Exploring How LPBF process parameters impact the interface characteristics of LPBF Inconel 718 deposited on Inconel 718 wrought substrates

• Published in: Optics and laser technology 2024-07, Vol.174, p.110571, Article 110571
• Main Authors: Shrivastava, Abhishek, Anand Kumar, S., Rao, Samrat, Nagesha, B.K.
• Format: Article
• Language: English
• Subjects: Inconel 718; Laser powder bed fusion (LPBF); melted interface zone (MIZ); primary dendritic arm spacing (PDAS); Relative density
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2024.110571

•Initial microstructure has fine dendritic grains near the interface, coarsening towards upper deposition regions.•Higher laser power and scan speed lowered micro-hardness in LPBF-deposited Inconel 718 and its interface.•Defects, like lack-of-fusion and porosity, emerged at the deposition-substrate junction, worsening with increased laser parameters. This work investigates the interface properties of LPBF Inconel 718 deposited on Inconel 718 wrought substrates fabricated using the laser powder bed fusion (LPBF) technique. The as-printed (S1, S2, S3, and S4) samples were characterized using optical microscopy (OM),scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and micro-hardness techniques.The samples showed the development of a melted interface zone (MIZ) at the wrought substrate-deposition interface for all processing conditions. The developed interface showed a dendritic grain structure, signifying the remelting of the wrought substrate followed by rapid solidification. The MIZ thickness increased with an increase in laser power and scan speed (28.5 % increase in the MIZ thickness with a ∼ 12 % increase in normalized enthalpy). The assessment of the MIZ showed a high-quality interface. However, with an increase in scanning speed, the density of the MIZ decreases owing to increased porosity and lack-of-fusion (LOF) defects. The S1 condition (250 W and 850 mm/s) resulted in a highly dense part with no visible porosity, LOF defects, and a high relative density (∼99.9 %) in the MIZ region. The S4 condition showed the presence of large porosities and LOF defects at the deposition-MIZ interface, signifying an inferior bond between the deposition and substrate. The microstructural characterization of the LPBF-processed and MIZ region showed an increase in the primary dendritic arm spacing (PDAS) with increasing laser power due to a reduced cooling rate. The micro-hardness characterization of the sample shows a decrease in the hardness of the MIZ attributed to the dissolution of strengthening phases due to remelting. The present work outcome demonstrates the effectiveness of the proposed methodology for manufacturing high-quality parts using LPBF technology.