Material interactions in laser polishing powder bed additive manufactured Ti6Al4V components

Tian, Yingtao and Gora, Wojciech S. and Cabo, Aldara P. and Parimi, Lakshmi L. and Hand, Duncan P. and Tammas-Williams, Samuel and Prangnell, Philip B. (2018) Material interactions in laser polishing powder bed additive manufactured Ti6Al4V components. Additive Manufacturing, 20. pp. 11-22. ISSN 2214-8604

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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.

Item Type:
Journal Article
Journal or Publication Title:
Additive Manufacturing
Additional Information:
This is the author’s version of a work that was accepted for publication in Additive Manufacturing. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Additive Manufacturing, 20, 2018 DOI: 10.1016/j.addma.2017.12.010
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/2200/2209
Subjects:
ID Code:
123965
Deposited By:
Deposited On:
12 Mar 2018 10:32
Refereed?:
Yes
Published?:
Published
Last Modified:
25 Oct 2020 05:24