Material interactions in laser polishing powder bed additive manufactured Ti6Al4V components

Yingtao Tian, Wojciech Stanisław Góra, Aldara Pan Cabo, Lakshmi L. Parimi, Duncan Paul Hand, Samuel Tammas-Williams, Philip B. Prangnell

Research output: Contribution to journalArticle

12 Citations (Scopus)
29 Downloads (Pure)

Abstract

Laser polishing (LP) is an emerging technique with the potential to be used for post-build, or in-situ, precision smoothing of rough, fatigue-initiation prone, surfaces of additive manufactured (AM) components. LP uses a laser to re-melt a thin surface layer and smooths the surface by exploiting surface tension effects in the melt pool. However, rapid re-solidification of the melted surface layer and the associated substrate thermal exposure can significantly modify the subsurface material. This study has used an electron beam melted (EBM) Ti6Al4V component, representing the worst case scenario in terms of roughness for a powder bed process, as an example to investigate these issues and evaluate the capability of the LP technique for improving the surface quality of AM parts. Experiments have shown that the surface roughness can be reduced to below Sa = 0.51 μm, which is comparable to a CNC machined surface, and high stress concentrating defects inherited from the AM process were removed by LP. However, the re-melted layer underwent a change in texture, grain structure, and a martensitic transformation, which was subsequently tempered in-situ by repeated beam rastering and resulted in a small increase in sub-surface hardness. In addition, a high level of near-surface tensile residual stresses was generated by the process, although they could be relaxed to near zero by a standard stress relief heat treatment.

Original languageEnglish
Pages (from-to)11-22
Number of pages12
JournalAdditive Manufacturing
Volume20
Early online date27 Dec 2017
DOIs
Publication statusPublished - Mar 2018

Keywords

  • Additive manufacturing
  • Laser polishing
  • Microstructure
  • Residual stresses
  • Titanium

ASJC Scopus subject areas

  • Biomedical Engineering
  • Materials Science(all)
  • Engineering (miscellaneous)
  • Industrial and Manufacturing Engineering

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