Surface integrity of hybrid CM247LC/Inconel 718 components produced by laser-directed energy deposition

High-temperature alloys pose significant challenges in additive manufacturing. These materials have unique properties, such as high resistance to mechanical and chemical degradation when exposed to high temperatures. Furthermore, when these alloys are used to produce hybrid components with other similar alloys, investigating their surface integrity is critical because any residual stress can lead to early stage cracks and poor fatigue performance. In this research, a hybrid manufacturing approach is employed to produce components from difficult to weld alloys, i.e. CM247LC deposited on IN718 through a laser based direct energy deposition (L-DED) process. The surface integrity, mechanical properties and microstructure of such hybrid components is investigated, especially their welding/joint areas. Crack-free processing regimes were established to deposit CM247LC while mitigating the negative effects onto the microstructure of the Inconel substrate. Especially, the thermal gradients were managed to deliver crack free sections of CM247LC with good interface bonding, strength and fine microstructure. It is important to note that this is achieved without any significant preheating that contrasts with what is reported in other investigations so far. Furthermore, end-use hybrid blisks with deposited CM247LC blades onto Inconel 718 disks (HUB) were manufactured and then machined within a single processing set-up. The results show that the substrate thickness, the machining between the deposited layers and the final machining and heat-treatment play a role in reducing residual stresses. Ultimately, such hybrid manufacturing approach can be considered a new solution for producing such components and also for their subsequent repair.