Densification, microstructure, and mechanical properties of heat-treated MAR-M247 fabricated by Binder Jetting

Additive Manufacturing (AM) enables the design of complex part geometries for high-temperature applications. Laser Powder Bed Fusion or Direct Energy Deposition of the nickel-based superalloy MAR-M247 poses a challenge in AM due to its poor weldability. Binder Jetting does not utilize a heat source and interaction with a liquid metal during build-up and thus has the potential to overcome this limitation. In this study, MAR-M247 was manufactured by Binder Jetting and subsequently characterized regarding density and microstructure. Combinations of two different Hot-Isostatic-Pressing (HIP) treatments (T = 1120–1180 °C, p = 1000–1500 bar, t = 4 h) and four different heat-treatments involving solution treatment (T = 1250 °C, t = 4 h) and different aging steps (T = 700–1000 °C, t = 12–24 h) were applied to study the densification and microstructural evolution of binder-jetted MAR-M247. The influence of the build direction in combination with HIP is studied concerning the resulting density and mechanical properties at room temperature. The results show that close-to-full densification can be achieved after HIP. Subsequent solution treatment and double-aging after HIP lead to a favorable bimodal microstructure. A process chain for binder-jetted MAR-M247 is presented, which yields tensile properties comparable to those of analogously post-processed cast material. Further possibilities of microstructural optimization and the design philosophy are discussed in the light of the Binder Jetting process-chain.