Abstract
Selective Laser Melting (SLM) of Inconel 718 superalloy offers unparalleled design freedom for complex geometries, yet it presents significant challenges related to high thermal gradients, rapid solidification, and subsequent residual stress development, which profoundly influence part integrity and performance. This study investigates the transient thermal stress evolution and its direct correlation with microstructural changes during the SLM process of Inconel 718. A coupled thermo-mechanical finite element model (FEM) was employed to simulate the layer-by-layer deposition, capturing the dynamic temperature fields and stress accumulation. The simulation results revealed complex transient stress states, with localized tensile stresses reaching critical levels during cooling. Experimentally, SLM-fabricated Inconel 718 samples were characterized using X-ray Diffraction (XRD) for residual stress, Electron Backscatter Diffraction (EBSD) for grain structure and phase identification, and Scanning Electron Microscopy (SEM) for microstructural features, including Laves phase formation. A strong correlation was established between regions predicted to experience high transient thermal stresses and the formation of deleterious non-equilibrium phases, such as Laves phase, particularly at melt pool boundaries and interdendritic regions. The findings underscore the critical role of thermal stress in dictating microstructural evolution and highlight the potential for optimizing SLM parameters to mitigate stress and improve material properties, thereby enhancing the reliability of additively manufactured Inconel 718 components.
