Process-Property Correlation of Heat Treated Aluminium 6061 Cold Spray Coatings

Aluminium alloy 6061 powder was cold sprayed onto polished Aluminium 6061 substrates to produce coating samples, which were subjected to annealing and T6 heat treatment processes. The samples were cross-sectioned and polished to reveal the particle-substrate interfaces. The single-splat particle-substrate interfaces were examined under optical microscopy and SEM, and a comparison was made between the un-treated, annealed and T6-conditioned samples. From the images, the effects of annealing and T6 heat treatment on the particle-substrate interfacial phenomena and interfacial defects were examined. The T6-conditioned coating was found to have a 70% higher coating adhesive bond strength than the as-sprayed coating, while the stress-relieved coating was also found to have a 39% higher coating adhesive bond strength than the as-sprayed coating.  An investigation of the modes of coating adhesion failure will also be made between the un-treated, annealed and T6-conditioned samples, and correlated with the image analysis of the single-splat particle-substrate interfaces.