Effect of heat treatment in dissimilar welds of additively manufactured laser welded 316L-Inconel 718 joints

Laser powder bed fusion for metals is a method of producing end use components for industrial use. Powder bed fusion machines are relatively small and are usually used to create only the critical part of the larger assembly. Therefore, L-PBF manufactured parts must be attached to each other for example by welding. The industrial world needs to be able to join the printed superalloy components to the traditionally manufactured components to reach better corrosion, wear and/or heat resistance. The problem is that there is limited amount of information about the suitable welding parameter values for these applications. This study examines how the standard heat treatment cycles affect to the quality of the weld, and if the post-heat treatment is reducing undesired phases in the heat affected zone. It is also examined how post weld heat treatment for Inconel 718 affects the base material in IN718-316L dissimilar welds. Tests show that post-weld heat treatment has a positive effect on weld hardness on IN718 side. After welding, the hardness drops to 50% of the nominal hardness. When the welds are heat treated according to AMS5662, the hardness values are restored. Tests also show that the heat treatment does not have significant effect on tensile or hardness properties of 316L.