Microstructure and mechanical properties of Inconel 718 produced by selective laser melting: Sample orientation dependence and effects of post heat treatments

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 713; pp. 294 - 306
• Main Authors: Deng, Dunyong, Peng, Ru Lin, Brodin, Håkan, Moverare, Johan
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 24.01.2018; Elsevier BV
• Subjects: Cellular manufacture; Cellular precipitates; Cellular structure; Crystallographic orientation; Crystallography; Dendritic structure; Dependence; Dislocations; Ductility; Electron backscatter diffraction; Heat treating; Heat treatment; Laser beam melting; Laves phase; Mechanical properties; Melting; Microstructure; Nickel base alloys; Nickel based superalloy; Residual stress; Selective laser melting; Superalloys; Tensile strength; Mechanical properties; Crystallographic orientation; Nickel based superalloy; Selective laser melting; Microstructure; Residual stress
• ISSN: 0921-5093; 1873-4936; 1873-4936
• DOI: 10.1016/j.msea.2017.12.043

Inconel 718 produced by selective laser melting (SLM) has been characterized with focus on the microstructure, the dependence of sample orientation on the mechanical properties and the effects of post heat treatments. The as-manufactured IN718 has a very fine cellular-dendritic structure with fine Laves phases precipitating in the interdendritic region, and electron backscatter diffraction (EBSD) analysis shows that both the vertically and horizontally built samples have relatively weak texture. The vertically built samples show lower tensile strength but higher ductility than the horizontally built samples, and the mechanism is shown to be partly due to the crystallographic feature but more importantly due to the different amount of residual stress and dislocations accumulated in these two kinds of samples. Applying heat treatments can significantly increase the strength while decrease the ductility correspondingly, and difference in yield strength between the vertically and horizontally built samples decreases with increasing the heat treatment temperatures, mainly due to the removal of residual stress and dislocations.