Improvement of strength and ductility by combining static recrystallization and unique heat treatment in Co-20Cr-15W-10Ni alloy for stent application

Kosuke Ueki, Soh Yanagihara, Kyosuke Ueda, Masaaki Nakai, Takayoshi Nakano, Takayuki Narushima

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The Co-20Cr-15W-10Ni (CCWN, mass%) alloy has excellent corrosion resistance and strength-ductility balance and is applied in almost all balloon-expandable stent platforms. To further reduce the invasiveness of stent placement, it is necessary to reduce the diameter of the stent. That is, both high strength and high ductility should be achieved while maintaining a low yield stress. In our previous studies, it was discovered that low-temperature heat-treatment (LTHT) at 873 K improves the elongation of the CCWN alloy. In this study, we focused on the grain refinement by swaging and static recrystallization to improve the strength of the alloy. The as-swaged alloy was recrystallized at 1373-1473 K for 100-300 s, followed by LTHT. A fine grain structure with an average grain size of 3-17 µm was obtained by static recrystallization. The η-phase (M12X-M6X type precipitates, M: metallic elements, X: C and/or N) formed during the recrystallization at 1373-1448 K. The alloys recrystallized at 1448 and 1473 K had a homogeneous structure with a small variation in the grain size. On the other hand, the alloys recrystallized at 1373 and 1423 K had an inhomogeneous structure in which fine and coarse grains were mixed. Both the strength and ductility of the CCWN alloy were improved by combining high-temperature short-time recrystallization and LTHT.

Original languageEnglish
Title of host publicationTHERMEC 2021 - International Conference on Processing and Manufacturing of Advanced Materials Processing, Fabrication, Properties, Applications
EditorsMihail Ionescu, Christof Sommitsch, Cecilia Poletti, Ernst Kozeschnik, Tara Chandra
PublisherTrans Tech Publications Ltd
Pages1503-1509
Number of pages7
ISBN (Print)9783035736304
DOIs
Publication statusPublished - 2021
Externally publishedYes
EventInternational Conference on Processing and Manufacturing of Advanced Materials Processing, Fabrication, Properties, Applications, THERMEC 2021 - Vienna, Austria
Duration: 2021 May 102021 May 14

Publication series

NameMaterials Science Forum
Volume1016 MSF
ISSN (Print)0255-5476
ISSN (Electronic)1662-9752

Conference

ConferenceInternational Conference on Processing and Manufacturing of Advanced Materials Processing, Fabrication, Properties, Applications, THERMEC 2021
CountryAustria
CityVienna
Period21/5/1021/5/14

Keywords

  • Co-Cr alloy
  • Heat treatment
  • Mechanical properties
  • Static recrystallization
  • Stent

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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