Investigating the Cause and Threat of Lack of Fusion in 316L Parts

Abstract

Abstract This study connects information from tensile strength data, fractography, computed tomographic (CT) scanning data, and previous additive manufacturing (AM) research to determine the cause of a unique lack of fusion (LOF) phenomenon in Laser Powder Bed Fused (LPBF) 316L parts. Motivation for the study comes from the need to understand the structural capability of an LPBF IBR operating under vibration excitation within a spin rig. A minimalist approach (limited data and analysis) is used to assess structural capability. Therefore, small amounts of information are leveraged within a systematic approach that is applied to the LOF root cause analysis. The results show a unique repeatability in LOF occurrences for a specific geometry within a build volume. Correlating the build strategies to previous AM research, the LOF phenomena appears connected to melt pool characteristics that are functions of geometric features and scan strategies. The important takeaway from this study is that the LOF in the specimen is not representative of the defect characteristics in the IBR and does not reflect the risk level of spinning the IBR in a vibratory environment.