Electropulsing-enhanced dissolution of Laves phase and tensile properties in laser additively manufactured 718Plus alloy

Electropulsing technique was first used for laser additive manufacturing (LAM) of Ni-based superalloy, and the effect of electropulsing treatment (EPT) on the dissolution behavior of Laves phase and tensile properties was investigated. The results show that EPT reduces the thermodynamic potential barrier during the Laves phase dissolution process by altering the free energy of the system, enabling the dissolution of Laves phase at a relatively low temperature (1050 °C). Moreover, the Laves phase preferentially dissolves in the region of small curvature radius under the current detour effect. Based on the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model, the dissolution kinetics of Laves phase under EPT was analyzed. The quantitative relationship of Laves phase dissolution kinetics under EPT and conventional heat treatment (CHT) was established. Theoretical analysis and quantitative calculations reveal that the diffusion coefficient of the EPT at 1050 °C is 10 times higher than under CHT. The decrease in Laves phase volume fraction leads to a significant increase in elongation. The lower treatment temperatures and shorter times effectively suppressed abnormal grain growth, resulting in a significant increase in elongation of the EPT-3 sample to 39.5 %. The failure mechanisms and crack initiation of as-deposited, EPT-3 and CHT-6 samples were systematically analyzed. It can be found that the required microstructure of the alloy can be rapidly achieved at lower temperatures by applying EPT. Compared with CHT, the EPT technology provides a clean, efficient, and limitless potential new post-treatment method for LAM Ni-based superalloys.