A comparative study of microstructures and nanomechanical properties of additively manufactured and commercial metallic stents

E. Langi, L. G. Zhao, P. Jamshidi, M. Attallah, V. V. Silberschmidt, H. Willcock, F. Vogt

Research output: Contribution to journalArticlepeer-review

Abstract

Additive manufacturing emerges as an innovative technology to fabricate medical stents used to treat blocked arteries. However, there is a lack of direct comparison of underlying microstructure and mechanical properties of additively manufactured and commercial stents. In this study, additively manufactured and commercial 316 L stainless steel stents were investigated comparatively, with electrochemical polishing being used to improve the surface finish of the former stent. Microstructural characterisation of both stents was carried out through optical microscopy, scanning electron microscopy, and electron backscatter diffraction. Their hardness and elastic modulus were studied using Berkovich nanoindentation, with an emphasis on the effect of grain orientation. In addition, spherical nanoindentation was used to generate indentation stress-strain curves based on load-displacement responses. The obtained results showed that electrochemical polishing was effective in diminishing the average surface roughness, with a reduction of Ra value from 8.45 µm to 5.96 µm. The additively manufactured stent demonstrated the hierarchical grain microstructure with columnar grains and cellular sub-grains, as opposed to equiaxed fine grains and twins in the commercial stent. The hardness and modulus of additively manufactured stents were higher than those of the commercial ones. The grains close to the (111) orientation exhibited the highest hardness and elastic modulus followed by (101) and (001) orientations. The indentation stress-strain curves, yield strength, and hardening behaviour were similar for the additively manufactured and commercial stents. This work provides a fundamental understanding of the microstructure and properties of the additively manufactured stent and represents an important step towards innovative manufacturing of stents.

Original languageEnglish
Article number103372
Number of pages15
JournalMaterials Today Communications
Volume31
Early online date14 Mar 2022
DOIs
Publication statusE-pub ahead of print - 14 Mar 2022

Bibliographical note

Funding Information:
We acknowledge the support from the EPSRC UK (Grant Number: EP/R001650/1 ; Title: Smart peripheral stents for the lower extremity–design, manufacturing, and evaluation). The authors acknowledge use of the facilities, and the assistance of Dr Keith Yendall in the Loughborough Materials Characterisation Centre. Research data for this paper are available upon request to the projects_ principal investigator Professor Liguo Zhao at Loughborough University, UK (email: L.Zhao@Lboro.ac.uk ).

Publisher Copyright:
© 2022 Elsevier Ltd

Keywords

  • Additive manufacturing
  • Material microstructure
  • Mechanical properties
  • Metallic stents
  • Nanoindentation
  • Selective laser melting

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Materials Chemistry

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