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How Temperature Gradient Influences the Formation of Residual Stresses in Metallic Parts Made by L-PBF

  • Rapid cooling rates and steep temperature gradients are characteristic of additively manufactured (AM) parts and important factors for residual stress formation which have implications on structural integrity. This study examined the influence of heat input on the distribution of residual stresses in two prisms produced by laser powder bed fusion (L-PBF) of austenitic stainless steel 316L. The layers of the prisms were exposed using two distinct helix scanning strategies: one scanned from the centre to the perimeter and the other from the perimeter to the centre. Residual stresses were characterised at one plane perpendicular to the building direction at half of its build height using neutron diffraction. In addition, the defect distribution was analysed via micro X-ray computed tomography (µCT) in a twin specimen. Both scanning strategies reveal residual stress distributions typical for AM: compressive stresses in the bulk and tensile stresses at the surface. However, temperatureRapid cooling rates and steep temperature gradients are characteristic of additively manufactured (AM) parts and important factors for residual stress formation which have implications on structural integrity. This study examined the influence of heat input on the distribution of residual stresses in two prisms produced by laser powder bed fusion (L-PBF) of austenitic stainless steel 316L. The layers of the prisms were exposed using two distinct helix scanning strategies: one scanned from the centre to the perimeter and the other from the perimeter to the centre. Residual stresses were characterised at one plane perpendicular to the building direction at half of its build height using neutron diffraction. In addition, the defect distribution was analysed via micro X-ray computed tomography (µCT) in a twin specimen. Both scanning strategies reveal residual stress distributions typical for AM: compressive stresses in the bulk and tensile stresses at the surface. However, temperature gradients and maximum stress levels differ due to the different heat input. Regarding the X-ray µCT results, they show an accumulation of defects at the corners where the laser direction turned through 90°. The results demonstrate that neutron diffraction and X-ray µCT can be successfully used as non-destructive methods to analyse through-thickness residual stress and defect distribution in AM parts, and in the presented case, illustrate the influence of scanning strategies. This approach contributes to deeper assessment of structural integrity of AM materials and components.zeige mehrzeige weniger

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Metadaten
Autor*innen:Alexander Ulbricht
Koautor*innen:Simon Altenburg, Maximilian Sprengel, Tobias Thiede, Itziar Serrano Munoz, Tatiana Mishurova, Gunther Mohr, Alexander Evans, Giovanni Bruno
Dokumenttyp:Vortrag
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2019
Organisationseinheit der BAM:8 Zerstörungsfreie Prüfung
8 Zerstörungsfreie Prüfung / 8.0 Abteilungsleitung und andere
8 Zerstörungsfreie Prüfung / 8.5 Röntgenbildgebung
9 Komponentensicherheit
9 Komponentensicherheit / 9.3 Schweißtechnische Fertigungsverfahren
9 Komponentensicherheit / 9.4 Integrität von Schweißverbindungen
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:AGIL; Additive manufacturing; Neutron diffraction; Residual stress; Thermography
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Additive Fertigung
Material / Degradation von Werkstoffen
Veranstaltung:First European Conference on Structural Integrity of Additively Manufactured Materials (ESIAM19)
Veranstaltungsort:Trondheim, Norwegen
Beginndatum der Veranstaltung:09.09.2019
Enddatum der Veranstaltung:11.09.2019
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:28.11.2019
Referierte Publikation:Nein
Eingeladener Vortrag:Nein
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