Recent Advances in Cold-Sprayed Aluminum Alloy 7075 Metal Matrix Composite Coatings: Surface Engineering, Feedstock Design, Post-Processing Strategies, and Emerging Applications

Cold spray technology has emerged as a transformative solid-state processing route for fabricating high-performance metal matrix composite (MMC) coatings, particularly for lightweight, high-strength aluminum alloy 7075 (AA7075). This review provides a comprehensive overview of recent advances in cold-sprayed AA7075-based MMC coatings, focusing on critical aspects such as surface engineering, powder feedstock design, post-deposition treatments, and reinforcement strategies. The integration of hard ceramic and nanostructured reinforcements, including B4C, SiC, boron nitride nanoplatelets or tubes (BNNPs/BNNTs), and graphene nanoplatelets (GNPs), has improved the mechanical strength, wear resistance, and corrosion behavior of these coatings. Special emphasis is placed on functionally graded architectures, hybrid reinforcement systems, and densification methods such as heat treatment and hot isostatic pressing. The review also highlights emerging applications in aerospace, defense, and space technologies, including radiation shielding, structural repair, and metallization of polymer substrates. Remaining challenges, such as reinforcement dispersion, interface integrity, and process optimization, are discussed, along with future research directions involving machine learning, real-time diagnostics, and environmental validation. Overall, this review provides an integrated understanding of the processing, microstructure, properties, and applications of cold-sprayed AA7075-based MMC coatings and identifies key research gaps and future directions.