Reduced Tensile Ductility Induced by Intergranular Cracking of Laser Powder Bed Fused Alloy 718 at 650°C

Abstract

The limited high-temperature ductility of laser powder bed fused (LPBF) Inconel 718 restricts its use in aerospace and nuclear industries. This study elucidated the mechanisms responsible for reduced ductility of LPBF Inconel 718 at 650°C compared with room temperature (RT). Although strength and ductility were high at RT, tensile properties fell sharply at 650°C, with elongation dropping to 21% of RT. The ductility loss manifests as pronounced intergranular fracture, driven by inherent strain localization along high-angle grain boundaries at 650°C and intensified by MC-type carbide precipitation at grain boundaries. A damage model integrated within a crystal plasticity framework, incorporating geometrically necessary dislocation (GND) and statistically stored dislocation (SSD), successfully simulated GND-dominated intergranular fracture at 650°C and SSD-dominated transgranular fracture at RT. This study uncovers tensile fracture mechanisms of LPBF Inconel 718 across temperatures, providing insights for the reliable use of additively manufactured superalloys in high-temperature applications.