Effect of Laves-decorated dendrite structure on hydrogen embrittlement in selective laser-melted nickel-based alloy

• The hydrogen embrittlement property of SLM-718 alloy was investigated;. • Dendrite structures with high-density dislocations and Laves phases were identified;. • The hydrogen trapping behavior of dendrite walls was confirmed by SKPFM and HMT. • Atomic-scale analysis revealed the hydrogen-effect deformation behavior of Laves phases;. • Hydrogen induced the fracture of Laves phase and debonding of Laves/matrix interface. The effects of the Laves-decorated dendrite structure on the hydrogen-assisted cracking behavior of the SLM-718 alloy were investigated. The Laves phase exhibits a hydrogen desorption activation energy of 47.67 ± 7.85 kJ mol −1 . The results of in situ scanning Kelvin probe force microscopy and hydrogen microprint technique provide direct evidence of the hydrogen trapping by the Laves phase. The high-density dendrite walls consisting of entangled dislocations exhibit an inhibitory effect on hydrogen diffusion. Atomic-scale characterization reveals that dislocation stacking at the Laves/γ-matrix interface induces the formation of dislocation defects and a high-stress concentration in the Laves phase. The presence of hydrogen further promotes the formation of micropore defects and the embrittlement of the Laves phase. Hydrogen-promoted dislocation slip localization and hydrogen-induced reduction of interatomic bonding are the primary reasons for the Laves phase fracture and debonding at the Laves/γ-matrix interface. The coalescence of micropore defects ultimately leads to hydrogen-induced crack formation. Graphical abstract: (a 1 ) Schematic diagram of the in situ scanning Kelvin probe force microscopy (SKPFM) test; (a 2 ) Electron channeling contrast imaging (ECCI) analysis of the marked region for SKPFM test, showing the morphology of the cellular dendrite structure; (a 3 ) Volta potential difference maps of the SKPFM specimen at 2 and 194 h after hydrogen charging, showing the potential difference between the Laves phase and the γ-matrix; (b) SEM image of the HMT specimen, showing the distribution of Ag particles along the cellular dendrite wall; (c) Hydrogen desorption rate curves of the TDS specimens with 24 h of hydrogen charging at heating rates of 100, 200, and 300 °C h − 1 ; (d) ECCI image showing the interaction between the DSBs and Laves phase, leading to the formation of micropore and microcrack; (e) Schematic illustration showing the deformation mechanism of Laves phase and the initiation and propagation of hydrogen-assisted cracks.