Interfacial characterization in laser directed energy deposited functionally graded multi-material steel

Functionally graded multi materials (FG-MM) represent an emerging class of engineered structures in which chemical composition varies spatially along pre-defined orientations. FG-MM have gained attention for enabling integration of dissimilar properties within a single component. Additive manufacturing has advanced the fabrication of FG-MM, however, interfacial region between the constituents remains a key limitation in their performance. In this study, the interfacial behaviour of laser directed energy deposition fabricated austenitic and martensitic FG-MM steel components is investigated. Two interface configurations namely direct interface and gradual interface were investigated. The interfaces were characterized through phase analysis, microstructural evaluation, and Vickers hardness profile. The results indicate that the introduction of a compositional gradient between dissimilar steels promotes a smoother material transition as both austenitic and martensitic phases can co-exist when deposited altogether in similar quantities, which leads to a more progressive evolution of microstructure and hardness across the interface.