Microstructures and hardening mechanisms of a 316L stainless steel/Inconel 718 interface additively manufactured by multi-material selective laser melting

• Main Authors: Mohd. Yusuf, Shahir, Mazlan, Nurainaa, Musa, Nur Hidayah, Zhao, Xiao, Chen, Ying, Yang, Shoufeng, Nordin, Nur Azmah, Mazlan, Saiful Amri, Gao, Nong
• Format: Article
• Language: English
• Published: MDPI 2023
• Subjects: Q Science (General); TJ Mechanical engineering and machinery
• Online Access: http://eprints.utm.my/105796/1/ShahirMohdYusuf2023_MicrostructuresandHardeningMechanismsofa316L.pdf; http://eprints.utm.my/105796/; http://dx.doi.org/10.3390/met13020400

For the first time, the interfacial microstructures and hardening mechanisms of a multi-material (MM) 316L stainless steel/Inconel 718 (316L SS/IN 718) interface fabricated by a novel multi-material selective laser melting (MM SLM) additive manufacturing (AM) system have been investigated in this study. MM 316L SS/IN 718 parts were successfully built with high densification levels (>99%) and low porosity content (average: ~0.81%). Microscopy analysis indicates that the interfacial microstructures are characterised by dense dislocation tangling networks, NbC and TiC, and very small amounts of Laves phase (<2 wt. %). In addition, equiaxed grains (average: 45 ± 3 μm) are attained in the interfacial region, whereas both individual IN 718 and 316L SS regions exhibit show columnar grains with average sizes of 55 ± 5 μm and 85 ± 3 μm, respectively. Vickers microhardness (HV) and nanoindentation measurements exhibit that the hardness values of the interfacial region are between those of the individual material regions. A strengthening model is built to assess the contribution of intrinsic strength, solid solution, precipitations, dislocations, and grain boundaries to the overall interfacial hardness of the as-built MM alloy.