Work

Thickness-dependent fatigue failure mechanisms in cold-sprayed AA7075 repairs: From coating cracking to interfacial delamination

Year: 2026

Type: article

Abstract: Cold spray (CS) is a solid-state additive deposition technique of growing interest for repairing and protecting aerospace structural components. This study investigates how variations in CS repair thickness influence the fatigue behaviour of AA7075 coatings on AA7075-T6 substrates, simulating real-world post-processing through controlled material removal. Results show that CS coatings reduced overall fatigue life; however, thicker coatings (> 0.5 mm) showed only a moderate (~30%) reduction compared to uncoated material, while thinner coatings (≤ 0.5 mm) exhibited a greater (~70–85%) reduction when considering a redefined stress state. Failure mechanisms are thickness-dependent: thin coatings fail predominantly through CS cracking, which induces sharp, geometric stress concentrations at crack tips and accelerates substrate failure, while thicker coatings fail via interfacial delamination. Mirror and camera-assisted in-situ crack observation, supported by fractography, confirmed that in thick coatings cracks initiated at spray-induced substrate craters, whereas in thin coatings initiation occurred within the CS during the first loading cycle at surface or near-surface pores. These findings highlight the importance of optimising CS repair thickness, and interfacial morphology, as well as considering in-service bending and shear stress distributions, to maximise fatigue durability in aluminium repairs.

Source: International Journal of Fatigue

DOI: 10.1016/j.ijfatigue.2026.109702