Characterization of Properties of Laser Powder Bed Fusion Three-Dimensional-Printed Inconel 718 for Centrifugal Turbomachinery Applications

Abstract

This paper presents the results of a comprehensive effort to characterize the properties of Inconel 718 produced by a form of laser powder bed fusion (LPBF) additive manufacturing (AM) or three-dimensional (3D)-printing, subsequently subjected to hot isostatic pressing (HIP) and heat treatment according to standards F3055-14a and AMS 5663, respectively. Material property data, while broadly available for traditional Inconel 718 presentations (e.g., forgings or castings) is currently lacking for the 3D-printed material. It is expected that while limited in size, the experimental data sets presented provide sufficient information to glean the capability of LPBF Inconel 718. These include: (1) chemical composition, electron backscatter diffraction (EBSD), and X-ray energy dispersive spectroscopy (XEDS) characterization of 3D-printed material structure; (2) tensile properties—0.2% yield stress, ultimate stress, modulus of elasticity, and elongation to failure—based on 108 samples, as functions of temperature and sample print orientation; (3) creep rupture data including the Larson-Miller parameter, based on 21 samples; and (4) high cycle fatigue data based on 21 samples as a function of temperature. Results are compared to available standards and/or data for forged, cast, and other AM Inconel 718. A key observation of this study, based on the EBSD results, is that while the material appears to approach full recrystallization following heat treatment, there is a detectable fraction of the material that does not fully recrystallize, resulting in a material with mechanical properties (e.g., yield stress and creep rupture) measurably lower than those of forgings, but higher than those of castings.