Evaluation of the role of hatch-spacing variation in a lack-of-fusion defect prediction criterion for laser-based powder bed fusion processes

Ryan Harkin, Hao Wu, Sagar Nikam, Shuo Yin, Rocco Lupoi, Patrick Walls, Wilson McKay, S McFadden

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
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Abstract

Lack of fusion (LOF) defects impact adversely on the mechanical properties of additively manufactured components produced via laser-based powder bed fusion. Following a stress-relieving heat treatment, the tensile properties and hardness of Ti6Al4V components were found to be negatively impacted by the presence of LOF defects. This work considers a geometrical-based inequality for the prediction of LOF defects. We critically evaluate an LOF criterion using both the experimentally and analytically obtained melt pool geometries. Experimentally, we determined melt pool dimensions by analysing a single-layer, multi-track deposition with oversized hatch spacing in order to establish depth and width from non-overlapping melt pools. Analytically, Rosenthal-based predictions of melt pool size (width and depth) are applied. To investigate LOF defects, we used hatch spacing as the main parameter variation to investigate defects while keeping all other controllable parameters unchanged. An original LOF criterion from the literature was found to be an adequate predictor of LOF defects when experimentally obtained melt pool geometry was used. Critically, however, the analytical expressions for melt pool geometry were found to be in error and this caused the LOF criterion to fail in predicting LOF defects in all cases where defects were observed experimentally. However, an adaptation to the LOF prediction criterion is proposed whereby it is recommended that a correction factor R2c=0.7 (or Rc=0.83) is used with the analytically derived melt pool geometry. Furthermore, this correction is extended into the laser power versus scanning speed operating space to give minimum (corrected) line energy for LOF avoidance in Ti6Al4V components.
Original languageEnglish
Pages (from-to)659-673
Number of pages15
JournalThe International Journal of Advanced Manufacturing Technology
Volume126
Issue number1-2
Early online date3 Mar 2023
DOIs
Publication statusPublished online - 3 Mar 2023

Bibliographical note

Funding Information:
This research (authors RH, HW, SN, SMF) leading to these results received funding from INTERREGVA (Project ID: IVA5055, Project Reference Number: 047). The North West Centre for Advanced Manufacturing (NW CAM) project is supported by the European Union’s INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB). The views and opinions in this document do not necessarily reflect those of the European Commission or the Special EU Programmes Body (SEUPB). Catalyst based in Northern Ireland may be contacted for further information in relation to the NW CAM project.

Publisher Copyright:
© 2023, The Author(s).

Keywords

  • Defects
  • Titanium alloy
  • Additive manufacturing
  • Powder bed fusion

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