Integration of additive manufacturing and coating technologies for aerospace components: performance, challenges, and future directions

The aerospace industry has been a catalyst for the adoption of additive manufacturing (AM) and coating technologies to achieve superior performance (e.g., improved performance, lightweight structures, and increased durability). However, AM components fabricated directly through AM processes do not typically meet aerospace standards for surface characteristics, due to high surface roughness ( Ra = 5–20 μm), residual porosity (0.1-2.0%), and tensile residual stress. This review examines the synergistic potential of combining AM and coating technologies to improve the performance of aerospace materials by investigating the relationships among structure, properties, and performance. The evaluation of AM-induced microstructural features and their impact on coating adhesion, thermal stability, and environmental resistance are discussed for four different methods of integrating AM and coatings: (1) Substrate tailoring through process parameter optimization, (2) Functionally graded material (FGM) interlayer development, (3) In-situ surface modifications during the AM process, and (4) Hybrid fabrication methods (combining traditional and advanced methods). Critical challenges identifying all four methods are explored. These include the coefficient of thermal expansion (CTE) mismatch between metallic substrates (12–18 ×10 -6 °C -1 ) and ceramic coatings (8–11 ×10 -6 °C -1 ). Other challenges are residual stress accumulation during the fabrication of AM components and the coating process, as well as degradation mechanisms that occur during AM, such as porosity-induced oxidation and columnar grain boundary diffusion. Lastly, a tiered roadmap for the industrial adoption of AM coatings is presented, along with emerging materials (high entropy alloys and nanocomposites) and self-healing properties.