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Effects of as-built surface with varying number of contour passes on high-cycle fatigue behavior of additively manufactured nickel alloy 718

Published

Author(s)

Orion Kafka, Jake Benzing, Nicholas Derimow, Philipp Schumacher, Lucas Koepke, Chad Beamer, Donald Godfrey, Nik Hrabe

Abstract

High cycle fatigue life of laser-powder bed fusion (L-PBF) parts depends on several factors; as-built surfaces, when present, are a particular concern. This work measures as-built L-PBF surfaces with X-ray computed tomography, and uses rotating beam fatigue testing to measure high cycle fatigue life. Surfaces with different, but consistent, characteristics are achieved by building vertical specimens and changing only the number of contour passes. In this way, specimens with three different levels of surface roughness are compared to standard polished specimens. The results from this show that surface roughness increases with decreasing number of contour passes, but the impact on fatigue lifetime is not trivially related. Electron microscopy and x-ray computed tomography images show multiple initiation points and complex surface topology, but that surface feature depth is not necessarily correlated to failure location. Two primary conclusions are that 1) for the case of as-built surfaces loaded in bending, one contour pass is sufficient to achieve peak as-built performance; 2) surface feature depth, even when measured using metal-penetrating imaging, is not strongly associated with failure location in our data. When assessing AM surfaces, more factors (e.g., grain orientation) may be required to mechanistically understand the performance implications.
Citation
International Journal of Fatigue

Keywords

additive manufacturing, IN718, fatigue, x-ray computed tomography, surface roughness

Citation

Kafka, O. , Benzing, J. , Derimow, N. , Schumacher, P. , Koepke, L. , Beamer, C. , Godfrey, D. and Hrabe, N. (2023), Effects of as-built surface with varying number of contour passes on high-cycle fatigue behavior of additively manufactured nickel alloy 718, International Journal of Fatigue, [online], https://doi.org/10.1016/j.ijfatigue.2023.107872, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936456 (Accessed April 18, 2024)
Created August 5, 2023, Updated August 21, 2023