Microstructure and mechanical properties of IN718 alloy by wire-laser directed energy deposition

IN718 alloy components are widely employed in high-temperature parts for aerospace applications. However, traditional machining methods are not only time-consuming but also lead to inefficient material utilization. This study introduces the fabrication of IN718 alloy through wire-laser directed energy deposition (W-LDED) technique. The alloy’s phase composition, microstructure, types of precipitated phases, and grain characteristics are characterized using X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and electron backscatter diffraction. The mechanical properties of the alloy are evaluated using a universal tensile testing machine and a microhardness tester. The matrix of the IN718 alloy consists of the γ phase, with Laves precipitate phase located at the grain boundaries or sub-grain boundaries. Notable differences in surface microstructures and properties are observed across various planes. The XOY surface predominantly exhibits equiaxed grains with the smallest average grain size, whereas the XOZ and YOZ surfaces comprise a mix of equiaxed grains and coarse columnar grains, with the YOZ surface displaying the largest average grain size. The highest tensile strength, reaching 842.5 MPa, is recorded along the Y direction, accompanied by an elongation of 17.5%. Conversely, the highest elongation, at 29.5%, is noted in the X direction, with a tensile strength of 818.7 MPa. The hardness values of the XOY, XOZ, and YOZ surfaces are 314HV_0.2, 267HV_0.2, and 229HV_0.2, respectively.