Demonstration and Analysis of Conditions to Obtain a High Strength Inconel 625 to Stainless Steel 304L Interface by Directed Energy Deposition

This is the authors' abstract. We don't add key points for this paper.

Functional grading (FG) is often used to bond dissimilar metals. However, that approach is complicated from a manufacturing perspective, and the associated challenges can outweigh the benefits of FG. Here, we investigate a directly bonded interface by transitioning from stainless steel 304L (SS304L) to Inconel 625 (IN625) using powder-feed directed energy deposition with a laser beam energy source (DED-LB). Both cracking and the presence of carbide phases have been reported in this multi-materials system. Conditions that unambiguously achieve crack-free joints have not yet been established. With DED-LB, we consistently observe solidification cracking in melt pools containing > 50 wt pct SS304L, while no cracking is observed in melt pools with < 40 wt pct SS304L. Variations on the most up-to-date solidification cracking model are applied to gain insight into the cracking dependencies. Parameters that give rise to defect-free single layers also enable defect-free multilayer prints despite the additional thermal cycling. Upon printing and testing full-sized ASTM E8 tensile specimens, the interface is sufficiently strong that failure occurs solely within the SS304L region, indicating a joint strength of > 650 MPa. Thus, a simple method to attain high strength joints for these dissimilar metal alloys is demonstrated.