Thermal stability of Ni-based superalloys fabricated through additive manufacturing: A review

Additive manufacturing (AM) is a cutting-edge technique that builds parts by adding layers from a digital design and depositing materials selectively where required. AM is vital in industries like aerospace, healthcare, and automotive because of benefits like design flexibility, cost-efficiency, and customization over conventional methods. Ni-based superalloys AM processes involve phenomena like solidification, phase change, different microstructure characteristics, and melting pool boundaries, affecting both microstructure and mechanical properties. Ni-based superalloys are regarded as potential candidates for high-temperature applications, thanks to their capability to benefit from various strengthening mechanisms such as precipitation hardening and solid solution strengthening. This comprehensive review explores the thermal stability and high temperature softening resistance of additively manufactured (AMed) Ni-based superalloys, from microstructural and mechanical points of view. This review explores the thermal stability and high temperature softening resistance of additively manufactured Ni-based superalloys. It explores the interplay of alloying elements at high temperature, additive manufacturing parameters, and initial microstructure, focusing on grain boundary/sub-boundary networks evolution. The influence of solute drag effect, second phases Zenner pinning effect, and post-processing treatments on microstructural changes such as second phase characteristics, recrystallization (static and dynamic), grain growth phenomena, and textural variations is also analyzed. High temperature mechanical properties of AM-Ni-based superalloys are evaluated, including yield and tensile strength, elongation, work-hardening behavior, creep, and fatigue properties. Hydrogen embrittlement is a significant reason for failure, so this issue is briefly assessed in AM-Ni-based superalloys. Results show that understanding relationships between processing, microstructure, post-processing treatment, and properties is crucial for thermal stability control.