Akademik Veri Yönetim Sistemi
RAPID PROTOTYPING JOURNAL, cilt.30, sa.2, ss.287-304, 2024 (SCI-Expanded)
Purpose – In recent years, additive manufacturing (AM) has started to be used for manufacturing real functional parts and assemblies for critical
applications in aerospace, automotive, and machinery industries. Most complex or assembled parts require internal features (IF) such as holes,
channels, slots, or guides for locational and mating requirements. Therefore, it is critical to understand and compare the structural and mechanical
properties of additively manufactured and conventionally machined IFs.
Design/methodology/approach – In this study, mechanical and microstructural properties of Inconel 718 (Inc718) alloy internal features,
manufactured either as-built with AM or machining of additively manufactured (AMed) part thereafter were investigated.
Findings – The results showed that the average ultimate tensile strength (UTS) of additively manufactured center internal feature (AM-IF) is almost
analogous to the machined internal feature (M-IF). However, the yield strength of M-IF is greater than that of AM-IF due the greater surface roughness
of the internal feature in AM-IF, which is deemed to surpass the effect of microstructure on the mechanical performance. The results of digital image
correlation (DIC) analysis suggest that AM-IF and M-IF conditions have similar strain values under the same stress levels but the specimens with as built
IF have a more locally ductile region around their IF, which is confirmed by hardness test results. But this does not change global elongation behavior.
The microstructural evolution starting from as-built (AB) and heat-treated (HT) samples to specimens with IF are examined. The microstructure of HT
specimens has bimodal grain structure with d phase while the AB specimens display a very fine dendritic microstructure with the presence of carbides.
Although they both have close values, machined specimens have a higher frequency of finer grains based on SEM images.
Originality/value – It was shown that the concurrent creation of the IF during AM can provide a final part with a preserved ultimate tensile
strength and elongation but a decreased yield strength. The variation in UTS of AM-IF increases due to the surface roughness near the internal
feature as compared to smooth internal surfaces in M-IF. Hence, the outcomes of this study are believed to be valuable for the industry in terms of
determining the appropriate production strategy of parts with IF using AM and postprocessing processes.