Boosting the mechanical properties at 815°C of laser-directed energy-deposited Inconel 625 alloy by introducing the Laves phase

This study aims to enhance the high-temperature mechanical properties of the laser-directed energy-deposited Inconel 625 alloy. Varied sizes, morphologies and volume fractions of the Laves phase were effectively regulated, high-temperature tensile properties and stress rupture life were systematically investigated, and the underlying mechanisms were revealed thoroughly. The results demonstrate that when the Laves phase morphology transitions from long-striped to granular, with optimised dimensions (length: 1-2 μm, width: 0.2-0.6 μm) and a precise volume fraction of 1.2%, the alloy exhibits a notable enhancement in mechanical performance: yield strength increases from 192.67 MPa to 217.33 MPa, tensile strength rises from 324.67 MPa to 348.33 MPa and stress rupture life extends from 24 h to 31 h. The boost in the high-temperature tensile strength was attributed to the precipitation of γ'' and δ phases near the Laves phase or the pinning effect at the Laves/γ interface. The extended stress rupture life results from δ phases hindering dislocation motion while promoting dynamic recovery. This study confirmed that retaining a controlled amount of Laves phase significantly enhances the mechanical properties of the Inconel 625 alloy, providing valuable insights for laser additive manufacturing and repaired nickel-based superalloy above 800°C.