Binder jetting of “Hard-to-Weld” high gamma prime nickel-based superalloy RENÉ 108

Abstract The ultra-high strength of high γ’ nickel (Ni)-based superalloys with low ductility comes with the price of high susceptibility to cracking and a high residual stress state when processed with conventional powder bed fusion technologies. Binder jet additive manufacturing (BJAM) is an interesting alternative to other additive manufacturing (AM) modalities since it does not require melting to fuse powder material but selectively adheres powder with a binder. While there are several studies on the use of melting and solidification-based AM technologies, limited literature is available on the use of BJAM for high γ’ Ni-based superalloys. This study presents the advantages and disadvantages associated with the BJAM of RENE 108 superalloy. The BJAM microstructure is characterized in the green, brown and sintered states. The formation of parallel primitive lines perpendicular to the build direction is observed after printing. This leads to persistent lines of porosity and a relative density above 96% after a sintering cycle. A fully dense microstructure is obtained after hot isostatic pressing (HIP) of the material. The formation of HfO2 and Ta-rich carbides along prior particle boundaries (PPBs) is also observed during the sintering stage. Precipitation along PPBs is intrinsic to the powder metallurgy of Ni-based superalloys and influenced by the debinding conditions of the parts. They have a strong impact on the mechanical properties of the material. At low temperatures ( 760 °C), the deformation becomes intergranular, and fracture occurs at the PPBs. The ductility of BJAM RENE 108 becomes slightly lower than the DS material while the strength of the materials remains comparable.