Enhancement in low cycle fatigue life of LPBF processed Inconel 625 superalloy by heat treatment

Abstract

Inconel 625 is one among the most diverse materials for applications based on high temperature applications such as power plants, heat exchangers, automotive turbochargers etc. Low cycle fatigue (LCF) behaviour of additively manufactured (AM-AR) Inconel 625 (IN625), manufactured using Laser Powder bed fusion (LPBF) and effect of post heat treatment was investigated in the present study. Symmetrical triangular waveforms and strain amplitudes ranging from ±0.4 to ± 0.8 % were used to study LCF behaviour at room temperature. The fatigue life of additive manufactured and solution-treated (AM-ST) samples was found to be improved, due to better carbide homogenisation and reduced defect volume compared to that of AM-AR IN625. Fatigue life was improved by 2000–3000 cycles after solution treatment. A continuous cyclic hardening was observed till peak stress level at all strain amplitudes. The number of cycles to failure was found to decrease with rise in strain amplitude. TEM micrographs revealed the solute-dislocation pinning interactions. SEM fractography revealed the striations in the slow crack propagation zone and dimples due to microvoid coalescence in the fast propagation zone. © 2025 Elsevier B.V.