Inhibition of interfacial cracks in 304L-Inconel718 bimetal fabricated via laser powder bed fusion

• Published in: Additive manufacturing 2024-08, Vol.94, p.104463, Article 104463
• Main Authors: Li, Yinghui, Liu, Zhuangzhuang, Wei, Zhengyu, Hu, Pengfei, Chen, Jiawang, Liu, Lijing, Shu, Guogang, Xie, Jianxin
• Format: Article
• Language: English
• Subjects: 304 L; Crack; Inconel718; Laser powder bed fusion
• ISSN: 2214-8604
• DOI: 10.1016/j.addma.2024.104463

Multi-material additive manufacturing is crucial for intricate component fabrication, yet challenges, such as interfacial cracks and weak bonding, persist. This work investigated the laser powder bed fusion (L-PBF) of bimetallic components (stainless steel 304L-nickel-based alloy Inconel718) crucial in aerospace and nuclear applications. It is found that the interfacial cracks predominantly occur within the compositional transition zone where the proportion of 304 L is between 45 wt% and 75 wt%, characterized by brittle Laves phases along grain boundaries. Experimental and finite element simulations of melt pool reveal that a higher ratio of temperature gradient (G̅) to the grain growth rate (R̅) (G̅/R̅) results in straight grain boundaries with underdeveloped secondary dendrites. This leads to the formation of continuous liquid film and strip-like Laves phase at grain boundaries, causing interfacial cracks during L-PBF. To suppress these cracks, this work proposes manipulating grain boundaries into a tortuous morphology through promoting the growth of secondary dendrites. By controlling the G̅/R̅ ratios below the critical value (