Dynamic recrystallisation pathways governing creep-induced microstructural evolution in additively manufactured Inconel 718

Understanding how creep deformation alters microstructure is critical for assessing the long-term stability of high-temperature alloys. This study investigates creep-induced microstructural evolution in Inconel 718 (IN718) produced by laser beam powder bed fusion (PBF-LB), through the use of electron backscatter diffraction (EBSD). Constant-load creep tests were conducted at 625–675 °C and 625–690 MPa on vertically built material subjected to two post-processing heat treatments designed to produce contrasting grain boundary and dislocation structures. EBSD-based analysis of grain boundary character, recrystallisation fraction, twin density and geometrically necessary dislocation (GND) density, before and after creep exposure shows that creep stability is governed by the dominant dynamic recrystallisation (DRX) pathway activated during deformation. A high-temperature solution plus double ageing treatment promotes deformation-dominated DRX, characterised by sustained GND accumulation, stable low-angle boundary networks and controlled twin evolution, resulting in creep resistance comparable to wrought IN718. In contrast, a lower-temperature heat treatment exhibits recovery-dominated behaviour, with GND annihilation, increased high-angle boundary formation and accelerated damage accumulation. By treating creep as a driver of microstructural evolution, this study demonstrates the value of EBSD-derived metrics for identifying active deformation pathways and provides mechanistic insight into the microstructural design of IN718 for high-temperature service. • Creep stability in LPBF IN718 is controlled by the active DRX pathway. • EBSD metrics quantify deformation- and recovery-dominated creep behaviour. • Deformation-dominated DRX promotes stable boundaries and enhanced creep life. • Recovery-dominated behaviour accelerates boundary instability and damage. • Heat treatment governs DRX pathway and creep resistance in LPBF IN718