Fatigue Resistance of PBF-Lb IN625-RAM2 Alloy

The mechanical and fatigue behavior of a reactively modified Inconel 625 alloy (IN625-RAM2) produced by Laser Powder Bed Fusion (PBF-LB) was investigated. The alloy achieved near-full density (≈8.30 g/cm³) and exhibited a refined, irregular grain structure with localized equiaxed regions from ceramic-induced nucleation and Zener pinning. It showed high tensile strength (YS 680–770 MPa, UTS 1170–1250 MPa) with modest anisotropy. Under fully reversed loading (R = –1), fatigue limits at 2×10⁶ cycles were 110–122 MPa in the as-built condition and 180–187 MPa after electropolishing, improving fatigue efficiency from ~10% to ~15% of UTS. Compared with reference alloys (AISI 316L, Ti6Al4V, IN718), IN625-RAM2 combined high strength with moderate fatigue resistance, emphasizing the critical role of surface quality in optimizing PBF-LB nickel alloys.