Effect of sintering duration on microstructure and properties of Inconel 718 superalloy prepared by electric field-activated sintering

Abstract The electric field activated sintering technology (E-FAST) employs low voltage, high-intensity alternative current and axial pressure to complete the densification of metal powders with desirable mechanical property. The Inconel 718 nickel-based superalloy was sintered with the sintering durations of 490 s, 550 s and 610 s under the sintering temperature of 950 °C and the pressure of 70 MPa by using E-FAST. The effect of sintering duration on densification and microstructure of Inconel 718 alloy was studied. Results show that high densification levels were reached in all samples. Formation mechanisms of defects including impurity accumulation, indented pores and gully defects were discussed. Besides, the increase of sintering duration promotes the growth of the grain size, with the largest average grain size of 7.75 μm sintered with 610 s. The proportion of twin boundaries decreases rapidly with the increase of sintering duration. With the benefits of E-FAST, the yield strength of the sintered samples exceeded 497 MPa, and the engineering stain at fracture point was >0.8. The findings have both theoretical and practical applications for the collaborative control of the mechanical and microstructural property of nickel-based superalloy in E-FAST process.