Anisotropic Stress Rupture Properties-Microstructure Relationships in SLM Inconel 718 Alloy

The anisotropic of stress rupture properties of additive manufacturing superalloys at high temperatures affect their further applications in the aerospace field. In this study, selective laser melting (SLM) was used to prepare Inconel 718 blocks with axial direction normal or parallel to the building direction. The microstructure of different specimens was designed by process parameter control and post-processing. Tensile properties of horizontal and vertical specimens were tested at room temperature, and the stress rupture tests were performed at 650 °C under 690 MPa. The relationship between different microstructure and the anisotropy of stress rupture properties was studied. It is found that the grain morphology, grain boundary state and the morphology and location of precipitated phase have strong influence on the anisotropy. After the newly designed post-treatment including HIP + solution + aging, the normal temperature tensile property of vertical and horizontal specimens are maintained at a high level, besides the stress rupture life of vertical and horizontal specimens has the average time reach 173 and 131 hours at high temperature, respectively. This provides a basis for how to reduce the anisotropic stress rupture properties of SLM Inconel 718, which will have a positive impact on its wider application in engineering.