Adhesion mechanisms, evaluation techniques and modeling strategies in PVD coatings: From fundamentals to data-driven design

Reliable adhesion remains the principal life-limiting factor for Physical Vapor Deposition (PVD) coatings used in aerospace, cutting, and biomedical components - responsible for more than half of all coating failures. This review provides a unified, design-oriented synthesis of adhesion mechanisms, evaluation techniques, process-structure-property linkages, and emerging hybrid modeling strategies. The dominant interfacial bonding mechanisms, mechanical interlocking, chemical and van der Waals interactions, and thermo-mechanical mismatch, are critically analyzed in relation to measurable interfacial energy and residual stress. Experimental evaluation methods are systematically compared, from conventional scratch and indentation tests to advanced diagnostics such as laser-induced spallation and acoustic-emission analysis. The influence of process parameters including substrate preparation, temperature, bias voltage, gas ratio, and coating architecture on adhesion strength and failure modes is summarized using quantitative trends reported across PVD systems. Computational approaches are reviewed, encompassing analytical and finite-element cohesive-zone models as well as multiscale and machine-learning-based frameworks for predictive adhesion mapping and design optimization. A four-pronged design framework is proposed, substrate-controlled, interface-engineered, process-parameter-controlled, and architecture-engineered strategies, to guide the development of high-adhesion coatings. Finally, key challenges and future directions are identified, emphasizing physics-informed data-driven models, automated characterization, and nanostructured interface design for next-generation PVD technologies.