Fatigue behavior of additively manufactured 17-4 PH stainless steel: Synergistic effects of surface roughness and heat treatment

By P. D. Nezhadfar, R. Shrestha, N. Phan, Nima Shamsaei. International Journal of Fatigue, 2019

155 citations recorded by the source corpus.

Abstract In this study, the synergistic effects of heat treatment and surface roughness on the microstructure and mechanical properties of laser powder bed fusion (L-PBF) 17-4 precipitation hardening (PH) stainless steel (SS) were investigated under monotonic tensile and fatigue loading. Five different heat treatment procedures, with and without primary solution treating cycle, i.e. Condition A (CA), were applied on L-PBF specimens in both as-built and machined surface conditions. Monotonic tensile tests were conducted at a strain rate of 0.001 s−1 and, uniaxial fully-reversed (R = −1) strain-controlled fatigue tests were carried out at various strain amplitudes ranging from 0.001 to 0.004 mm/mm. The heat treatment procedures were found to have a significant effect on the microstructure and mechanical properties of L-PBF 17-4 PH SS with the CA thermal cycle improving the fatigue strength considerably. This is due to the more homogenized microstructure obtained after performing the CA thermal cycle. In addition, eliminating the effect of surface roughness by machining and polishing processes enhanced the fatigue strength of the material, somewhat comparable to the one of the wrought counterpart. Fractography analysis revealed surface micro-notches and internal pores as the primary crack initiating factors in the as-built and machined specimens, respectively.

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Citations in the corpus

• Steels in additive manufacturing: A review of their microstructure and properties (2020, background): “AM induced defects in the microstructure such as voids, oxides and un-melted particles, as well as surface defects such as enhanced surface roughness affect the material’s fatigue behaviour under cyclic loading [98,99].”
• High cycle fatigue behavior and life prediction for additively manufactured 17-4 PH stainless steel: Effect of sub-surface porosity and surface roughness (2020, unknown): “Moreover, regardless of surface condition, more experimental variability was observed in N2 data than the Ar data adopted from the previous investigation [34].”
• Additive manufacturing of steels: a review of achievements and challenges (2020, background): “Some studies into the fatigue behaviour of AM 17–4 PH stainless steel have analysed the effect of subsequent heat treatments on the fatigue performances of these samples [132].”