Influence of surface preparation on the adhesion of Ti-6Al-4V repair coatings produced by cold gas spray

In the last decades, repair applications became of growing interest in the aerospace industry. A fast and cost-efficient method to restore the original shape of damaged engine components is cold gas spraying. Recent studies have demonstrated that a crucial factor for the bonding between the coating and the substrate is the surface preparation. In this study, we investigated the influence of surface preparation on the adhesion of Ti-6Al-4V coatings. Three different methods: (i) grit-blasting with abrasive Al₂O₃-particle which is frequently used in industry, (ii) polishing, and (iii) laser-structuring were used to pre-treat the substrate surface before the spraying process. Afterwards, the surface roughness and morphology were measured with a non-contact optical profilometer. For the cold spray process, a commercially available Ti-6Al-4V powder with a particle size smaller than 45 µm was used. Repair coatings with thicknesses between 0.2 and 2 mm were fabricated and the mechanical properties, adhesion, and microstructure were determined. The fracture toughness of the interfaces was obtained by the indentation method and the results revealed a higher interface fracture toughness for the polished substrates compared to the specimens prepared by grit-blasted.