Investigation of fatigue performance for friction surfacing groove repairs of high-strength aluminum alloys

Friction stir-based solid state layer deposition techniques are presumed to have significant potential for repair applications. The main advantage is mostly related to the lower heat input during layer deposition, minimizing thermal effects to the surrounding structure. This work presents the application of a friction surfacing (FS) approach for groove repair of similar material combinations of AA2024 and AA7475, respectively. Regarding the process stability, a reduction of travel speed within the groove area improves the bonding of the deposit to the subjacent structure. To further consolidate and enhance the bonding of the deposit, hybrid friction diffusion bonding (HFDB), which is a friction stir-based materials processing technique, has successfully been applied. For the optimized FS groove repair strategy, including HFDB post-processing, fatigue testing was performed, revealing an improvement of the fatigue properties compared to the grooved reference material. The AA2024 repaired grooves present mechanical properties approaching the AA2024 base material. The repair of the AA7475 grooves also led to an improvement; however, the AA7475 results stay below the respective reference material and, therefore, the improvement is less pronounced compared to AA2024. The results provide the first benchmark for fatigue properties of FS-repaired grooves and highlight this technique as a simple and efficient approach for repair at low thermal input, minimizing effects on the surrounding structure.