing. Coatings were deposited on mild steel substrates using heated air at varying parameters. Computational modeling (COMSOL) was employed to simulate gas dynamics and particle velocities, identifying optimal conditions (6 atm, 600 °C, 15 mm, 90°) for effective deposition. Experimental validation showed that coatings formed under these conditions exhibited uniform microstructure, minimal porosity, and excellent adhesion. SEM and XRD confirmed dense solid-state bonding without new phase formation. Profilometry indicated increased surface roughness with higher powder feed rates. Corrosion testing in NaCl solution revealed a significant reduction in corrosion current density compared to bare steel, attributed to synergistic sacrificial and barrier mechanisms. Tribological tests demonstrated lower friction and wear due to embedded TiO₂. The combination of modeling and experimentation enabled successful process optimization for high-performance Al–Zn–TiO₂ coatings.