Microstructure and properties of TLPB joints of IN718 with 3D waveform structure prepared by SLM

Inconel 718 (IN718) superalloys with multi-size 3D waveform structures were prepared by selective laser melting (SLM) technology, and the transient liquid phase bonding (TLPB) of IN718 was carried out using a rapidly solidified BNi2 filler containing melting point depressant (MPD) elements. In this study, the microstructure and mechanical properties of TLPB joints after brazing at 1080 °C for 20 min were investigated, and the effects of different 3D waveform structures on the formation and properties of TLPB joints were analyzed. The experimental results show that there are three zones in the TLPB joint of IN718 superalloy: (i) the isothermally solidified zone (ISZ) consisting of γ-Ni solid solution, (ii) the athermally solidified zone (ASZ) consisting of Ni 3 B, CrB, Ni 6 Si 2 B phases, and fine Ni 3 Si particles, and (iii) the diffusion affected zone (DAZ) consisting of Cr rich borides and Cr-Nb-Mo rich borides. And a region with high Cr content was found in the ASZ. In addition, the shear strength of the joint increased gradually with the increase of the groove depth of the 3D waveform structure. The shear strength of the TLPB joints reached a maximum of 515.17 MPa when the groove depth of the IN718 3D waveform was 0.8 mm, and the fracture mode of the joints gradually changed from brittle fracture to mixed tough-brittle fracture.