Ni-Based Superalloy Strengthened by In-situ Alumina Formation During Laser Powder Bed Fusion with Recycled Powder

Considering the high material costs, economics, and sustainability of the additive manufacturing (AM) industry, powder reuse is essential for the Laser Powder Bed Fusion (LPBF) AM process. Given that powder quality is a critical determinant of the mechanical performance of LPBF-fabricated parts, it is crucial to investigate the effects of powder reuse on powder characteristics and the properties of the final LPBF parts. This study examines the microstructure and mechanical properties of LPBF specimens fabricated by reusing IN718 powder up to 10 times, employing a virgin powder supplementation approach. The average particle size of the reused powder progressively increased as the number of powder reuse cycles was increased. Additionally, repeated reuse caused the powder to oxidize and form alumina spots on the powder surface. LPBF specimens manufactured with reused powder contain fine alumina of less than 100 nm in an austenite matrix. The presence of alumina influenced the recrystallization behavior during the 1065°C homogenization heat treatment. Additionally, the oxide dispersion strengthening effect imparted by the alumina led to simultaneous enhancements in both tensile strength and elongation of the LPBF specimens tested at 25°C and 650°C.