A comparative review of solid-state cold spray versus fusion-based additive manufacturing of Inconel 718: Microstructure and mechanical performance

Inconel 718 (IN718) is a nickel-based, precipitation-strengthened superalloy widely used in the aerospace industry due to its high-temperature strength and exceptional creep resistance. Compared to traditional manufacturing, additive manufacturing (AM) offers shorter lead times, fabricates geometrically complex components, enables the consolidation of multiple components into a single integrated part, supports multi-material builds, allows for part customization, and facilitates the repair of high-value IN718 components. Over the past decade, fusion-based AM methods such as laser powder bed fusion, directed energy deposition, and wire-arc additive manufacturing have been widely studied and adopted for industrial applications. Meanwhile, solid-state cold spray AM (CSAM) has emerged as an alternative for IN718, depositing material without melting and thereby reducing fusion-related issues such as oxidation, hot cracking, and elemental segregation. CSAM has enabled high-deposition-rate fabrication of free-standing builds with simple geometries in addition to its established use in coatings and repair. This review provides an in-depth comparison of CSAM and fusion-based AM routes for IN718. It compares the as-built microstructures, their evolution under standard and tailored heat treatments, and the resulting mechanical properties for different AM routes. Fatigue behavior, including high-cycle fatigue strength and room-temperature fatigue crack growth rates, is also covered. Furthermore, the article highlights the limited fatigue data available for CSAM IN718 and the lack of systematic heat treatment studies, which currently restricts the definition of durability and damage-tolerance limits for CSAM repairs and freestanding parts in high-reliability applications such as aerospace.