SUMMARY

Laser-based directed energy deposition (DED) presents numerous opportunities for developing advanced materials and enables the repair and manufacture of parts for end use. However, significant roadblocks are observed while processing high ɣ’ Nickel-based superalloys, primarily due to the lack of understanding of its constitutive material behavior caused by the inherent process variability. Exploring materials through the DED-graded alloy approach by varying crack-susceptible constituents in the composition enables synthesizing unique materials and expands the processability envelope with the required property response. However, the ability to explore sufficiently large datasets of material properties produced by this approach is limited due to the time-intensive nature of conventional materials characterization techniques. To address this knowledge, the proposed work will focus on the following key objectives (1) Role of AM process parameters and compositions on crack formation in high ɣ’ Ni Superalloys. (2) Establishing high throughput CPSP correlations of high ɣ’ Ni-superalloys. (3) DED process optimization to avoid hot cracking. This dissertation will leverage the use of advanced material characterization methodologies for high throughput assessment of mechanical properties and then establish CPSP correlations with their respective higher-order statistical microstructural descriptors obtained at different processing conditions. Utilizing this material database, this work explores the role of ɣ’ constituents (Al & Ti) and their processing conditions on its material properties. Subsequently, coupling the thermomechanical stresses identified through numerical simulations and rationalizing the relationship between process variability and crack formation, this research aims to develop a process-materials framework for repairing Ni-based superalloys.