Abstract
Selective Laser Melting (SLM) is an additive manufacturing technology used to directly produce metallic parts from thin powder layers. To evaluate the anisotropic mechanical properties, tensile test specimens of the Ni-base alloy Hastelloy X were built with the loading direction oriented either parallel (z-specimens) or perpendicular to the build-up direction (xy- specimens). Specimens were investigated in the “as-built” condition and after high temperature heat treatment. Tensile tests at room temperature and at 850°C of “as-built” material have shown different mechanical properties for z- and xy-specimens. The anisotropy is reflected in the Young's modulus, with lower values measured parallel to the build-up direction. It is shown that the anisotropy is significantly reduced by a subsequent recrystallization heat treatment. The characterization of microstructural and textural anisotropy was done by Electron Back Scatter Diffraction (EBSD) analysis. Predictions of Young's modulus calculated from the measured textures compare well with the data from tensile tests.
Highlights
Ni-base superalloys are extensively used for components in aero- and industrial gas turbine engines [1, 2]
Texture and microstructural anisotropy in Selective Laser Melting (SLM) made Hastelloy X specimens are analyzed using Electron Back Scatter Diffraction (EBSD) and correlated with anisotropic material behavior observed during mechanical testing (Young’s modulus)
We report on processing routes to reduce the amount of anisotropy by (i) optimized laser scanning strategy, and (ii) suitable heat treatment
Summary
Ni-base superalloys are extensively used for components in aero- and industrial gas turbine engines [1, 2]. Progress in Ni-base alloy performance would not be possible without the parallel improvement of processing technology. Additive manufacturing processes such as selective laser melting (SLM) [4, 5] are prospective candidates to complement or replace conventional machining/production processes such as cutting and casting. The high thermal gradients in SLM processing cause crystals to grow preferentially in welldefined directions, resulting in specific microstructures and textures [8]. Suitable scanning strategies favor either sharp single component textures or more uniformly distributed crystal orientations [9]. Texture and microstructural anisotropy in SLM made Hastelloy X specimens are analyzed using EBSD (electron backscatter diffraction) and correlated with anisotropic material behavior observed during mechanical testing (Young’s modulus). We report on processing routes to reduce the amount of anisotropy by (i) optimized laser scanning strategy, and (ii) suitable heat treatment
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