High temperature oxidation of Ni-based superalloy 247 produced by electron beam powder bed fusion additive manufacturing

This study investigates high temperature oxidation of Ni-base superalloy 247 processed by electron beam powder bed fusion (PBF-EB) compared with a conventionally cast (CC) counterpart. In terms of mass-gain during isothermal thermogravimetry at 1100 o C, the CC alloy outperformed the PBF-EB alloy. However, the PBF-EB alloy suffers from deeper internal oxidation due to its fine grain structure while shortening the transient oxidation stage. On the other hand, the CC alloy forms a non-homogeneous scale due to inhomogeneous distribution of bulky carbides and takes longer time to transition towards a steady-stage oxidation. The findings are analyzed and rationalized in the context of prior literature and thermodynamic-kinetic modeling. • In terms of specific mass-gain, CC 247 outperforms PBF-EB 247 • Fine-grained PBF-EB 247 shows deep internal oxidation and short transient stage • Cr consumption drive Al towards the surface, but kinetics is grain-size dependent