Effect of Initial Powder Condition on Precipitation Behavior in Cold Sprayed Al7075 Alloy Coatings

Abstract

This study explores the potential of cold spray technology for repairing high-strength Al7075 alloy components, particularly in the aerospace industry. The gas-atomized powder contains a dendritic cell structure with solutes segregated at the dendritic cell boundaries. Thus, direct aging of atomized powder fails to induce the formation of strengthened precipitates. Therefore, the effect of different powder pre-treatments on the deposition efficiency, microstructure, and aging behavior of the coatings was investigated. Cold spray coatings were deposited using as-received powder, solutionized, and solutionized + aged powders, revealing a significant improvement in thickness for coatings obtained using solutionized (110%) and solutionized + aged (80%) powders compared to the coating from the as-received atomized powder. Further, coatings deposited using as-received, solutionized, and solutionized + aged powders, were aged at 120 °C for various durations and the aging response of different coatings were studied. Microstructural studies revealed that gas-atomized powders exhibited dendritic structures with segregated solutes. Solutionizing eliminated the dendritic features, promoting deposition efficiency upon cold spraying. Aging of the coating from the solutionized powder led to the formation of ultrafine η' precipitates (29 ± 8 nm length, 2 ± 1 nm diameter) at peak-aged condition (after 8 h). These findings demonstrate the effectiveness of powder pre-treatment in tailoring the microstructure and deposition behavior of cold-sprayed Al7075 coatings, offering a promising approach for repair applications.