Recent Advances in Additive Manufacturing Technologies for Ni-Based Inconel Superalloys – A Comprehensive Review

Ni-based superalloys exhibit exceptional high-temperature mechanical properties. A specific group, “Inconel superalloys,” has been a focus of extensive research owing to their ability to withstand high-temperatures, making them an inevitable candidate for aerospace applications. Superalloy components are traditionally manufactured through casting, forging, and post-machining, leading to material wastage and higher manufacturing costs. In this regard, additive manufacturing (AM) is increasingly used for fabricating complex shaped Inconel based components for critical aerospace application. AM is particularly advantageous for easy fabrication of intricate designs while having high material utilization, and reduced build time, still achieving controlled and targeted properties for expensive and difficult-to-machine Inconel superalloy components. Nevertheless, the complex layer-by-layer processing technique leads to completely different microstructural evolutions with respect to the as-cast counterparts which is also reflected in altered mechanical performance. This is particularly crucial considering that Inconel consists of different alloying elements, leading to the formation of multiple phases like γ, γ′ γ′′, etc. The current article reports a comprehensive overview of the following two topics: (i) commonly practiced AM techniques for fabricating Inconel superalloys and (ii) processing– microstructure–mechanical properties correlations for the most studied additively manufactured Inconel superalloys, IN718, IN625, IN738LC, and IN939. Special attention is dedicated in elucidating the influence of heat-treatment schedules on both the microstructure and mechanical properties of Inconel superalloys. This extensive research would prove beneficial in optimizing the types and processing parameters for AM of Inconel superalloys to attain the targeted microstructure, and phases, and also to design the suitable post-manufacturing heat-treatment schedule. Such correlation holds significant potential for realizing enhanced mechanical performance for additively manufactured Inconel components for industrial applications.