Bonding dissimilar metals by Additive Manufacturing (AM) can create structures with complex geometries and tailored material properties. Bonding can be difficult due to the formation of unintended intermetallic phases that may form. In this work, bonding of Inconel 625/stainless steel 304 and Inconel 718/GRCop-84 bimaterial systems system is studied. The additive platform used is a TRUMPF TruLaser Cell 3000 laser powder feed DED system. Bimaterial single bead and single-layer pad specimens have been fabricated that successfully avoid gross defects such as voids, cracks and deleterious phases. CALPHAD simulations have guided the choice of process parameters needed to avoid the formation of intermetallics. Most importantly, the avoidance of intermetallics requires control of melt pool remelt ratios in order to control compositional transitions across the interface. Scanning Electron Microscopy and Energy Dispersive X-Ray Spectroscopy are used to evaluate the presence of intermetallic phases in the deposits. In the IN6256/SS304 system, tensile specimens have been fabricated and tested showing strong bonds in specimens designed to avoid intermetallics. Methods from this work show potential for achieving high-strength bonds across a wide range of bimaterial systems.
Learning Objectives:
- Understand how to fabricate strong interfaces in bimaterial structures
- Understand process control for DED processes to achieve strong bimaterial interfaces
- Understand the use of CALPHAD simulations to guide the choice of processing parameters to achieve strong interfaces.
