Challenges in Standardizing Additive Manufacturing for Nuclear Components and Associated Material Testing III: Fatigue Test of Type316L Stainless Steel for Standardization of AM Materials in the Nuclear Field – 1st Report

Abstract This paper reports on the fatigue life of objects manufactured by additive manufacturing (AM) using Type 316L Stainless Steel (Type 316L SS), an austenitic stainless steel commonly used in the nuclear power industry. Fatigue tests were performed with axial strain control from low cycles to high cycles of about 1 million times, and the strain amplitude εta for the target fracture life was set using a prediction equation for conventional materials. Powder Bed Fusion (PBF) and Directed Energy Deposition (DED) were used as AM methods to manufacture the test objects. In addition, the effects of heat treatment conditions (with or without Heat Isostatic Pressing (HIP)), test direction (horizontal/vertical), and surface condition (polished/as-built) were evaluated as factors that are thought to affect fatigue life. As a result of conducting fatigue tests on specimens manufactured using PBF or DED, the surface condition of the as -built surface showed a shorter life than the polished surface, but no clear significant differences were observed for other factors. In this paper, a prediction equation for conventional materials was used, but the predicted values for specimens manufactured using AM were equivalent to those for the conventional material, indicating that this prediction equation may also be applicable to AM specimens. In addition, both the PBF and DED specimens had fatigue lives that satisfied the rules on design and construction of the Japan Society of Mechanical Engineers (JSME).