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2020 (English)In: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810, Vol. 36, article id 101672Article in journal (Refereed) Published
Abstract [en]
Laser powder bed fusion (LPBF) of Ni-based superalloys shows great potential for high temperature applications, for example, as a burner repair application for gas turbines where the thin-walled structure is important. It motivates this work to investigate the evolution of microstructure and the anisotropic mechanical behavior when plate-like specimens are built with a thickness from 4 mm down to 1 mm. By performing texture analysis using neutron diffraction, a clear transition in fiber texture from <011> to <001> is indicated when the specimen becomes thinner. The residual stress shows no thickness dependence, and at the subsurface the residual stress reaches the same level as the yield strength. Due to the rough as-built surface, a roughness compensation method for mechanical properties of thin-walled structures is outlined and demonstrated. Tensile tests from room temperature up to 700 °C have been carried out. Anisotropic mechanical behavior is found at all temperatures, which is strongly related to the anisotropic texture evolution. Stronger texture evolution and grain rotations are discovered when the tensile loading is applied along the building direction. The mechanical behavior has been compared to a wrought material, where the high dislocation density and the subgrain structure of the LPBF material result in a higher yield strength. Combining the statistical texture analysis by neutron diffraction with mechanical testing, EBSD grain orientation mapping and the investigation of dislocation structures using transmission electron microscopy, this work illustrates the significance of texture for the thin-wall effect and anisotropic mechanical behavior of LPBF materials.
Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Hastelloy X; Hot tensile test; Crystallographic texture, roughness; Residual stress; Dislocation density
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-171983 (URN)10.1016/j.addma.2020.101672 (DOI)000600807800193 ()2-s2.0-85095614801 (Scopus ID)
Note
Funding agencies: Swedish Governmental Agency for Innovation Systems (Vinnova)Vinnova [2016-05175]; Center for Additive Manufacturing-metal (CAM2); AFM at Linkoping University; faculty grant SFO-MATLiU [2009-00971]
2020-12-162020-12-162023-09-08Bibliographically approved