Splat Formation and Adhesion Mechanisms of Cold Gas Sprayed Al Coatings on Al₂O₃

In this study, aluminum is deposited by cold gas spraying on smooth and rough alumina substrates. SEM examination of single particle splats on polycrystalline Al₂O₃ suggests that mechanical interlocking is the primary bonding mechanism for cold gas sprayed metals on rough ceramic surfaces. Coating cross-sections on monocrystalline, atomically smooth sapphire substrates were examined by means of high-resolution TEM, revealing nanosized Al grains close to the interface, which could be an indicator of recrystallisation induced by local heating and the deformation energy stored in the particle during impact.