Design Frameworks and Tribological Performance of Cold Spray Additively Manufactured Coatings: Materials, Mechanisms, and Engineering Applications

Cold spray additive manufacturing (CS) has emerged as a transformative solid-state deposition technique for designing advanced functional surfaces with tailored tribological performance. By accelerating micron-scale particles to supersonic velocities and depositing them below their melting point, CS enables the fabrication of dense, oxidation-resistant coatings with strong metallurgical bonding and beneficial compressive residual stresses. These distinctive attributes create unique opportunities for the design-driven engineering of wear-resistant surfaces across aerospace, automotive, marine, biomedical, and industrial sectors. Despite a growing literature on CS processing and properties, a comprehensive framework linking design principles encompassing material selection, coating architecture, process parameter optimization, and post-processing strategies to tribological outcomes is absent from the field. This review addresses that gap by critically examining the design space of CS coatings and positioning tribological performance as an outcome of deliberate engineering decisions. The relationships between coating architecture and tribological behavior, specifically friction control, wear resistance, adhesion-cohesion integrity, and surface roughness, are examined under varying environmental and loading conditions. Design strategies involving composite and hybrid coatings incorporating solid lubricants, ceramic reinforcements, and nanostructured architectures are discussed in the context of achieving specific functional objectives. The influence of process parameters, such as particle velocity, gas temperature, substrate preparation, and post-treatments including heat treatment, friction stir processing, and laser shock peening, on tribological outcomes is critically synthesized. Environmental performance under high-temperature, corrosive, and extreme wear conditions is analyzed through a design lens. A design decision framework summarizing material-process-property linkages for CS tribological coatings is presented to provide practical guidance for engineers and researchers. Future directions include AI-driven process optimization, multi-material architectures, and the integration of CS within broader design-for-manufacturing workflows.