Characterisation of alloys 690 and 52i fabricated using laser powder bed fusion

This study presents the first comprehensive investigation into the Additive Manufacture (AM) of nickel-based Alloys 690 and 52i using Laser Powder Bed Fusion (LPBF), with a view towards application in high-temperature, corrosion-resistant components for nuclear and power generation industries. Specimens fabricated from gas atomised powder achieved almost full density (99.95%) and underwent a conventional solution anneal heat treatment. A comprehensive set of microstructural, mechanical property, and corrosion properties was undertaken to assess their performance viability. LPBF Alloy 52i demonstrated superior 0.2% Proof Strength (PS) and Ultimate Tensile Strength (UTS) compared to both wrought and LPBF Alloy 690, at ambient and elevated temperatures (300°C), for all build orientations. Strength differences between orientations were attributed to microstructural anisotropy, consistent with wrought studies. Microstructural characterisation revealed differences in pore morphology, carbide distribution and oxide inclusions; with LPBF Alloy 52i exhibiting plate-like aluminium oxides linked to higher oxygen content of the virgin powder. Corrosion testing indicated enhanced intergranular corrosion resistance in both LPBF alloys compared to wrought Alloy 690, attributed to finer and more continuous grain boundary carbides. These results support the potential of LPBF Alloys 690 and 52i for structural applications in demanding environments and provide early data for material qualification efforts in nuclear engineering.