Interfacial bonding features of Ni coating on Al substrate with different surface pretreatments in cold spray

• Oxide-free interfacial area affects the interfacial atomic diffusion.
• Voids are formed at the interface of the particle and grit-blasted substrates.
• Polished and ground substrates lead to higher coating mass and bonding strength.

The effect of the substrate surface pretreatment on the Ni–Al interfacial bonding features in cold spray was investigated. Oxide-free interfacial area is found to be the essential factor that affects the interfacial atomic diffusion and metallurgical bonding. Voids are formed at the interface between the particle and grit-blasted substrates, significantly reducing the oxide-free interfacial area. However, those voids cannot be found at the interface between the particle and polished and ground substrates. Therefore, the polished and ground substrates can provide higher coating mass and coating-substrate bonding strength than the grit-blasted ones.