Abstract
This study confirmed that Al2O3 particles were formed in IN718 alloys during the fabrication by both selective laser melting (SLM) and electron beam melting (EBM). Different heat pattern and atmospheres in SLM and EBM result in different distribution and volume fraction of Al2O3 particles. The Al2O3 oxides would act as nucleation sites for the precipitation of Nb/Ti carbides, leading to the formation of unique core-shell composites with Al2O3 in the center and Ti/Nb at the periphery. In order to investigate the oxygen content introduced during SLM and EBM, the volume fraction of Al2O3 formed in spark plasm sintering (SPS)-fabricated substrate, by consolidating the pre-oxidized IN718 raw powders at 800 °C, was utilized. The oxygen contents introduced to IN718 substrates during SLM and EBM fabrication were calculated to be 0.030 wt% and 0.099 wt%, respectively.
Highlights
Additive manufacturing (AM) is a novel materials fabrication process which can allow direct molding of raw powders into arbitrary configurations mapped out by 3D CAD data [1,2,3]
Based on a different contrast in the backscattered electron microscopy (BSE) images, it is recognized that there are several black precipitates uniformly dispersed in each AM-fabricated sample, i.e., (d) a high number density and a small size of the particles in selective laser melting (SLM)-IN718 substrate, (e) several sparser black particles with a larger size are distributed in electron beam melting (EBM)-IN718 substrate
The detailed area fraction of the black precipitates in each sample was calculated with ImageJ software, which is corresponded to 0.269% in SLM, 0.883% in EBM, and 0.133% in spark plasm sintering (SPS)
Summary
Additive manufacturing (AM) is a novel materials fabrication process which can allow direct molding of raw powders into arbitrary configurations mapped out by 3D CAD (computer-aided design) data [1,2,3]. The process of AM technologies on the industrial production today splits broadly into two types, based on the difference of the heat source, namely, selective laser melting (SLM) and electron beam melting (EBM), where a laser beam and an electron beam are used as heat source, respectively [4] Both the SLM and EBM processes are capable of fabricating fully dense metallic parts with high dimensional precision and superior surface integrity [2,5]. The residuals/oxides formed in AM-fabricated IN718 Ni-based alloys were examined, in which the microstructural difference resulting from heat source was illustrated through observing SLM- and EBM-fabricated IN718 alloys. The oxygen contents introduced into IN718 substrates, during SLM and EBM fabrication, were quantitatively analyzed by comparing the SPS results
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