Evaluation of in-situ alloyed Inconel 625 from elemental powders by laser directed energy deposition

Additive manufacturing (AM) is becoming a mainstream technique for the fabrication of performance-critical products. In-situ alloying from elemental powders shows enormous potential to realize cost-effective alloy development and reduce the complexity of powder material management for industry. In this study, laser directed energy deposition (DED) was applied to investigate the feasibility of in-situ alloying of Inconel 625 using elemental powders. Three levels of laser scanning speed were used to illustrate its effects on the microstructure and mechanical properties of in-situ alloyed samples. It was discovered that the lower laser scanning speed favors uniform in-situ alloying. At the lowest scanning speed adopted, the existence of unmelted particles is almost negligible. Moreover, at the as-built state, the in-situ alloyed Inconel 625 obtained at the lowest laser scanning speed has an averaged ultimate tensile strength of 1020 MPa, and an averaged fracture strain of 23.14%, comparable to those obtained using pre-alloyed powders under the same DED process condition. Meanwhile, its micro-hardness is 339 HV, higher than that made by pre-alloyed powders (298 HV). Microstructure characterization was also performed to reveal the underlying mechanism of in-situ alloying. This study not only demonstrates that quality Inconel 625 components can be additively manufactured through in-situ alloying from elemental powders, but also provides insights on alloy development using the flexible, high-throughput approach.