Impact of heat treatment on mechanical behaviour of Inconel 718 processed with tailored microstructure by selective laser melting. (5th October 2017)

• Record Type: Journal Article
• Authors: Popovich, V.A.; Borisov, E.V.; Popovich, A.A.; Sufiiarov, V.Sh.; Masaylo, D.V.; Alzina, L.
• Is Part Of: Materials & design. Volume 131(2017)
• Page Start: 12
• Page End: 22
• Publication Date: 2017-10-05
• Subjects: Additive manufacturing -- Ni-base alloy -- Microstructural design -- Heat treatment -- Mechanical properties; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2017.05.065
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: Additive manufacturing (AM) technologies are known to allow the production of parts with an extreme degree of complexity, enabling design and functional part optimization. However, the resulting microstructures and mechanical properties of AM materials are not well understood due to unique and complex thermal cycles observed during processing. This study aims to adjust the microstructure of Inconel 718 specimens produced by selective laser melting (SLM). The microstructural design was achieved through process parameters manipulation and post-process heat treatment. The effects of heat treatment on microstructure, process induced defects, deformation behaviour and failure mechanisms were studied. Directional columnar grained microstructure accompanied by interdendritic Laves phases and carbide particles was observed in as-processed material. Hot isostatic pressing (HIP) improved mechanical properties, which was attributed to dissolution of undesirable Laves and δ-phase as well as pore closure. All investigated samples maintained their intended tailored microstructural build up with distinct differences in mechanical properties. The results presented in this study show the capability of the SLM process to produce parts with mechanical properties better than conventional Inconel material. The microstructural design demonstrated here can be exploited in AM fabrication of complex components requiring challenging high-temperature mechanical performance. Graphical abstract: Highlights: Microstructural design was enabled via SLM process by producing fine and coarse grained regions in Inconel 718. Heat treatment (H/T) did not lead to recrystallization and the desired texture and grain morphology were preserved. Hot isostatic pressing (HIP) improved mechanical properties by dissolution of Laves, δ-phase and reduction of pores. By applying HIP + HT post-processing the intended tailored microstructure remained. RT tensile properties and high temperature ductility of HIP + H/T samples are superior to those of wrought material.