Tuning pores and mechanical properties for the heterogeneous interface of laser directed energy deposited IN718/316 L laminate via in-situ laser surface remelting

Abstract

In the past decades, laser directed energy deposition (L-DED) of multi-material attracts much attention for the integration of structure and performance. However, interfacial pores and limited mechanical properties are still bottlenecks. The present study introduces the in-situ laser surface remelting (LSR) treatment to L-DED of IN718/316 L laminate. During the LSR process, the continuous-wave (CW) near-infrared fiber printing laser rescans the whole surface after completely depositing the bottom material. When the bottom material was selected as 316 L and IN718, the pores around the heterogeneous interface were obviously eliminated and the proportion of high angle grain boundaries (HAGBs) was respectively lifted by 85.1% and 149.1% with slightly reduced average grain diameter after LSR treatment. Eventually, 8.5% and 58.9% increase in the elongation were respectively achieved. According to the numerical investigation, the “pinch-off” of bubble is observed during LSR process for the first time and the necking is enhanced with increased remelting laser power when the bottom material is IN718. Furthermore, the pore below the molten pool is prone to enlarge with stress concentration. This work can provide a novel guidance for the defect-free AM-built laminate.