Radhakrishnan, J., Kumar, P., Li, S., Zhao, Y., & Ramamurty, U. (2022). Unnotched fatigue of Inconel 718 produced by laser beam-powder bed fusion at 25 and 600°C. Acta Materialia, 225, 117565. https://doi.org/10.1016/j.actamat.2021.117565
Abstract:
The microstructures and mechanical properties of as-built Inconel 718 produced using laser beam powder bed fusion (LB-PBF) process were investigated at room temperature (RT) and 600 °C. Emphasis was on the high cycle fatigue behavior evaluated using the rotating bend fatigue tests, and role of the lack of fusion pores (LOFs) on the fatigue resistance. Results show that the unnotched fatigue strength (σf) at 600 °C is 23% lower compared to RT due to the lower work hardening rate at 600 °C, which facilitates easy crack initiation at favorably located and oriented LOFs. However, dynamic recrystallization at the crack tip regions retards the short fatigue cracks (SFCs) and leads to a substantially higher fatigue life at 600 °C compared to RT for stress amplitudes (σa) higher than σf. Post facto analysis was carried out to understand the initiation and growth behavior of SFCs including the effect of plasticity/oxidation induced crack closure. The LB-PBF induced microstructural characteristics such as solidification cells with high dislocation density are effective in resisting the growth of SFCs at 600 °C compared to RT. These results highlight the importance of microstructural aspects on the fatigue resistance of additively manufactured alloys for high temperature applications.
License type:
Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
Funding Info:
This research / project is supported by the Agency for Science, Technology and Research - Structural Metals and Alloys Programme
Grant Reference no. : A18B1b0061