High Temperature Tensile and Fatigue Behaviors of Additively Manufactured IN625 and IN718

Abstract

Recent advancement and research efforts in additive manufacturing (AM) have made it a promising technology to fabricate nickel-base superalloy parts in near net shapes. IN625 and IN718 are the commonly used superalloys in elevated-temperature applications in the aerospace and energy sectors. However, the fatigue performance of the additively manufactured (AM) components often depends on the defects like porosity, micro-cracks, and lack-of-fusions, etc. In addition, the presence of columnar grains and residual stresses also affects their fatigue performance. In this study, IN625 and IN718 specimens were fabricated via both laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED) followed by stress-relief and standard heat treatments. Both alloys exhibited similar defect characteristics and grain morphologies. High-temperature fatigue properties of both IN625 and IN718 were tested at two strain amplitudes of 0.005 and 0.01 mm/mm and at two elevated temperatures of 427 and 625 °C. The fatigue lives of both alloys decreased with increasing testing temperatures. AM IN718 showed inferior fatigue performance at both test temperature and strain amplitudes in L-PBF conditions while in LP-DED condition both alloys have shown comparable fatigue performance.