Cold spraying of Al-aerospace alloys: Ease of coating deposition at high stagnation temperatures

Cold spray is the only solid-state coating technique to deposit thick metallic coatings. Deposition of metallic and metallic alloy powders is carried out at the temperature lower than the melting point. Since spraying of Al-based aerospace alloys are associated with nozzle clogging, successful deposition is restricted to nitrogen or helium as the main process gas with a polymer nozzle. Deposition of the alloys using air as process gas at elevated stagnation temperatures (up to 600 degrees C) has benefits in the repair and refurbishment sector, especially in aerospace. In this study, the effect of elevated stagnation temperatures (from 400 to 600 degrees C) using air as the main process gas on the deposition characteristics of aerospace grade Al-alloys (Cp-Al, Al-2024, Al-6061 and Al-7075) is studied. Deposition of the alloys at various stagnation temperatures is studied using FEM and correlated with the coating thickness. The deposition behaviour is studied using various parameters such as lattice misfit calculations and solid solution strengthening calculations. The ease of cold spray deposition of Al-aerospace alloys is systematically studied and listed as Al-6061 > Cp-Al > Al-7075 > Al-2024 for the first time.