High Temperature Tensile and Fatigue Behaviors of Additively Manufactured IN625 and IN718
Reza Ghiaasiaan, Arun Poudel, Nabeel Ahmad, Paul Gradl, Shuai Shao, Nima Shamsaei
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.