Accelerated Alloy Development for AM by Mimicking AM Process Conditions

Nickel-based superalloys are extensively utilized in demanding environments characterized by elevated temperatures and corrosive atmospheres. In recent years, the application of additive manufacturing (AM) techniques, especially electron-beam powder bed fusion (PBF-EB), has gained significant attention due to their potential to enable design freedom, weight reduction, and advanced geometries. However, a major limitation of some nickel-based superalloys, particularly the highly γ′-strengthened ones, lies in their pronounced crack susceptibility when transitioning from casting to additive manufacturing processes. The development of nickel-based superalloys with reduced cracking tendencies, tailored for AM, remains a time-intensive and costly challenge. The large number of constituents and their complex interactions impedes identifying simple cause-effect relationships regarding processability as well as mechanical properties and makes alloy development very challenging. Experimental alloy development is further complicated by the fact that atomizing powder of each potential alloy composition would be extremely time-consuming, expensive and, hence, impractical. This contribution introduces Successive Electron Beam Remelting (SEBR) as a novel and cost-effective approach for alloy development for additive manufacturing with the PBF-EB process. The SEBR process involves iterative remelting of bulk alloy samples, wherein the melt pool depth is progressively reduced during successive remelting steps. The intention is to mimic the layer-wise solidification and microstructural evolution characteristic of PBF-EB processes, including the occurrence of AM-relevant cracking phenomena. Initial experiments have demonstrated the formation of cracks within and adjacent to the remelted zone produced by the SEBR process. The morphology of these cracks as well as the crack density exhibit a strong correlation with those observed in actual PBF-EB builds. Hence, the evaluation of crack susceptibility through SEBR appears feasible and may offer a rapid and cost-efficient pathway to assess the processability of novel nickel-based alloys for additive manufacturing without the need for powder.