Low cycle fatigue behavior of additively manufactured Haynes 282: Effect of post-processing and test temperature

Abstract

This study investigated the fully reversed (R = -1), strain-controlled low cycle fatigue behavior of laser powder bed fused Haynes 282 at temperatures ranging from −195 to 871 °C and at strain amplitudes of 0.010 and 0.005 mm/mm. By comparing the fatigue behaviors of hot isostatically pressed (HIP) specimens in machined surfaces (HIP/M) and the Non-HIP ones in un-machined surfaces (Non-HIP/UM), the combined effect of surface condition and hot isostatic pressing was analyzed and discussed. The Non-HIP/UM specimens showed shorter fatigue lives compared to HIP/M ones from −195 to 649 °C, which was attributed to the presence of surface micro-notches and volumetric defects. This difference attenuated above 649 °C due to the combined effects of increased plastic deformation, which mitigated the negative impact of surface anomalies, and oxidation, which accelerated crack initiation and growth. The tests at −195 °C tended to suppress cyclic plastic deformation, especially at the lower strain amplitude, which led to improved fatigue lives. Lastly, both HIP/M and Non-HIP/UM specimens exhibited similar stress responses with respect to test temperature; at 21, 204, 760, and 871 °C, cyclic softening occurred due to shearing of γ′ precipitates by persistent slip bands, while at other temperatures, the softening was balanced or overcome by cyclic hardening due to deformation twinning (i.e., at −195 °C) and dislocation multiplication during ordinary slip (i.e., at 427 and 649 °C).