The anisotropy of creep deformation, life, damage, activation energy, and fracture mode for LPBF Inconel 718 by small punch creep test

Abstract

Insufficient knowledge of creep behavior in laser powder bed fusion (LPBF) Inconel 718 alloys hinders their prolonged high-temperature service, particularly concerning creep anisotropy. Utilizing the micro specimen advantages of the small punch creep test (SPCT), we performed a comprehensive analysis of creep anisotropy behavior, creep thermal activation energy, and fracture mechanisms. (1) During aging heat treatment, X-specimens and Z-specimens exhibit considerable creep anisotropy, which is markedly reduced with solution and aging heat treatment. (2) Creep thermal activation energy ranking is: X-specimen (618.33 kJ/mol) > rolled Inconel 718 (419.90 kJ/mol) > Z-specimen (263.65 kJ/mol), highlighting the creep resistance discrepancies between X-specimens, Z-specimens, and conventional rolled material. (3) Using the interrupted SPCT revealed that the fracture of X-specimens occurs via straight crack growth during the creep process, while Z-specimens fail owing to circumferential crack growth. This study’s key contributions lie in determining the creep thermal activation energy of LPBF Inconel 718 and elucidating its creep damage and fracture anisotropy. These findings address the knowledge gap regarding creep anisotropy in LPBF Inconel 718 and facilitate its wider engineering applications.