Unveiling Si's role in Laves phase dissolution in IN718 through experimentally guided molecular insights

D Pati and S Biswal and D Sahoo and S Chatterjee and M Chakraborty and M Paliwal, JOURNAL OF ALLOYS AND COMPOUNDS, 1036, 181742 (2025).

DOI: 10.1016/j.jallcom.2025.181742

Improving IN718's high-temperature performance while reducing costs is critical for aircraft engine manufacturing. A cost-effective approach is to utilise recycled materials with higher Si content. However, Si promotes Laves phase formation, which degrades mechanical properties. Despite its industrial significance, no prior studies have explored heat treatment strategies for IN718 alloys with Si above 0.15 wt%. This study bridges that gap by experimentally investigating Laves phase dissolution in as-cast IN718 with 0.2 and 0.4 wt% Si at 1100, 1150, and 1175 degrees C for varying durations. Advanced SEM-BSE and TEM analyses confirm Si's role in accelerating Laves phase dissolution, notably at 1100 degrees C, 0.4 wt% Si IN718 exhibits a steeper Laves phase decline, revealing a Si- driven dissolution mechanism. Molecular Dynamics (MD) simulations, employing optimized hybrid potentials, validate Si's impact at the atomic scale. Diffusion coefficient calculations and RDF results confirm that Si enhances Fe and Nb diffusion, accelerating the Fe-Nb bond breaking in the Laves phase. Furthermore, MD simulations establish that Nb diffusion primarily governs dissolution kinetics. A novel dissolution model, incorporating MD-derived diffusivity values, is developed to predict Laves phase evolution with time and temperature. This work provides the first integrated experimental-computational framework for optimizing heat treatment in high Si IN718.

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