Microstructure, mechanical behaviour and strengthening mechanisms in Hastelloy X manufactured by electron beam and laser beam powder bed fusion

Amal Shaji Karapuzha, Darren Fraser, Daniel Schliephake, Stefan Dietrich, Yuman Zhu, Xinhua Wu, Aijun Huang

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Understanding the microstructure and mechanical properties associated with different metal additive manufacturing techniques is crucial for its wide-scale acceptance in industries. In this work, we aim to understand the microstructural variations and mechanical properties of Hastelloy X (HX) manufactured by electron beam powder bed fusion (PBF-EB) and laser-based powder bed fusion (PBF-LB) process. The size and shape of melt pool and grains were analysed and correlated to final microstructure. The elevated powder bed temperature during PBF-EB was found to promote the formation of grain-boundary precipitates. The higher thermal gradient and cooling rate in PBF-LB resulted in higher tensile residual stress (σmax = 447 ± 10 MPa) within the parts in comparison to PBF-EB parts (σmax = 16 ± 13 MPa). The as-fabricated PBF-EB HX specimens showed a lower tensile strength of 590 MPa but a higher elongation of 60%, whereas its PBF-LB counterparts demonstrated a significantly higher tensile strength of 825 MPa but a lower elongation of 38%. This notable difference in the mechanical behaviour of PBF-EB and PBF-LB built HX was attributed to the columnar microstructure,<100> crystallographic texture and underlying strengthening mechanisms. Furthermore, the mechanical properties of PBF-EB and PBF-LB built HX specimens were predicted using multiple strengthening mechanisms, which demonstrated a good agreement with that of experimentally measured.

Original languageEnglish
Article number158034
Number of pages19
JournalJournal of Alloys and Compounds
DOIs
Publication statusAccepted/In press - 23 Nov 2020

Keywords

  • Additive manufacturing
  • Hastelloy X
  • Mechanical properties
  • Microstructure
  • Powder bed fusion

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